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1.
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   

2.
Balloon observations of the cosmic diffuse component of hard X-rays were conducted with two independent directional counters in two energy bands, from 20 keV to 120 keV and from 90 keV to 4 MeV. The build-up effect of primary X-rays and the altitude dependence of atmospheric X-rays were properly taken into account in the analysis of the growth curves. These two experiments gave consistent results in the overlapping energy region. If the differential energy spectrum of the photon flux is represented by a power lawE ?α, the value of α is 2.3 up to 100 keV, gradually increases to 2.8 at about 500 keV, and decreases to 2.0 thereabove. The spectrum above 300 keV is in parallel to the Apollo-15 spectrum, whereas the absolute intensity is somewhat smaller. The shape of the spectrum suggests the necessity of a multi-component theory on the origin of cosmic diffuse X-rays.  相似文献   

3.
The spectral and temporal measurements in the hard X-ray region between 20-200 keV not only determines the extended behaviour of thermal X-ray spectrum below 10 keV but also provide a unique insight into the non-thermal processes in relativistic astrophysical plasma. From our present understanding of the X-ray sources, a significant fluxin the 20-200 keV band is expected from a variety of astrophysical phenomena, however, the available spectral data on the galactic and extragalactic X-ray source is very limited. This is mainly due to the fact that sensitivity of the detector systems used for earlier measurements was relatively poor. Since 1997, we have been carrying out a programme of hard X-ray observations galactic and extragalactic sources, in the 20-200 keV energy band using a highly sensitive balloon borne experiment. The X-ray telescope consists of three modules of large area scintillation counters specially configured in the back-to-back geometry and have a combined sensitivity of ∼ 10-6 ph cm-2 s-1 keV-1 for an on-source observations of 3 hrs. A total of 30 hours of ceiling data above an altitude of 3 mbar has been collected in 4 successful balloon flights from Hyderabad, India. Almost a dozen galactic and extragalactic X-ray sources were targeted and tracked during these observations. A positive detection was made in each case and in some cases the observed spectra extended right up to 150 keV. A brief account of the observed spectral and temporal features on some of the sources along with accurate measurement of diffuse background spectrum and a weak gamma ray burst will be presented in the paper. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

4.
The intensity of the diffuse component of cosmic X-rays was measured with use of a rotating collimator system borne on a sounding rocket. A part of background counts proportional to the field of view of proportional counters enabled us to determine the intensity of the diffuse component to be 0.66±0.07 photons cm–2 sec–1 keV–1 in the energy range between 3.6 and 9.0 keV. The spectrum in this energy range was found to be comparatively flat. The intensity of Sco X-1 was also measured and its time variation was investigated.  相似文献   

5.
Soft X-rays (0.2–1.0 keV) have been detected from the high galactic latitude source MX 2140-60 in a rocket experiment. The measured flux of 10–10 erg cm–2 s–1 combined with OSO-7 measurements in 2–40 keV X-rays, are best fit by a power law photon spectrum with spectral index 2.3 and a neutral hydrogen column densityN H=(3–7) 1020 atoms cm–2. The observations support the source identification with the cluster of galaxies SC 2146-594, as suggested by Lugger.  相似文献   

6.
Experimental results on the intensity, energy spectrum and time variations in hard X-ray emission from Cyg X-1 based on a balloon observation made on 1971, April 6 from Hyderabad (India) are described. The average energy spectrum of Cyg X-1 in the 22–154 keV interval on 1971 April 6 is best represented by a power law dN/dE=(5.41±1.53)E –(1.92±0.10) photons cm–2s–1 keV–1 which is in very good agreement with the spectrum of Cyg X-1 derived from an earlier observation made by us on 1969 April 16 in the 25–151 keV band and given by dN/dE=(3.54±2.44)E –(1.89±0.22) photons cm–2s–1 keV–1. A thermal bremsstrahlung spectrum fails to give a good fit over the entire energy range for both the observations. Comparison with the observations of other investigators shows that almost all balloon experiments consistently give a spectrum of E –2, while below 20 keV the spectrum varies fromE –1.7 toE –5. There is some indication of a break in the Cyg X-1 spectrum around 20 keV. Spectral analysis of data in different time intervals for the 1971 April 6 flight demonstrates that while the source intensity varies over time scales of a few minutes, there is no appreciable variation in the spectral slope. Analysis of various hard X-ray observations for long term variations shows that over a period of about a week the intensity of Cyg X-1 varies upto a factor of four. The binary model proposed by Dolan is examined and the difficulties in explaining the observed features of Cyg X-1 by this model are pointed out.  相似文献   

