首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 48 毫秒
1.
We present a suborbital rocket payload capable of performing soft X-ray spectroscopy on extended sources. The payload can reach resolutions of ??100 (??/ ????) over sources as large as 3.25° in diameter in the 17?C107 Å bandpass. This permits analysis of the overall energy balance of nearby supernova remnants and the detailed nature of the diffuse soft X-ray background. The main components of the instrument are: wire grid collimators, off-plane grating arrays and gaseous electron multiplier detectors. This payload is adaptable to longer duration orbital rockets given its comparatively simple pointing and telemetry requirements and an abundance of potential science targets.  相似文献   

2.
We undertake a spectral study of a sample of bright X-ray sources taken from six XMM-Newton fields at high galactic latitudes, where AGN are the most populous class. These six fields were chosen such that the observation had an exposure time more than 60 ksec, had data from the EPIC-pn detector in the full-Frame mode and lying at high galactic latitude |b|>25∘. The analysis started by fitting the spectra of all sources with an absorbed power-law model, and then we fitted all the spectra with an absorbed power-law with a low energy black-body component model.The sources for which we added a black body gave an F-test probability of 0.01 or less (i.e. at 99% confidence level), were recognized as sources that display soft excess. We perform a comparative analysis of soft excess spectral parameters with respect to the underlying power-law one for sources that satisfy this criterion. Those sources, that do not show evidence for a soft excess, based on the F-test probability at a 99% confidence level, were also fitted with the absorbed power-law with a low energy black-body component model with the black-body temperature fixed at 0.1 and 0.2 keV. We establish upper limits on the soft excess flux for those sources at these two temperatures. Finally we have made use of Aladdin interactive sky atlas and matching with NASA/IPAC Extragalactic Database (NED) to identify the X-ray sources in our sample. For those sources which are identified in the NED catalogue, we make a comparative study of the soft excess phenomenon for different types of systems.  相似文献   

3.
Assuming that soft X-ray sources in symbiotic stars result from strong thermonuclear runaways, and supersoft X-ray sources from weak thermonuclear runaways or steady hydrogen burning symbiotic stars, we investigate the Galactic soft and supersoft X-ray sources in symbiotic stars by means of population synthesis. The Galactic occurrence rates of soft X-ray sources and supersoft X-ray sources are from ～2 to 20 yr?1, and ～2 to 17 yr?1, respectively. The numbers of X-ray sources in symbiotic stars range from 2390 to 6120. We simulate the distribution of X-ray sources over orbital periods, masses and mass accretion rates of white dwarfs. The agreement with observations is reasonable.  相似文献   

4.
The use of rotating modulation collimators in high resolution solar X-ray spectroscopy is discussed with reference to the recent flight of a sounding rocket payload. This rocket carried an experiment which combined a modulation collimator and a Bragg crystal spectrometer to make moderately high resolution spectral and spatial measurements simultaneously. The response of the instrument to extended sources is described. It is shown that the technique is particularly suited to long term observations of active region emission, but that useful measurements can be made even during a short rocket flight.Our observations were made in 1972 October 26 between 0432 UT and 0436 UT. During the flight a scan of the solar X-ray spectrum was made which covered the wavelength range 1.45–1.71 nm. A small flare commenced at about 0432 UT in McMath calcium plage region 12094; the emission from this provided the major contribution to the observed spectrum. X-ray emission from a group of active regions in the SW and the small McMath region 12090 has also been detected.Spectral and spatial observations have been combined to investigate the conditions in both active region and flare plasmas.  相似文献   

5.
Cosmic X-rays in the energy range between 0.210 keV were observed with polypropylene window proportional counters on board a sounding rocket. The field of view crossed the galactic plane in the Sgr region and reached galactic latitudes of 50° and –90°. A new soft X-ray source was found in the Aries-Taurus region. The soft X-ray flux from the direction of NGC 1275 was conspicuous, whereas that of Sgr region source were very weak. The distribution of the intensity of diffuse soft X-rays over the scanned region indicates the galactic emission of soft X-rays.  相似文献   

6.
The distribution of hard and soft X-ray sources in our Galaxy is investigated (excluding Supernova remnants and globular clusters sources), and their physical nature is suggested. Hard X-ray sources are connected with massive binary systems, soft ones are binary systems with massive primary and an initially extremely small mass ratio.  相似文献   

