- ID:
- ivo://CDS.VizieR/J/A+A/392/741
- Title:
- Stellar Catalogue in the Chandra DFS
- Short Name:
- J/A+A/392/741
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar catalogues in five passbands (UBVRI) over an area of approximately 0.3{deg}^2^, comprising about 1200 objects, and in seven passbands (UBVRIJK) over approximately 0.1{deg}^2^, comprising about 400 objects, in the direction of the Chandra Deep Field South are presented. The 90% completeness level of the number counts is reached at approximately U=23.8, B=24.0, V=23.5, R=23.0, I=21.0, J=20.5, K=19.0. These multi-band catalogues have been produced from publicly available, single passband catalogues. A scheme is presented to select point sources from these catalogues, by combining the SExtractor parameter CLASS_STAR from all available passbands. Probable QSOs and unresolved galaxies are identified by using the previously developed {chi}^2^-technique (Hatziminaoglou et al., 2002, Cat. <J/A+A/384/81>), that fits the overall spectral energy distributions to template spectra and determines the best fitting template. Approximately 15% of true galaxies are misclassified as stars by the {chi}^2^ method. The number of unresolved galaxies and QSOs identified by the {chi}^2^-technique, allows us to estimate that the remaining level of contamination by such objects is at the level of 2.4% of the number of stars. The fraction of missing stars being incorrectly removed as QSOs or unresolved galaxies is estimated to be similar. The resulting stellar catalogues and the objects identified as likely QSOs and unresolved galaxies with coordinates, observed magnitudes with errors and assigned spectral types by the {chi}^2^-technique are presented and are publicly available.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/575/A12
- Title:
- Stellar CharactEristics Pisa Estimation gRid
- Short Name:
- J/A+A/575/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar age determination by means of grid-based techniques that adopt asteroseismic constraints is a well established method nowadays. However some theoretical aspects of the systematic and statistical errors affecting these age estimates still have to be investigated. We study the impact on stellar age determination of the uncertainty in the radiative opacity, in the initial helium abundance, in the mixing-length value, in the convective core overshooting, and in the microscopic diffusion efficiency adopted in stellar model computations. We extended our SCEPtER grid to include stars with mass in the range [0.8; 1.6]M_{sun}_ and evolutionary stages from the zero-age main sequence to the central hydrogen depletion. For the age estimation we adopted the same maximum likelihood technique as described in our previous work. To quantify the systematic errors arising from the current uncertainty in model computations, many synthetic grids of stellar models with perturbed input were adopted. We found that the current typical uncertainty in the observations accounts for 1{sigma} statistical relative error in age determination, which on average ranges from about -35% to +42%, depending on the mass. However, owing to the strong dependence on the evolutionary phase, the age's relative error can be higher than 120% for stars near the zero-age main sequence, while it is typically of the order of 20% or lower in the advanced main-sequence phase. The systematic bias on age determination due to a variation of +/-1 in the helium-to-metal enrichment ratio {Delta}Y/{Delta}Z is about one-fourth of the statistical error in the first 30% of the evolution, while it is negligible for more evolved stages. The maximum bias due to the presence of the convective core overshooting is -7% and -13% for mild and strong overshooting scenarios. For all the examined models, the impact of a variation of +/-5% in the radiative opacity was found to be negligible. The most important source of bias is the uncertainty in the mixing-length value {alpha}_ml_ and the neglect of microscopic diffusion. Each of these effects accounts for a bias that is nearly equal to the random error uncertainty. Comparison of the results of our technique with other grid techniques on a set of common stars showed general agreement. However, the adoption of a different grid can account for a variation in the mean estimated age up to 1Gyr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/402/1005
- Title:
- Stellar cluster dynamical masses in NGC3310
- Short Name:
- J/MNRAS/402/1005
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gas and star velocity dispersions have been derived for eight circumnuclear star-forming regions (CNSFRs) and the nucleus of the spiral galaxy NGC 3310 using high-resolution spectroscopy in the blue and far red. Stellar velocity dispersions have been obtained from the CaII triplet in the near-IR, using cross-correlation techniques, while gas velocity dispersions have been measured by Gaussian fits to the H{beta} {lambda}4861{AA} and [OIII] {lambda}5007{AA} emission lines.
- ID:
- ivo://CDS.VizieR/J/MNRAS/396/2295
- Title:
- Stellar cluster dynamical masses in NGC2903
- Short Name:
- J/MNRAS/396/2295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gas and star velocity dispersions have been derived for four circumnuclear star-forming regions (CNSFRs) and the nucleus of the spiral galaxy NGC 2903 using high-resolution spectroscopy in the blue and far red. Stellar velocity dispersions have been obtained from the CaII triplet lines at {lambda}{lambda} 8494, 8542, 8662{AA}, using cross-correlation techniques, while gas velocity dispersions have been measured by Gaussian fits to the H{beta} {lambda} 4861{AA} line.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A3
- Title:
- Stellar clusters from UKIDSS Galactic Plane Survey
- Short Name:
- J/A+A/542/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Data mining techniques must be developed and applied to analyse the large public data bases containing hundreds to thousands of millions entries. We develop methods for locating previously unknown stellar clusters from the UKIDSS Galactic Plane Survey (GPS) catalogue data.
