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1221. Chandra deep protocluster survey
ID:
ivo://CDS.VizieR/J/MNRAS/400/299
Title:
Chandra deep protocluster survey
Short Name:
J/MNRAS/400/299
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present X-ray point-source catalogues for a deep ~400ks Chandra ACIS-I (Advanced CCD Imaging Spectrometer) exposure of the SSA22 field. The observations are centred on a z=3.09 protocluster, which is populated by Lyman break galaxies (LBGs), Ly{alpha} emitters (LAEs) and extended Ly{alpha}-emitting blobs (LABs). The survey reaches ultimate (3 count) sensitivity limits of ~5.7x10^-17^ and ~3.0x10^-16^erg/cm^2^/s for the 0.5-2 and 2-8keV bands, respectively (corresponding to L_2-10keV_~5.7x10^42^erg/s and L_10-30keV_~2.0x10^43^erg/s at z=3.09, respectively, for an assumed photon index of {GAMMA}=1.4). These limits make SSA22 the fourth deepest extragalactic Chandra survey yet conducted, and the only one focused on a known high-redshift structure. In total, we detect 297 X-ray point sources and identify one obvious bright extended X-ray source over a ~330arcmin^2^ region. In addition to our X-ray catalogues, we provide all available optical spectroscopic redshifts and near-infrared and mid-infrared photometry available for our sources.
1222. Chandra Galactic Bulge Survey
ID:
ivo://CDS.VizieR/J/MNRAS/458/4530
Title:
Chandra Galactic Bulge Survey
Short Name:
J/MNRAS/458/4530
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of the Chandra Galactic Bulge Survey (GBS), we present a catalogue of optical sources in the GBS footprint. This consists of two regions centered at Galactic latitude b=1.5{deg} above and below the Galactic Centre, spanning (lxb)=(6{deg}x1{deg}). The catalogue consists of 2 or more epochs of observations for each line of sight in r', i' and H{alpha} filters. The catalogue is complete down to r'=20.2 and i'=19.2mag; the mean 5{sigma} depth is r'=22.5 and i'=21.1mag. The mean root-mean-square residuals of the astrometric solutions is 0.04-arcsec. We cross-correlate this optical catalogue with the 1640 unique X-ray sources detected in Chandra observations of the GBS area, and nd candidate optical counterparts to 1480 X-ray sources. We use a false alarm probability analysis to estimate the contamination by interlopers, and expect ~10 0 per cent of optical counterparts to be chance alignments. To determine the most likely counterpart for each X-ray source, we compute the likelihood ratio for all optical sources within the 4{sigma} X-ray error circle. This analysis yields 1480 potential counterparts (~90 per cent of the sample). 584 counterparts have saturated photometry (r'<=17, i'<=16), indicating these objects are likely foreground sources and the real counterparts. 171 candidate counterparts are detected only in the i' -band. These sources are good qLMXB and CV candidates as they are X-ray bright and likely located in the Bulge.
1223. Chandra HiPS Service
ID:
ivo://cxc.harvard.edu/hips
Title:
Chandra HiPS Service
Short Name:
CXC hips service
Date:
18 Jul 2019
Publisher:
Chandra X-ray Observatory
Description:
The Chandra X-ray Observatory Data Archive provides a reference survey via the HiPS protocol. For detailed information on the Chandra Observatory and datasets see: http://cxc.harvard.edu/ for general Chandra information; http://cxc.harvard.edu/cda/ for the Chandra Data Archive; http://cxc.harvard.edu/csc/ for Chandra Source Catalog information.
