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1.
D. I. Karasev A. A. Lutovinov M. G. Revnivtsev R. A. Krivonos 《Astronomy Letters》2012,38(10):629-637
We present the results of Chandra and XMM-Newton observations for six hard X-ray sources (IGR J12134-6015, IGR J18293-1213, IGR J18219-1347, IGR J17350-2045, IGR J18048-1455, XTE J1901+014) from the INTEGRAL all-sky survey. Based on these observations, we have improved significantly the localization accuracy of the objects and, therefore, have managed to identify their optical counterparts. Using data from the publicly available 2MASS and UKIDSS infrared sky surveys as well as data from the SOFI/NTT telescope (European Southern Observatory), we have determined the magnitudes of the optical counterparts, estimated their types and (in some cases) the distances to the program objects. A triplet of iron lines with energies of 6.4, 6.7, and 6.9 keV has been detected in the X-ray spectrum of IGR J18048-1455; together with the detection of pulsations with a period of ～1440 s from this source, this has allowed it to be classified as a cataclysmic variable, most likely an intermediate polar. In addition, broadband X-ray spectra of IGR J12134-6015 and IGR J17350-2045 in combination with infrared and radio observations suggest an extragalactic nature of these objects. The source IGR J18219-1347 presumably belongs to the class of high-mass X-ray binaries. 相似文献
2.
The X-ray source IGR J16318-4848 was the first source discovered by INTEGRAL on January 29, 2003. The high energy spectrum
exhibits such a high column density that the source is undetectable in X-rays below 2 keV. On February 23–25, 2003 we triggered
a Target of Opportunity (ToO) Program using the EMMI and SOFI instruments on the New Technology Telescope of the European
Southern Observatory (La Silla) to get optical and near-infrared (NIR) observations. We discovered the optical counterpart,
and confirmed the already proposed candidate in the NIR. NIR spectroscopy revealed a large amount of emission lines, including
forbidden iron lines and P-Cygni profiles, showing a strong similarity with CI Cam, another strongly absorbed source. Together
with the spectral energy distribution (SED), these data point to a high luminosity, high temperature source, with an intrinsic
absorption greater than the interstellar absorption, but two orders of magnitude below the X-ray absorption. All these observations
show that IGR J16318-4848 is a high mass X-ray binary (HMXB) at a distance between 0.9 and 6.2 kpc, the mass donor being an
early-type star, probably a sgB[e] star, surrounded by a dense and absorbing circumstellar material. This would make the second
HMXB with a sgB[e] star as the mass donor after CI Cam.
Other sources, discovered by INTEGRAL near IGR J16318-4848 in the direction of the Norma arm, present the same characteristics,
at least in X-rays. Such sources may represent a different evolutionary state of X-ray binaries previously undetected with
the lower energy space telescopes; if it is so, a new class of strongly absorbed X-ray binaries is being unveiled by INTEGRAL.
Out of the 15 sources present in this region, only one might be associated with an unidentified EGRET source: IGR J16393-4643.
Therefore these obscured INTEGRAL sources do not seem to be powerful high energy (E > 100 MeV) emitters.
Based on observations collected at the European Southern Observatory, Chile (proposal ESO N∘ 70.D-0340). 相似文献
3.
J. B. Stevens M. J. Coe D. A. H. Buckley 《Monthly notices of the Royal Astronomical Society》1999,309(2):421-429
The fields of eight X-ray sources in the Magellanic Clouds believed to be Be/X-ray binaries have been searched for possible Be-star counterparts. BVR c and H α CCD imaging was employed to identify early-type emission stars through colour indices and H α fluxes. Spectroscopy of five sources confirms the presence of H α emission in each case. Based on the positional coincidence of emission-line objects with the X-ray sources, we identify Be-star counterparts to the ROSAT sources RX J0032.9-7348, RX J0049.1-7250, RX J0054.9-7226 and RX J0101.0-7206, and to the recently discovered ASCA source AX J0051-722. We confirm the Be star nature of the counterpart to the HEAO1 source H0544-66. In the field of the ROSAT source RX J0051.8-7231 we find that there are three possible counterparts, each showing evidence for H α emission. We find a close double in the error circle of the EXOSAT source EXO 0531.1-6609, each component of which could be a Be star associated with the X-ray source. 相似文献
4.