- ID:
- ivo://CDS.VizieR/J/AJ/138/227
- Title:
- Stellar clusters in NGC 6334 complex
- Short Name:
- J/AJ/138/227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The full stellar population of NGC 6334, one of the most spectacular regions of massive star formation in the nearby Galaxy, has not been well sampled in past studies. We analyze here a mosaic of two Chandra X-ray Observatory images of the region using sensitive data analysis methods, giving a list of 1607 faint X-ray sources with arcsecond positions and approximate line-of-sight absorption. About 95% of these are expected to be cluster members, most lower mass pre-main-sequence stars. Extrapolating to low X-ray levels, the total stellar population is estimated to be 20,000-30,000 pre-main-sequence stars.
- ID:
- ivo://CDS.VizieR/J/AN/341/996
- Title:
- Stellar companions of (C)TOIs
- Short Name:
- J/AN/341/996
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first results of a new survey are reported, which explores the 2nd data release of the ESA-Gaia mission, in order to search for stellar companions of (Community) TESS Objects of Interest and to characterize their properties. In total, 193 binary and 15 hierarchical triple star systems are presented, detected among 1391 target stars, which are located at distances closer than about 500pc around the Sun. The companions and the targets are equidistant and share a common proper motion, as it is expected for gravitationally bound stellar systems, proven with their accurate Gaia astrometry. The companions exhibit masses in the range between about 0.08M_{sun}_ and 3M_{sun}_ and are most frequently found in the mass range between 0.13 and 0.6M_{sun}_. The companions are separated from the targets by about 40 up to 9900au, and their frequency continually decreases with increasing separation. While most of the detected companions are late K to mid M dwarfs, also 5 white dwarf companions were identified in this survey, whose true nature is revealed by their photometric properties.
- ID:
- ivo://CDS.VizieR/J/AN/342/840
- Title:
- Stellar companions of (C)TOIs
- Short Name:
- J/AN/342/840
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the latest results of our ongoing multiplicity study of (Community) TESS Objects of Interest, using astro- and photometric data from the ESA-Gaia mission, to detect stellar companions of these stars and to characterize their properties. In total, 107 binary, 5 hierarchical triple star systems, as well as one quadruple system were detected among 585 targets surveyed, which are all located at distances closer than about 500pc around the Sun. As proven with their accurate Gaia EDR3 astrometry, the companions and the targets are located at the same distance and share a common proper motion, as it is expected for components of gravitationally bound stellar systems. The companions exhibit masses in the range between about 0.09M_{sun}_ and 4.5M_{sun}_ and are most frequently found in the mass range between 0.15 and 0.6M_{sun}_. The companions are separated from the targets by about 120 up to 9500au and their frequency is the highest and constant within about 500au while it continually decreases for larger separations. Beside mainly early to mid M dwarfs, also 5 white dwarf companions were identified in this survey, whose true nature was revealed by their photometric properties.
- ID:
- ivo://CDS.VizieR/J/MNRAS/490/5088
- Title:
- Stellar companions of exoplanet host stars
- Short Name:
- J/MNRAS/490/5088
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new survey is presented, which explores the second data release of the ESA-Gaia mission, in order to search for stellar companions of exoplanet host stars, located at distances closer than about 500pc around the Sun. In total, 176 binaries, 27 hierarchical triples, and one hierarchical quadruple system are detected among more than 1300 exoplanet host stars, whose multiplicity is investigated, yielding a multiplicity rate of the exoplanet host stars of at least about 15 per cent. The detected companions and the exoplanet host stars are equidistant and share a common proper motion, as it is expected for gravitationally bound stellar systems, proven with their accurate Gaia astrometry. The companions exhibit masses in the range between about 0.078 and 1.4M_{sun}_ with a peak in their mass distribution between 0.15 and 0.3M{sun}_. The companions are separated from the exoplanet host stars by about 20 up to 9100au, but are found most frequently within a projected separation of 1000au. While most of the detected companions are early M dwarfs, eight white dwarf companions of exoplanet host stars are also identified in this survey, whose true nature is revealed with their photometric properties. Hence, these degenerated companions and the exoplanet host stars form evolved stellar systems with exoplanets, which have survived (physically but also dynamically) the post-main-sequence evolution of their former primary star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/2498
- Title:
- Stellar companions of exoplanet host stars
- Short Name:
- J/MNRAS/421/2498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To understand the influence of additional wide stellar companions on planet formation, it is necessary to determine the fraction of multiple stellar systems amongst the known extrasolar planet population. We target recently discovered radial velocity exoplanetary systems observable from the Northern hemisphere and with sufficiently high proper motion to detect stellar companions via direct imaging. We utilize the Calar Alto 2.2-m telescope in combination with its lucky imaging camera AstraLux. 71 planet host stars have been observed so far, yielding one new low-mass (0.239+/-0.022M_{sun}_) stellar companion, 4.5-arcsec (227 au of projected separation) north-east of the planet host star HD 185269, detected via astrometry with AstraLux. We also present follow-up astrometry on three previously discovered stellar companions, showing for the first time common proper motion of the 0.5-arcsec companion to HD 126614. Additionally, we determined the achieved detection limits for all targets, which allow us to characterize the detection space of possible further companions of these stars.