X-ray Spectrum of the Black Hole Candidate X1755-338
X-ray Spectrometry
X-ray SpectrometryImre Szalo´kiInstitute of Experimental Physics,University of Debrecen,Bem te´r18/a,H-4026Debrecen,HungaryJa´nos Osa´nHungarian Academy of Sciences,KFKI Atomic Energy Research Institute,P.O.Box.49,H-1525Budapest,Hungary Rene´E.Van Grieken*Department of Chemistry,University of Antwerp,B-2610Antwerp,BelgiumReview ContentsOverview4069 Detection4071 Instrumentation and X-ray Optics4074 Quantification and Fundamental Data4078 Tomography,Holography,and X-ray Scattering4081 Total Reflection X-ray Fluorescence Analysis4083 Electron Probe Microanalysis4084 Particle-Induced X-ray Emission4086 X-ray Absorption Spectrometry4087 Applications4089 Sample Preparation4089ED-XRF4089Micro-XRF4089TXRF4090EPMA4090PIXE4091XAS4092Standards4093 Literature Cited4093OVERVIEWIn this review,we focus on the most significant and essential progress in X-ray spectrometry(XRS),published in the period 2004-2005,covering the developments and improvements in the performance of detection and instrumentation of X-ray techniques and X-ray optics,new quantification models in X-ray spectra and data evaluation,calculation and experimental determination of fundamental atomic data,tomography and holography methods for2D or3D imaging of microstructures,electron probe micro-analysis(EPMA),total reflection X-ray fluorescence(TXRF), particle-induced X-ray emission(PIXE)analysis,and X-ray absorp-tion spectrometry(XAS).Finally,different applications in each subfield of XRS are shown.This review involves only a selected minority of the published papers and we try to look over the current trends in this analytical field with a critically selected citing of papers,to support the research activity of the community of X-ray scientists.Since our last review,an international group of scientists published two overviews on XRS(A1,A2)in the Journal of Analytical Atomic Spectrometry,covering the period2003-2004 in the main field of this analytical spectroscopic method and instruments.These review articles involve all the important sections of XRS in nine chapters:reviews,instrumentation, spectrum analysis,matrix correction and calibration,X-ray optics and microfluorescence,synchrotron radiation,TXRF,portable and mobile X-ray fluorescence(XRF),and on-line XRF and applications. In the present review,we follow another way for classification of the information published in the literature in the2004-2005 period:detection,instrumentation(except of detectors)and optics,quantification models and related fundamental data,to-mography,and holography methods as the main tool of X-ray imaging,TXRF,EPMA,PIXE,XAS,and a final chapter that reviews the application of these methods in geology,environmen-tal research,industry,biology.and medicine.Current trends in pixel-type detectors were reviewed by Wermes(A3)showing their necessity in X-ray imaging devices,radiography,autoradiography, protein crystallography,and X-ray astrophysics research.The fundamental aims of R&D activity in the field of detectors are to arrange less material in the detector bulk,to build high-speed readout electronics,and to construct large radiation-tolerant detectors.The author describes the working principle and structure of different categories of pixilated detectors:hybrid pixel detectors when the sensor module and the electronic chips are connected by short bumps,diamond detectors and their applica-tions for protein crystallography and radiography.The author describes the dream of the detector developer:a fully monolithic pixilated detector where both the sensor bulk and the electronic circuits are in one entity and these devices can be produced by commercially available technology,and he outlines that this will not be possible in the future due to the lack of proper technology.In the past decade,the greatest hit in XRS was probably the cryogenically cooled quantum detectors such as superconductive tunnel junction(STJ),transition edge sensors(TESs),and micro-calorimeters.These provide excellent energy resolution for a wide range of X-ray energies,from the optical range up to several kiloelectronvolts.Kurakado published(A4)a short characteriza-tion about nonequilibrium superconductivity and STJ detectors. The tutorial paper introduces the reader into the main features, such as high count rate capability,stability against temperature fluctuation,ultra-high-energy resolution,and the working principle of the STJs.The most common Nb/Al/AlOx/Al/Nb structure has excellent working parameters and very high stability against temperature variation from50to500mK.A100×100µm2AlAnal.Chem.2006,78,406910.1021/ac060688j CCC:$33.50©2006American Chemical Society Analytical Chemistry,Vol.78,No.12,June15,20064069 Published on Web00/00/0000STJ located on a Si3N4membrane,covered by a1.3-µm-thick Pb absorber,was described;this device had an energy resolution of 12.4eV and the noise was4eV at5.9-keV X-ray nkosz et al.(A5)reviewed quantitative X-ray microanalysis for biological and glass material samples in order to verify the fundamental parameter method on the basis of the application of standard samples.The principal aim of their investigation was to determine the analytical capability of a microbeam(X-ray beam diameter of ∼30µm)XRF spectrometer equipped with capillary optics.They considered all the possible sources of uncertainty of the whole analysis:operating stability of the detector and X-ray source, sample movement,and errors originating from the spectral deconvolution calculations.The sample thickness was estimated on the basis of the measurement of the elastic and inelastic scattered intensities of the source radiation,and it was applied for the matrix correction as well.The authors demonstrate their analytical considerations and calculations by some examples using the synchrotron microbeam XRF technique for quantitative analysis of human brain tissue samples with both monoenergetic and polychromatic excitation modes.The accuracy for glass standard samples was found between4and40%relative. Janulewicz et al.(A6)reviewed the state-of-the-art of the tabletop type X-ray lasers(XRLs)and described the working principle of these lasers and their characteristic spectral output properties, from a practical point of view.They concluded that the XRL sources are competitive in comparison with the third-generation synchrotron radiation(SR)facilities:brilliance of the beam and time-resolved measurements.The author details the operating processes of two types of XRFs based on the quantum pumping mechanisms in generating the excitation states:(i)recombination and(ii)collisional-type XRLs.The size of the XRLs is the central problem in development research;it can be decreased in the case of a hybrid-type XRL,when the pumping medium is gas plasma in a capillary tube in which the inverse population is generated by a short picosecond optical laser beam,entering into the axial direction of the capillary.Most observed objects in the sky naturally emit X-ray radiation that transports information on the atomic-level processes occurring in the source objects,on the motion of the bulk material,etc.,or the transmission of X-rays through absorption can be studied.Therefore,the detectors of X-ray telescopes are the central devices in the sky observatories, such as Chandra and XMM-Newton.Porter reviewed(A7)the low-temperature detectors developed for space missions such as X-ray cameras and dispersive X-ray spectrometers.The Astro-E2 launched in2005was the first mission that contained a low-temperature microcalorimeter-based observatory,and three more low-temperature detector-based observatories are being developed (NeXT,Constellation-X,ZEUS).Due to the high-level ionization of the individual atoms in different sky objects,very complex X-ray emission spectra must be detected resolving the satellite lines. The newest spectrometers that suit this requirement are high-energy resolution microcalorimeters.The other essential group of X-ray detectors are the CCD cameras;these have moderate spectral sensitivity and therefore they have to be used with selective absorbing filters for energy-sensitive X-ray imaging.In the future observatories,new detector types are needed,which have∼1000pixels with a high-energy resolution below4eV at 6-keV X-ray energy,in a miniature,monolithic arraying form,having three-dimension wiring layers,cryogenic multiplexing schemes,complex and flexible electronics,and finally an as low as possible mass.SR is widely used for all fields of XRS for the characterization of materials for basic research and for practical aims.In view of the lack of a detailed description of this analytical technique for the nonsynchrotron-expert forensic community,Kempson and co-workers(A8)published a review paper on application of synchro-tron radiation in forensic trace analysis.The authors pointed out the benefits of SR and discuss XRF techniques,described the tomographic method,X-ray diffraction,and scattering applications, and finally,they highlighted the X-ray absorption near edge structure(XANES)and extended X-ray absorption fine-structure (EXAFS)methods and their significant contribution to the characterization of materials.They outlined the unique advanta-geous spectroscopic characters of the synchrotron beams:high brightness,energy tenability,nearly100%of polarization and coherence,and possibility of time-resolved measurements;finally they showed some examples demonstrating the benefit of ap-plication of the SR in this practical field.A general tutorial paper was published by Van der Veen and Pfeiffer(A9)about the properties of coherent hard X-ray beams and their use in structural analysis of solid materials.Because of a fully coherent X-ray beam is provided by SR,it is suitable for such experiments where the interference of the X-ray beam gives information on the inner structure of the investigated object material.In the near-forward scattering direction,the differences in the phases between waves traversing different parts of the object enable imaging the object structure into a phase contrast. In larger scattering angles the interference provides coherent diffractive imaging without lenses and it is called holography without reference beam.The authors give a simple mathematical description of the investigated effects:transverse coherence, longitudinal coherence,phase contrast,X-ray photon correlation spectroscopy,diffracting imaging,and waveguide analysis on the basis of the Fraunhoffer diffraction pattern.In this last review period,an increasing number of papers were published on the1D and2D waveguides due to the strong needs of a microsized X-ray beam,which has a high flux density,for the analysis of submicrometer-sized objects.Egorov and Egorov published a tutorial on state-of-art of X-ray waveguides(A10),with