7.
We present a detailed study of the bremsstrahlung gamma-ray emissivity of the galactic disk. We show that there are large uncertainties in the production spectrum of photons in the medium energy range (10–100 MeV) due to our lack of knowledge of the interstellar electron spectrum below a few hundred MeV. In fact, gamma-ray observations can be of great help in determining this spectrum. At present, the spectral shape of the local gamma-ray emissivity above 30 MeV is available, thanks to the SAS-II and the COS-B satellites. Comparing it to our calculations, we determine the local interstellar electron flux in the 50–500 MeV range; the corresponding integrated gamma-ray emissivity above 100 MeV is equal to 2.4×10–25 photons s–1 (H-atom)–1, 60% higher than previously accepted values.  相似文献   

8.
The brightness distribution of diffuse soft X-rays in the pulse height range 0.15–0.3 keV (L-band) and 0.5–0.8 keV (M-band) are obtained over a quarter of the sky centered at the galactic anticenter with 1.5 m polypropylene window proportional counters on board a sounding rocket. In theL-band three enhanced regions are noticed on the map. They coincide with the northern and southern Hi holes and the inner part of the galactic radio Loop II.In the northern Hi hole theN H dependence of theL-band flux and the hardness ratioM/L can be fitted with a local hot plasma model with the absorption by a low velocity neutral hydrogen gas (|V|<25 km s–1) along the line of sight. The X-ray feature of Loop II is similar to that of Loop I. In the lowN H region (<3×1020 H atoms cm–2) theM/L value is lower than 0.3, whereas it varies in the range 0.1–0.4 at low latitudes (|b|<300). This fact seems to be interpreted in terms of a model that a number of hot plasma clouds contribute to X-ray emission.  相似文献   

9.
Diffuse cosmic X-rays in the energy range 20–125 keV were measured in four balloon flights from Hyderabad, India during 1968–70 using almost identical X-ray telescopes mounted on oriented platforms. The results from these flights show that the spectrum of the diffuse cosmic X-rays can be represented by the form dN/dE=29E –2.1±0.3 photons/(cm2 sr s keV) in 20–125 keV interval after corrections for photoelectric absorption and Compton scattering effects in the atmosphere. The best fit spectrum of all published results in the energy interval 20–200 keV can be represented by the form dN/dE=36E –2.1±0.1 photons/(cm2 sr s keV) after similar corrections are effected, and there is no need for a change of spectral index in this energy interval. The intensity at 20 keV obtained from the above spectrum agrees well with that given by the spectral form dN/dE=10E –1.7±0.1 photons/(cm2 sr s keV) in the energy interval 1–20 keV in several rocket experiments. Therefore it is concluded that if there is a break in the spectrum, it occurs between 10 and 20 keV with a change of spectral index by about 0.5, or the index is continuously changing from 1.7±0.1 to 2.1±0.1 in 10–20 keV interval. The implications of the results are briefly discussed.  相似文献   

10.
The energy spectrum of diffuse hard X-rays measured in the range 10–40 keV shows a rather sharp change of slope. The logarithmic derivative of the spectrum changes around 20–30 keV by the increment significantly greater than 0.5 within an interval smaller than 50 keV.  相似文献   

