- ID:
- ivo://CDS.VizieR/J/A+A/628/A61
- Title:
- X-shooter spectra of 43 metal-poor M dwarfs
- Short Name:
- J/A+A/628/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of the project is to define metallicity/gravity/temperature scales for different spectral types of metal-poor M dwarfs. We obtained intermediate-resolution ultraviolet (UVB), optical (VIS), and near-infrared (NIR) spectra of 43 metal-poor M dwarfs (16 sdMs, 16 esdMs, and 12 usdMs with the ESO VLT X-shooter spectrograph. We compared our atlas of spectra to the BT-Settl synthetic spectral energy distribution over a wide range of metallicities, gravities, and effective temperatures to infer the physical properties for the whole M dwarf sequence at sub-solar metallicities and constrain the latest atmospheric models. The BT-Settl models accurately reproduce the observed spectra across the 450--2500 nm wavelength range except for a few regions. We find that the best fits for gravities of log(g)=5.0-5.5 for the three metal classes. We infer metallicities of [Fe/H]=-0.5, -1.5, and -2.0+/-0.5dex and effective temperatures of 3700-2600K, 3800-2900K, and 3700-2900K for sdMs, esdMs, and usdMs, respectively.
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- ID:
- ivo://CDS.VizieR/J/A+A/551/A107
- Title:
- X-shooter spectra of 24 young stellar objects
- Short Name:
- J/A+A/551/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The lack of knowledge of photospheric parameters and the level of chromospheric activity in young low-mass pre-main sequence stars introduces uncertainties when measuring mass accretion rates in accreting (Class II) young stellar objects. A detailed investigation of the effect of chromospheric emission on the estimates of mass accretion rate in young low-mass stars is still missing. This can be undertaken using samples of young diskless (Class III) K and M-type stars. Our is to measure the chromospheric activity of Class III pre main sequence stars to determine its effect on the estimates of the accretion luminosity (Lacc) and mass accretion rate (dMacc/dt) in young stellar objects with disks. Using VLT/X-shooter spectra, we analyzed a sample of 24 nonaccreting young stellar objects of spectral type between K5 and M9.5. We identified the main emission lines normally used as tracers of accretion in Class II objects, and we determined their fluxes in order to estimate the contribution of the chromospheric activity to the line luminosity. We have used the relationships between line luminosity and accretion luminosity derived in the literature for Class II objects to evaluate the impact of chromospheric activity on the accretion rate measurements. We find that the typical chromospheric activity would bias the derived accretion luminosity by L_acc,noise_<10^-3^L_{sun}_, with a strong dependence on the Teff of the objects. The noise on Macc depends on stellar mass and age, and the typical values of log(M_acc,noise_) range between ~-9.2 to -11.6M_{sun}_/yr. Values of L_acc_<10^-3^L_{sun}_ obtained in accreting low-mass pre main sequence stars through line luminosity should be treated with caution because the line emission may be dominated by the contribution of chromospheric activity.
- ID:
- ivo://CDS.VizieR/J/A+A/548/A56
- Title:
- X-shooter spectra of 12 young stellar objects
- Short Name:
- J/A+A/548/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-quality, medium-resolution X-shooter/VLT spectra in the range 300-2500nm for a sample of 12 very low mass stars in the {sigma} Orionis cluster. The sample includes eight stars with evidence of disks from Spitzer and four without disks, with masses ranging from 0.08 to 0.3M_{sun}_. The aim of this first paper is to investigate the reliability of the many accretion tracers currently used to measure the mass accretion rate in low-mass young stars and the accuracy of the correlations between these secondary tracers (mainly accretion line luminosities) found in the literature. We use our spectra to measure the accretion luminosity from the continuum excess emission in the UV and visual; the derived mass accretion rates range from 10^-9^M_{sun}_/yr down to 5x10^-11^M_{sun}_/yr, allowing us to investigate the behavior of the accretion-driven emission lines in very low mass accretion rate regimes. We compute the luminosity of ten accretion-driven emission lines from the UV to the near-IR, which are all obtained simultaneously. In general, most of the secondary tracers correlate well with the accretion luminosity derived from the continuum excess emission. We recompute the relationships between the accretion luminosities and the line luminosities, and we confirm the validity of the correlations given in the literature, with the possible exception of H{alpha}. Metallic lines, such as the CaII IR triplet or the NaI line at 589.3nm, show a larger dispersion. When looking at individual objects, we find that the hydrogen recombination lines, from the UV to the near-IR, give good and consistent measurements of L_acc_ that often better agree than the uncertainties introduced by the adopted correlations. The average L_acc_ derived from several hydrogen lines, measured simultaneously, have a much reduced error. This suggests that some of the spread in the literature correlations may be due to the use of nonsimultaneous observations of lines and continuum. Three stars in our sample deviate from this behavior, and we discuss them individually.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A33
- Title:
- X-Shooter spectroscopy of YSOs in Lupus
