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1.
We present the observations of an intense X-ray burst from the recurrent transient source SAXJ1747.0-2853 located near the Galactic center. The burst was detected by the ART-P telescope onboard the Granat observatory on October 20, 1991. The burst time profile exhibits features that clearly point to an increase in the photospheric radius of the neutron star at the burst onset. This increase is attributable to an expansion of its outer hydrogen-rich atmospheric envelope under radiation pressure. After hydrogen-envelope outflow and photospheric contraction, the radiation flux emerging from deep within the star continued to rise, which several seconds later led to a recurrent, weaker photospheric expansion attributable to the outflow of the outer helium-envelope layers. Based on the described picture, we determined the distance to the source, d=7.9±0.4 kpc. No radiation was detected by the ART-P telescope from the source in quiescence. Actually, the source itself was discovered only seven years later by the BeppoSAX satellite during its X-ray activity.  相似文献   

2.
We present the results of our study of the emission from the transient burster MX 0836-42 using its observations by the INTEGRAL and RXTE X-ray and gamma-ray observatories in the period 2003–2004. The source’s broadband X-ray spectrum in the energy range 3–120 keV has been obtained and investigated for the first time. We have detected 39 X-ray bursts from this source. Their analysis shows that the maximum 3–20-keV flux varies significantly from burst to burst, F ～ (0.5–1.5) × 10?8 erg cm?2 s?1. Using the flux at the maximum of the brightest detected burst, we determined an upper limit for the distance to the source, D ? 8 kpc.  相似文献   

3.
We present X-ray images from the P78-1 satellite for a long-lasting burst at 20 cm wavelength mapped with the Very Large Array on 19 May, 1979 by Velusamy and Kundu (1981). The decimeter wave observations were originally interpreted in terms of two models, one invoking thermal electrons radiating at low harmonics of the gyrofrequency, and the other invoking mildly relativistic electrons emitting gyrosynchrotron radiation. If indeed the 20 cm source is thermal, it should also be visible in soft X-rays, while if it is nonthermal, the soft X-ray emission should be weak or spatially or temporally distinct from the 20 cm burst. We find that only one of the three 20 cm sources was approximately co-spatial with the soft X-ray source, and that it was only partially thermal. The 20 cm burst is therefore primarily decimeter type IV emission from mildly relativistic electrons of the post-flare phase. The long lifetime (? 2h) and smooth temporal variation of the burst belie its nonthermal nature and suggest continuous acceleration as well as long term storage of energetic electrons.  相似文献   

4.
While all but one of the gamma-ray bursts observed in the X-ray band showed an X-ray afterglow, about 60 per cent of them have not been detected in the optical band. We demonstrate that in many cases this is not as a result of adverse observing conditions, or delay in performing the observations. We also show that the optically non-detected afterglows are not affected by particularly large Galactic absorbing columns, since its distribution is similar for both the detected and non-detected burst subclasses. We then investigate the hypothesis that the failure of detecting the optical afterglow is due to absorption at the source location. We find that this is a marginally viable interpretation, but only if the X-ray burst and afterglow emission and the possible optical/UV flash do not destroy the dust responsible for absorption in the optical band. If dust is efficiently destroyed, we are led to conclude that bursts with no detected optical afterglow are intrinsically different. Prompt infrared observations are the key to solving this issue.  相似文献   

5.
We present the results of the analysis of Rossi X-ray Timing Explorer ( RXTE ) observations of the new X-ray transient, SWIFT J1753.5−0127, during its outburst in 2005 July. The source was caught at the peak of the burst with a flux of 7.19e-09 erg s−1cm−2 in the 3–25 keV energy range and observed until it decreased by about a factor of 10. The photon index of the power-law component, which is dominant during the entire outburst, decreases from ∼1.76 to 1.6. However, towards the end of the observations the photon index is found to increase, indicating a softening of the spectra. The presence of an ultrasoft thermal component, during the bright phases of the burst, is clear from the fits to the data. The temperature associated with this thermal component is 0.4 keV. We believe that this thermal component could be due to the presence of an accretion disc. Assuming a distance of 8.5 kpc,   L X/ L Edd≃ 0.05  at the peak of the burst, for a black hole of mass  10 M⊙  . The source is found to be locked in the low/hard state during the entire outburst and likely falls in the category of the X-ray transients that are observed in the low/hard state throughout the outburst. We discuss the physical scenario of the low/hard state outburst for this source.  相似文献   

