Search

Start Over Subject x-ray binary stars Capability Type Simple Cone Search
31. Chandra X-ray sources of NGC 1399
ID:
ivo://CDS.VizieR/J/ApJ/736/90
Title:
Chandra X-ray sources of NGC 1399
Short Name:
J/ApJ/736/90
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a wide-field study of the globular cluster (GC)/low-mass X-ray binary (LMXB) connection in the giant elliptical NGC 1399. The large field of view of the Advanced Camera for Surveys/WFC, combined with Hubble Space Telescope and Chandra high resolution, allow us to constrain the LMXB formation scenarios in elliptical galaxies. We confirm that NGC 1399 has the highest LMXB fraction in GCs of all nearby elliptical galaxies studied so far, even though the exact value depends on galactocentric distance due to the interplay of a differential GC versus galaxy light distribution and the GC color dependence. In fact, LMXBs are preferentially hosted by bright, red GCs out to >5R_eff_ of the galaxy light. The finding that GCs hosting LMXBs follow the radial distribution of their parent GC population argues against the hypothesis that the external dynamical influence of the galaxy affects the LMXB formation in GCs. On the other hand, field-LMXBs closely match the host galaxy light, thus indicating that they are originally formed in situ and not inside GCs. We measure GC structural parameters, finding that the LMXB formation likelihood is influenced independently by mass, metallicity, and GC structural parameters. In particular, the GC central density plays a major role in predicting which GCs host accreting binaries. Finally, our analysis shows that LMXBs in GCs are marginally brighter than those in the field, and in particular the only color-confirmed GC with L_X_>10^39^erg/s shows no variability, which may indicate a superposition of multiple LMXBs in these systems.
32. Classification of Swift and XMM-Newton sources
ID:
ivo://CDS.VizieR/J/A+A/657/A138
Title:
Classification of Swift and XMM-Newton sources
Short Name:
J/A+A/657/A138
Date:
22 Feb 2022
Publisher:
CDS
Description:
With the advent of very large X-ray surveys, an automated classification of X-ray sources becomes increasingly valuable. This work proposes a revisited naive Bayes classification of the X-ray sources in the Swift-XRT and XMM- Newton catalogs into four classes - AGN, stars, X-ray binaries (XRBs), and cataclysmic variables (CVs) - based on their spatial, spectral, and timing properties and their multiwavelength counterparts. An outlier measure is used to identify objects of other natures. The classifier is optimized to maximize the classification performance of a chosen class (here XRBs), and it is adapted to data mining purposes. We augmented the X-ray catalogs with multiwavelength data, source class, and variability properties. We then built a reference sample of about 25000 X-ray sources of known nature. From this sample, the distribution of each property was carefully estimated and taken as reference to assign probabilities of belonging to each class. The classification was then performed on the whole catalog, combining the information from each property. Using the algorithm on the Swift reference sample, we retrieved 99%, 98%, 92%, and 34% of AGN, stars, XRBs, and CVs, respectively, and the false positive rates are 3%, 1%, 9%, and 15%. Similar results are obtained on XMM sources. When applied to a carefully selected test sample, representing 55% of the X-ray catalog, the classification gives consistent results in terms of distributions of source properties. A substantial fraction of sources not belonging to any class is efficiently retrieved using the outlier measure, as well as AGN and stars with properties deviating from the bulk of their class. Our algorithm is then compared to a random forest method; the two showed similar performances, but the algorithm presented in this paper improved insight into the grounds of each classification. This robust classification method can be tailored to include additional or different source classes and can be applied to other X-ray catalogs. The transparency of the classification compared to other methods makes it a useful tool in the search for homogeneous populations or rare source types, including multi-messenger events. Such a tool will be increasingly valuable with the development of surveys of unprecedented size, such as LSST, SKA, and Athena, and the search for counterparts of multi-messenger events.
33. Collinder 261 Chandra sources & optical counterparts
ID:
ivo://CDS.VizieR/J/ApJ/837/130
Title:
Collinder 261 Chandra sources & optical counterparts
Short Name:
J/ApJ/837/130
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first X-ray study of Collinder 261 (Cr261), which at an age of 7Gyr is one of the oldest open clusters known in the Galaxy. Our observation with the Chandra X-Ray Observatory is aimed at uncovering the close interacting binaries in Cr261, and reaches a limiting X-ray luminosity of L_X_~4x10^29^erg/s (0.3-7keV) for stars in the cluster. We detect 107 sources within the cluster half-mass radius r_h_, and we estimate that among the sources with L_X_>~10^30^erg/s, ~26 are associated with the cluster. We identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of Cr261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, we estimate that Cr261 has an approximate mass of 6500M_{sun}_, roughly the same as the old open cluster NGC6791. The X-ray emissivity of Cr261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity.
34. Deep Chandra observations of NGC 4649. I.
ID:
ivo://CDS.VizieR/J/ApJS/204/14
Title:
Deep Chandra observations of NGC 4649. I.
