- ID:
- ivo://nasa.heasarc/cxoxassist
- Title:
- Chandra XAssist Source List
- Short Name:
- Chan/XAssist
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This database table contains the latest Chandra XAssist source list. XAssist is a NASA-funded project for the automation of X-ray astrophysics, with emphasis on galaxies. It is capable of data reprocessing, source detection, and preliminary spatial, temporal, and spectral analysis for all sources with sufficient counts. The bulk of the system is written in Python, which in turn drives underlying software, e.g., CIAO for Chandra data. Pipelines running on Chandra observations of galaxies have generated the source list which comprises this HEASARC table. The pipeline also includes fields requested by users for various projects, most notably observations of a sample of quasars and several deep field observations have been processed. Note that the pipline processing is completely automated; therefore, users should visually inspect the results of any queries. This table was first created by the HEASARC in May 2005 based on the Chandra source list available at the XAssist website. In September 2010, the HEASARC switched over to using the "pipeline4" Chandra source list. It is updated on a weekly basis when and if the XAssist source list file at <a href="https://asd.gsfc.nasa.gov/xassist/pipeline4/chandra/master_srclist.csv">https://asd.gsfc.nasa.gov/xassist/pipeline4/chandra/master_srclist.csv</a> is updated. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/changalxrb
- Title:
- Chandra X-Ray Binary Catalog of SINGS Galaxies
- Short Name:
- CHANGALXRB
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors of this catalog presented new Chandra constraints on the X-ray luminosity functions (XLFs) of X-ray binary (XRB) populations, as well as their scaling relations, for a sample of 38 nearby galaxies (D = 3.4-29 Mpc). The galaxy sample is drawn primarily from the Spitzer Infrared Nearby Galaxies Survey (SINGS) and contains a wealth of Chandra (5.8 Ms total) and multiwavelength data, allowing for star formation rates (SFRs) and stellar masses (M<sub>*</sub>) to be measured on subgalactic scales. The authors divided the 2478 X-ray-detected sources into 21 subsamples in bins of specific SFR (sSFR=SFR/M<sub>*</sub>) and constructed XLFs. To model the XLF dependence on sSFR, they fitted a global XLF model, containing contributions from high-mass XRBs (HMXBs), low-mass XRBs (LMXBs), and background sources from the cosmic X-ray background that respectively scale with SFR, M<sub>*</sub>, and sky area. They found an HMXB XLF that is more complex in shape than previously reported and an LMXB XLF that likely varies with sSFR, potentially due to an age dependence. When applying the global model to XLF data for each individual galaxy, the authors discovered a few galaxy XLFs that significantly deviated from their model beyond statistical scatter. Most notably, relatively low-metallicity galaxies have an excess of HMXBs above ~10<sup>38</sup>erg/s, and elliptical galaxies that have relatively rich populations of globular clusters (GCs) show excesses of LMXBs compared to the global model. Additional modeling of how the XRB XLF depends on stellar age, metallicity, and GC specific frequency is required to sufficiently characterize the XLFs of galaxies. In this work, the authors utilized 5.8 Ms of Chandra ACIS data, combined with UV-to-IR observations, for 38 nearby (D < ~30 Mpc) Spitzer Infrared Nearby Galaxies Survey (SINGS; Kennicutt+ <a href="https://ui.adsabs.harvard.edu/abs/2003PASP..115..928K">2003PASP..115..928K</a>) galaxies to revisit scaling relations of the HMXB and LMXB X-ray luminosity functions (XLFs) with SFR and M<sub>*</sub>, respectively. This table contains the X-ray properties for 4442 X-ray point sources, including those with L<sub>X</sub> < 10<sup>35</sup>erg/s, which were excluded from the XLF analysis. This table was created by the HEASARC in April 2023 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/243/3">CDS Catalog J/ApJS/243/3</a> file table7.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/AJ/155/241
- Title:
- Chandra X-ray detection of YSOs in Serpens South
- Short Name:
- J/AJ/155/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a Chandra study of the deeply embedded Serpens South star-forming region, examining cluster structure and disk properties at the earliest stages. In total, 152 X-ray sources are detected. Combined with Spitzer and 2MASS photometry, 66 X-ray sources are reliably matched to an IR counterpart. We identify 21 class I, 6 flat spectrum, 16 class II, and 18 class III young stars; 5 were unclassified. Eighteen sources were variable in X-rays, 8 exhibiting flare-like emission and one source being periodic. The cluster's X-ray luminosity distance was estimated: the best match was to the nearer distance of 260 pc for the front of the Aquila Rift complex. The ratio of N_H_ to A_K_ is found to be ~0.68x10^22^, similar to that measured in other young low-mass regions, but lower than that measured in the interstellar medium and high-mass clusters (~(1.6-2)x10^22^). We find that the spatial distribution closely follows that of the dense filament from which the stars have formed, with the class II population still strongly associated with the filament. There are four subclusters in the field, with three forming knots in the filament, and a fourth to the west, which may not be associated but may be contributing to the distributed class III population. A high percentage of diskless class IIIs (upper limit 30% of classified X-ray sources) in such a young cluster could indicate that processing of disks is influenced by the cluster environment and is not solely dependent on timescale.