the general description of the operating principles and the spectroscopic characteristic properties and possible applications.X-ray microanalytical methods are more widely applied in archaeometry and in cultural heritage conservation research, especially nondestructive micro-X-ray analytical methods.Selected presentations of the7th International Conference on Nondestruc-tive Testing and Microanalysis for the Diagnosis and Conservation of the Cultural and Environmental Heritage,dealing with different types of instrumental analysis of materials and artifacts of cultural-historical value,were published in Cultural Heritage Conservation and Environmental Impact Assessment by Non-Destructive Testing and Micro-Analysis(A11).The publication gives a survey of the possible solutions for analytical problems in the cultural heritage sector,using portable energy-dispersive XRF spectrometers, TXRF,microfocus X-ray tomography,confocal micro-XRF,and micro-XAS.4070Analytical Chemistry,Vol.78,No.12,June15,2006The in-field analysis of hazardous material and environ-mental samples obviously requires portable XRF spectrometers. Melquiades and Appoloni published a review article(A12)about the basic methodology aspects of laboratory and portable X-ray boratory measurements can be slow,sometimes laborious,and of course more expensive;however,they are more precise in comparison with portable XRF spectrometers.The use of portable spectrometers allows rapid mapping and ranking of contaminated sites,and a large number of semiquantitative data can be generated on site in nearly real time.The authors overview the possible detector types that are suitable for the portable technique and concluded that the Peltier cooled detectors(Si-PIN,CdZnTe,Si drift)are the most appropriate devices because no cryogenic cooling is required.The most significant applications and portable designs were summarized in a separate table involving the characteristic parameters:excitation source,re-quired sample preparation technique,possible matrixes for sample bulk,and minimum detection levels for different elements.The authors give some examples for applications published in the literature,and they discuss the main steps of in-field analysis such as preconcentration techniques and data evaluation methods. Finally,in this introductory section,we mention an article about the direct analysis of biological samples applying TXRF analysis, published Marco and Herna´ndez-Caraballo(A13).They claim that, for the purpose of direct analysis of biological origin samples,the most suitable XRS method is TXRF due to the limited matrix effect and the multielement character.TXRF is used mostly after a sample digestion procedure;however,in some cases,the biologi-cal wet samples can be analyzed without preparation due to the low matrix interference.This technique has advantageous proper-ties such as shorter analysis time,low reagent consumption,and simplified analysis procedure.DETECTIONCryogenic energy-dispersive(ED)detectors have a superior energy resolution due to the very low operating temperature,that reduces the thermal noise,and to the appearance of low excitation states of electron energies.The working principle is based on the fact that one absorbed X-ray photon(the energy is∼1keV) generates an∼100times higher number of charge carriers in the superconductive-type detectors than in conventional Si sensors. This effect leads to the excellent2-4-eV energy resolution in the X-ray energy range of several kiloelectronvolts,while the best energy resolution of the conventional Si(Li)detectors is∼120eV at5.9-keV energy.The microcalorimeters are principally very sensitive solid-state thermometers changing their temperature through the absorption of X-ray energy quanta.The construction of the STJs is based on two superconductive electrodes separated by a tunneling barrier.The tunneling current between the electrodes depends on the absorbed X-ray energy in the barrier layer,and this changing of current can be applied as a signal of detected X-ray quanta.Metallic magnetic calorimeters(MMC)for high-resolution XRS were developed by Fleischmann and co-workers(B1);they show an fwhm of3.4eV for X-ray energies up to6.5keV.This type of detector is based on a paramagnetic sensor placed in a magnetic field and in contact with a metallic absorber. The magnetization of the sensor indicates the temperature of the absorber calorimeter.The spectroscopic capability of this cryo-genic MMC detector was demonstrated by55Fe spectra with separation of the Mn-K R1and Mn-K R2peaks.A German physics research group(B2)developed a prototype of a new construction of an STJ detector having two thin electrode layers separated by a thin tunnel barrier,and on this layer a lead absorber is layered. Due to the high absorption properties of the Pb layer,the quantum efficiency of the STJ detector increased considerably from1%up to50%of X-ray energy of6keV.This structure helps reduce the doubling of the peaks.The achieved energy resolution of the detector was10.8eV at an energy of5.9keV,at a working temperature of70mK.The authors are going to install this type of detector into a new high-resolution cryogenic spectrometer used in an electron microscope.The microcalorimeters offer the most impressive energy resolution,2-3eV,in the energy range of2-6 keV(B3).However,their detectable count rate is low,∼500 counts/s.In contrast with these operating properties the STJs have a little bit less resolution capability,which is∼3-12eV in the energy range of2-6keV,but their maximum count rate should be10times higher than in the case of the microcalorimeters.The authors developed a new STJ with structure of Nb-Al-AlO x-Al-Nb for high count rate detection of synchrotron radiation. They produced an impressive count rate at10000counts/s with an energy resolution between7and15eV fwmh.Their device was able to detect100000counts/s as well,but then the energy resolution deteriorated to43eV.The first industrially applied spectrometer was reviewed by Hollerith et al.(B4),who used an Ir/Au TES in a scanning electron microscopy(SEM).The superconductor layer of the detector is 400×400mm2with a250×250mm2Au absorber with a thickness of500nm.Due to the500times smaller detector area of this TES compared to the conventional Si(Li)detectors,the solid angle has to be decreased by mounting a polycapillary lens in front of the Ir/Au ing this X-ray optics,the detectable count rate was improved by a factor of5at the Si-K R energy.Three American authors(B5)outlined the general and specific properties of the microcalorimeters and their applicability to SEM analysis.They called the attention to the following facts:(i)the spectral resolution of the microcalorimeters is better than the best alternative detection technology in wavelength-dispersive spec-trometry(WDS),(ii)this energy-dispersive property is signifi-cantly better than what Si(Li)technology can provide,(iii)the detection efficiency is between Si(Li)and WDS modes,(iv)the disadvantageous detection characters of this cryogenic detector are the limited count rate and the limited geometrical efficiency capabilities compared to WDS and Si(Li)detection.These nonideal working characteristics can be avoided by the development of appropriate microcalorimeter array detector system that should be the ideal detector for EPMA of low atomic number elements. Bechstein and co-workers(B6)characterized a cryogenic super-conductive tunnel junction detector set that consists of Nb/Al/ AlO x/Al/Nb layers segmented in four individual structures having an area between70×70µm2and200×200µm2.The aim of their investigation was to clarify the dependence of the detection efficiency and the energy resolution properties on the impinging X-ray energy(up to1500eV)and the count rate and its influence on the detector response function.The X-ray microbeam had a 5-µm diameter,and this size allowed scanning the beam vertically and irradiating different parts of the detector surface.The authorsAnalytical Chemistry,Vol.78,No.12,June15,20064071found an unexpected degradation of the energy resolution in a wide edge zone.The laterally resolved measurements provide a better understanding of the physical processes in STJs and promote design of an improved detector layout.A Japanese research group(B7)developed a new design for a set of STJ detectors,capable of providing multispectra of X-rays for purposes of X-ray computer tomography in the energy range below1keV. The typical size of each individual STJ on the multipixel chip is ∼100×100µm2.An energy resolution of41eV fwhm was observed at5.9-keV energy,and that value is three times better than the theoretical limit of conventional Si detectors.The authors carried out experiments with their STJ chip in the5-25-keV energy range and concluded that this type of cryogenic detector is a promising candidate for3-D X-ray absorption and fluorescence CT imaging.Bruijn et al.reported(B8)a new development of a cryogenic5×5matrix-shaped array of microcalorimeters using Ti/Au TES with Cu/Bi absorber and Si3N4cooling connector.The array was tested with irradiation of5.9-keV monoenergetic X-ray, and the response spectra had a6-7eV fwhm.An Italian research group reviewed(B9)a similar experiment with TES that consists of a300×400µm2thin and25-µm-thick polycrystalline Sn foil acting as an energy absorber.The TES surface was protected against possible chemical damaging during the photolithographic procedure.The TES microcalorimeter was tested at radiation beamline GILDA of the European Synchrotron Radiation Facility (ESRF),detecting X-ray fluorescence spectra emitted by a Renais-sance gold luster on ceramic;during this analysis,the energy resolution of the TES was found to be70eV between6-and9-keV X-ray energy.On the basis of their experimental results,the authors concluded that the TES calorimeters are very applicable for the synchrotron based X-ray fluorescence analysis.A special monolithic X-ray detector based on the connection of an SDD and a CsI(Tl)scintillation device was reviewed by Marisaldi et al. (B10).In this coupled detector,the SDD worked as a direct X-ray sensor for photons that interacted in the Si body of the SDD and in parallel as a photodetector for photons generated in the scintillation crystal.The source of the electronic signal is dis-criminated on the basis of the pulse shape evaluation and that process yields the correct determination of the deposited photon energy in the complex detector for both X-ray andγ-ray energy ranges.The authors systematically tested the dependence of the detector efficiency on the operating temperature and found that, at10°C,the energy efficiency is nearly100%for the8-200keV of energy range.They concluded that this type of combined detector would be of great interest in X-andγ-ray detection in astrophysics due