1224. Chandra Local Volume Survey: NGC 404 sources
ID:
ivo://CDS.VizieR/J/ApJ/763/128
Title:
Chandra Local Volume Survey: NGC 404 sources
Short Name:
J/ApJ/763/128
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a comprehensive X-ray point-source catalog of NGC 404 obtained as part of the Chandra Local Volume Survey. A new 97ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of ~123ks. Our survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of ~6x10^35^erg/s in the 0.35-8keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. We searched overlapping Hubble Space Telescope observations for optical counterparts to our X-ray detections, but find only two X-ray sources with candidate optical counterparts. We find 21 likely low-mass X-ray binaries (LMXBs), although this number is a lower limit due to the difficulties in separating LMXBs from background active galactic nuclei. The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented. The XLFs in the soft band (0.5-2keV) and the hard band (2-8keV) have a limiting luminosity at the 90% completeness limit of 10^35^erg/s and 10^36^erg/s, respectively, significantly lower than previous X-ray studies of NGC 404. We find the XLFs to be consistent with those of other X-ray populations dominated by LMXBs. However, the number of luminous (>10^37^erg/s) X-ray sources per unit stellar mass in NGC 404 is lower than is observed for other galaxies. The relative lack of luminous XRBs may be due to a population of LMXBs with main-sequence companions formed during an epoch of elevated star formation ~0.5Gyr ago.
1225. Chandra observations of h Persei
ID:
ivo://CDS.VizieR/J/AJ/137/3210
Title:
Chandra observations of h Persei
Short Name:
J/AJ/137/3210
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe Chandra/ACIS-I observations of the massive ~13-14Myr-old cluster, h Persei, part of the famous Double Cluster (h and {chi} Per) in Perseus. Combining the list of Chandra-detected sources with new optical/IR photometry and optical spectroscopy reveals ~165 X-ray bright stars with V<~23. Roughly 142 have optical magnitudes and colors consistent with cluster membership.
1226. Chandra observations of NGC 4636
ID:
ivo://CDS.VizieR/J/ApJ/695/1094
Title:
Chandra observations of NGC 4636
Short Name:
J/ApJ/695/1094
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the X-ray point-source population in the nearby Virgo elliptical galaxy NGC 4636 from three Chandra X-ray observations. These observations, totaling ~193ks after time filtering, were taken with the Advanced CCD Imaging Camera (ACIS) over a three-year period. Using a wavelet decomposition detection algorithm, we detect 318 individual point sources. For our analysis, we use a subset of 277 detections with >=net 10 counts (a limiting luminosity of approximately 1.2x10^37^erg/s in the 0.5-2keV band, outside the central 1.5' bright galaxy core). We present a radial distribution of the point sources. Between 1.5' and 6' from the center, 25% of our sources are likely to be background sources (active galactic nuclei (AGNs)) and 75% are low-mass X-ray binaries (LMXBs) within the galaxy, while at radial distances greater than 6', background sources (AGN) will dominate the point sources. We find 77 matches between X-ray point sources and globular cluster (GC) candidates found in deep optical images of NGC 4636. In the annulus from 1.5' to 6' of the galaxy center, 48 of the 129 X-ray point sources (37%) with >=10 net counts are matched with GC candidates. Since we expect 25% of these sources to be background AGN, the percentage matched with GCs could be as high as 50%. Of these matched sources, we find that ~70% are associated with the redder GC candidates, those that are thought to have near-solar metal abundance.
1227. CHANDRA observations of NGC 2264
ID:
ivo://CDS.VizieR/J/AJ/127/2659
Title:
CHANDRA observations of NGC 2264
Short Name:
J/AJ/127/2659
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of a Chandra observation of a field in NGC 2264. The observations were taken with the ACIS-I camera with an exposure time of 48.1ks. We present a catalog of 263 sources, which includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. We found 41 variable sources, 14 of which have a flarelike light curve, and two of which have a pattern of a steady increase or decrease over a 10-hr period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being premain-sequence stars with ages younger than 3Myr.