E. V. Filippova S. S. Tsygankov A. A. Lutovinov R. A. Sunyaev 《Astronomy Letters》2005,31(11):729-747
We present spectra for 34 accretion-powers X-ray pulsars and one millisecond pulsar that were within the field of view of the INTEGRAL observatory over two years (December 2002–January 2005) of its in-orbit operation and that were detected by its instruments at a statistically significant level (> 8σ in the energy range 18–60 keV). There are seven recently discovered objects of this class among the pulsars studied: 2RXP J130159.6-635806, IGR/AX J16320-4751, IGR J16358-4726, AX J163904-4642, IGR J16465-4507, SAX/IGR J18027-2017, and AX J1841.0-0535. We have also obtained hard X-ray (>20 keV) spectra for the accretion-powered pulsars RX J0146.9+6121, AX J1820.5-1434, and AX J1841.0-0535 for the first time. We analyze the evolution of spectral parameters as a function of the intensity of the sources and compare these with the results of previous studies. 相似文献
5.
D. C. Hannikainen M. G. Rawlings P. Muhli O. Vilhu J. Schultz J. Rodriguez 《Monthly notices of the Royal Astronomical Society》2007,380(2):665-668
The International Gamma-Ray Astrophysics Laboratory observatory has been (re-)discovering new X-ray sources since the beginning of nominal operations in early 2003. These sources include X-ray binaries, active galactic nuclei, cataclysmic variables, etc. Amongst the X-ray binaries, the true nature of many of these sources has remained largely elusive, though they seem to make up a population of highly absorbed high-mass X-ray binaries. One of these new sources, IGR J19140+0951, was serendipitously discovered on 2003 March 6 during an observation of the galactic microquasar GRS 1915+105. We observed IGR J19140+0951 with the United Kingdom Infrared Telescope in order to identify the infrared counterpart. Here we present the H - and K -band spectra. We determined that the companion is a B0.5-type bright supergiant in a wind-fed system, at a distance ≲5 kpc. 相似文献
6.
We present the results of our analysis of the RXTE observations for two transient sources, IGR J17091-3624 and IGR J18539+0727, in April 2003. The derived energy spectra of the sources and the power-density spectra of their light curves make it possible to classify them as low/hard-state X-ray binaries. The parameters of the power spectrum for IGR J18539+0727 lead us to tentatively conclude that the compact object in this binary is a black hole. 相似文献
7.
We present results of optical identifications of six hard X-ray sources from the INTEGRAL and Swift all-sky surveys (IGR J03249+4041,
SWIFT J1449.5+8602, SWIFT J1542.0-1410, IGR J17009+3559, IGR J18151-1052, IGR J18538-0102). Our optical observations were
performed in 2009–2011 with the 6-m BTA telescope (Special Astrophysical Observatory, Nizhnii Arkhyz, Russia) and the 1.5-m
RTT-150 telescope (Turkish National Observatory, Antalya, Turkey). The optical spectra obtained for each of the program sources
have allowed us to establish the nature of the objects and to measure their redshifts from the positions of emission and absorption
lines. Five sources are shown to be extragalactic—four of them are identified with Seyfert 1 or 2 galaxies and the fifth source
belongs to the class of X-ray-bright, optically normal galaxies (XBONGs). The sixth object (IGR J18151-1052) is located in
our Galaxy and is an X-ray binary (XRB), a suspected cataclysmic variable. Apart from the optical spectra, we provide the
X-ray spectra for five sources in the 0.6–10 keV energy band obtained from XRT/Swift data. 相似文献
8.
M. G. Revnivtsev 《Astronomy Letters》2003,29(10):644-648
We analyzed the RXTE observations of two strongly absorbed sources, IGR J16318-4848 and IGR J16358-4726. We were able to obtain the 3–25 keV spectra of the sources by taking into account the contribution of the Galactic diffuse background to the X-ray flux recorded with the RXTE/PCA spectrometer. The spectra of the sources are well described by a power-law decrease of the photon flux with energy with a photon index of ～1 and strong photoabsorption. The photoabsorption column density nHL for IGR J16318-4848 derived from the RXTE observation on March 14.1, 2003, is shown to be much higher than its value obtained by the XMM observatory on February 10.7, 2003. This result may suggest that the source has variable absorption that may depend on the orbital phase of the system. We point out that all of the three X-ray sources discovered by the INTEGRAL observatory in the region (l,b)～(336,0) (IGR J16318-4848, IGR J16320-4751, and IGR J16358-4726) have strong intrinsic photoabsorption and may be high-mass binaries. Their proximity to the region where the tangent to the Galactic spiral arm passes, i.e., to the region of enhanced concentration of young high-mass stars, can serve as an indirect confirmation of this assumption. If our assumption about the positions of the sources in the Norma spiral arm is valid, then we can roughly estimate their heliocentric distances: ～6–8 kpc. 相似文献
9.