to the advantageous spectroscopic capabilities, i.e.,the high detection efficiency from low-energy X-rays up to several hundred kiloelectronvolts.Goulon et al.published(B11) the spectroscopic properties of their advanced detector systems, especially SDD arrays,used for XRF spectrometry at the ID12 beamline in ESRF in Grenoble in the last15years.An improved energy resolution was achieved during this period:82eV at Si-K R and126eV at Fe-K R,by means of mathematical spectral deconvolution.Now,the SDD has become a commercial detector in varying sizes and shapes,in large array form,including200-400detection channels for different applications of conventional and specific X-ray emission analysis such as XRF tomography and holography or EXAFS analysis.They discussed the use of SDD as ED detectors,the modes of minimization of the electronic readout noise,and the first result of a35-element SDD array consisting of7×7individual cylindrical SDDs.A special annular SDD,developed for PIXE analysis,was tested and reviewed(B12). PIXE always suffers from the small solid angle of detection; therefore,this new Peltier-cooled SDD was designed with annular shape in order to maximize the detection angle.The area of the detector is60mm2,and the working distance is only1mm.This commercial ED detector is able to collect at high rate of1 Mcounts/s with an energy resolution better than200eV at6.4-keV X-ray energy.In comparison with conventional Si(Li)detec-tors,the solid angle and the count rate capability are both larger by2orders of magnitude.A novel SDD with integrated FET was published by Lechner and co-workers(B13);it has a new chip layout that allows constructing the readout anode in a smaller size than earlier designed,which reduced the anode capacitance of120fF instead of200-250fF in the case of commercial SDDs. This improved detector structure and properties yielded a better energy resolution:147eV at5.9-keV X-ray energy at-10°C detector temperature.On the basis of these results,the authors proposed a new SDD device with increased effective area in order to achieve higher geometrical efficiency.Eggert and colleagues (B14)also studied the improvement possibilities of SDDs with enlarged active detector surface area,from5to10mm2;that required more intensive cooling from-15°C down to-20°C, reducing the leakage current that causes degradation of the energy resolution.On the basis of their experimental results,they concluded that instead of enlargement of the active area of the SDD detector a group of segmented detectors with a small(5 mm2)sensitive surface is more reasonable to apply.On the other hand,in cases when a low count rate is available,a large sensitive area is more reasonable.The research group of Sokolov reviewed their results(B15)of systematic study about Si(Li),Si PIN,and CdZnTe X-ray detectors,cooled by Peltier effect devices in order to develop a portable ED X-ray spectrometer.They found that the spectroscopic characters of the Peltier-cooled Si(Li)detector was similar to those of detector cooled with liquid nitrogen,and it was selected as the most suitable type of detector for XRF analysis.They showed in this article illustrative spectra from the studied semiconductor detectors using55Fe and241Am radioactive sources.Streli and co-workers(B16)published their experimental comparison of Si(Li)detectors and SDD equipped both with a thin polymer window in order to detect low X-ray energies from 200eV.With the Si(Li),it was possible to detect down to the C K R and the limit for SDD was O.The detection limit for this latter element was found to be36ng in the case of SDD and4ng for a Si(Li)detector,which shows the better applicability of the Si(Li) detector for XRF analysis of low-Z elements.Their results suggest that the SDDs should be a promising candidate as a future detection device for low atomic X-ray radiation especially at the case of a high X-ray flux.In ref B17,Wright et al.emphasized that there is a strong demand for more efficient,more radiation-tolerant sensors in X-andγ-ray physics,SR applications and medical imaging.For these detection tasks,an excellent solution is offered by the3-D detector architecture in which the electrodes traverse the detector bulk,neglecting the limitation of the distance between electrodes by the thickness of the wafer.This3-D structure allows faster charge collection and a very low depletion4072Analytical Chemistry,Vol.78,No.12,June15,2006voltage of1-20kV;on the other hand,the planar pixel detectors need∼80V.The authors performed a simulation model calcula-tion for the charge collection in these two types of detectors and found that the current pulse was produced in∼5ns,and in case of a pixilated planar detector,this value was found to be∼80ns. The3-D Medipix1sensor was created on high-resistivity n-type Si bulk,the electrodes were formed by photochemical etching, and the p-type electrodes were etched and doped with B by diffusion.Finally,the electrode pores were metallized with a Ti layer and Au and Al.The energy resolution of the gaseous ED detectors is more and more comparable to that of the semiconductor detectors;in addition,the structure of this low-cost detector is not complex and constructing it is much easier than for high-purity Ge or Si(Li) detectors.Beyond that they can have large area window for the entering X-rays and they have less sophisticated operating requirements than solid-state detectors,up to25-keV X-ray energy.A Portuguese research group(B18)improved their xenon-filled gas proportional-scintillation counter,applying a polyimide window with6-mm diameter with∼30%transmission at250eV for soft X-ray energies below3keV.The pressure was set as800Torr, and the gas was continuously purified by convection,using nonevaporable getters allowing the same operating gas during several months.The gaseous detector is also one of the most suitable devices for two-dimensional X-ray imaging because this type of detector can be constructed with a large sensitive area.A European research group at ELETTRA(B19)reviewed a two-dimensional X-ray imaging detector based on a single-photon counter that has a gas electron multiplier(GEM)inner structure. The GEM detector was applied for detecting X-rays having energy of8keV,and it was capable of time-resolving spectral data down to millisecond time.The sensitive area of the detector was56×56mm,divided into seven xy cells;the voltage of the drift cathode was set at4000V.On the basis of the electronic signals,each cells of the GEM can be subdivided into virtual pixels(ViP)having a sensitive spatial resolution of∼100µm(fwhm).This detection property depends significantly on the speed of the applied electronics and the gas gain,which was∼104.The authors concluded on the basis of their experience that the ViP detector offers a high quantum efficiency up to25-keV X-ray energy using 2×105Pa pressure of Xe mixture gas,and the time resolution, which determines the special resolution,can be improved down to a few hundred nanoseconds.A special application of large-area gaseous detector was shown by the research group of Despre´s (B20)by construction of a new radiographic scanning system. The detector was built by two orthogonally oriented gas microstrip detectors used for scanning a human body with a speed of15 cm/s.Both detectors consisted of1764channels,and the individual pixel sizes in the obtained X-ray image were0.254×0.254mm2.Due to the favorable detection properties,such as short signal evaluation and large sensitive area,this newly constructed device is a future candidate for low-dose radiography,since the entrance dose rate at the irradiated human skins was0.1mSv while at the case of conventional X-ray films this value is close to1.45mSv.A review article was published by Shekhtman(B21)describing the newest design of micropattern detectors and gap-resistive plate chambers and the general operating effects and processes,the design structure,and their influence on the properties of the gaseous detectors.The efficiency through the absorption strongly correlated with the atomic number of the gas material(Ar,Kr, Xe)and its pressure.The article overviewed the most important application areas of the gaseous detectors:(i)wire chambers for medical radiography applications and for SR,and(ii)micropattern gas detectors and gas electron multiplier-based detectors for high count rate synchrotron experiments.Newbury(B22)tested and applied a silicon multicathode drift detector for X-ray spectrometry on a SEM investigating spectros-copy parameters such as the output count rate,energy resolution, and peak stability in the ED spectra.He demonstrated the capability of this multichannel SDD for recording an X-ray spectrum image of an Al-Ni alloy containing4wt%Fe as well in a128×128pixel size with220-kHz output rate.The X-ray spectrum image was generated by fixing the excitation electron beam,and the SDD array was readout,and in this way the overall mapping time was found to be185s while100Mb information was paring with a Si(Li)detector having a50mm2 area,he found that the array SDD has a better resolution,namely, 134eV fwhm at6.4keV(the resolution of Si(Li)was140-145 eV),and the SDD can achieve a shorter peaking time for a given resolution.The main advantages of the silicon drift detectors(SDD)are the high count rate capability,the possibility of a large effective detection area,and the relatively high working temperature(-10°C to room temperature).The main idea is that the signal charges generated in the bulk crystal are transported to the electrodes in a controlled way,mainly parallel to the large surface of the detector.Gatti and Rehak(B23)reviewed the principal properties of the SDD,discussed different applications in charged particle physics and XRS,and gave a short description about their physical structure and the physical processes in the detector bulk,e.g., for55Fe spectra recorded with a ring-shaped SDD at-10°C,in which spectra the two Mn lines were clearly resolved.The working capabilities of two standard Si PIN and conven-tional Si(Li)detectors were studied by Kump and co-workers (B24)using55Fe and109Cd annular radioactive sources and the same measuring geometrical configuration set up.The0.3-mm-thick PIN diode had a7-mm2active area,and the energy resolution at count rates∼1000counts/s was found to be195eV,while the parameters for the Si(Li)detector were30mm2,and fwhm of175 eV(and this value is worse than the average energy resolution of commercial Si(Li)detectors).The authors compared the analytical capabilities of these detectors by quantitative analysis of SRM2710 soil standard sample,a similar dependence of sensitivities versus atomic number was found up to Z)30,and over this value,much less sensitivity was obtained with the PIN diode due to the lower detection efficiency.A new set of large area HPGe detector was reviewed in ref B25for the purpose of PIXE analysis.The detector set is built in annular form of eight individual detectors,and each item had a 100-mm2effective area;this provides high quantum efficiency.The detector chambers are mounted vertically,and each subdetector acts as an individual detector;however,they use a common main amplifier.The fwhm of the set of detectors was found to be between144and168.The authors outlined the unique spectro-scopic properties of this set,which can be used for detection ofAnalytical Chemistry,Vol.78,No.12,June15,20064073。