6.
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7.
MXB 1658-298 is a transient Low-Mass X-ray Binary (LMXB), which shows eclipses, dips and bursts in its light curve. This source has undergone three active periods separated by long quiescent phases. The latest phase of enhanced X-ray emission was observed during 2015–2016. We have analysed broadband data from Swift/XRT and NuSTAR observations carried out in 2015. During NuSTAR observation, one thermonuclear X-ray burst took place. The X-ray emission during the burst was brighter by a factor of \(\sim 200\), compared to the pre-burst emission. This work focuses on the spectral analysis of MXB 1658-298 during the persistent and the burst phases using NuSTAR observation of 2015. We have also determined the temperature and radius evolution during the burst using the time-resolved spectroscopy. The burst phase shows mild Photospheric Radius Expansion (PRE).  相似文献   

8.
The main aim of this paper is to estimate, from multispectral observations, the plasma parameters in a microwave burst source which was also the site of spike emission. This information is essential for the determination of the spike emission process. By analyzing one-dimensional source distributions observed with the SSRT at 5.7 GHz and correlating them with Yohkoh X-ray and Nobeyama 17 GHz images, we have concluded that the microwave emitting region was larger than the soft X-ray loop-top source, and that the origin of the burst could be explained by gyrosynchrotron emission of non-thermal electrons in a magnetic field of approximately 100 G. It has been shown that the source of 5.7 GHz spikes observed during the burst was located close to an SXR-emitting loop with high density and temperature and a relatively low magnetic field. Thus, plasma emission is the most favourable radiation mechanism for the generation of the sub-arc-second microwave pulses.  相似文献   

9.
We present an analysis of the Swift Burst Alert Telescope (BAT) and X-ray telescope (XRT) data of GRB060602B, which is most likely an accreting neutron star in a binary system and not a gamma-ray burst. Our analysis shows that the BAT burst spectrum is consistent with a thermonuclear flash (type I X-ray burst) from the surface of an accreting neutron star in a binary system. The X-ray binary nature is further confirmed by the report of a detection of a faint point source at the position of the XRT counterpart of the burst in archival XMM–Newton data approximately six year before the burst and in more recent XMM–Newton data obtained at the end of 2006 September (nearly four months after the burst). Since the source is very likely not a gamma-ray burst, we rename the source Swift J1749.4−2807, based on the Swift /BAT discovery coordinates. Using the BAT data of the type I X-ray burst, we determined that the source is at most at a distance of  6.7 ± 1.3 kpc  . For a transiently accreting X-ray binary, its soft X-ray behaviour is atypical: its 2–10 keV X-ray luminosity (as measured using the Swift /XRT data) decreased by nearly three orders of magnitude in about 1 day, much faster than what is usually seen for X-ray transients. If the earlier phases of the outburst also evolved this rapidly, then many similar systems might remain undiscovered because the X-rays are difficult to detect and the type I X-ray bursts might be missed by all the sky surveying instruments. This source might be part of a class of very fast transient low-mass X-ray binary systems of which there may be a significant population in our Galaxy.  相似文献   

10.
We propose to explain the recent observations of gamma-ray burst early X-ray afterglows with SWIFT by the dissipation of energy in the reverse shock that crosses the ejecta as it is decelerated by the burst environment. We compute the evolution of the dissipated power and discuss the possibility that a fraction of it can be radiated in the X-ray range. We show that this reverse shock contribution behaves in a way very similar to the observed X-ray afterglows if the following two conditions are satisfied. (i) The Lorentz factor of the material which is ejected during the late stages of source activity decreases to small values  Γ < 10  and (ii) a large part of the shock-dissipated energy is transferred to a small fraction  (ζ≲ 10−2)  of the electron population. We also discuss how our results may help to solve some puzzling problems raised by multiwavelength early afterglow observations such as the presence of chromatic breaks.  相似文献   