We suggest that the mass of four compact stars SAX J1808.4-3658, KS 1731-260, SAX J1750.8-2900 and IGR J17191-2821 can be determined from the difference in the observed kiloHertz quasi periodic oscillations (kHz QPO-s) of these stars. The stellar radius is very close to the marginally stable orbit Rms as predicted by Einstein’s general relativity. It may be noted that the first of these stars was suggested to be a strange star more than a decade back by Li et al. (1999a) from the unique millisecond X-ray pulsations with an accurate determination of its rotation period. It showed kHz QPO-s eight years back and so far it is the only set that has been observed. This is the first time we give an estimate of the mass of the star and of three other compact stars in low-mass X-ray binaries using their observed kHz QPO-s. 相似文献
10.
The discovery of kilohertz quasi-periodic oscillations (kHz QPOs) in low-mass X-ray binaries (LMXBs) with the Rossi X-Ray Timing Explorer has stimulated extensive studies of these sources. Recently, Osherovich & Titarchuk suggested a new model for kHz QPOs and the related correlations between kHz QPOs and low-frequency features in LMXBs. Here we use their results to study the mass-radius relation for the atoll source 4U 1728-34. We find that, if this model is correct, 4U 1728-34 is possibly a strange star rather than a neutron star. 相似文献
11.
D. I. Karasev A. A. Lutovinov A. Yu. Tkachenko G. A. Khorunzhev R. A. Krivonos P. S. Medvedev M. N. Pavlinsky R. A. Burenin M. V. Eselevich 《Astronomy Letters》2018,44(8-9):522-540
We present the results of our optical identifications of several hard X-ray sources from the INTEGRAL all-sky survey obtained over 14 years of observations. Having improved the positions of these objects in the sky with the X-ray telescope (XRT) of the Swift observatory and the XMMNewton observatory, we have identified their counterparts using optical and infrared sky survey data. We have obtained optical spectra for more than half of the objects from our sample with the RTT-150 and AZT-33IK telescopes, which have allowed us to establish the nature of the objects and to measure their redshifts. Six sources are shown to be extragalactic in origin and to belong to Seyfert 1 and 2 galaxies (IGR J01017+6519, IGR J08215-1320, IGR J08321-1808, IGR J16494-1740, IGR J17098-2344, IGR J17422-2108); we have failed to draw definitive conclusions about the nature of four more objects (IGR J11299-6557, IGR J14417-5533, IGR J18141-1823, IGR J18544+0839), but, judging by circumstantial evidence, they are most likely also extragalactic objects. For one more object (IGR J18044-1829) no unequivocal identification has been made. 相似文献
12.
A. A. Lutovinov A. I. Mironov R. A. Burenin M. G. Revnivtsev S. S. Tsygankov M. N. Pavlinsky I. V. Korobtsev M. V. Eselevich 《Astronomy Letters》2013,39(8):513-522
Four hard X-ray sources from the INTEGRAL and Swift catalogs have been identified. X-ray and optical spectra have been obtained for each of the objects being studied by using data from the INTEGRAL, Swift, ROSAT, and Chandra X-ray observatories as well as observations with the RTT-150 and AZT-33IK optical telescopes. Two sources (SWIFT J1553.6+2606 and SWIFT J1852.2+8424) are shown to be extragalactic in nature: the first is a quasar, while the recordedX-ray flux from the second is the total emission from two Seyfert 1 galaxies at redshifts 0.1828 and 0.2249. The source IGR J22534+6243 resides in our Galaxy and is an X-ray pulsar with a period of ～46.674 s that is a member of a high-mass X-ray binary with a Be star. The nature of yet another Galactic source, SWIFT J1852.8+3002, is not completely clear and infrared spectroscopy is needed to establish it. 相似文献
13.