黑洞的由来的英语作文
黑洞的由来的英语作文The Origin of Black Holes: A Journey into Cosmic Mysteries。
Introduction。
Black holes, enigmatic entities lurking in the depthsof space, have captivated the imagination of scientists and laypersons alike. Their origins, shrouded in cosmic mystery, have been the subject of intense study and speculation. In this essay, we embark on a journey to unravel the secretsof black holes, exploring their formation, properties, and significance in the universe.Formation of Black Holes。
The genesis of black holes begins with the demise of massive stars. When a massive star exhausts its nuclear fuel, it undergoes a cataclysmic event known as a supernova explosion. During this explosive phase, the outer layers ofthe star are ejected into space, while its core undergoes gravitational collapse. If the core's mass exceeds acritical threshold, it collapses into a singularity—a point of infinite density—giving birth to a black hole.The process of black hole formation can also occur through the gravitational collapse of dense stellar remnants, such as neutron stars, or through the merger of two compact objects, such as neutron stars or black holes. These pathways lead to the creation of different types of black holes, ranging from stellar-mass black holes to supermassive black holes found at the centers of galaxies.Properties of Black Holes。
关于黑洞的英文作文
关于黑洞的英文作文Title: Exploring the Enigma of Black Holes。
Black holes, the enigmatic cosmic entities, have captivated the imagination of scientists and laypeoplealike since their theoretical discovery. Their existence challenges the very fabric of our understanding of space, time, and gravity. In this essay, we will delve into the mysterious realm of black holes, exploring their formation, properties, and significance in the cosmos.Firstly, let us unravel the genesis of black holes. These cosmic behemoths are born from the remnants of massive stars undergoing gravitational collapse. When astar exhausts its nuclear fuel, it can no longer sustainthe outward pressure generated by nuclear fusion, leadingto a catastrophic collapse under its own gravity. For stars with sufficient mass, this collapse results in theformation of a black hole, where the gravitational pull becomes so intense that not even light can escape its grasp.The boundary surrounding a black hole, known as the event horizon, marks the point of no return. Once an object crosses this threshold, it is inexorably drawn into the black hole's gravitational abyss, with no hope of escape. Beyond the event horizon lies the singularity, a point of infinite density where the laws of physics as we know them break down, and our understanding reaches its limits.Despite their elusive nature, black holes betray their presence through various observable phenomena. One such manifestation is the accretion disk, a swirling mass of gas and dust spiraling into the black hole's maw. As these materials accelerate and heat up due to gravitational forces, they emit powerful radiation across the electromagnetic spectrum, from radio waves to X-rays, offering astronomers valuable insights into the nature of these cosmic monsters.Moreover, black holes are not solitary entitiesdrifting aimlessly in space; they often reside at the heart of galaxies, exerting a profound influence on theirsurroundings. Supermassive black holes, with massesmillions or even billions of times that of the Sun, inhabit the cores of galaxies, shaping their structure and evolution. The interplay between black holes and their host galaxies is a dynamic dance of gravitational forces, influencing the formation of stars and the evolution of cosmic structures on a grand scale.In recent years, the study of black holes has entered a new era of discovery and exploration. Advancements in observational techniques, such as gravitational wave detectors and space-based telescopes, have allowed scientists to peer deeper into the heart of these cosmic abysses than ever before. The groundbreaking detection of gravitational waves from merging black holes has provided direct evidence of their existence and opened new avenues for studying their properties and behavior.Furthermore, black holes hold profound implications for our understanding of fundamental physics and the nature of the universe. The enigma of black hole thermodynamics, the paradoxes of information loss, and the quest for a unifiedtheory of gravity and quantum mechanics continue to fuel scientific inquiry and debate. By unraveling the mysteries of black holes, we may unlock the secrets of the universe itself, gaining deeper insights into the nature of space, time, and the underlying fabric of reality.In conclusion, black holes stand as cosmic enigmas, challenging our perceptions and expanding the boundaries of human knowledge. From their mysterious origins to their profound influence on the cosmos, black holes continue to inspire awe and fascination among scientists and the public alike. As we journey further into the depths of space and unravel the secrets of these celestial giants, we move one step closer to unraveling the mysteries of the universe itself.。
Black Hole(黑洞的科普,选修课)
超大质量黑洞从吸积盘中吸积的概念图
Part.8 结语
Classification of black holes
分类 质量 大小
超重黑洞
~105–1010 M太阳
~0.001–400 AU
中介质量黑洞
~103 M太阳
~103 km ≈ R地球
恒星黑洞
~10 M太阳
~30 km
微型黑洞
up to ~M月球
up to ~0.1 mm
质量达到太阳十倍的黑洞
吸积accretion by black hole
黑洞通常是因为它们聚拢周围的气体产生辐射而被发 现的，这一过程被称为吸积。
黑洞拉伸，撕裂并吞噬恒星 恒星被黑洞吞噬
蒸发 Black hole evaporation
20世纪70年代，英国科学家霍金等人以量子力学 为基础，对黑洞作了更缜密的考察，结果发现黑 洞会像“蒸发”那样稳定地往外发射粒子。
Black Hole
Introduction to black hole
黑洞是时空曲 率大到光都法 从其视界逃脱 的天体
Physicists
米切尔预言的黑洞
历史上，第一个意识到一个致密 天体密度可以大到连光都无法逃 逸的人是英国地理学家John Michell。他在1783年写给亨 利· 卡文迪什一封信中提出这个想 法的，他认为一个和太阳同等质 量的天体，如果半径只有3公里， 那么这个天体是不可见的，因为 光无法逃离天体表面。
坍缩和爆发的压力进而使核心被压缩成致密的星 核，而致密星核又分化为白矮星、中子星、黑洞。
视频：黑洞的产生
中子星的奥本海默极限
奥本海默（1904～1967）在1939年研究提出
如果中子星的质量超过3.2 m⊙(太阳质量的3.2倍)（精 细的模型给出值在2～3 m⊙之间），则其的中子间的泡 利斥力就再也阻挡不住星体引力坍缩，会进一步被压 缩成一个体积很小而质量巨大的高密度引力源——黑 洞。上述3.2 m⊙（常记作3）的中子星界限被称作“奥 本海默极限”，任何超此极限的恒星都难以停留在中 子星阶段。
黑洞介绍英语作文带翻译
黑洞介绍英语作文带翻译Title: Exploring the Enigma of Black Holes。
Black holes are among the most intriguing and enigmatic phenomena in the universe. Formed from the collapse of massive stars, these cosmic entities possess gravitational forces so strong that even light cannot escape their grasp. In this essay, we delve into the mysteries of black holes, exploring their formation, properties, and the profound impact they have on our understanding of the universe.黑洞是宇宙中最引人入胜和神秘的现象之一。
这些天体是由大质量恒星的坍缩形成的，它们具有如此强大的引力，以至于连光都无法逃脱它们的吸引。
在本文中，我们深入探讨黑洞的形成、特性以及它们对我们对宇宙的理解产生的深远影响。
Formation of Black Holes。
Black holes originate from the remnants of massive stars that have exhausted their nuclear fuel and undergogravitational collapse. When a massive star reaches the end of its life cycle, it can no longer sustain nuclear fusion reactions to counteract the inward pull of gravity. Consequently, the star's core collapses under its own weight, leading to the formation of a black hole.黑洞起源于已经耗尽核燃料并且发生引力坍缩的大质量恒星的残骸。
Discovery of 0.08 Hz QPO in the power spectrum of black hole candidate XTE J1118+480
a r X i v :a s t r o -p h /0005212v 1 10 M a y 2000A&A manuscript no.(will be inserted by hand later)ASTRONOMYANDASTROPHY SICS1.IntroductionThe transient X-ray source XTE J1118+480was discov-ered with the RXTE All-Sky Monitor on March 29th,2000.Subsequent RXTE pointed observations revealed a power law energy spectrum with a photon index of about 1.8up to at least 30keV.No X-Ray pulsations were detected (Remillard et al.,2000)In hard X-rays the source was observed by BATSE up to 120keV (Wil-son&McCollough 2000).Uemura,Kato &Yamaoka(2000)reported the optical counterpart of 12.9magnitude in un-filtered CCD.The optical spectrum was found typical for the spectrum of an X-Ray Nova in outburst (Garcia et al.2000).Pooley &Waldram (2000)using Ryle Telescope detected a noisy radiosource with flux density of 6.2mJy at 15GHz.All existing observations show that XTE J1118+480is similar to the black hole transients in close binaries with a low mass companion.50503-01-01-00Mar.2922:510.750407-01-01-00Apr.1309:28 5.050407-01-01-01Apr.1314:18 3.150407-01-02-00Apr.1507:51 1.150407-01-02-01Apr.1704:44 4.150407-01-02-02Apr.1819:21 1.050407-01-02-03Apr.1821:27 1.850407-01-03-01Apr.2420:350.750407-01-03-02Apr.2701:570.950407-01-04-02May 111:25 1.850407-01-04-01May 405:15 1.02Revnivtsev,Sunyaev &Borozdin:QPO in XTEJ1118+480Fig.1.The RXTE/ASM light curve (1.3-12.2keV)of the transient XTE J1118+480.Arrows show the dates of RXTE pointed observations,used in our analysis.3.ResultsThe power spectrum of XTEJ1118+480with a strong QPO feature is shown in Fig.2.The simplest Lorenz approximation of the detected QPO peak gives the cen-troid frequency 0.085±0.002Hz and the width 0.034±0.006Hz (the Q parameter ∼2–3).The amplitude of the QPO ≈10%rms.The power density spectrum (PDS)of the source is typical for a black hole candidates in the low/hard spectral state.The power spectrum is almost flat at frequencies below ∼0.03Hz,roughly a power law with slope ∼1.2from 0.03to 1Hz with following steepen-ing to slope ∼1.6at higher frequencies.The total ampli-tude of detected variability of the source is close to 40%rms.We did not detect any X-ray variability of the source flux at the frequencies higher than ∼70Hz.The 2σup-per limits on the kHz QPOs in the frequency band 300–1000Hz are of the order of 5–6%for QPO with quality Q ∼10,this is in 1.5–3times lower than typical ampli-tudes of observed kHz QPOs in the neutron star PDSs (e.g.van der Klis 2000).Our preliminary analysis of the XTE J1118+480ra-diation spectrum confirms that it is very hard:it was detected by High Energy Timing Experiment (HEXTE)up to energies of ∼130–150keV with the power law slope α∼1.8with possible cutoffat the highest en-ergies (>∼130keV)The spectrum of XTE J1118+480is very similar to that of the transient source GRS 1737–37(Sunyaev et al.1997,Trudolyubov et al.1999a,Cui et al.1997).A detailed spectral analysis of XTE J1118+480will be presented elsewhere.Fig.2.Power spectrum of XTE J1118+4804.DiscussionLow frequency QPO peaks were reported earlier in the power spectra of several black hole candidates in their low/hard state –at ∼0.03–0.07Hz with Q ∼1for Cyg X-1(Vikhlinin et