- Short Name:
- J/A+A/602/A33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A homogeneous determination of basic stellar parameters of young stellar object (YSO) candidates is needed to confirm their pre-main sequence evolutionary stage, membership to star forming regions (SFRs), and to get reliable values of the quantities related to chromospheric activity and accretion. We used the code ROTFIT and synthetic BT-Settl spectra for the determination of the atmospheric parameters (Teff and logg), the veiling (r), the radial (RV) and projected rotational velocity (vsini), from X-Shooter spectra of 102 YSO candidates (95 of infrared Class II and seven Class III) in the Lupus SFR. The spectral subtraction of inactive templates, rotationally broadened to match the vsini of the targets, enabled us to measure the line fluxes for several diagnostics of both chromospheric activity and accretion, such as H{alpha}, H{beta}, CaII, and NaI lines. We have shown that 13 candidates can be rejected as Lupus members based on their discrepant RV with respect to Lupus and/or the very low logg values. At least 11 of them are background giants, two of which turned out to be lithium-rich giants. Regarding the members, we found that all ClassIII sources have H{alpha} fluxes compatible with a pure chromospheric activity, while objects with disks lie mostly above the boundary between chromospheres and accretion. YSOs with transitional disks displays both high and low H{alpha} fluxes. We found that the line fluxes per unit surface are tightly correlated with the accretion luminosity (L_acc_) derived from the Balmer continuum excess. This rules out that the relationships between L_acc_ and line luminosities found in previous works are simply due to calibration effects. We also found that the CaII-IRT flux ratio is always small, indicating an optically thick emission source. The latter can be identified with the accretion shock near the stellar photosphere. The Balmer decrement reaches instead, for several accretors, high values typical of optically thin emission, suggesting that the Balmer emission originates in different parts of the accretion funnels with a smaller optical depth.
16195. XSL atmospheric parameters
- ID:
- ivo://CDS.VizieR/J/A+A/627/A138
- Title:
- XSL atmospheric parameters
- Short Name:
- J/A+A/627/A138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The X-shooter Spectral Library (XSL) is an empirical stellar library at medium spectral resolution covering the wavelength range from 3000 to 24800 angstrom. This library aims to provide a benchmark for stellar population studies. In this work, we present a uniform set of stellar atmospheric parameters, effective temperatures, surface gravities, and iron abundances for 754 spectra of 616 XSL stars. We used the full-spectrum fitting package ULySS with the empirical MILES library as reference to fit the ultraviolet-blue (UVB) and visible (VIS) spectra. We tested the internal consistency and we compared our results with compilations from the literature. The stars cover a range of effective temperature 2900<Teff<38000K, surface gravity 0<logg<5.7, and iron abundance -2.5<[Fe/H]<+1.0, with a couple of stars extending down to [Fe/H]=-3.9. The precisions of the measurements for the G- and K-type stars are 0.9%, 0.14, and 0.06 in Teff, log g and [Fe/H], respectively. For the cool giants with logg<1, the precisions are 2.1%, 0.21, and 0.22, and for the other cool stars these values are 1%, 0.14, and 0.10. For the hotter stars (Teff>6500K), these values are 2.6%, 0.20, and 0.10 for the three parameters.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/105
- Title:
- XSTPS RR Lyrae in the north Galactic cap
- Short Name:
- J/ApJ/788/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of RR Lyrae stars (RRLs) observed by the Xuyi Schmidt Telescope Photometric Survey (XSTPS). The area we consider is located in the north Galactic cap, covering ~376.75 deg^2^ at RA~150{deg} and DE~27{deg} down to a magnitude limit of i~19. Using the variability information afforded by the multi-epoch nature of our XSTPS data, combined with colors from the Sloan Digital Sky Survey, we are able to identify candidate RRLs. We find 318 candidates, derive distances to them, and estimate the detection efficiency. The majority of our candidates have more than 12 observations, and for these we are able to calculate periods. These also allow us to estimate our contamination level, which we predict is between 30% and 40%. Finally, we use the sample to probe the halo density profile in the 9-49 kpc range and find that it can be well fitted by a double power law. We find good agreement between this model and the models derived for the south Galactic cap using the Watkins et al. (2009, J/MNRAS/398/1757) and Sesar et al. (2010, J/ApJ/708/717) RRL data sets, after accounting for possible contamination in our data set from Sagittarius stream members. We consider non-spherical double power-law models of the halo density profile and again find agreement with literature data sets, although we have limited power to constrain the flattening due to our small survey area. Much tighter constraints will be placed by current and future wide-area surveys, most notably ESA's astrometric Gaia mission. Our analysis demonstrates that surveys with a limited number of epochs can effectively be mined for RRLs. Our complete sample is provided as accompanying online material; as an example the first few entries of each electronic table are shown in the text.