L. Ducci L. Sidoli S. Mereghetti A. Paizis P. Romano 《Monthly notices of the Royal Astronomical Society》2009,398(4):2152-2165
We have developed a stellar wind model for OB supergiants to investigate the effects of accretion from a clumpy wind on the luminosity and variability properties of high-mass X-ray binaries. Assuming that the clumps are confined by ram pressure of the ambient gas and exploring different distributions for their mass and radii, we computed the expected X-ray light curves in the framework of the Bondi–Hoyle accretion theory, modified to take into account the presence of clumps. The resulting variability properties are found to depend not only on the assumed orbital parameters but also on the wind characteristics. We have then applied this model to reproduce the X-ray light curves of three representative high-mass X-ray binaries: two persistent supergiant systems (Vela X−1 and 4U 1700−377) and the supergiant fast X-ray transient IGR J11215−5952. The model can reproduce the observed light curves well, but requiring in all cases an overall mass loss from the supergiant about a factor of 3–10 smaller than the values inferred from ultraviolet lines studies that assume a homogeneous wind. 相似文献
14.
L. Sidoli P. Romano L. Ducci A. Paizis G. Cusumano V. Mangano H. A. Krimm S. Vercellone D. N. Burrows J. A. Kennea N. Gehrels 《Monthly notices of the Royal Astronomical Society》2009,397(3):1528-1538
We report on new X-ray outbursts observed with Swift from three Supergiant Fast X-ray Transients (SFXTs): XTE J1739−302, IGR J17544−2619 and IGR J08408−4503. XTE J1739−302 underwent a new outburst on 2008 August 13, IGR J17544−2619 on 2008 September 4 and IGR J08408−4503 on 2008 September 21. While the XTE J1739−302 and IGR J08408−4503 bright emission triggered the Swift /Burst Alert Telescope, IGR J17544−2619 did not, thus we could perform a spectral investigation only of the spectrum below 10 keV. The broad-band spectra from XTE J1739−302 and IGR J08408−4503 were compatible with the X-ray spectral shape displayed during the previous flares. A variable absorbing column density during the flare was observed in XTE J1739−302 for the first time. The broad-band spectrum of IGR J08408−4503 requires the presence of two distinct photon populations, a cold one (∼0.3 keV) most likely from a thermal halo around the neutron star and a hotter one (1.4–1.8 keV) from the accreting column. The outburst from XTE J1739−302 could be monitored with a very good sampling, thus revealing a shape which can be explained with a second wind component in this SFXT, in analogy to what we have suggested in the periodic SFXT IGR J11215−5952. The outburst recurrence time-scale in IGR J17544−2619 during our monitoring campaign with Swift suggests a long orbital period of ∼150 d (in a highly eccentric orbit), compatible with what previously observed with INTEGRAL . 相似文献
15.
J. Wang H. K. Chang C. M. Zhang D. H. Wang L. Chen J. L. Qu L. M. Song 《Astrophysics and Space Science》2012,342(2):357-364
We take the recently published data of twin kHz quasi-period oscillations (QPOs) in neutron star (NS) low-mass X-ray binaries (LMXBs) as the samples, and investigate the morphology of the samples, which focuses on the quality factor, peak frequency of kHz QPOs, and try to infer their physical mechanism. We notice that: (1) The quality factors of upper kHz QPOs are low (2～20 in general) and increase with the kHz QPO peak frequencies for both Z and Atoll sources. (2) The distribution of quality factor versus frequency for the lower kHz QPOs are quite different between Z and Atoll sources. For most Z source samples, the quality factors of lower kHz QPOs are low (usually lower than 15) and rise steadily with the peak frequencies except for Sco X-1, which drop abruptly at the frequency of about 750 Hz. While for most Atoll sources, the quality factors of lower kHz QPOs are very high (from 2 to 200) and usually have a rising part, a maximum and an abrupt drop. (3) There are three Atoll sources (4U 1728-34, 4U 1636-53 and 4U 1608-52) of displaying very high quality factors for lower kHz QPOs. These three sources have been detected with the spin frequencies and sidebands, in which the source with higher spin frequency presents higher quality factor of lower kHz QPOs and lower difference between sideband frequency and lower kHz QPO frequency. 相似文献
16.