al.1992,1994,Kouveliotou et al.1992a),at ∼0.3Hz for GRO J0422+32(Kouveliotou et al.1992b,Vikhlinin et al.1995),∼0.8Hz for GX 339-4(e.g.Grebenev et al,1991)and in the high/soft state of LMC X-1(Ebisawa,Mitsuda &Inoue 1989)and XTE J1748–288(Revnivtsev,Trudolyubov &Borozdin 2000).Impressive QPOs with harmonics were observed in the power spec-tra of Nova Muscae 1991(e.g.Takizawa et al.1997,Belloni et al.1997),GRS 1915+105(e.g.Greiner et al.1996,Trudolyubov et al.1999b).The detection of low fre-quency QPO in the power spectrum of XTE J1118+480allows us to add another black hole candidate to this sam-ple.In all these cases the QPO peak lies close to the first (low frequency)break in the power spectrum (see also Wijnands &van der Klis 1999).The optical counterpart of XTE J1118+480is suffi-ciently bright to check for the presence of corresponding low frequency optical variability with f ∼0.085Hz.The power spectra of black hole candidates are dras-tically different from those of neutron stars in LMXBs in similar low/hard spectral state.Sunyaev and Revnivt-sev (2000)presented a comparison of power spectra for 9black hole candidates and 9neutron stars.None of the black hole candidates from this sample show a significant variability above ∼100Hz,while all 9neutron stars were noisy well above 500Hz,with the significant contribution of high-frequency noise f >150Hz to the total variability of the source.The power spectrum of the newly discov-Revnivtsev,Sunyaev&Borozdin:QPO in XTE J1118+4803 ered X-ray transient XTE J1118+480(see Fig2)looksvery similar to other black hole PDSs(see Fig.1of Sun-yaev and Revnivtsev,2000).The detection of low frequency QPO,lack of high-frequency noise and a hard energy spectrum detected upto∼150keV in X-rays are supportive arguments for theearlier identification of XTE J1118+480as a black holecandidate.Acknowledgements.This research has made use of dataobtained through the High Energy Astrophysics ScienceArchive Research Center Online Service,provided by theNASA/Goddard Space Flight Center.The work has been sup-ported in part by RFBR grant00-15-96649.ReferencesBelloni T.,van der Klis M.,Lewin W.H.G et al.1997,A&A322,857Cui W.,Heindl W.,Swank J.et al.1997,ApJ,487,73Ebisawa K.,Mitsuda K.,Inoue H.1989,PASJ,41,519Garsia M.,Brown W.,Pahre M.,J.McClintock2000,IAUC7392Grebenev S.,Sunyaev R.,Pavlinsky M.et al.1991,SvAL17,413Greiner J.,Morgan E.,Remillard R.1996,ApJ473,107Kouveliotou,Finger&Fishman et al.1992a,IAUC5576Kouveliotou,Finger&Fishman et al.1992b,IAUC5592Pooley G.G,Waldram E.M.,2000,IAUC7390Remillard R.,Morgan E.,Smith D,Smith E.2000,IAUC7389Revnivtsev M.,Trudolyubov S.,Borozdin K.2000,MNRAS312,151Sunyaev R.,Churazov E.,Revnivtsev M.et al.1997,IAUC6599Sunyaev R.,Revnivtsev M.2000,A&A in press,astro-ph/0003308Takizawa M.,Dotani T.,Mitsuda K.et al.1997,ApJ489,272Trudolyubov S.,Churazov E.,Gilfanov M.et al.1999a,A&A,342,496Trudolyubov S.,Churazov E.,Gilfanov M.et al.1999b,Astr.Lett.25,718Uemura M.,Kato T.,Yamaoka H.2000,IAUC7390van der Klis M.2000,ARA&A in press,astro-ph/0001167Vikhlinin A.,Churazov E.,Gilfanov M.et al.1992,IAUC5576Vikhlinin A.,Churazov E.,Gilfanov M.et al.1994,ApJ,424,395Vikhlinin A.,Churazov E.,Gilfanov M.et al.1995,ApJ,441,779Wijnands R.,van der Klis M.1999,514,939Wilson C.&McCollough M.2000,IAUC7390Zhang W.,Morgan E.,Jahoda K.,Swank J.,Strohmayer T.,Jernigan G.,Klein R.,1996,ApJ,469,29L。
x射线波长色散谱法英语
x射线波长色散谱法英语X-ray Wavelength Dispersive Spectrometry.X-ray wavelength dispersive spectrometry, oftenreferred to as XWDS, is an analytical technique used in materials science, geology, and other fields to characterize the elemental composition of materials. This technique employs the interaction of X-rays with matter, specifically the absorption and scattering of X-rays by atoms within the material. By analyzing the wavelengths of the scattered X-rays, scientists can determine the elemental composition of the sample.The fundamental principle of XWDS lies in the interaction of X-rays with atoms. When an X-ray beamstrikes a material, it interacts with the atoms within the material, causing them to emit characteristic X-rays. These characteristic X-rays have specific wavelengths that are unique to each element. By measuring the wavelengths of these emitted X-rays, it is possible to identify theelements present in the sample.The wavelength dispersive spectrometry setup typically consists of an X-ray source, a sample holder, and a wavelength dispersive detector. The X-ray source emits a beam of X-rays that strikes the sample. The sample absorbs some of the X-rays and scatters the rest. The scattered X-rays pass through the wavelength dispersive detector, which measures the wavelengths of the scattered X-rays. This information is then used to identify the elements present in the sample.One of the key advantages of XWDS is its ability to provide qualitative and quantitative information about the elemental composition of materials. It can detect elements with high sensitivity and accuracy, making it a valuable tool for materials analysis. Additionally, XWDS is non-destructive, meaning that the sample can be studied without altering its properties.XWDS finds applications in various industries and research fields. In materials science, it is used to studythe composition and structure of alloys, ceramics, and other materials. In geology, XWDS is employed to analyze the mineralogy of rocks and ores. It is also used in environmental science to study the composition of soils and sediments.However, XWDS has some limitations. One majorlimitation is its sensitivity to light elements such as carbon and oxygen. These elements have low atomic numbers and therefore emit X-rays with long wavelengths that are difficult to detect. Additionally, the technique requires high-quality X-ray sources and detectors, which can be expensive and complex to maintain.Despite these limitations, XWDS remains a valuable tool for elemental analysis. With the continuous development of X-ray sources and detectors, as well as improvements in data analysis techniques, the sensitivity and accuracy of XWDS are expected to improve further.In conclusion, X-ray wavelength dispersive spectrometry is a powerful technique for elemental analysis. It providesqualitative and quantitative information about the composition of materials, making it a valuable tool in materials science, geology, and other fields. While it has some limitations, the continued advancement of technology is expected to enhance its capabilities and make it even more useful in future research and applications.。
科学英语：黑洞可能是研究暗物质理想的实验场所
A new NASA computer simulation shows that dark matter particles colliding in the extreme gravity of a black hole can produce strong, potentially observable gamma-ray light. Detecting this emission1 would provide astronomers2 with a new tool forunderstanding both black holes and the nature of dark matter, an elusive3 substance accounting4 for most of the mass of the universe that neither reflects, absorbs nor emits light. "While we don't yet know what dark matter is, we do know it interacts with the rest of the universe through gravity, which means it must accumulate around supermassive black holes," said Jeremy Schnittman, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "A black hole not only naturally concentrates dark matter particles, its gravitational force amplifies5 the energy and number of collisions that may produce gamma rays."In a study published in The Astrophysical Journal on June 23, Schnittman describes the results of a computer simulation he developed to follow the orbits of hundreds of millions of dark matter particles, as well as the gamma rays produced when they collide, in the vicinity of a black hole. He found that some gamma rays escaped with energies far exceeding what had been previously6 regarded as theoretical limits.In the simulation, dark matter takes the form of Weakly Interacting Massive Particles, or WIMPS7, now widely regarded as the leading candidate of what dark matter could be. In this model, WIMPs that crash into other WIMPs mutually annihilate8 and convert into gamma rays, the most energetic form of light. But these collisions are extremely rare under normal circumstances.Over the past few years, theorists have turned to black holes as dark matter concentrators, where WIMPs can be forced together in a way that increases both the rate and energies of collisions. The concept is a variant9 of the Penrose process, first identified in 1969 by British astrophysicist Sir Roger Penrose as a mechanism10 for extracting energy from a spinning black hole. The faster it spins, the greater the potential energy gain.In this process, all of the action takes place outside the black hole's event horizon, the boundary beyond which nothing can escape, in a flattened11 region called the ergosphere. Within the ergosphere, the black hole's rotation12 drags space-time along with it and everything is forced to move in the same direction at nearly speed of light. This creates a natural laboratory more extreme than any possible on Earth.词汇解析：1 emissionn.发出物，散发物；发出，散发参考例句：Rigorous measures will be taken to reduce the total pollutant emission.采取严格有力措施，降低污染物排放总量。
x射线荧光光谱法 英文
x射线荧光光谱法英文X-Ray Fluorescence Spectrometry (XRF)。