Short Name:
J/ApJS/204/14
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the X-ray source catalog for the Chandra monitoring observations of the elliptical galaxy, NGC 4649 (M60). The galaxy has been observed with Chandra ACIS-S3 in six separate pointings, reaching a total exposure of 299ks. There are 501 X-ray sources detected in the 0.3-8.0keV band in the merged observation or in one of the six individual observations; 399 sources are located within the D_25_ ellipse. The observed 0.3-8.0keV luminosities of these 501 sources range from 9.3x10^36^erg/s to 5.4x10^39^erg/s. The 90% detection completeness limit within the D_25_ ellipse is 5.5x10^37^erg/s. Based on the surface density of background active galactic nuclei (AGNs) and detection completeness, we expect ~45 background AGNs among the catalog sources (~15 within the D_25_ ellipse). There are nine sources with luminosities greater than 10^39^erg/s, which are candidates for ultraluminous X-ray sources. The nuclear source of NGC 4649 is a low-luminosity AGN, with an intrinsic 2.0-8.0keV X-ray luminosity of 1.5x10^38^erg/s. The X-ray colors suggest that the majority of the catalog sources are low-mass X-ray binaries (LMXBs). We find that 164 of the 501 X-ray sources show long-term variability, indicating that they are accreting compact objects. We discover four transient candidates and another four potential transients. We also identify 173 X-ray sources (141 within the D_25_ ellipse) that are associated with globular clusters (GCs) based on Hubble Space Telescope and ground-based data; these LMXBs tend to be hosted by red GCs. Although NGC 4649 has a much larger population of X-ray sources than the structurally similar early-type galaxies, NGC 3379 and NGC 4278, the X-ray source properties are comparable in all three systems.
35. Deep Chandra obs. of X-ray point sources in M87
ID:
ivo://CDS.VizieR/J/ApJ/862/73
Title:
Deep Chandra obs. of X-ray point sources in M87
Short Name:
J/ApJ/862/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of X-ray source populations in M87, the cD galaxy of the Virgo cluster, using 12 archival Chandra observations with a total exposure of ~680ks spanning about a decade. A total of 346 point-like sources are detected down to a limiting 0.5-8keV luminosity of 4x10^37^erg/s and out to a galactocentric radius of ~40kpc. We cross-correlate the X-ray sources with published catalogs of globular clusters (GCs), derived from the ACS Virgo Cluster Survey and the Next Generation Virgo Cluster Survey. This results in 122 matches, making it one of the largest samples of GC-hosting X-ray sources in an external galaxy. These sources, most likely low-mass X-ray binaries (LMXBs), correspond to ~5% of all known GCs within the Chandra field-of-view. Conversely, ~50% of the detected X-ray sources are found in a GC. Moreover, red (metal-rich) GCs are ~2.2 times more likely to host an X-ray source than blue (metal-poor) GCs. We also examine 76 currently known ultra-compact dwarf galaxies around M87 but find no significant X-ray counterparts. After statistically accounting for the cosmic X-ray background, we identify ~110 field-LMXBs. The GC-LMXBs and field-LMXBs differ in their luminosity function and radial distribution, which indicates that the latter cannot be primarily originated from GCs. Using another set of deep Chandra observations toward ~100kpc northwest of the M87 center, we statistically constrain the abundance of field-LMXBs in the stellar halo, which is consistent with that found in the central region. We also identify 40 variable X-ray sources, among which one source is likely a black hole binary residing in a GC.
36. Deep Chandra survey of the SMC. III. HMXBs
ID:
ivo://CDS.VizieR/J/ApJ/887/20
Title:
Deep Chandra survey of the SMC. III. HMXBs
Short Name:
J/ApJ/887/20
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have compiled the most complete census of high-mass X-ray binaries (HMXBs) in the Small Magellanic Cloud with the aim to investigate the formation efficiency of young accreting binaries in its low-metallicity environment. In total, we use 123 X-ray sources with detections in our Chandra X-ray Visionary Program (XVP), supplemented by 14 additional (likely and confirmed) HMXBs identified by Haberl & Sturm (2016, J/A+A/586/A81) that fall within the XVP area, but are neither detected in our survey (nine sources) nor matched with any of the 127 sources identified in the XVP data (five sources). Specifically, we examine the number ratio of the HMXBs [N(HMXBs)] to (a) the number of OB stars, (b) the local star formation rate (SFR), and (c) the stellar mass produced during the specific star formation burst, all as a function of the age of their parent stellar populations. Each of these indicators serves a different role, but in all cases we find that the HMXB formation efficiency increases as a function of time (following a burst of star formation) up to ~40-60Myr, and then gradually decreases. The formation efficiency peaks at ~30-40Myr with average rates of N(HMXB)/SFR=339_-83_^+78^(M_{sun}_/yr)^-1^, and N(HMXB)/M*=(8.74_-0.92_^+1.0^)x10^-6^M_{sun}_^-1^, in good agreement with previous estimates of the average formation efficiency in the broad ~20-60Myr age range.