11.
Using the X-ray data from the SMM Satellite and the optical data from the Yunnan Observatory, we analysed the Class 3B flare of 1980 July 14. We obtained the time variation of the X-ray spectrum, calculated the total number of electrons at the time of the flare and their mean energy and measured and compared the positions of the Hα flare and the X-ray burst source. The results show 1) that the hard X-ray burst was caused by high-energy non-thermal electron beam; 2) that the soft X-ray burst was basically generated by thermal bremsstrahlung of hot plasma, but the contribution by non-thermal electrons must also be included; 3) that the determined height of the X-ray burst source depends on the flare model and the magnetic field configuration of the active region. The results obtained support the newly emergent flux model of flares.  相似文献   

12.
We consider the very-high-energy (VHE) gamma-ray observations of the blazar 1ES 2344+514 in 2003 in comparison with the data of its ASM/RXTE X-ray monitoring. A VHE gamma-ray flux was detected from the observed object at a confidence level of ≈ 5σ and it was estimated to be 1.85 ± 0.68 Crab (E ≥ 1 TeV). The observations revealed a VHE gamma-ray burst from the object that occurred in September 2003 and that lasted for no more than 4 days. The burst was also confirmed in the X-ray (2–12 keV) energy range. Analysis of the observational data showed evidence of a correlation between the fluxes in the two energy ranges and invoking the previous observations of 1ES 2344+514 in 2002 allowed this correlation to be refined in a wide range of fluxes.  相似文献   

13.
We have observed the eclipsing low-mass X-ray binary MS 1603.6+2600 with Chandra for 7 ks. The X-ray spectrum is well fit with a single absorbed power law with an index of ∼2. We find a clear sinusoidal modulation in the X-ray light curve with a period of  1.7 ± 0.2 h  , consistent with the period of 1.85 h found before. However, no (partial) eclipses were found. We argue that if the X-ray flare observed in earlier X-ray observations was a type I X-ray burst, then the source can only be an accretion disc corona source at a distance of ∼11–24 kpc (implying a height above the Galactic disc of ∼8–17 kpc). It has also been proposed in the literature that MS 1603.76+2600 is a dipper at ∼75 kpc. We argue that, in this dipper scenario, the observed optical properties of MS 1603.6+2600 are difficult to reconcile with the optical properties one would expect on the basis of comparisons with other high-inclination, low-mass X-ray binaries, unless the X-ray flare was not a type I X-ray burst. In that case, the source can be a nearby soft X-ray transient accreting at a quiescent rate, as was proposed by Hakala et al., or a high-inclination source at ∼15–20 kpc.  相似文献   

14.
Klassen  A.  Karlický  M.  Aurass  H.  Jiřička  K. 《Solar physics》1999,188(1):141-154
Due to the emission of shock-accelerated electrons, broadband radio observations display propagating super Alfvénic shock waves in the low corona ('type II bursts'). We study the 9 July 1996 flare (AR NOAA 7978) focusing on the aspect of shock generation. This event's radio spectrogram shows two different type II bursts in sequence. Radio imaging data (Paris, Meudon Observatory) reveal that both bursts appear at different sites above the H flare. The driver of the first type II burst seems to propagate with twice the speed of the second one. The projected source site of the first type II burst (seen earlier and at higher frequencies) is spatially situated further away from the H flare site than the source of the second type II burst. We try to understand this by comparing with Yohkoh soft X-ray images. The first shock source occurs near the top of high soft X-ray loop structures. Its driver can be a guided fast mode magnetic disturbance. The second type II source appears in-between two high soft X-ray loop systems. This might be a piston-driven disturbance powered by an evaporation front. We get a consistent picture only by assuming a very inhomogeneous Alfvén speed in the active region's atmosphere.  相似文献   

15.
The existence of either pre- or post-burst emission can provide substantial new information about the burst source and its local environment. We have data from serveral events serendipitously in or near the OSSE field of view at the time of the burst. We present pre- and post-burst flux limits from one such event, GRB 940301. The OSSE data for other periods when scheduled observations have included burst locations will enable us to search for pre- and post- burst emission on many time scales.  相似文献   