X-ray fluorescence spectrometry (XRF) is an analytical technique used to determine the elemental composition of materials by measuring the X-rays emitted by the material when it is exposed to a high-energy X-ray beam. This method is widely used in various fields, including geology, environmental science, forensic science, archaeology, and materials science.Principle of Operation.XRF is based on the principle that when a material is irradiated with high-energy X-rays, electrons in the atoms of the material are excited and ejected from their orbits. The resulting vacancies are filled by electrons from higher energy levels, releasing X-rays with energiescharacteristic of the elements present in the material.The energy of the emitted X-rays is specific to each element, and the intensity of the X-rays is proportional to the concentration of the element in the material. By measuring the energies and intensities of the emitted X-rays, it is possible to identify and quantify the elements present in the sample.Instrumentation.A typical XRF spectrometer consists of the following components:X-ray source: Generates high-energy X-rays that bombard the sample.Sample chamber: Holds the sample to be analyzed.Detector: Converts X-rays into electrical signals.Multichannel analyzer (MCA): Digitizes and analyzes the electrical signals from the detector.Types of XRF Spectrometers.There are several types of XRF spectrometers, each with its own advantages and limitations:Energy-dispersive XRF (EDXRF): Uses a solid-state detector to measure the energies of the emitted X-rays. EDXRF is relatively inexpensive and easy to operate, but it has lower energy resolution compared to other types of XRF spectrometers.Wavelength-dispersive XRF (WDXRF): Uses a crystal monochromator to separate the emitted X-rays by wavelength. WDXRF offers higher energy resolution than EDXRF, but it is more complex, expensive, and time-consuming to operate.Total reflection XRF (TXRF): Utilizes total reflection conditions to enhance the sensitivity for analyzing trace elements in liquids. TXRF is highly sensitive, but it requires sample preparation and is not suitable for solid samples.Applications of XRF.XRF is a versatile analytical technique with a wide range of applications:Geochemistry: Determining the elemental composition of rocks, minerals, and soils.Environmental science: Monitoring pollutants in air, water, and soil.Forensic science: Analyzing trace evidence, such as gunshot residue and paint chips.Archaeology: Studying the composition of artifacts and ancient materials.Materials science: Characterizing the elemental composition of metals, alloys, and other materials.Advantages of XRF.Nondestructive: Does not damage the sample being analyzed.Multi-elemental: Can identify and quantify multiple elements simultaneously.Rapid: Provides real-time analysis results.Sensitive: Can detect elements at trace levels.Versatile: Can be applied to various sample types, including solids, liquids, and powders.Limitations of XRF.Limited sensitivity: Cannot detect elements present in very low concentrations.Matrix effects: The presence of other elements in the sample can affect the accuracy of the analysis.Sample preparation: May require sample preparation,such as grinding or homogenization.Cost: XRF spectrometers can be expensive, especially WDXRF systems.Conclusion.X-Ray Fluorescence Spectrometry is a powerful analytical technique that provides valuable information about the elemental composition of materials. It is widely used in various fields and offers advantages such as non-destructiveness, multi-elemental analysis, and rapid results. However, it has limitations in sensitivity and potential matrix effects, which should be considered when selecting this technique for specific applications.。
黑洞介绍英语作文带翻译
黑洞介绍英语作文带翻译Title: Exploring the Enigma of Black Holes。
Introduction。
Black holes have long captured the imagination of scientists and the public alike. These enigmatic cosmic entities, formed from the collapse of massive stars, possess gravitational forces so intense that not even light can escape their grasp. In this essay, we will delve into the fascinating world of black holes, exploring their properties, formation, and the profound implications they hold for our understanding of the universe.Properties of Black Holes。
At the heart of every black hole lies a singularity, a point of infinite density where the laws of physics, as we currently understand them, break down. Surrounding this singularity is the event horizon, the boundary beyond whichnothing can escape the black hole's gravitational pull. It is this event horizon that gives black holes their name, as it appears "black" to outside observers.Formation of Black Holes。
发现黑洞【高中英语外刊阅读】
Recently,scientists produced the first real image of a black hole, shining a light onone of the universe’s great mysteries, in a galaxy called Messier 87. The image is not a photograph but an image created by the Event Horizon Telescope (EHT)project. Using a network of eight ground-based telescopes across the world, the EHT collected data to produce the image. The black hole itself is unseeable, as it’s impossible for light to escape from it; what we can see is its even thorizon. The EHT was also observing a black hole located at the centre of the Milky Way, but was unable to produce an image. While Messier 87 is furtheraway, it was easier to observe, due to its larger size.The golden ring is the event horizon, the moment an object approaching a black hole reaches a point of no return, unable to escape its gravitational pull. Objects that pass into the event horizon are thought to go through spaghettification（意大利面条化）,a process, first described by Stephen Hawking, in which they will be stretchedout like a piece of pasta by gravitational forces.Heino Falcke,professor of radio astronomy and astroparticle physics at Radboud University in Nijmegen, and chair of the EHT science council, says the image shows asilhouette（剪影）of the hole against the surrounding glow of the event horizon, all of the matter being pulled into the hole. At the centre of the black hole is a gravitational singularity, where all matter is crushed into aninfinitely small space. The black hole lies 55m light years away from us. It is around 100bn km wide,larger than the entire solar system and 6.5bn times the mass of our sun.Through creating an image of a black hole, something previously thought to be impossible, the EHT project has made a break through in the understanding ofblack holes, whose existence has long been difficult to prove. The image will help physicists to better understand how black holes work and images of the event horizon are particularly important for testing the theory of general relativity.1.What’s the text mainly about?A.The image of a black hole.B.The photo created by the EHT.C.The event horizon of the black hole.D.The introduction of the EHT project.2.How does EHT collect data?A.By producing the image of a black hole.B.By studying the golden ring in the photo.C.By observing the center of the Milky Way.D.By using a network of eight ground-based telescopes.3.What do we know about the black hole from the text?A.Its image shows a silhouette of the event horizon.B.There is a possibility that light can escape from it.C.All matter is crushed into small space at its centre.D.Objects will be stretched out outside the event horizon.4.What does the last paragraph mainly present?A.Creating an image of a black hole is thought to be impossible.B.It’sstill hard for physicists to prove the existence of the black hole.C.The image will help physicists to test the theory of general relativity.D.The image of a black hole created by EHT project is highly significant.。
探索黑洞英语作文高中
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As I stare into the endless abyss of the black hole, my mind is filled with wonder and awe. It is as if I am peering into the depths of the unknown, a place where time and space cease to exist. The sheer power and gravitational pull of a black hole is mind-boggling, capable of devouring anything that comes too close. It is a cosmic monster, a celestial phenomenon that both fascinates and terrifies.The concept of a black hole is mind-bending. It is a region in space where the gravitational pull is so strong that nothing, not even light, can escape its grasp. It is a point of no return, a cosmic trap that swallows everything in its path. The thought of being sucked into a black hole is both thrilling and terrifying. It is a place where the laws of physics break down, where time stands still and reality becomes distorted.Scientists have been studying black holes for decades, trying to unravel the mysteries that lie within. They have made remarkable discoveries, such as the fact that black holes can emit jets of high-energy particles, creating dazzling displays of light in the darkness of space. They have also theorized about the existence of wormholes, hypothetical tunnels that could potentially connect different parts of the universe. The study of black holes has opened up a whole new realm of possibilities and has challenged our understanding of the universe.While black holes may seem like a threat, they also have the potential to teach us valuable lessons about the nature of the universe. They are a reminder of the vastness and complexity of space, and of our own insignificance in the grand scheme of things. They force us to question our understanding of reality and to confront our deepest fears and curiosities. Black holes are a testament to the beauty and mystery of the cosmos, a reminder that there is still so much we have yet to discover.In conclusion, black holes are one of the mostfascinating and enigmatic phenomena in the universe. They challenge our understanding of space and time, and force us to question our place in the cosmos. While they may be terrifying and mysterious, they also hold the potential to unlock the secrets of the universe and expand our knowledge of the unknown. The study of black holes is a journey into the depths of the universe, a quest for knowledge and understanding that will continue to captivate and inspire us for generations to come.。
黑洞无处不在 A GALAXY FULL OF BLACK HOLE
Credit: European Southern Observatory (ESO) - Very Large Telescope
10
Where do black holes come from?
Mid-Mass: Scientists are finding these in the centers of large, dense star clusters.
Years
“Weird” motions of objects nearby
Movie courtesy Max-Planck-Institute for extraterrestrial Physics, Germany.
22
How do we know it’s there?
Hot material falling into the black hole.
Credit: European Southern Observatory
9
Where do black holes come from?
Supermassive: Extremely massive black holes have been found in the centers of many galaxies - including our own!
A Galaxy Full of Black Holes
Harvard-Smithsonian Center for Astrophysics 1 Origins Education Forum - STScI Navigator Public Engagement Program - JPL
1915: Einstein’s Theory of Gravity predicted the possibility of black holes, but no one believed they actually existed! 1967: Term “Black Hole” coined 1970’s: Convincing evidence that black holes are real Today: NASA space telescopes have discovered evidence for black holes throughout the universe
胸片读片和心影改变
胸片读片和心影改变
A really good film will show anterior ribs too, there should
Be 6 to qualify as a good inspiratory film.
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胸片读片和心影改变
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Quality (cont.)
• Is the film over or under penetrated if under penetrated you will not be able to see the thoracic vertebrae.
Why do I say posterior here?
When X-ray beams pass through the anterior chest on to the film Under the patient, the ribs closer to the film (posterior) are most apparent.
胸片读片和心影改变
（摘自《临床心脏X线诊疗学》刘玉清主编）
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正位解剖
胸片读片和心影改变
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侧位解剖
胸片读片和心影改变
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胸片读片和心影改变
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动脉导管未闭-肺动脉段突出
胸片读片和心影改变
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房缺-肺动脉段突出
胸片读片和心影改变
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二尖瓣狭窄-左房大
胸片读片和心影改变
胸片读片和心影改变
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Quality (cont)
• Check for rotation
– Does the thoracic spine align in the center of the sternum and between the clavicles?