16197. XTE Master Catalog
- ID:
- ivo://nasa.heasarc/xtemaster
- Title:
- XTE Master Catalog
- Short Name:
- RXTE
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This database table was created for the purpose of providing a comprehensive, accurate, and easily accessible tracking of Rossi X-Ray Timing Explorer (RXTE) pointed observations. It does not list observations made during slews: those are listed in the <a href="/W3Browse/xte/xteslew.html">XTESLEW</a> database table. The XTEMASTER table includes both observations that have already completed and those still scheduled to be done. The XTEMASTER table is regenerated automatically on a quasi-regular basis whenever the RXTE Science Operations Facility (SOF) updates their short-term or long-term schedules and transfers the new version(s) to the HEASARC. At that time, it will also incorporate all the latest information on which targets have been observed (using the daily RXTE ObsCats at <a href="https://heasarc.gsfc.nasa.gov/FTP/xte/timelines/obscat/">https://heasarc.gsfc.nasa.gov/FTP/xte/timelines/obscat/</a>) and which observations have been archived in the public RXTE Data Archive at <a href="https://heasarc.gsfc.nasa.gov/FTP/xte/data/archive/">https://heasarc.gsfc.nasa.gov/FTP/xte/data/archive/</a>. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/ApJS/173/538
- Title:
- XUV-Disk galaxies in the Local Universe
- Short Name:
- J/ApJS/173/538
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have initiated a search for extended ultraviolet disk (XUV-disk) galaxies in the local universe. Here we compare GALEX UV and visible-NIR images of 189 nearby (D<40Mpc) S0-Sm galaxies included in the GALEX Atlas of Nearby Galaxies (Gil de Paz et al. 2007, Cat. J/ApJS/173/185) and present the first catalog of XUV-disk galaxies. We find that XUV-disk galaxies are surprisingly common but have varied relative (UV/optical) extent and morphology. Type 1 objects (>~20% incidence) have structured, UV-bright/optically faint emission features in the outer disk, beyond the traditional star formation threshold. Type 2 XUV-disk galaxies (~10% incidence) exhibit an exceptionally large, UV-bright/optically low surface brightness (LSB) zone having blue UV-K_s_ outside the effective extent of the inner, older stellar population, but not reaching extreme galactocentric distance.