37. Determination of black hole masses
ID:
ivo://CDS.VizieR/J/ApJ/699/453
Title:
Determination of black hole masses
Short Name:
J/ApJ/699/453
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of correlations between X-ray spectral and timing properties observed from a number of Galactic black hole (BH) binaries during hard-soft state spectral evolution. We analyze 17 transition episodes from eight BH sources observed with Rossi X-Ray Timing Explorer. Our scaling technique for BH mass determination uses a correlation between the spectral index and quasi-periodic oscillation (QPO) frequency. In addition, we use a correlation between the index and the normalization of the disk "seed" component to cross-check the BH mass determination and estimate the distance to the source. We use GRO J1655-40 as a primary reference source for which the BH mass, distance, and inclination angle are evaluated by dynamical measurements with unprecedented precision among other Galactic BH sources. We apply our scaling technique to determine BH masses and distances for Cygnus X-1, GX 339-4, 4U 1543-47, XTE J1550-564, XTE J1650-500, H 1743-322, and XTE J1859-226. A good agreement of our results for sources with known values of BH masses and distance provides independent verification for our scaling technique.
38. Distances of X-ray binaries
ID:
ivo://CDS.VizieR/J/other/NewA/47.81
Title:
Distances of X-ray binaries
Short Name:
J/other/NewA/47.
Date:
21 Oct 2021
Publisher:
CDS
Description:
The X-ray luminosity functions of galaxies have become a useful tool for population studies of X-ray binaries in them. The availability of long term light-curves of X-ray binaries with the All Sky X-ray Monitors opens up the possibility of constructing X-ray luminosity functions, by also including the intensity variation effects of the galactic X-ray binaries. We have constructed multiple realizations of the X-ray luminosity functions (XLFs) of Milky Way, using the long term light-curves of sources obtained in the 2-10keV energy band with the RXTE-ASM. The observed spread seen in the value of slope of both HMXB and LMXB XLFs are due to inclusion of variable luminosities of X-ray binaries in construction of these XLFs as well as finite sample effects. XLFs constructed for galactic HMXBs in the luminosity range 10^36^-10^39^erg/s is described by a power-law model with a mean power-law index of -0.48 and a spread due to variability of HMXBs as 0.19. XLFs constructed for galactic LMXBs in the luminosity range 10^36^-10^39^erg/s has a shape of cut-off power-law with mean power-law index of -0.31 and a spread due to variability of LMXBs as 0.07.
39. Galactic Bulge accreting binaries spectroscopy
ID:
ivo://CDS.VizieR/J/MNRAS/440/365
Title:
Galactic Bulge accreting binaries spectroscopy
Short Name:
J/MNRAS/440/365
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the identification of optical counterparts to 23 GBS X-ray sources. All sources are classified as accreting binaries according to the emission-line characteristics inferred from medium-resolution spectroscopy. To distinguish accreting binaries from chromospherically active objects, we develop criteria based on H{alpha} and HeI {lambda}{lambda}5786, 6678 emission-line properties available in the literature. The spectroscopic properties and photometric variability of each object is discussed and a classification is given where possible. At least 12 of the 23 systems show an accretion-dominated optical spectrum and another 6 show stellar absorption features in addition to emission lines indicating that they are probably accreting binaries in quiescence or in a low accretion rate state. Two sources are confirmed to be eclipsing: CX207 and CX794. CX207 is likely a magnetic cataclysmic variable (CV), while CX794 is a nova-like CV in the period gap. Finally, the large broadening (2100km/s FWHM) of the H{alpha} emission lines in CX446 and CX1004 suggests that they are also high-inclination or even eclipsing systems. Whether the compact object is a white dwarf in an eclipsing CV, a neutron star or a black hole in a high-inclination low-mass X-ray binary remains to be established.
40. Galactic ridge X-ray emission
ID:
ivo://CDS.VizieR/J/A+A/564/A107
Title:
Galactic ridge X-ray emission
Short Name:
J/A+A/564/A107
Date:
21 Oct 2021
Publisher:
CDS
Description:
We predict a thin diffuse component of the Galactic ridge X-ray emission (GRXE) arising from the scattering of the radiation of bright X-ray binaries (XBs) by the interstellar medium. This scattered component has the same scale height as that of the gaseous disk (~80pc) and is therefore thinner than the GRXE of stellar origin (scale height ~130pc). The morphology of the scattered component is furthermore expected to trace the clumpy molecular and HI clouds. We calculate this contribution to the GRXE from known Galactic XBs assuming that they are all persistent. The known XBs sample is incomplete, however, because it is flux limited and spans the lifetime of X-ray astronomy (~50-years), which is very short compared with the characteristic time of 1000-10000 years that would have contributed to the diffuse emission observed today due to time delays. We therefore also use a simulated sample of sources, to estimate the diffuse emission we should expect in an optimistic case assuming that the X-ray luminosity of our Galaxy is on average similar to that of other galaxies. In the calculations we also take into account the enhancement of the total scattering cross-section due to coherence effects in the elastic scattering from multi-electron atoms and molecules.

Limit your search

more »

  • 297