- ID:
- ivo://CDS.VizieR/J/A+A/506/1055
- Title:
- Hot stars emitting in X-ray. I.
- Short Name:
- J/A+A/506/1055
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Following the advent of increasingly sensitive X-ray observatories, deep observations of early-type stars became possible. However, the results for only a few objects or clusters have until now been reported and there has been no large survey comparable to that based upon the ROSAT All-Sky Survey (RASS). A limited survey of X-ray sources, consisting of all public XMM observations (2XMMi) and slew survey data (XMMSL1), is now available. The X-ray counterparts to hot, massive stars have been searched for in these catalogs. About 300 OB stars were detected with XMM. Half of them were bright enough for a spectral analysis to be possible, and we make available the detailed spectral properties that were derived. The X-ray spectra of O stars are represented well by low (<1keV) temperature components and seem to indicate that an absorption column is present in addition to the interstellar contribution. The X-ray fluxes are well correlated with the bolometric fluxes, with a scatter comparable to that of the RASS studies and thus larger than found previously with XMM for some individual clusters. These results contrast with those of B stars that exhibit a large scatter in the L_X-L_BOL relation, no additional absorption being found, and the fits indicate a plasma at higher temperatures. Variability (either within one exposure or between multiple exposures) was also investigated whenever possible: short-term variations are far more rare than long-term ones (the former affects a few percent of the sample, while the latter concerns between one third and two thirds of the sources).
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/619/A148
- Title:
- Hot stars observed by XMM-Newton. II.
- Short Name:
- J/A+A/619/A148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a survey of Oe and Be stars in the X-ray range. To this aim, we cross-correlated XMM-Newton and Chandra catalogs of X-ray sources with a list of Be stars, finding 84 matches in total. Of these, 51 objects had enough counts for a spectral analysis. This paper provides the derived X-ray properties (X-ray luminosities, and whenever possible, hardness ratios, plasma temperatures, and variability assessment) of this largest ever sample of Oe and Be stars. The targets display a wide range in luminosity and hardness. In particular, the significant presence of very bright and hard sources is atypical for X-ray surveys of OB stars. Several types of sources are identified. A subset of stars display the typical characteristics of O-stars, magnetic OB stars, or pre-main-sequence (PMS) objects: their Be nature does not seem to play an important role. However, another subset comprises gamma Cas analogs, which are responsible for the luminous and hard detections. Our sample contains seven known gamma Cas analogs, but we also identify eight new gamma Cas analogs and one gamma Cas candidate. This nearly doubles the sample of such stars.
- ID:
- ivo://CDS.VizieR/J/A+A/355/651
- Title:
- HRI observations of PMS stars in NGC 2264
- Short Name:
- J/A+A/355/651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze six ROSAT HRI observations pointed toward the Star Forming Region (SFR) NGC 2264. Three are pointed to the southern star formation core, the other three about 20' to the north. We detect 169 X-ray sources, ~95% of which are likely to be Pre Main Sequence (PMS) stars, significantly enlarging the known population of the SFR in the area covered by the observations. Using published BVRI photometry we place the X-ray sources with well defined optical counterparts on the HRI diagram and estimate their masses and ages. Our comparison of the mass function and age distribution of the X-ray sources with results previously obtained for NGC 2264, demonstrates that deep X-ray observations provide, at least in this case, a very efficient method of selecting SFR members and does not introduce stronger biases than other methods.