16199. XXL Survey. DR2
- ID:
- ivo://CDS.VizieR/IX/52
- Title:
- XXL Survey. DR2
- Short Name:
- IX/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the second data release (DR2) of the XXL Survey, contextually with the appearance of a second A&A special issue dedicated to XXL. This intermediate release includes the following catalogues and data: The X-ray point source catalogue (3XLSS) and the associated multiwavelength catalogues in the XXL-N and XXL-s areas (XXL paper XXVII). The same paper also provides the list of XMM pointings used, and a supplementary catalogue of redshifts obtained with the AAOmega spectrograph in the XXL-S area. The XXL-365-GC galaxy cluster catalogue (XXL paper XX) with the complete subset of clusters for which the selection function is well determined plus all X-ray clusters which are, to date, spectroscopically confirmed. The ATCA 2.1 GHz radio source catalogue in the XXL-S area (XXL paper XXVIII), together with the catalogue of ther optical and near infrared counterparts (XXL paper XXVI). The GMRT 610 MHz radio source catalogue in the XXL-N area (XXL paper XXIX). FITS images of the XXL-North field: continuum radio mosaic from observations with the Giant Meterwave Radio Telescope (GMRT) at 610MHz, and the corresponding noise map. A complete spectrophotometric sample of galaxies within X-ray detected, optically spectroscopically confirmed groups and clusters (G&C), including also field objects, in the XXL-N area (XXL paper XXII). The list of brightest cluster galaxies (BCGs) in the XXL-N area (XXL paper XXVIII). FITS images of the two radio galaxies described in XXL paper XXXIV. ATCA XXL-S source classification data (XXL paper XXXVI) http://sci.esa.int/xmm-newton/60686-tracing-the-universe-x-ray-survey-\ supports-standard-cosmological-model/ List of XXL DR2 papers: XVI. The clustering of X-ray selected galaxy clusters at z~0.3 XVII. X-ray and Sunyaev-Zel'dovich properties of the redshift 2.0 galaxy cluster XLSSC 122 XVIII. ATCA 2.1 GHz radio source catalogue and source counts for the XXL-South field XIX. A realistic population of simulated X-ray AGN: Comparison of models with observations XX. The 365 cluster catalogue XXI. The environment and clustering of X-ray AGN in the XXL-South field XXII. The XXL-North spectrophotometric sample and galaxy stellar mass function in X-ray detected groups and clusters XXIII. The mass scale of XXL clusters from ensemble spectroscopy XXIV. The final detection pipeline XXV. Cosmological analysis of the C1 cluster number counts XXVI. Optical and near infrared identification of the ATCA 2.1 GHz radio sources in the XXL-S field XXVII. The 3XLSS point source catalogue XXVIII. Galaxy luminosity functions of the XXL-N clusters XXIX. GMRT 610 MHz continuum observations XXX. Characterisation of the XLSSsC N01 supercluster and analysis of the galaxy stellar populations XXXI. Classification and host galaxy properties of 2.1 GHz ATCA XXL-S radio sources XXXII. Spatial clustering of the XXL-S AGN XXXIII. Chandra constraints on the AGN contamination of z > 1 XXL galaxy clusters XXXIV. Double irony in XXL-North. A tale of two radio galaxies in a supercluster at z = 0.14 XXXV. The role of cluster mass in AGN activity XXXVI. Evolution and black hole feedback of high-excitation and low-excitation radio galaxies in XXL-S
16200. XXL Survey: First results
- ID:
- ivo://CDS.VizieR/IX/49
- Title:
- XXL Survey: First results
- Short Name:
- IX/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The quest for the cosmological parameters that describe our universe continues to motivate the scientific community to undertake very large survey initiatives across the electromagnetic spectrum. Over the past two decades, the Chandra and XMM-Newton observatories have sup- ported numerous studies of X-ray-selected clusters of galaxies, active galactic nuclei (AGNs), and the X-ray background. The present paper is the first in a series reporting results of the XXL-XMM survey; it comes at a time when the Planck mission results are being finalised. We present the XXL Survey, the largest XMM programme totaling some 6.9Ms to date and involving an international consortium of roughly 100 members. The XXL Survey covers two extragalactic areas of 25deg^2^ each at a point-source sensitivity of ~5x10^-15^erg/s/cm^2^ in the [0.5-2]keV band (completeness limit). The survey's main goals are to provide constraints on the dark energy equation of state from the space-time distribution of clusters of galaxies and to serve as a pathfinder for future, wide-area X-ray missions. We review science objectives, including cluster studies, AGN evolution, and large-scale structure, that are being conducted with the support of approximately 30 follow-up programmes. List of XXL papers: I. Scientific motivations - XMM-Newton observing plan - Follow-up observations and simulation programme. II. The bright cluster sample: catalogue and luminosity function. III. Luminosity-temperature relation of the bright cluster sample. IV. Mass-temperature relation of the bright cluster sample. VI. The 1000 brightest X-ray point sources. VII. A supercluster of galaxies at z = 0.43. VIII. MUSE characterisation of intracluster light in a z~0.53 cluster of galaxies. IX. Optical overdensity and radio continuum analysis of a supercluster at z=0.43. X. K-band luminosity - weak-lensing mass relation for groups and clusters of galaxies. XI. ATCA 2.1 GHz continuum observations. XII. Optical spectroscopy of X-ray-selected clusters and the frequency of AGN in superclusters. XIII. Baryon content of the bright cluster sample. XIV. AAOmega redshifts for the southern XXL field.