16.
We present a discussion of the gradual burst event on May 13,1985 which is based on observations of the RATAN-600 telescope at ten fixed frequencies in the range between 37.5 and 0.95 GHz (0.8 and 31.6 cm wavelength) and on time profiles of patrol observations of the Observatory for Solar Radio Astronomy at Tremsdorf near Potsdam. This up to now most complete data set allows new conclusions on the extended spectral/spatial structure of the source region.There is strong evidence that only less than 24% of the microwave flux from this event is emitted by an excessive small-scale burst source while the bulk of the burst emission comes from a larger region consisting of two major components covered by the source area of the S-component radiation. The different components of the burst and S-component radiation are analyzed.  相似文献   

17.
We have discovered a triple-peaked X-ray burst from the low-mass X-ray binary (LMXB) 4U 1636−53 with the Rossi X-ray Timing Explorer ( RXTE ). This is the first triple-peaked burst reported from any LMXB using RXTE , and it is only the second burst of this kind observed from any source. (The previous one was also from 4U 1636−53, and was observed with EXOSAT .) From fits to time-resolved spectra, we find that this is not a radius-expansion burst, and the same triple-peaked pattern seen in the X-ray light curve is also present in the bolometric light curve of the burst. Similar to what was previously observed in double-peaked bursts from this source, the radius of the emitting area increases steadily during the burst, with short periods in between during which the radius remains more or less constant. The temperature first increases steeply, and then decreases across the burst also showing three peaks. The first and last peak in the temperature profile occur, respectively, significantly before and after the first and last peaks in the X-ray and bolometric light curves. We found no significant oscillations during this burst. This triple-peaked burst, as well as the one observed with EXOSAT and the double-peak bursts in this source, all took place when 4U 1636−53 occupied a relatively narrow region in the colour–colour diagram, corresponding to a relatively high (inferred) mass-accretion rate. No model presently available is able to explain the multiple-peaked bursts.  相似文献   

18.
With the observations from Rossi X-ray Timing Explorer, we search and study the X-ray bursts of accreting millisecond X-ray pulsar SAX J1748.9-2021 during its 2010 outburst. We find 13 X-ray bursts, including 12 standard type-I X-ray bursts and an irregular X-ray burst which lacks cooling tail. During the outburst, the persistent emission occurred at \(\sim (1\mbox{--}5)\%{\dot{\mathrm{M}}_{\mathrm{Edd}}}\). We use a combination model of a blackbody (BB), a powerlaw, and a line component to fit the persistent emission spectra. Another BB is added into the combination model to account for the emission of the X-ray bursts due to the thermonuclear burning on the surface of the neutron star. Finally, we modify the combination model with a multiplicative factor \(f_{\mathrm{a}}\), plus a BB to fit the spectra during the X-ray bursts. It is found that the \(f_{\mathrm{a}}\) is inversely correlated with the burst flux in some cases. Our analysis suggests that the ignition depth of the irregular X-ray burst is obviously smaller than those of the type-I X-ray bursts. We argue that the detected type-I X-ray bursts originate from helium-rich or pure-helium environment, while the irregular X-ray burst originates from the thermonuclear flash in a shallow ocean.  相似文献   

19.
We present the preliminary results of our analysis of the observations of the X-ray pulsar SAX J2103.5+4545 by the INTEGRAL Observatory in December 2002. We mapped this region of the sky in a wide energy range, from 3 to 200 keV. The detection of the source is shown to be significant up to energies of ～100 keV. The hard X-ray flux in the energy range 15–100 keV is variable and presumably depends on the orbital phase. We show that the shape of the pulsar spectrum and its parameters derived from 18–150-keV IBIS data are compatible with the RXTE observations of the source.  相似文献   

20.
We investigate the X-ray emission from the central regions of the prototypical starburst galaxy M82. Previous observations have shown a bright central X-ray point source, with suggestions as to its nature including a low-luminosity active galactic nucleus or an X-ray binary. A new analysis of ROSAT HRI observations finds four X-ray point sources in the central kiloparsec of M82, and we identify radio counterparts for the two brightest X-ray sources. The counterparts are probably young radio supernovae (SNe) and are amongst the most luminous and youthful SNe in M82. We therefore suggest that we are seeing X-ray emission from young SNe in M82, and in particular that the brightest X-ray source is associated with the radio source 41.95+57.5. We discuss the implications of these observations for the evolution of X-ray-luminous SNe.  相似文献   

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