理解黑洞需要一定的想象力和科学知识 英语
理解黑洞需要一定的想象力和科学知识英语Understanding Black Holes Requires a Certain Degree of Imagination and Scientific KnowledgeThe vastness of the universe is a constant source of fascination and wonder for human beings. As we gaze up at the night sky, our eyes are drawn to the twinkling stars, the enigmatic planets, and the mysterious celestial bodies that lie beyond our immediate reach. Among these cosmic enigmas, perhaps none have captured the public's imagination more than the phenomenon known as the black hole.Black holes are regions of space-time where the gravitational pull is so immense that nothing, not even light, can escape their grasp. These cosmic behemoths are the result of the collapse of massive stars at the end of their life cycle. When a star runs out of fuel, its core can no longer support the outward pressure that counteracts the inward pull of gravity, causing it to implode and form a singularity – a point in space-time where the laws of physics as we know them break down.Understanding the true nature of black holes requires a certaindegree of imagination and scientific knowledge. On the surface, the concept of a region of space-time where nothing can escape may seem straightforward, but the deeper one delves into the intricacies of black hole physics, the more complex and mind-bending the subject becomes.One of the key aspects of black holes that challenges our intuitive understanding is the concept of the event horizon. The event horizon is the point of no return – the boundary beyond which nothing, not even light, can escape the gravitational pull of the black hole. Visualizing this invisible barrier and comprehending its significance is a task that requires a significant amount of abstract reasoning.Imagine a person standing on the edge of a cliff, gazing out at the vast expanse of the ocean. As they look down, they can see the waves crashing against the rocks below, but they know that if they were to step over the edge, they would be unable to return. The event horizon of a black hole is analogous to this – it is the point at which the gravitational forces become so overwhelming that even the fastest-moving particles in the universe, photons of light, cannot escape.But the event horizon is just the tip of the iceberg when it comes to the complexities of black hole physics. As one delves deeper into the subject, the challenges to our understanding only grow moreprofound.Consider, for example, the concept of time dilation. According to Einstein's theory of general relativity, the passage of time is affected by the presence of strong gravitational fields. As an object approaches the event horizon of a black hole, the rate at which time passes for that object becomes increasingly slowed down relative to an observer outside the black hole. This means that from the perspective of an external observer, the object appears to be frozen in time, gradually becoming fainter and fainter as it crosses the event horizon.Visualizing this phenomenon requires a significant amount of imagination and a deep understanding of the principles of relativity. It challenges our everyday experience of time and forces us to consider the universe from a radically different perspective – one where the familiar laws of physics no longer apply in the same way.Another aspect of black holes that pushes the limits of our imagination is the nature of the singularity itself. At the center of a black hole, where all the matter and energy of the collapsed star is concentrated, the laws of physics as we know them break down completely. This point of infinite density and infinite curvature of space-time is known as the singularity, and it represents the ultimate limit of our current scientific understanding.Trying to comprehend the singularity, a region where the very fabric of space-time is torn apart, is a task that requires a leap of imagination that few can truly make. It forces us to confront the limitations of our own understanding and to grapple with the fundamental mysteries of the universe.Despite these challenges, the study of black holes has been a cornerstone of modern astrophysics and has led to numerous groundbreaking discoveries. Through the use of sophisticated telescopes and advanced mathematical models, scientists have been able to observe the behavior of black holes in unprecedented detail, shedding light on the most extreme and enigmatic phenomena in the cosmos.From the detection of gravitational waves, the ripples in the fabric of space-time caused by the collision of black holes, to the stunning images of the supermassive black hole at the center of the Milky Way, the study of black holes has pushed the boundaries of our scientific knowledge and our understanding of the universe.But perhaps the greatest contribution of the study of black holes is the way it has challenged our fundamental assumptions about the nature of reality. By confronting us with the limits of our own understanding, black holes have forced us to reckon with thepossibility that there are aspects of the universe that may forever remain beyond our grasp.In this sense, the study of black holes is not just a scientific endeavor, but a philosophical one as well. It reminds us that the universe is a vast and mysterious place, and that our knowledge, no matter how extensive, is always a work in progress. It challenges us to remain humble in the face of the unknown and to continue to explore the limits of our understanding with curiosity, wonder, and a willingness to adapt our perspectives as new evidence emerges.Ultimately, the study of black holes is a testament to the power of the human mind to grapple with the most complex and enigmatic phenomena in the universe. It requires a unique blend of imagination, scientific knowledge, and a willingness to embrace the unknown – qualities that have defined the pursuit of scientific discovery since the dawn of human civilization.。
介绍黑洞的前言英语作文
介绍黑洞的前言英语作文Title: Exploring the Enigma of Black Holes。
In the vast expanse of the cosmos, amidst the twinkling stars and swirling galaxies, exists a phenomenon that continues to captivate and perplex astronomers and physicists alike the enigmatic black hole. From its conception as a theoretical curiosity to its recent observations through advanced telescopes and detectors, the journey to understand these cosmic behemoths has been both exhilarating and challenging.At the heart of every black hole lies a singularity, a point of infinite density where the laws of physics as we know them cease to apply. Surrounding this singularity is the event horizon, an invisible boundary beyond which nothing, not even light, can escape the gravitational grip of the black hole. It is this characteristic that gives black holes their name, as they seemingly devour everything that crosses their path, leaving behind only mystery andspeculation.The formation of black holes is a fascinating process, occurring through various mechanisms such as the gravitational collapse of massive stars or the mergers of compact objects like neutron stars. When a star exhausts its nuclear fuel, it may undergo a supernova explosion, leaving behind a dense core. If this core has sufficient mass, it can collapse under its own gravity, forming a black hole. Alternatively, in the depths of space, two neutron stars or black holes can spiral inward toward each other, eventually merging to create a larger black hole, releasing gravitational waves that ripple through the fabric of spacetime.One of the most intriguing aspects of black holes is their profound effect on the surrounding space-time. According to Einstein's theory of general relativity, massive objects like black holes warp the fabric of spacetime, creating gravitational wells that dictate the motion of nearby matter and light. This distortion can result in fascinating phenomena such as gravitationallensing, where the gravitational field of a black hole bends and magnifies light from distant objects, offering a glimpse into regions of the universe otherwise hidden from view.Despite their elusive nature, scientists have made significant strides in the study of black holes in recent decades. Through the development of innovative technologies and collaborative efforts, astronomers have detected the signatures of black holes across the electromagnetic spectrum, from radio waves to X-rays and gamma rays. Observatories like the Event Horizon Telescope have even captured unprecedented images of the silhouette of a black hole against the backdrop of glowing gas and dust, providing invaluable insights into their structure and behavior.Furthermore, the study of black holes extends beyond astrophysics, with profound implications for our understanding of fundamental physics. Black holes serve as testing grounds for theories of gravity and quantum mechanics, offering potential clues to reconcile theinconsistencies between Einstein's theory of general relativity and the principles of quantum physics. By probing the extreme conditions near black holes, scientists hope to unlock the secrets of the universe on both macroscopic and microscopic scales.In conclusion, the exploration of black holes represents a thrilling frontier in our quest to unravel the mysteries of the cosmos. From their formation to their influence on the fabric of spacetime, black holes continue to intrigue and inspire scientists and enthusiasts alike. As technology advances and our understanding deepens, we stand poised on the brink of new discoveries that promise to reshape our perception of the universe and our place within it. The journey to comprehend the enigma of black holes is far from over, but with each observation and theoretical breakthrough, we edge closer to illuminating one of the most captivating phenomena in the cosmos.。
黑洞吞噬恒星作文英语
黑洞吞噬恒星作文英语Title: The Phenomenon of Black Holes Devouring Stars。
Introduction:The universe, a vast expanse filled with mysteries beyond comprehension, houses some of the most enigmatic entities known to humanity. Among these, black holes stand as enigmatic giants, capable of consuming entire stars with their gravitational might. In this discourse, we delve into the intricate phenomenon of black holes engulfing stars, exploring the mechanisms behind such cosmic events andtheir profound implications for our understanding of the universe.Formation of Black Holes:Black holes originate from the collapse of massive stars at the end of their life cycle. When a star exhausts its nuclear fuel, it undergoes gravitational collapse,compressing its core into an incredibly dense state. If the remnant mass exceeds a critical threshold known as the Chandrasekhar limit, gravitational forces overwhelm all other forces, leading to the formation of a black hole.The Event Horizon:At the heart of a black hole lies the singularity, a point of infinite density where the laws of physics as we know them break down. Surrounding the singularity is the event horizon, an invisible boundary beyond which escape becomes impossible due to the overwhelming gravitational pull. It is at this boundary that the fate of stars becomes intertwined with the destiny of black holes.The Stellar Dance:When a star ventures too close to a black hole, it becomes ensnared in a lethal gravitational embrace. The intense tidal forces exerted by the black hole deform the star, stretching it into a long, thin structure known as a tidal tail. As the star spirals inward, its outer layersare gradually stripped away, forming a swirling accretion disk around the black hole.The Final Plunge:As the remnants of the star's outer layers accrete onto the disk, they release an immense amount of energy in the form of radiation. This process, known as accretion, generates powerful jets of high-energy particles thatstream outward from the black hole's poles. Meanwhile, the star's core, now exposed and vulnerable, hurtles toward the event horizon, crossing the point of no return known as the photon sphere. In a final, cataclysmic act, the star's core is consumed by the black hole, adding to its mass and extending its reach across the cosmos.Cosmic Significance:The phenomenon of black holes devouring stars holds profound implications for our understanding of the universe. By studying the emission signatures associated with these events, astronomers can glean insights into the propertiesof black holes, such as their mass, spin, and accretion rate. Furthermore, the gravitational waves produced by such cataclysmic events provide a unique opportunity to probe the fabric of spacetime itself, offering clues about the nature of gravity and the structure of the universe on the largest scales.Conclusion:In the vast tapestry of the cosmos, the interplay between black holes and stars represents a cosmic ballet of destruction and creation. From the fiery demise of stars to the inexorable pull of black holes, these celestial phenomena shape the evolution of galaxies and the destiny of the universe itself. As we continue to unravel the mysteries of the cosmos, the phenomenon of black holes devouring stars stands as a testament to the awe-inspiring power and beauty of the cosmos.。