- ID:
- ivo://CDS.VizieR/J/PASJ/55/653
- Title:
- Chandra X-ray flares in rho Ophiuchi
- Short Name:
- J/PASJ/55/653
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the results of a systematic study of X-ray flares from low-mass young stellar objects, using two deep exposure Chandra observations of the main region of the {rho} Ophiuchi star-forming cloud. From 195 X-ray sources, including class I-III sources and some young brown dwarfs, we detected a total of 71 X-ray flares.
- ID:
- ivo://CDS.VizieR/J/AZh/91/679
- Title:
- Chandra X-Ray galaxy clusters at z <1.4
- Short Name:
- J/AZh/91/679
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A reconstruction of the total mass (the fraction of dark matter, intercluster gas, and the brightest galaxy of the cluster) of 128 X-ray galaxy clusters at redshifts 0.01-1.4 based on Chandra observations is presented. The total mass M200 and the baryonic mass Mb have been measured for all the sample objects, as well as the concentration parameter c200, which characterizes the size of the dark matter halo. The existence of a tight correlation between c200 and M200 is confirmed, c{prop.to}M^a^_vir_/(1+z)b with a=-0.56+/-0.15 and b=0.80+/-0.25 (95% confidence level), in good agreement with the predictions of numerical simulations and previous observations. Fitting the inner dark-matter density slope {alpha} with a generalized NFW model yields {alpha}=1.10+/-0.48 at the 2{sigma} confidence level, combining the results for the entire sample, for which the model gives a good description of the data. There is also a tight correlation between the inner slope of the dark-matter density profile {alpha} and the baryonic mass contentMb for massive galaxy clusters, namely, {alpha} decreases with increasing baryonic mass content. A simple power-law model is used to fit the {alpha}-M_b_ distributions, yielding the break point for the inner slope of the dark-matter density profile b=1.72+/-0.37 (68% confidence level).
- ID:
- ivo://CDS.VizieR/J/A+A/564/A120
- Title:
- Chandra X-ray observation of Gum 31
- Short Name:
- J/A+A/564/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gum 31 is a prominent, but still rather poorly studied HII region around the stellar cluster NGC 3324 at the northwestern periphery of the Carina nebula complex. Our aim was to reveal and characterize the young stellar population in Gum 31. An X-ray survey is the only efficient way to identify young stars in this region with extremely high galactic field-star contamination that can avoid the strong biases of infrared excess selected samples of disk-bearing young stars. We used the Chandra observatory to perform a deep (70ks) X-ray observation of the Gum 31 region and detected 679 X-ray point sources. This extends and complements the X-ray survey of the central Carina nebula regions performed in the Chandra Carina Complex Project (CCCP). Using deep near-infrared images from our recent VISTA survey of the Carina nebula complex, our comprehensive Spitzer point-source catalog, and optical archive data, we identify counterparts for 75% of these X-ray sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/654/347
- Title:
- Chandra X-ray observations in Eagle Nebula. I.