7.
《New Astronomy Reviews》2000,44(4-6):375-377
A possibility of obtaining information on small-scale inhomogeneities of the electron component of the local interstellar medium (LISM) was investigated using interstellar scintillations of extragalactic radio sources. We analysed Culgoora array observational variability data of 190 extragalactic radio sources, covering most of the sky, at 80 and 160 MHz. The variability at time scales from 1 month to 15 years is interpreted as refractive interstellar scintillations in fast-moving nearby (less than 150 pc) hot gas, near shock waves in the LISM. An all-sky map of scintillation indices, m, averaged over three–five sources closest to one another, shows several m maxima. Two of the three most pronounced maxima are probably connected with Loop I; the third one coincides with the soft X-ray (0.1–0.3 keV) background maximum near the South Galactic Pole. Other, less certain, m maxima probably correspond to the Orion star-formation region and to a soft X-ray maximum near the North Galactic Pole. The ‘free-of-gas’ tunnel in the direction l=240° corresponds to low values of m. The estimated time scale of interstellar scintillations on the above-mentioned LISM structures is in agreement with that of the observed radio-source variations.  相似文献   

8.
We suggest to identify the elementary flare bursts with the excitation of the small kernels that occur in flare loops that are observed in soft X-ray pictures of flares. We stress the need of simultaneous observations of spatial structure and time variations of hard X-ray bursts sources in various wavelength regions.  相似文献   

9.
Analysis of recent observations of the elliptical galaxies NGC 4472 and NGC 4649 with the Chandra X-ray space telescope has revealed faint soft X-ray sources at their centers. The sources are located at the galactic centers, to within 1″, and are most likely associated with the radiation from the supermassive black holes that are assumed to be at the optical centers of these galaxies. Interest in these and several other similar objects stems from the unusually low luminosity of the supermassive black hole embedded in a dense interstellar medium. The sources have soft energy spectra in the Chandra energy range 0.2–10 keV. The source is detected at a 3σ confidence level only in the range 0.2–0.6 keV with a luminosity of ～6×1037 erg s?1 in NGC 4649 and in the range 0.2–2.5 keV with a luminosity of ～ 1.7×1038 erg ?1 in NGC 4472.  相似文献   

10.
We have studied the energetics of two impulsive solar flares of X-ray class X1.7 by assuming the electrons accelerated in several episodes of energy release to be the main source of plasma heating and reached conclusions about their morphology. The time profiles of the flare plasma temperature, emission measure, and their derivatives, and the intensity of nonthermal X-ray emission are compared; images of the X-ray sources and magnetograms of the flare region at key instants of time have been constructed. Based on a spectral analysis of the hard X-ray emission from RHESSI data and GOES observations of the soft X-ray emission, we have estimated the spatially integrated kinetic power of nonthermal electrons and the change in flare-plasma internal energy by taking into account the heat losses through thermal conduction and radiation and determined the parameters needed for thermal balance. We have established that the electrons accelerated at the beginning of the events with a relatively soft spectrum directly heat up the coronal part of the flare loops, with the increase in emission measure and hard X-ray emission from the chromosphere being negligible. The succeeding episodes of electron acceleration with a harder spectrum have virtually no effect on the temperature rise, but they lead to an increase in emission measure and hard X-ray emission from the footpoints of the flare loops.  相似文献   

11.
《New Astronomy Reviews》2000,44(7-9):387-394
The excellent soft X-ray sensitivity of the PSPC detector onboard the ROSAT satellite provided the first chance to study precisely the spectral and timing properties of Narrow-Line Seyfert 1 galaxies. ROSAT observations of Narrow-Line Seyfert 1 galaxies have revealed (1) the existence of a giant soft X-ray excess, (2) a striking, clear correlation between the strength of the soft X-ray excess emission and the FWHM of the Hβ line, (3) the general absence of significant soft X-ray absorption by neutral hydrogen above the Galactic column, (4) short doubling time scales down to about 1000 s, (5) the existence of persistent giant (above a factor of 10), and rapid (less than 1 day) X-ray variability in extragalactic sources. The soft X-ray results on Narrow-Line Seyfert 1 galaxies indicate that their black hole regions are directly visible, further supporting the Seyfert 1 nature of these objects. The extreme X-ray properties of Narrow-Line Seyfert 1 galaxies make them ideal objects for understanding many of the problems raised generally by the Seyfert phenomenon.  相似文献   