介绍黑洞的英语作文短片
介绍黑洞的英语作文短片1Black holes are one of the most mysterious and fascinating objects in the universe. They possess incredibly powerful gravitational forces that are so strong that not even light can escape from them. This makes them impossible to observe directly. However, scientists have found ingenious ways to detect their presence indirectly. One such method is by observing the effects of a black hole on nearby matter. When matter gets close to a black hole, it is heated to extremely high temperatures and emits intense radiation that can be detected by telescopes.For instance, the study of the X-ray emissions from the accretion disks around black holes has provided valuable insights. The famous Cygnus X-1, for example, is one of the earliest and most studied black hole candidates. Another important achievement is the detection of gravitational waves produced by the merger of two black holes. This groundbreaking discovery not only confirmed the existence of black holes but also opened up a new window for studying the universe.In conclusion, despite the challenges in directly observing black holes, the progress made in understanding them through indirect means has been remarkable, and continues to deepen our knowledge of the universe's most extreme phenomena.2Black holes are one of the most mysterious and fascinating phenomena in the universe. They are formed through a complex process that involves the collapse of massive stars. When a star much larger than our sun runs out of fuel and can no longer support its own weight, it undergoes a gravitational collapse. The core of the star collapses inward with such tremendous force that it creates an object with an incredibly strong gravitational pull, from which nothing, not even light, can escape.In many science fiction movies, black holes are depicted in various imaginative ways. They are often shown as portals to other dimensions or as cosmic monsters that swallow entire galaxies. These depictions not only entertain us but also fuel our curiosity about the unknown.The study of black holes has opened up new frontiers in our understanding of the universe. It challenges our current theories of physics and forces us to think beyond the boundaries of conventional knowledge. The mystery and allure of black holes continue to captivate scientists and enthusiasts alike, driving us to explore the vastness of space and uncover its deepest secrets.3Black holes are one of the most mysterious and fascinating phenomena in the universe. They have a profound impact on thesurrounding spacetime. The gravitational pull of a black hole is so intense that it can distort spacetime to an extreme degree. This distortion causes objects near the black hole to experience extreme gravitational forces and behave in unusual ways.For example, consider the theory of gravitational lensing. When light passes near a black hole, its path is bent due to the gravitational distortion of spacetime. This effect has been observed and studied in various astronomical observations, providing valuable evidence for our understanding of black holes and their influence.Another interesting aspect is the concept of the event horizon. Once an object crosses this boundary, it is impossible for it to escape the gravitational pull of the black hole. This idea has led to many scientific experiments and hypotheses aimed at exploring the nature and properties of black holes.Scientists have also proposed the idea of extracting energy from black holes through a process known as the Penrose process. This theoretical concept involves the conversion of rotational energy of the black hole into usable energy.In conclusion, the study of black holes and their effects on spacetime continues to expand our knowledge of the universe and challenges our understanding of fundamental physics.Black holes have long fascinated scientists and the public alike. The study of black holes has a rich history that dates back to Einstein's theory of relativity. According to this theory, massive objects can distort spacetime to such an extent that a black hole can form.For many years, black holes were theoretical entities. But with the advancement of technology, we have been able to observe and study them more closely. Modern telescopes and observatories have provided us with valuable data and images.The discovery of gravitational waves, predicted by Einstein's theory, has also opened new doors in the study of black holes. When two black holes merge, they produce gravitational waves that can be detected on Earth.Scientists are constantly working to understand the nature of black holes, their formation, and their effects on the universe. They are using advanced computer simulations and mathematical models to gain deeper insights.In conclusion, our understanding of black holes has come a long way from theoretical concepts to actual observations and discoveries. The journey is far from over, and there is still much to learn and explore about these mysterious cosmic objects.Black holes are one of the most mysterious and fascinating objects in the universe. They have a gravitational pull so strong that nothing, not even light, can escape. The study of black holes has opened up new frontiers in our understanding of the cosmos.The future development of black hole research holds immense potential and scientific value. One exciting area is the combination of black hole studies with quantum mechanics. This could help us solve some of the most profound questions in physics, such as the nature of space and time at the most fundamental level.For instance, researchers are exploring how the extreme gravitational environment near a black hole might affect the behavior of quantum particles. This could lead to a revolutionary understanding of the interplay between gravity and quantum physics, which has puzzled scientists for decades.Another aspect is the role of black holes in the evolution of galaxies. Understanding how black holes interact with the surrounding matter and influence the formation and growth of galaxies could provide crucial insights into the structure and dynamics of the universe.In conclusion, the study of black holes is not only about uncovering the mysteries of these cosmic giants but also about advancing our knowledge of the fundamental laws of nature and the universe as a whole.。
美国宇航局的新X射线望远镜将让黑洞重新成为大家关注的焦点
美国宇航局的新X射线望远镜将让黑洞重新成为大家关注的焦点NASA will be launching a new telescope expected to bring black holes and supernovae into unprecedented focus, mission scientists announced Wednesday. NASA科学家周三宣布，美国宇航局将发射一个新的望远镜，预计黑洞和超新星将重新成为大家关注的焦点The Nuclear Spectroscopic Telescope Array, a mission to hunt for black holes, is scheduled to launch no sooner than June 13 from the Kwajalein Atoll in the Marshall Islands, located north of the equator. It will look at some of the most mysterious phenomena in the universe, from the high-speed particle jets that blast from black holes to the remnants of exploded stars known as supernovae. It will even shed light on mysteries closer to home, such as what powers the sun’s corona, a ghostly glow of charged particles that heats up to a million degrees.定核光谱天文望远镜阵列，使命是寻找黑洞，位于赤道以北，马绍尔群岛的夸贾林环礁，最早定于6月13日发射。
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IKI, Space Research Institute, Profsoyuznaya, 84/32, Moscow 117296, Russia Department of Physics (Theoretical Physics), University of Oxford, 1 Keble Road, Oxford OX1 3NP
The TTM is a coded mask imaging spectrometer on board the KVANT module of the MIR space station. It has an
2 OBSERVATIONS
2
H.C. Pan, G. K. Skinner, R. A. Sunyaev, and K. N. Borozdin Table 1. Spectral parameters of X1755-338, GX339-4, LMC X-1 & LMC X-3.
NH
(3)
L(4) + L(4) DB PL
2
=dof
1:37 0:43 1:9 0:9 6 12 0:88 0:25 2:7 0:4 < 1 2:33 0:56 2:3 0:6 < 3 0:59 0:08 2:1 0:3 0:25 0:06 2:7 1:1 0:72 0:10 1:2 0:4 0:85 0:03 2:3 0:2 1:06 0:05 2:1 0:2
: :
ABSTRACT
1 INTRODUCTION
More than two dozen X-ray binary systems, which have been classed as `Black Hole Candidates' (e.g. Tanaka 1989; Stella et al. 1994), have now been detected in our galaxy and the Large Magellanic Cloud. In some cases the evidence for the presence of a black hole comes directly from dynamical studies, e.g. Cyg X-1 (Paczynski 1974), LMC X-3 (Cowley et al. 1983), LMC X-1 (Hutchings et al. 1987), A0620-00 (McClintock & Remillard 1986), GS2023+338 (Casares et al. 1992), and GS1124-68 (GRS1124-68) (Remillard et al. 1992). In others the evidence for the presence of a black hole is less direct; X-ray light curves and spectra indicate that the systems are all members of a single class and show characteristics which are quite distinct from those of X-ray binaries known to contain a neutron star (e.g. Tanaka 1989; 1990).
Accepted 1995 February. in original form 1994 November 1
astro-ph/9502099 27 Feb 1995
We report the rst detection of a hard power-law tail in the X-ray spectrum of the black hole candidate (BHC) binary X1755-338, which was observed in 1989 March-September during the TTM Galactic Centre survey. In addition, an ultrasoft thermal component with a temperature of 1 1 1 4 keV was also detected. We demonstrate that the soft and hard X-ray components of X1755-338 vary independently, as in the spectra of the well known BHCs LMC X-1, LMC X-3 and GX339-4 in their high (intensity) state. If the hard tail observed from X1755-338 is generated near the black hole by energetic electrons up-scattering low energy photons, the un-correlated variations imply that the soft X-rays from accretion disc may not be the main photon seeds needed for inverse Comptonization. The TTM observations strongly suggest that X1755-338 does indeed belong to the family of BHCs. Key words: binaries:spectroscopic { stars:activity { stars:individual:X1755-338 { Xrays:stars.
The X-ray spectra typically have a at power-law high energy tail. In addition there is frequently an ultrasoft thermal component. Some sources are observed in two states. Among the best established black hole binaries a `high' state with a composite spectrum including an ultrasoft component and a at power-law type tail at high energies, is shown by Cyg X-1, LMC X-3, LMC X-1, A0620-00 and GS1124-68 (Tanaka 1989; Ebisawa et al. 1994), while a low state in which the X-ray spectrum can be approximated by a powerlaw with photon index 1.5-1.8 as shown by Cyg X-1 (e.g. Tanaka 1989; 1990), GS2023+338 (in't Zand et al. 1992; Pan et al. 1993), and GS1124-68 (Ebisawa et al. 1994). When
Mon. Not. R. Astron. Soc. 000, 000{000 (1995)
X-ray Spectrum of the Black Hole Candidate X1755-338
H.C. ofPan1 3,and Space Research, University of A. aev2, and K. N.B15 2TT 2 G. K. Skinner1, R. Birmingham, Edgbaston, Birmingham Borozdin School Physics
Date X1755-338(5) 89 Mar 31 89 Aug 23 89 Sep 10 GX339-4(5) 89 Mar 25 LMC X-1(5) 88 Nov 13-Dec 2 88 Dec 4-5 LMC X-3(5) 89 Mar 2 89 May 30-Jun 10 Notes: Disc-blackbody(1) rin (cos i)1=2 Tin 5:2 2:0 5:2 0:7 5:1 1:7 18:1 0:4 39 10 36 5 28 4 24 5 1:14 0:22 1:33 0:06 1:28 0:15 0:78 0:01 0:83 0:06 0:90 0:07 1:16 0:07 0:94 0:05 Power-law(2) Scale
BHC sources are in the `high' state, the soft and hard components vary independently (e.g. Tanaka 1989; 1990). X1755-338 is an X-ray binary source located in the general direction of the Galactic Centre. It was previously noted as an unusually soft X-ray source by Jones (1977) and was suggested later as a black hole candidate by White & Marshall (1984), and White et al. (1984), based on its similar location to a group of BHCs on the X-ray color-color diagram. The Einstein SSS observations of X1755-338 (White & Marshall 1984) give an interstellar hydrogen column density NH = (2:2 1:2) 1021 H cm 2 , far below that expected from sources close to the Galactic Bulge. X-ray dips with 4.4 hour period were observed from X1755-338 with EXOSAT (White et al. 1984; Mason et al. 1985). The X-ray ux in the 1-9 keV band decreases by as much as 40% in the dips which appear to be energy independent as suggested by insigni cant change of the hardness ratio from non-dip to dip periods (White et al. 1984). We observed X1755-338 in 1989 March-September during the period of the TTM Galactic Centre Survey. In this letter we present results of the TTM observations of X1755338 and report the rst detection of a power-law hard tail in the spectrum of X1755-338.