1228. Chandra observations of 2106 radio-quiet QSOs
ID:
ivo://CDS.VizieR/J/MNRAS/492/719
Title:
Chandra observations of 2106 radio-quiet QSOs
Short Name:
J/MNRAS/492/719
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Chandra observations of 2106 radio-quiet quasars in the redshift range 1.7<=z<=2.7 from the Sloan Digital Sky Survey (SDSS), through data release fourteen (DR14, 2018ApJS..235...42A), that do not contain broad absorption lines (BAL) in their rest-frame UV spectra. This sample adds over a decade worth of SDSS and Chandra observations to our previously published sample of 139 quasars from SDSS DR5 which is still used to correlate X-ray and optical/UV emission in typical quasars. We fit the SDSS spectra for 753 of the quasars in our sample that have high-quality (large exposure time and small off-axis observation angle) X-ray observations, and analyze their X-ray properties (aox and daox) with respect to the measured CIV and MgII emission-line rest-frame equivalent width (EW) and the CIV emission-line blueshift. We find significant correlations (at the >=99.99% level) between aox and these emission-line parameters, as well as between daox and CIV EW. Slight correlations are found between daox and CIV blueshift, MgII EW, and the ratio of CIV EW to MgII EW. The best-fit trend in each parameter space is used to compare the X-ray weakness (daox) and optical/UV emission properties of typical quasars and weak-line quasars (WLQs). The WLQs clearly deviate from the expectation for every relationship, typically exhibiting much weaker X-ray emission than predicted by the typical quasar relationships. The best-fit relationships for our typical quasars are consistent with predictions from the disk-wind quasar model. The behavior of the WLQs with respect to our typical quasars can be explained by an X-ray shielding model.
1229. Chandra observations of Trumpler 14 and 16
ID:
ivo://CDS.VizieR/J/ApJ/589/509
Title:
Chandra observations of Trumpler 14 and 16
Short Name:
J/ApJ/589/509
Date:
21 Oct 2021
Publisher:
CDS
Description:
The region around the {eta} Carinae Nebula has three OB associations, which contain a Wolf-Rayet star and several massive O3 stars. An early Chandra ACIS-I image was centered on {eta} Car and includes Trumpler 16 and part of Trumpler 14. The Chandra image confirms the well-known result that O and very early B stars are X-ray sources with LX~=10^-7^Lbol over an X-ray luminosity range of about 100. Two new, anomalously strong X-ray sources have been found among the hot star population: Tr 16-244, a heavily reddened O3 I star, and Tr 16-22, a heavily reddened O8.5 V star. Two stars have an unusually large LX/Lbol: HD 93162, a Wolf-Rayet star (and possible binary), and Tr 16-22, a possible colliding-wind binary. In addition, a population of sources associated with cool stars is detected. In the color-magnitude diagram, these X-ray sources sit above the sequence of field stars in the Carina arm. The OB stars are on average more X-ray luminous than the cool star X-ray sources. X-ray sources among A stars have X-ray luminosities similar to those of cooler stars and may be due to cooler companions. Upper limits are presented for B stars that are not detected in X-rays. These upper limits are also the upper limits for any cool companions that the hot stars may have. Hardness ratios are presented for the most luminous sources in bands 0.5-0.9, 0.9-1.5, and 1.5-2.04keV. The available information on the binary nature of the hot stars is discussed, but binarity does not correlate with X-ray strength in a simple way.
1230. CHANDRA obs. of YSOs in OMC-2 and OMC-3
ID:
ivo://CDS.VizieR/J/ApJ/566/974
Title:
CHANDRA obs. of YSOs in OMC-2 and OMC-3
Short Name:
J/ApJ/566/974
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report X-ray results of the Chandra observation of OMC-2 and OMC-3. A deep exposure of ~100ks detects ~400 X-ray sources in the field of view of the ACIS array, providing one of the largest X-ray catalogs in a star-forming region. Coherent studies of the source detection, time variability, and energy spectra are performed. We classify the X-ray sources into Class I, Class II, and Class III+MS based on the J-, H-, and K-band colors of their near-infrared counterparts and discuss the X-ray properties (temperature, absorption, and time variability) along these evolutionary phases.