11.
Since its launch on March 8, 1967, the OSO-III has continuously observed solar and cosmic X-rays over the 7.7–210 keV range. The sun emits many impulsive X-ray bursts having fluxes several orders of magnitude above the background level of 8 × 10–9 ergs(cm2-sec)–1 at 7.7 keV and characteristic times on the order of 5 min. Ninety-five such events having fluxes >3 × 10–5 ergs(cm2-sec)–1 were detected in the period from March 8 to June 15, 1967. The cosmic X-ray source Lupus XR-1 has been observed to have a power law spectral form and no significant time variations over a 40-day period. Upper limits have been obtained on the hard X-ray flux of the peculiar galaxy M 87.  相似文献   

12.
The attempts at unified model fitting to explain the spectral variations in Cyg X-3 suggest equally probable fits with a combination of an absorbed blackbody and a separately absorbed power law with an exponential cut-off or a composite of absorbed free-free emission with a power law hard X-ray component apart from the iron emission line. These seemingly ordinary but ad hoc mixtures of simple X-ray emission mechanisms have a profound implication about the geometry of the X-ray source. While the first set suggests a black-hole nature of the compact object, the second combination is consistent with a neutron star binary picture. The spectral variability at hard X-ray energies above 30 keV can provide crucial input for the unified picture. In this paper, we present spectral observations of Cyg X-3, made in our on-going survey of galactic and extragalactic X-ray sources in the 20–200 keV energy region, using Large Area Scintillation counter Experiment. The data show a clear power-law photon spectrum of the form dN/dE ∼ E−2.8 in the 20 to 130 keV energy range. A comparison with earlier data suggests that the total number of X-ray photons in the entire 2–500 keV energy band is conserved at all time for a given luminosity level irrespective of the state. We propose that this behaviour can be explained by a simple geometry in which a thermal X-ray source is embedded in a hot plasma formed by winds from the accretion disk within a cold shell. The high/soft and low/hard X-ray states of the source are simply the manifestation of the extent of the surrounding scattering medium in which the seed photons are Comptonized and hot plasma can be maintained by either the X-ray driven winds or the magneto-centrifugal winds.  相似文献   

13.
A balloon-borne gemanium spectrometer was flown in an attempt to detect line-emission from Cyg X-1 and the Crab nebula in the energy range 30–270 keV. The experiment was carried out on 29–30 September, 1982. A line feature at 145 keV was observed from Cyg X-1. The intensity is (1.34±0.31)×10–2 photons cm–2 s–1 and the width is 14.3 keV FWHM. From the Crab nebula, a weak line feature with 1.8 excess was found around 78 keV.  相似文献   

14.
The fluxes and spectra of galactic and extragalactic neutrinos at energy 1011–1019 eV are calculated. In particular, the neutrino flux from the normal galaxies is calculated taking into account the spectral index distribution. The only assumption that seriously affects the calculated neutrino flux atE v 1017 eV is the power-like generation spectrum of protons in the entire considered energy region.The normal galaxies with the accepted parameters generate the metagalactic equivalent electron component (electrons+their radiation) with energy density e8.5×10–7 eV cm–3, while the density of the observed diffuse X-ray radiation alone is 100 times higher. This requires the existence of other neutrino sources and we found the minimized neutrino flux under two limitations: (1) the power-law generation spectrum of protons and (2) production of the observed energy density of the diffuse X-an -radiation. These requirements are met in the evolutionary model of origin of the metagalactic cosmic rays with modern energy density M83.6×10–7 eV cm–3.The possibility of experiments with cosmic neutrinos of energyE v 3×1017 eV is discussed. The upper bound on neutrino-nucleon cross-section <2.2×10–29 cm2 is obtained in evolutionary model from the observed zenith angular distribution of extensive air showers.In Appendix 2 the diffuse X-and -ray flux arising together with neutrino flux is calculated. It agrees with observed flux in the entire energy range from 1 keV up to 100 MeV.  相似文献   

