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17751. X-ray data for 56 protoplanetary disk sources
ID:
ivo://CDS.VizieR/J/A+A/625/A66
Title:
X-ray data for 56 protoplanetary disk sources
Short Name:
J/A+A/625/A66
Date:
21 Oct 2021
Publisher:
CDS
Description:
Consistent modeling of protoplanetary disks requires the simultaneous solution of both continuum and line radiative transfer, heating and cooling balance between dust and gas and, of course, chemistry. Such models depend on panchromatic observations that can provide a complete description of the physical and chemical properties and energy balance of protoplanetary systems. Along these lines we present a homogeneous, panchromatic collection of data on a sample of 85 T Tauri and Herbig Ae objects for which data cover a range from X-rays to centimeter wavelengths. Datasets consist of photometric measurements, spectra, along with results from the data analysis such as line fluxes from atomic and molecular transitions. Additional properties resulting from modeling of the sources such as disc mass and shape parameters, dust size and PAH properties are also provided for completeness. The purpose of this data collection is to provide a solid base that can enable consistent modeling of the properties of protoplan- etary disks. To this end, we performed an unbiased collection of publicly available data that were combined to homogeneous datasets adopting consistent criteria. Targets were selected based on both their properties but also on the availability of data. Data from more than 50 different telescopes and facilities were retrieved and combined in homogeneous datasets directly from public data archives or after being extracted from more than 100 published articles. X-ray data for a subset of 56 sources represent an exception as they were reduced from scratch and are presented here for the first time. Compiled datasets along with a subset of continuum and emission-line models are stored in a dedicated database and distributed through a publicly accessible online system. All datasets contain metadata descriptors that allow to backtrack them to their original resources. The graphical user interface of the online system allows the user to visually inspect individual objects but also compare between datasets and models. It also offers to the user the possibility to download any of the stored data and metadata for further processing.
17752. X-ray detection of radio-selected SF galaxies
ID:
ivo://CDS.VizieR/J/A+A/542/A16
Title:
X-ray detection of radio-selected SF galaxies
Short Name:
J/A+A/542/A16
Date:
21 Oct 2021
Publisher:
CDS
Description:
X-ray surveys contain sizable numbers of star forming galaxies, beyond the AGN which usually make the majority of detections. Many methods to separate the two populations are used in the literature, based on X-ray and multiwavelength properties. We aim at a detailed test of the classification schemes and to study the X-ray properties of the resulting samples. We build on a sample of galaxies selected at 1.4GHz in the VLA-COSMOS survey, classified by Smolcic et al. (2008ApJS..177...14S) according to their optical colours and observed with Chandra. A similarly selected control sample of AGN is also used for comparison. We review some X-ray based classification criteria and check how they affect the sample composition. The efficiency of the classification scheme devised by Smolcic et al. (2008ApJS..177...14S) is such that ~30% of composite/misclassified objects are expected because of the higher X-ray brightness of AGN with respect to galaxies. The latter fraction is actually 50% in the X-ray detected sources, while it is expected to be much lower among X-ray undetected sources. Indeed, the analysis of the stacked spectrum of undetected sources shows, consistently, strongly different properties between the AGN and galaxy samples. X-ray based selection criteria are then used to refine both samples. The radio/X-ray luminosity correlation for star forming (SF) galaxies is found to hold with the same X-ray/radio ratio valid for nearby galaxies. Some evolution of the ratio may be possible for sources at high redshift or high luminosity, tough it is likely explained by a bias arising from the radio selection. Finally, we discuss the X-ray number counts of star forming galaxies from the VLA- and C-COSMOS surveys according to different selection criteria, and compare them to the similar determination from the Chandra Deep Fields. The classification scheme proposed here may find application in future works and surveys.
17753. X-ray detections in the {sigma} Ori cluster
ID:
ivo://CDS.VizieR/J/A+A/521/A45
Title:
X-ray detections in the {sigma} Ori cluster
Short Name:
J/A+A/521/A45
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigated the X-ray emission from young stars and brown dwarfs in the {sigma} Orionis cluster ({tau}=~3Ma, d=~385pc) and its relation to mass, the presence of circumstellar discs, and separation to the cluster centre by taking advantage of the superb spatial resolution of the Chandra X-ray Observatory.
17754. X-ray emission at the low-mass end
ID:
ivo://CDS.VizieR/J/ApJ/414/846
Title:
X-ray emission at the low-mass end
Short Name:
J/ApJ/414/846
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used all tha available data from the Einstein Observatory Imaging Proportional Counter (IPC), and a critical compilation of catalogued optical data, to measure the 0.16-3.5 keV X-ray emission from 88 K and 169 M stars of luminosity classes IV, V and VI within 25 pc from the Sun. The IPC detected 54 out of the 88 K stars, 70 out of the 138 M stars with M_v_ less than 13.4 (corresponding approximatively to M5), and 15 out of the 31 fainter M stars. We have identified a subsample of surveyed stars that is statistically representative of the population of K and M stars in the solar neighborhood.
17755. X-ray Emission from Abell Clusters of Galaxies
ID:
ivo://CDS.VizieR/J/A+A/278/379
Title:
X-ray Emission from Abell Clusters of Galaxies
Short Name:
J/A+A/278/379
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of ROSAT All-Sky Survey (RASS, see cat. <IX/10>) have been used to investigate the X-ray properties of a complete sample of Abell clusters within a 561 square degree region at high galactic latitude; the mean redshift of the sample is 0.17.