- ID:
- ivo://CDS.VizieR/J/ApJ/865/33
- Title:
- HST and Chandra obs. of the GLIMPSE-C01 star cluster
- Short Name:
- J/ApJ/865/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of Hubble Space Telescope and Chandra X-Ray Observatory observations of the GLIMPSE-C01 (hereafter GC01) star cluster. Color-magnitude and color-color diagrams suggest a cluster age of >~2Gyr up to ~10Gyr (dependent on GC01's metallicity), a distance of 3.3-3.5kpc, and strong differential reddening with A_V_=14-22. After performing astrometric corrections, we find that nine of the 15 X-ray sources have at least one near-infrared (NIR) counterpart within the 2{sigma} Chandra positional error circles. However, given the very high density of NIR sources in the cluster, most of these counterparts are likely due to chance coincidence. We jointly analyze the X-ray and NIR properties to assess the likelihood of true associations. Based primarily on their X-ray properties, we identify a low-mass X-ray binary candidate (source X2), a cataclysmic variable (CV) candidate (source X1), and an active binary (AB) candidate (source X9). Source X11 is detected during an X-ray flaring episode with a flare luminosity (L_X_=2.1x10^33^erg/s) and has a quiescent luminosity L_X_<8.0x10^30^erg/s, in 0.5-8keV at the distance of GC01, suggesting that the source is either an AB or CV. We also discuss the limits on an intermediate-mass black hole at the center of GC01 and the challenges of X-ray source classification imposed by the limitations of the existing data and instrumentation along with future prospects in the James Webb Space Telescope era.
- ID:
- ivo://CDS.VizieR/J/ApJS/248/31
- Title:
- HST & Chandra obs. of elliptical galaxies
- Short Name:
- J/ApJS/248/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate X-ray binary (XRB) luminosity function (XLF) scaling relations for Chandra-detected populations of low-mass XRBs (LMXBs) within the footprints of 24 early-type galaxies. Our sample includes Chandra and Hubble Space Telescope observed galaxies at D<~25Mpc that have estimates of the globular cluster (GC) specific frequency (S_N_) reported in the literature. As such, we are able to directly classify X-ray-detected sources as being coincident with unrelated background/foreground objects, GCs, or sources that are within the fields of the galaxy targets. We model the GC and field LMXB population XLFs for all galaxies separately and then construct global models characterizing how the LMXB XLFs vary with galaxy stellar mass and S_N_. We find that our field LMXB XLF models require a component that scales with S_N_ and has a shape consistent with that found for the GC LMXB XLF. We take this to indicate that GCs are "seeding" the galactic field LMXB population, through the ejection of GC LMXBs and/or the diffusion of the GCs in the galactic fields themselves. However, we also find that an important LMXB XLF component is required for all galaxies that scales with stellar mass, implying that a substantial population of LMXBs are formed "in situ," which dominates the LMXB population emission for galaxies with S_N_<~2. For the first time, we provide a framework quantifying how directly associated GC LMXBs, GC-seeded LMXBs, and in situ LMXBs contribute to LMXB XLFs in the broader early-type galaxy population.
- ID:
- ivo://CDS.VizieR/J/ApJ/595/685
- Title:
- HST imaging in Chandra Deep Field-South
- Short Name:
- J/ApJ/595/685
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present quantitative morphological analyses of 37 Hubble Space Telescope (HST)/WFPC2 counterparts of X-ray sources in the 1Ms Chandra Deep Field South (CDFS, Cat. <J/ApJS/139/369>). We investigate (1) one-dimensional surface brightness profiles via isophotal ellipse fitting; (2) two-dimensional, point-spread function convolved, bulge+disk+nucleus profile fitting; (3) asymmetry and concentration indices compared with all ~3000 sources in our three WFPC2 fields; and (4) near-neighbor analyses comparing local environments of X-ray sources versus the field control sample. Significant nuclear point-source optical components appear in roughly half of the resolved HST/WFPC2 counterparts, showing a narrow range of FX/Fopt, nuc consistent with the several HST-unresolved X-ray sources (putative type 1 active galactic nuclei [AGNs]) in our fields.