15.
Rocket measurements, of the diffuse X-ray background in the energy range 2–18 keV, conducted from Thumba Equatorial Rocket Launching Station (TERLS), India, are presented. The estimates of the cosmic background are derived by the method which employs the Earth and its atmosphere as a shutter to intercept the celestial X-rays. The results are shown to be consistent with a power law photon spectrum.13.6 –3.3 +4.3 E –1.73±0.15 photons/cm2-sec-keV-ster the spectrum being much flatter than that observed at higher energies.  相似文献   

16.
We investigate the problem of transition from galactic cosmic rays to extragalactic ultra-high energy cosmic rays. Using the model for extragalactic ultra-high energy cosmic rays and observed all-particle cosmic ray spectrum, we calculate the galactic spectrum of iron nuclei in the energy range 108–109 GeV. The flux and spectrum predicted at lower energies agree well with the KASCADE data. The transition from galactic to extragalactic cosmic rays is distinctly seen in spectra of protons and iron nuclei, when they are measured separately. The shape of the predicted iron spectrum agrees with the Hall diffusion.  相似文献   

17.
A new imaging balloon-borne telescope for hard X-rays in the energy range from 30 to 100 keV is described. The imaging capability is provided by the use of an extended URA-based coded-mask. With only one motor and suitable stop pins, we can rotate a carbon-fiber wheel with most of the mask elements attached to it by 180°, and a bar, which is also part of the mask pattern and is allowed to rotate freely over the wheel, by 90°; this combined rotation creates an antimask of the original mask, except for the central element. This is a novel and elegant manner of providing an antimask without additional weight and complex mechanical manipulations. We show that the use of antimasks is a very effective method of eliminating systematic variations in the background map over the position-sensitive detector area. The expected sensitivity of the instrument for the 30–100 keV range is of the order of 7 × 10-5 photons cm-2 s-1 keV-1, for an integration time of 104 seconds at a residual atmosphere of 3.5 g cm-2. This telescope will provide imaging observations of bright galactic hard X-ray sources with an angular resolution of 2° in a 10° by 10° FOV, which is defined by a collimator placed in front of the detector system. We are particularly interested in the galactic center region, where recent imaging results in X-rays have shown the presence of an interesting source field. Results of computer simulations of the imaging system are reported.  相似文献   

18.
The hydrogen column density along the line of sight to Cyg X-1 is 7×1021 cm–2 as determined from the extinction of its optical counterpart HD 226 868. This value may be used to interpret soft X-ray measurements, including those previously reported, where it is not possible to determine the column density independently from the intrinsic spectral function. The correction for interstellar absorption is larger than previously thought. Application to an old observation suggests that an intense soft X-ray component was present in Cyg X-1, even though the data at 1 keV suggests that it was probably in a low state. This is consistent with the picture of Cyg X-1 suggested by Price and Thorne, in which transitions in Cyg X-1 are attributed to changes in the high energy cut-off of an intense soft component.Paper presented at the COSPAR Symposium on Fast Transients in X-and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.  相似文献   

19.
In the galactic latitude range 40°<|b|<80° several extinction indicators of extragalactic type show features with similar longitude dependence. Amplitudes of these variations correspond toB-extinction variations of about 0 . m 3–0 . m 4. The results favour the view that instead of nearly zero extinction, there are significant amounts of dust at high galactic latitudes.  相似文献   

20.
The diffuse far UV radiation ( 1350–1480 Å) observed in the sky region ofl II180°, 0°b II40° is analyzed in connection with the distributions of stars and dust grains as well as with optical properties of grains. Its intensity (starlight+scattered light) is about 6×10–7 erg cm–2 sec–1 sr–1 Å–1 in the direction ofb II0° andl II180°. The latitude dependence of the intensity is in approximate agreement with the plane parallel slab model of the galaxy with a reasonable set of parameters. The interstellar scattering gives an albedo close to unity and forward phase function of about 0.6, which are not inconsistent with the model of interstellar grains of Wickramasinghe. The upper limit of the extragalactic UV is 2×10–8 erg cm–2 sec–1 sr–1 Å–1 in the same region of wave-length.  相似文献   

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