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- ID:
- ivo://CDS.VizieR/J/ApJ/726/20
- Title:
- X-ray emission from quasars
- Short Name:
- J/ApJ/726/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an investigation into the X-ray properties of radio-intermediate and radio-loud quasars (RIQs and RLQs, respectively). We combine large, modern optical (e.g., SDSS) and radio (e.g., FIRST) surveys with archival X-ray data from Chandra, XMM-Newton, and ROSAT to generate an optically selected sample that includes 188 RIQs and 603 RLQs. This sample is constructed independently of X-ray properties but has a high X-ray detection rate (85%); it provides broad and dense coverage of the l-z plane, including at high redshifts (22% of objects have z=2-5), and it extends to high radio-loudness values (33% of objects have R*=3-5, using logarithmic units). We measure the "excess" X-ray luminosity of RIQs and RLQs relative to radio-quiet quasars (RQQs) as a function of radio loudness and luminosity, and parameterize the X-ray luminosity of RIQs and RLQs both as a function of optical/UV luminosity and also as a joint function of optical/UV and radio luminosity. RIQs are only modestly X-ray bright relative to RQQs; it is only at high values of radio loudness (R*>~3.5) and radio luminosity that RLQs become strongly X-ray bright.
- ID:
- ivo://CDS.VizieR/J/AJ/130/445
- Title:
- X-ray-luminous galaxy cluster RX J0142.0+2131
- Short Name:
- J/AJ/130/445
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric and spectroscopic study of stellar populations in the X-ray-luminous cluster of galaxies RX J0142.0+2131 at z=0.280. This paper analyzes the results of high signal-to-noise ratio spectroscopy, as well as g'-, r'-, and i'-band imaging, using the Gemini Multi-Object Spectrograph on Gemini North.
- ID:
- ivo://CDS.VizieR/J/ApJ/876/50
- Title:
- X-ray & MIR AGNs in Stripe 82 with eBOSS spectra
- Short Name:
- J/ApJ/876/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a Sloan Digital Sky Survey IV eBOSS program to target X-ray sources and mid-infrared-selected Wide-field Infrared Survey Explorer (WISE) active galactic nucleus (AGN) candidates in a 36.8deg^2^ region of Stripe 82. About half this survey (15.6deg^2^) covers the largest contiguous portion of the Stripe 82 X-ray survey. This program represents the largest spectroscopic survey of AGN candidates selected solely by their WISE colors. We combine this sample with X-ray and WISE AGNs in the field identified via other sources of spectroscopy, producing a catalog of 4847 sources that is 82% complete to r~22. Based on X-ray luminosities or WISE colors, 4730 of these sources are AGNs, with a median sample redshift of z~1. About 30% of the AGNs are optically obscured (i.e., lack broad lines in their optical spectra). BPT analysis, however, indicates that 50% of the WISE AGNs at z<0.5 have emission line ratios consistent with star-forming galaxies, so whether they are buried AGNs or star-forming galaxy contaminants is currently unclear. We find that 61% of X-ray AGNs are not selected as mid-infrared AGNs, with 22% of X-ray AGNs undetected by WISE. Most of these latter AGNs have high X-ray luminosities (Lx>10^44^erg/s), indicating that mid-infrared selection misses a sizable fraction of the highest luminosity AGNs, as well as lower luminosity sources where AGN-heated dust is not dominating the mid-infrared emission. Conversely, ~58% of WISE AGNs are undetected by X-rays, though we do not find that they are preferentially redder than the X-ray-detected WISE AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/161
- Title:
- X-ray obs. and membership probabilities of M37
- Short Name:
- J/ApJ/809/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Empirical calibrations of the stellar age-rotation-activity relation (ARAR) rely on observations of the co-eval populations of stars in open clusters. We used the Chandra X-ray Observatory to study M37, a 500-Myr-old open cluster that has been extensively surveyed for rotation periods (P_rot_). M37 was observed almost continuously for five days, for a total of 440.5ks, to measure stellar X-ray luminosities (L_X_), a proxy for coronal activity, across a wide range of masses. The cluster's membership catalog was revisited to calculate updated membership probabilities from photometric data and each star's distance to the cluster center. The result is a comprehensive sample of 1699 M37 members: 426 with P_rot_, 278 with X-ray detections, and 76 with both. We calculate Rossby numbers, R_0_=P_rot_/{tau}, where {tau} is the convective turnover time, and ratios of the X-ray-to-bolometric luminosity, L_X_/L_bol_, to minimize mass dependencies in our characterization of the rotation-coronal activity relation at 500Myr. We find that fast rotators, for which R_0_<0.09+/-0.01, show saturated levels of activity, with log(L_X_/L_bol_)=-3.06+/-0.04. For R_0_>=0.09+/-0.01, activity is unsaturated and follows a power law of the form R_0_^{beta}^, where {beta}=-2.03^+0.17^_-1.14_. This is the largest sample available for analyzing the dependence of coronal emission on rotation for a single-aged population, covering stellar masses in the range 0.4-1.3M_{sun}_, P_rot_ in the range 0.4-12.8 days, and L_X_ in the range 10^28.4-30.5^erg/s. Our results make M37 a new benchmark open cluster for calibrating the ARAR at ages of ~500Myr.
- ID:
- ivo://CDS.VizieR/J/ApJ/896/95
- Title:
- X-ray obs. of narrow- and broad-line Seyfert 1 gal.