17756. X-ray emission from A-type stars
ID:
ivo://CDS.VizieR/J/A+A/475/677
Title:
X-ray emission from A-type stars
Short Name:
J/A+A/475/677
Date:
21 Oct 2021
Publisher:
CDS
Description:
Being fully radiative, stars of spectral type A are not expected to harbor magnetic dynamos and hence such stars are not expected to produce X-ray emission. Indeed, while the X-ray detection rate of such stars in X-ray surveys is low, it is not zero and some of the brighter A-type stars have been detected on different occasions and with different instruments. To study systematically the puzzle of the X-ray emitting A-type stars, we carried out an X-ray study of all A-type stars listed in the Bright Star Catalogue using the ROSAT public data archive. We found a total of 312 bright A-type stars positionally associated with ROSAT X-ray sources; we analyzed the X-ray light curves as well as searched for evidence of RV variations to identify possible late-type companions producing the X-ray emission. In this paper we present a list of X-ray active A-type stars, including the collected data about multiplicity, X-ray luminosity and spectral peculiarities.
17757. X-ray emission from Galactic stellar bow shocks
ID:
ivo://CDS.VizieR/J/AJ/157/176
Title:
X-ray emission from Galactic stellar bow shocks
Short Name:
J/AJ/157/176
Date:
03 Nov 2021 07:20:14
Publisher:
CDS
Description:
We present a stacking analysis of 2.61 Ms of archival Chandra observations of stellar wind bow shocks. We place an upper limit on the X-ray luminosity of infrared-detected bow shocks of <2x10^29^ erg/s, a more stringent constraint than has been found in previous archival studies and dedicated observing campaigns of nearby bow shocks. We compare the X-ray luminosities and L_X_/L_bol_ ratios of bow shock driving stars to those of other OB stars within the Chandra field of view. Driving stars are, on average, of later spectral type than the field-of-view OB stars, and we do not observe any unambiguously high L_X_/L_bol_ ratios indicative of magnetic stars in our sample. We additionally assess the feasibility of detecting X-rays from stellar wind bow shocks with the proposed Lynx X-ray Observatory. If the X-ray flux originating from the bow shocks is just below our Chandra detection limit, the nearest bow shock in our sample (at ~0.4 kpc with an absorbing column of ~10^21^/cm^2^) should be observable with Lynx in exposure times on the order of ~100 ks.
17758. X-ray emission from quasars
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.
17759. X-ray emission from 28 SNe (IIn, Ibn or SLSN-I)
ID:
ivo://CDS.VizieR/J/ApJ/763/42
Title:
X-ray emission from 28 SNe (IIn, Ibn or SLSN-I)
Short Name:
J/ApJ/763/42
Date:
21 Oct 2021
Publisher:
CDS
Description:
Here we report on a search, using Swift/XRT and Chandra, for X-ray emission from 28 SNe that belong to classes whose progenitors are suspected to be embedded in dense circumstellar matter (CSM). Our sample includes 19 Type IIn SNe, one Type Ibn SN, and eight hydrogen-poor superluminous SNe (SLSN-I such as SN 2005ap). Two SNe (SN 2006jc and SN 2010jl) have X-ray properties that are roughly consistent with the expectation for X-rays from a collisionless shock in optically thick CSM. However, the X-ray emission from SN 2006jc can also be explained as originating in an optically thin region. Thus, we propose that the optical light curve of SN 2010jl is powered by shock breakout in CSM. We suggest that two other events (SN 2010al and SN 2011ht) were too X-ray bright during the SN maximum optical light to be explained by the shock-breakout model. We conclude that the light curves of some, but not all, SNe IIn/Ibn are powered by shock breakout in CSM. For the rest of the SNe in our sample, including all of the SLSN-I events, our X-ray limits are not deep enough and were typically obtained too early (i.e., near the SN maximum light) for definitive conclusions about their nature. Late-time X-ray observations are required in order to further test whether these SNe are indeed embedded in dense CSM.
17760. X-Ray emission from solar-type stars: F and G
ID:
ivo://CDS.VizieR/J/ApJ/315/687
Title:
X-Ray emission from solar-type stars: F and G
Short Name:
J/ApJ/315/687
Date:
21 Oct 2021
Publisher:
CDS
Description:
Results of a volume-limited X-ray survey of stars of luminosity classes IV and V in the spectral range F7-G9 observed with the Einstein Observatory are presented. Using survival analysis techniques, the stellar X-ray luminosity function in the 0.15-4.0 keV energy band for both single and multiple sources. It is shown that the difference in X-ray luminosity between these two classes of sources is consistent with the superposition of individual components in multiple-component systems, whose X-ray properties are similar to those of the single-component sources. The X-ray emission of the stars in our sample is well correlated with their chromospheric CA II H-K line emission and with their projected equatorial rotational velocity. Comparison of the X-ray luminosity function constructed for the sample of the dG stars of the local population with the corresponding functions derived elsewhere for the Hyades, the Pleiades, and the Orion Ic open cluster confirms that the level of X-ray emission decreases with stellar age.

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