12.
We measured the average soft X-ray emission from coronal holes observed on images obtained during AS & E rocket flights from 1974 to 1981. The variation of this emission over the solar cycle was then compared with photospheric magnetic flux measurements within coronal holes over the same period. We found that coronal hole soft X-ray emission could be detected and that this emission appeared to increase with the rise of the sunspot cycle from activity minimum to maximum. Our quantitative results confirmed previous suggestions that the coronal brightness contrast between holes and large-scale structure decreased during this period of the cycle. Gas pressures at the hole base were estimated for assumed temperatures and found to vary from about 0.03 dyne cm–2 in 1974 to 0.35 dyne cm–2 in 1981. The increase in coronal hole X-ray emission was accompanied by a similar trend in the surface magnetic flux of near-equatorial holes between 1975 and 1980 (Harvey et al., 1982).  相似文献   

13.
We study a solar flare that occurred on 10 September 2002, in active region NOAA 10105, starting around 14:52 UT and lasting approximately 5 minutes in the radio range. The event was classified as M2.9 in X-rays and 1N in Hα. Solar Submillimeter Telescope observations, in addition to microwave data, give a good spectral coverage between 1.415 and 212 GHz. We combine these data with ultraviolet images, hard and soft X-ray observations, and full-disk magnetograms. Images obtained from Ramaty High Energy Solar Spectroscopic Imager data are used to identify the locations of X-ray sources at different energies, and to determine the X-ray spectrum, while ultraviolet images allow us to characterize the coronal flaring region. The magnetic field evolution of the active region is analyzed using Michelson Doppler Imager magnetograms. The burst is detected at all available radio frequencies. X-ray images (between 12 keV and 300 keV) reveal two compact sources. In the 212 GHz data, which are used to estimate the radio-source position, a single compact source is seen, displaced by 25″ from one of the hard X-ray footpoints. We model the radio spectra using two homogeneous sources, and we combine this analysis with that of hard X-rays to understand the dynamics of the accelerated particles. Relativistic particles, observed at radio wavelengths above 50 GHz, have an electron index evolving with the typical soft–hard–soft behavior.  相似文献   

14.
The galactic distribution and physical nature of X-ray transient sources is investigated. Two types of transients are considered. The observational data on 41 X-ray transient sources are given, and the average parameters of hard and soft X-ray transients are estimated.  相似文献   

15.
Possible numbers of X-ray sources at various flux levels are considered and their contribution to the background evaluated. Our conclusions are: The mean spectrum of Quasi-Stellar Objects and the nuclei of Seyfert galaxies between optical and X-ray wavelengths is characterized by a spectral index well in excess of 1.0. These objects may make an important contribution to the soft X-ray background. Observations of Q.S.O. may allow a decisive test for the cosmological interpretation of the redshifts of the Q.S.O. With regard to galactic sources we find that few undetected sources of the Sgr-Sco type exist, that these sources are located in the immediate neighborhood of the galactic center and that they account for at least 80% of the total galactic source luminosity. However, many intrinsically much fainter galactic sources may exist.  相似文献   

16.
Sounding rocket measurements of the solar soft X-ray irradiance   总被引：1，自引：0，他引：1  
Bailey  S.M.  Woods  T.N.  Canfield  L.R.  Korde  R.  Barth  C.A.  Solomon  S.C.  Rottman  G.J. 《Solar physics》1999,186(1-2):243-257
Measurements of the solar soft X-ray (XUV: 2 nm to 30 nm) irradiance were performed from a sounding rocket payload flown from White Sands Missile Range, New Mexico on 4 October 1993 and again on 3 November 1994. The soft X-ray instrumentation comprised of silicon photodiodes with thin films deposited directly onto their active areas. The deposited material and its thickness in conjunction with the sensitivity of an uncoated diode determine the passband and the sensitivity of these photometric devices. The measurements are interpreted in terms of appropriate SERF 1 (Hinteregger, Fukui, and Gilson, 1981) model solar spectra. It is found that the data are consistent with a solar spectrum that is on average approximately a factor of two times the model solar spectra. It is shown that the measured irradiances are in reasonable agreement with other experiments.  相似文献   