- Short Name:
- J/ApJ/896/95
- Date:
- 03 Dec 2021 00:52:46
- Publisher:
- CDS
- Description:
- We present a detailed comparative systematic study using a sample of 221 narrow-line Seyfert 1 (NLSy1) galaxies in comparison to a redshift-matched sample of 154 broad-line Seyfert 1 (BLSy1) galaxies based on their observations using ROSAT and/or XMM-Newton in soft X-ray band (0.1-2.0keV). A homogeneous analysis is carried out to estimate their soft X-ray photon indices ({Gamma}_X_^s^) and its correlations with other parameters of nuclear activities such as Eddington ratios (REdd), bolometric luminosities (Lbol), black hole masses (MBH), and the widths of the broad component of H{beta} lines (FWHM(H{beta})). In our analysis, we found clear evidence of the difference in the {Gamma}_X_^s^ and R_Edd_ distributions among NLSy1 and BLSy1 galaxies, with steeper {Gamma}_X_^s^ and higher R_Edd_ for the former. Such a difference also exists in the spectral index distribution in hard X-ray ({Gamma}_X_^h^), based on the analysis of 53 NLSy1 and 46 BLSy1 galaxies in the 2-10keV energy band. The difference in REdd distributions does exist even after applying the average correction for the difference in the inclination angle of NLSy1 and BLSy1 galaxies. We also estimated R_Edd_, based on SED fitting of 34 NLSy1 and 30 BLSy1 galaxies over the 0.3-10keV energy band, and found that results are still consistent with REdd estimates based on the optical bolometric luminosity. Our analysis suggests that the higher REdd in NLSy1 is responsible for its steeper X-ray spectral slope compared to the BLSy1, consistent with the disk-corona model as proposed for the luminous AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/734/43
- Title:
- X-ray, optical and radio monitoring of 3C 111
- Short Name:
- J/ApJ/734/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 111 between 2004 and 2010 at X-ray (2.4-10keV), optical (R band), and radio (14.5, 37, and 230GHz) wave bands, as well as multi-epoch imaging with the Very Long Baseline Array (VLBA) at 43GHz. Over the six years of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. This shows a clear connection between the radiative state near the black hole, where the X-rays are produced, and events in the jet. The X-ray continuum flux and Fe line intensity are strongly correlated, with a time lag shorter than 90 days and consistent with zero.
- ID:
- ivo://CDS.VizieR/J/A+AS/128/29
- Title:
- X-ray/optical observations of A8-G2V stars
- Short Name:
- J/A+AS/128/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 1 lists the sample of 173 stars observed for this study. They are selected from the Bright Star Catalogue (Cat. <V/50>), with the following selection criteria: - Spectral type between A8 and G2; no spectral peculiarities noted; not double in spectral type classification (e.g., HR 32 with spectral type F2V+F6V is excluded); - Luminosity class V; - Right ascension between 0h and 2h, or between 14h and 24 h, declination south of +10 degrees (defining the region on the sky visible during the appointed observation times); - Binaries for which both components occurred in the BSC are excluded, if the separation is less than 10". Not listed are five stars for which no (Walraven photometric and ROSAT X-ray) data are available. These are HR 591, HR 5542, HR 6593, HR 8245 and HR 8735. Table 2 lists the Walraven photometric (VBLUW) data for all but four stars from Table 1. Also listed in Table 2 are the effective temperature, surface gravity and the reddening, as derived from comparison with theoretical colours. Table 5 lists the ROSAT All Sky Survey data for all but 11 stars from Table 1. For a description of the Walraven photometric system, see e.g. <GCPD/11>
- ID:
- ivo://CDS.VizieR/J/ApJ/880/29
- Title:
- X-ray polarization predictions in blazars
- Short Name:
- J/ApJ/880/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- X-ray polarization should provide new probes of magnetic field geometry and acceleration physics near the base of blazar jets, but near-future missions will have limited sensitivity. We thus use existing lower energy data and X-ray variability measurements in the context of a basic synchro-Compton model to predict the X-ray polarization level and the probability of detection success for individual sources, listing the most attractive candidates for an Imaging X-ray Polarimetry Explorer campaign. We find that, as expected, several high-peak blazars such as Mrk 421 can be easily measured in 100ks exposures. Most low-peak sources should only be accessible to triggered campaigns during bright flares. Surprisingly, a few intermediate peak sources can have anomalously high X-ray polarization and thus are attractive targets.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/1777
- Title:
- X-ray properties of 3 EDisCS galaxy clusters
- Short Name:
- J/MNRAS/371/1777
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present XMM-Newton observations of three optically selected z>0.6 clusters from the European Southern Observatory (ESO) Distant Cluster Survey (EDisCS), comprising the first results of a planned X-ray survey of the full EDisCS high-redshift sample. The EDisCS clusters were identified in the Las Campanas Distant Cluster Survey as surface brightness fluctuations in the optical sky and their masses and galaxy populations are well described by extensive photometric and spectroscopic observations. We detect two of the three clusters in the X-ray and place a firm upper limit on diffuse emission in the third cluster field. We are able to constrain the X-ray luminosity and temperature of the detected clusters and estimate their masses. We find that the X-ray properties of the detected EDisCS clusters are similar to those of X-ray-selected clusters of comparable mass and --- unlike other high-redshift, optically selected clusters --- are consistent with the T-sigma and L_X_-sigma relations determined from X-ray-selected clusters at low redshift. The X-ray determined mass estimates are generally consistent with those derived from weak-lensing and spectroscopic analyses. These preliminary results suggest that the novel method of optical selection used to construct the EDisCS catalogue may, like selection by X-ray luminosity, be well suited for identification of relaxed, high-redshift clusters whose intracluster medium is in place and stable by z=0.8.