- Short Name:
- J/ApJ/654/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and analyze the first high-resolution X-ray images ever obtained of the Eagle Nebula star-forming region. On 2001 July 30 the Chandra X-Ray Observatory obtained a 78ks image of the Eagle Nebula (M16) that includes the core of the young galactic cluster NGC 6611 and the dark columns of dust and cold molecular gas in M16 known as the "Pillars of Creation". We find a total of 1101 X-ray sources in the 17'x17' ACIS-I field of view. Most of the X-ray sources are low-mass pre-main-sequence or high-mass main-sequence stars in this young cluster. A handful of hard X-ray sources in the pillars are spatially coincident with deeply embedded young stellar objects seen in high-resolution near-infrared images recently obtained with the VLT (McCaughrean & Andersen, 2002A&A...389..513M). In this paper, we focus on the 40 X-ray sources in and around pillars 14 at the heart of the Eagle Nebula. None of the X-ray sources are associated with the evaporating gaseous globules (EGGs) first observed by Hester and coworkers) in HST WFPC2 images of M16, implying either that the EGGs do not contain protostars or that the protostars have not yet become X-ray active. Eight X-ray counts are coincident with the Herbig-Haro object HH 216, implying logLX~30.0.
- ID:
- ivo://CDS.VizieR/J/ApJ/687/1019
- Title:
- Chandra X-ray observations of M71
- Short Name:
- J/ApJ/687/1019
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observe the nearby, low-density globular cluster M71 (NGC 6838) with the Chandra X-Ray Observatory to study its faint X-ray populations. Five X-ray sources are found inside the cluster core radius, including the known eclipsing binary millisecond pulsar (MSP) PSR J1953+1846A. The X-ray light curve of the source coincident with this MSP shows marginal evidence for periodicity at the binary period of 4.2hr. Its hard X-ray spectrum and luminosity resemble those of other eclipsing binary MSPs in 47 Tuc, suggesting a similar shock origin of the X-ray emission. A further 24 X-ray sources are found within the half-mass radius, reaching to a limiting luminosity of 1.5x10^30^ergs/s (0.3-8keV). From a radial distribution analysis, we find that 18+/-6 of these 29 sources are associated with M71, somewhat more than predicted, and that 11+/-6 are background sources, both Galactic and extragalactic. M71 appears to have more X-ray sources in the range L_X_=10^30^-10^31^ergs/s than expected by extrapolating from other studied clusters using either mass or collision frequency. We explore the spectra and variability of these sources and describe the results of ground-based optical counterpart searches.
- ID:
- ivo://CDS.VizieR/J/ApJS/144/213
- Title:
- Chandra X-ray observations of M81
- Short Name:
- J/ApJS/144/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A Chandra X-Ray Observatory ACIS-S imaging observation is used to study the population of X-ray sources in the nearby Sab galaxy M81 (NGC 3031). A total of 177 sources are detected with 124 located within the D_25_ isophote to a limiting X-ray luminosity of ~3x10^36^erg/s. Source positions, count rates, luminosities in the 0.3-8.0 keV band, limiting optical magnitudes, and potential counterpart identifications are tabulated. Spectral and timing analysis of the 36 brightest sources are reported including the low-luminosity active galactic nucleus, SN 1993J, and the Einstein-discovered ultraluminous X-ray source X6.
- ID:
- ivo://CDS.VizieR/J/ApJ/588/1009
- Title:
- Chandra X-ray observations of NGC 2516
- Short Name:
- J/ApJ/588/1009
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive study of the Chandra X-ray observations of the young open cluster NGC 2516. We have analyzed eight individual Chandra observations. We have combined the data to achieve the greatest sensitivity, reaching down to log f_X_=-14.56(erg/s/cm^2^), or logLX=28.69(erg/s) at the distance of NGC 2516. Out of 284 X-ray sources detected, 155 are identified with photometric cluster members, with very little ambiguity.