17.
We present a radio survey of X-ray sources in the Large and Small Magellanic Clouds with the Australia Telescope Compact Array at 6.3 and 3.5 cm. Specifically, we have observed the fields of five LMC and two SMC supersoft X-ray sources, the X-ray binaries LMC X-1, X-2, X-3 and X-4, the X-ray transient Nova SMC 1992, and the soft gamma-ray repeater SGR 0525-66. None of the targets are detected as point sources at their catalogued positions. In particular, the proposed supersoft jet source RXJ 0513-69 is not detected, placing constraints on its radio luminosity compared to Galactic jet sources. Limits on emission from the black hole candidate systems LMC X-1 and X-3 are consistent with the radio behaviour of persistent Galactic black hole X-ray binaries, and a previous possible radio detection of LMC X-1 is found to be almost certainly a result of nearby field sources. The SNR N49 in the field of SGR 0525-66 is mapped at higher resolution than it has been previously, but there is still no evidence for any enhanced emission or disruption of the SNR at the location of the X-ray source.  相似文献   

18.
Population studies of EGRET gamma-ray sources indicate that there is a distinctive population of bright sources at low galactic latitudes. The sources have a distribution consistent with that of young galactic objects, with a concentration toward the inner spiral arms. There is a subgroup that displays strong variability with timescales from days to months. Following an earlier suggestion by Kaufman Bernadó et al. (2002), we explore the possibility that these sources could be high-mass microquasars. Detailed models for the gamma-ray emission that include inverse Compton interactions of electrons in the relativistic jets and photons from all local fields (stellar UV photons, synchrotron photons, soft X-ray photons from the accretion disk, and hard X-ray photons from a corona) are presented. We conclude that microquasars are excellent candidates for the parent population of the subgroup of variable low-latitude EGRET sources.  相似文献   

19.
High-resolution images of the decay phase of a soft X-ray flare observed by the S-054 experiment on Skylab are compared with interferometric scans of the radio burst obtained simultaneously at 2.8 cm (Felli et al., 1975). The spatial resulution of the radio instrument in one direction, although lower than the X-ray telescope resolution, is high enough for a detailed comparison. The comparison clarifies the relationship between the sources of soft X-ray and thermal radio emission in solar flares. The X-ray emission is localized in a loop-like structure which appears spatially coincident with the rapidly varying component of the radio burst. The more stable components of the radio source, which do not appear to contribute substantially to X-ray emission, are found to be spatially associated with the extremes of the X-ray loop. A model of plasma-filled loops is suggested which accounts for the emissions in both spectral ranges and for their spatial location and temporal development.On leave from Osservatorio Astrofisico di Arcetri, Florence, Italy.  相似文献   

20.
We have surveyed 188 ROSAT Position Sensitive Proportional Counter (PSPC) fields for X-ray sources with hard spectra ( α <0.5); such sources must be major contributors to the X-ray background at faint fluxes. In this paper we present optical identifications for 62 of these sources: 28 active galactic nuclei (AGN) which show broad lines in their optical spectra (BLAGN), 13 narrow emission line galaxies (NELGs), five galaxies with no visible emission lines, eight clusters and eight Galactic stars.
The BLAGN, NELGs and galaxies have similar distributions of X-ray flux and spectra. Their ROSAT spectra are consistent with their being AGN obscured by columns of 20.5< log( N H/cm−2)<23 . The hard spectrum BLAGN have a distribution of X-ray to optical ratios which is similar to that found for AGN from soft X-ray surveys (1< α OX<2) . However, a relatively large proportion (15 per cent) of the BLAGN, NELGs and galaxies are radio loud. This could be because the radio jets in these objects produce intrinsically hard X-ray emission, or if their hardness is caused by absorption, it could be because radio-loud objects are more X-ray luminous than radio-quiet objects. The eight hard sources identified as clusters of galaxies are the brightest, and softest group of sources and hence clusters are unlikely to be an important component of the hard, faint population.
We propose that BLAGN are likely to constitute a significant fraction of the faint, hard, 0.5–2 keV population and could be important to reproducing the shape of the X-ray background, because they are the most numerous type of object in our sample (comprising almost half the identified sources), and because all our high redshift ( z >1) identified hard sources have broad lines.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号