- ID:
- ivo://CDS.VizieR/J/ApJ/801/44
- Title:
- HST lensing analysis of the CLASH sample
- Short Name:
- J/ApJ/801/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a comprehensive lensing analysis in Hubble Space Telescope (HST) data of the complete Cluster Lensing And Supernova survey with Hubble cluster sample (CLASH). We identify previously undiscovered multiple images, allowing improved or first constraints on the cluster inner mass distributions and profiles. We combine these strong lensing constraints with weak lensing shape measurements within the HST field of view (FOV) to jointly constrain the mass distributions. The analysis is performed in two different common parameterizations (one adopts light-traces-mass (LTM) for both galaxies and dark matter while the other adopts an analytical, elliptical Navarro-Frenk-White (NFW) form for the dark matter) to provide a better assessment of the underlying systematics--which is most important for deep, cluster-lensing surveys, especially when studying magnified high-redshift objects. We find that the typical (median), relative systematic differences throughout the central FOV are ~40% in the (dimensionless) mass density, {kappa}, and ~20% in the magnification, {mu}. We show maps of these differences for each cluster, as well as the mass distributions, critical curves, and two-dimensional (2D)-integrated mass profiles. For the Einstein radii (z_s_=2) we find that all typically agree within 10% between the two models, and Einstein masses agree, typically, within ~15%. At larger radii, the total projected, 2D-integrated mass profiles of the two models, within r~2', differ by ~30%. Stacking the surface-density profiles of the sample from the two methods together, we obtain an average slope of dlog({Sigma})/dlog(r)~-0.64+/-0.1, in the radial range [5350]kpc. Last, we also characterize the behavior of the average magnification, surface density, and shear differences between the two models as a function of both the radius from the center and the best-fit values of these quantities.
- ID:
- ivo://CDS.VizieR/J/ApJ/881/42
- Title:
- HST phot. & GMOS spectra of Lynx E & W clusters
- Short Name:
- J/ApJ/881/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Few detailed investigations of stellar populations in passive galaxies beyond z~1 are based on deep spectroscopic observations, due to the difficulty in obtaining such data. We present a study of stellar populations, structure, and mass-to-light ratios (M/L) of a large sample of bulge-dominated galaxies in the two z=1.27 clusters Lynx E and Lynx W, based on deep ground-based optical spectroscopy combined with imaging from the Hubble Space Telescope. We find that Lynx E has a well-defined core of red passive galaxies, while Lynx W lacks such a core. If all the sample galaxies evolve similarly in size from z=1.27 to the present, the data would allow only 0.1dex size growth at a fixed dynamical mass. However, to link the Lynx central galaxies to brightest cluster galaxies similar to those of low-redshift clusters, the Lynx galaxies would have to grow by at least a factor 5, possibly through major merging. The M/L ratios and the Balmer absorption lines of the Lynx galaxies are consistent with passive evolution of the stellar populations from z=1.27 to the present and support ages of 1-3Gyr. The galaxies in the outskirts of the clusters contain younger stellar populations than found in the cluster cores. However, when evolved passively to z~0 both populations are consistent with the observed populations in the Coma cluster galaxies. The bulge-dominated emission line galaxies in the clusters are dominated by stellar populations with subsolar metallicities. Thus, additional enrichment of these is required to produce Coma-like stellar populations by z~0.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/55
- Title:
- HST/WFC3 SNR discoveries in M83 (NGC5236)
- Short Name:
- J/ApJ/788/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an optical/NIR imaging survey of the face-on spiral galaxy M83, using data from the Hubble Space Telescope Wide Field Camera 3 (WFC3). Seven fields are used to cover a large fraction of the inner disk, with observations in nine broadband and narrowband filters. In conjunction with a deep Chandra survey and other new radio and optical ground-based work, these data enable a broad range of science projects to be pursued. We provide an overview of the WFC3 data and processing and then delve into one topic, the population of young supernova remnants (SNRs). We used a search method targeted toward soft X-ray sources to identify 26 new SNRs. Many compact emission nebulae detected in [FeII]1.644{mu}m align with known remnants and this diagnostic has also been used to identify many new remnants, some of which are hard to find with optical images. We include 37 previously identified SNRs that the data reveal to be <0.5" in angular size and thus are difficult to characterize from ground-based data. The emission line ratios seen in most of these objects are consistent with shocks in dense interstellar material rather than showing evidence of ejecta. We suggest that the overall high elemental abundances in combination with high interstellar medium pressures in M83 are responsible for this result.
- ID:
- ivo://CDS.VizieR/J/A+AS/126/509
- Title:
- HS 47.5/22: X-ray catalogue
- Short Name:
- J/A+AS/126/509
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 4 contains the parameters of the PSPC pointings which form the medium deep survey in HS 47.5/22, table 5 is the final X-ray source catalogue, and table 6 gives the results of the optical follow-up observations.