In this work a new family of relativistic models of electrically charged compact star has been obtained by solving Einstein–Maxwell field equations with preferred form of one of the metric potentials and a suitable form of electric charge distribution function. The resulting equation of state (EOS) has been calculated. The relativistic stellar structure for matter distribution obtained in this work may reasonably models an electrically charged compact star whose energy density associated with the electric fields is on the same order of magnitude as the energy density of fluid matter itself (e.g. electrically charged bare strange stars). Based on the analytic model developed in the present work, the values of the relevant physical quantities have been calculated by assuming the estimated masses and radii of some well known strange star candidates like X-ray pulsar Her X-1, millisecond X-ray pulsar SAX J 1808.4-3658, and 4U 1820-30. 相似文献
17.
Magaretha L. Pretorius 《Monthly notices of the Royal Astronomical Society》2009,395(1):386-393
The European Space Agency γ-ray telescope, INTEGRAL , is detecting relatively more intrinsically rare cataclysmic variables (CVs) than were found by surveys at lower energies. Specifically, a large fraction of the CVs that are INTEGRAL sources consists of asynchronous polars and intermediate polars (IPs). IP classifications have been proposed for the majority of CVs discovered by INTEGRAL , but, in many cases, there is very little known about these systems. In order to address this, I present time-resolved optical data of five CVs discovered through INTEGRAL observations. The white dwarf spin modulation is detected in high-speed photometry of three of the new CVs (IGR J15094−6649, IGR J16500−3307 and IGR J17195−4100), but two others (XSS J12270−4859 and IGR J16167−4957) show no evidence of magnetism, and should be considered unclassified systems. Spectroscopic orbital period ( P orb ) measurements are also given for IGR J15094−6649, IGR J16167−4957, IGR J16500−3307 and IGR J17195−4100. 相似文献
18.
C. M. Zhang H. X. Yin Y. H. Zhao F. Zhang L. M. Song 《Monthly notices of the Royal Astronomical Society》2006,366(4):1373-1377
We analyzed the recently published kHz quasi-period oscillaiton (QPO) data in the neutron star low-mass X-ray binaries (LMXBs), in order to investigate the different correlations of the twin-peak kHz QPOs in bright Z sources and in the less luminous Atoll sources. We find a power-law relation ν1 ∼ν b 2 between the upper and the lower kHz QPOs with different indices: b ≃ 1.5 for the Atoll source 4U 1728-34 and b ≃ 1.9 for the Z source Sco X-1. The implications of our results for the theoretical models for kHz QPOs are discussed. 相似文献
19.
Melvyn B. Davies & Brad M. S. Hansen 《Monthly notices of the Royal Astronomical Society》1998,301(1):15-24
We investigate the conditions by which neutron star retention in globular clusters is favoured. We find that neutron stars formed in massive binaries are far more likely to be retained. Such binaries are likely to then evolve into contact before encountering other stars, possibly producing a single neutron star after a common envelope phase. A large fraction of the single neutron stars in globular clusters are then likely to exchange into binaries containing moderate-mass main-sequence stars, replacing the lower-mass components of the original systems. These binaries will become intermediate-mass X-ray binaries (IMXBs), once the moderate-mass star evolves off the main sequence, as mass is transferred on to the neutron star, possibly spinning it up in the process. Such systems may be responsible for the population of millisecond pulsars (MSPs) that has been observed in globular clusters. Additionally, the period of mass-transfer (and thus X-ray visibility) in the vast majority of such systems will have occurred 5–10 Gyr ago, thus explaining the observed relative paucity of X-ray binaries today, given the MSP population. 相似文献
20.
Some new families of electrically charged stellar models of ultra-compact star have been studied. With the help of particular form of one of the metric potentials the Einstein–Maxwell field equations in general relativity have been transformed to a system of ordinary differential equations. The interior matter pressure, energy–density, and the adiabatic sound speed are expressed in terms of simple algebraic functions. The constant parameters involved in the solution have been set so that certain physical criteria satisfied. Based on the analytic model developed in the present work, the values of the relevant physical quantities have been calculated by assuming the estimated masses and radii of some well known potential strange star candidates like X-ray pulsar Her X-1, millisecond X-ray pulsar SAX J 1808.4-3658, and 4U 1820-30. The analytical equations of state of the charged matter distribution may play a significant role in the study of the internal structure of highly compact charged stellar objects in general relativity. 相似文献