- ID:
- ivo://CDS.VizieR/J/MNRAS/455/357
- Title:
- 2MASS J18212815+1414010 field stars
- Short Name:
- J/MNRAS/455/357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the OSIRIS camera at the 10.4m Gran Telescopio Canarias (GTC) to monitor the astrometric motion of the L4.5 dwarf 2M1821+14 over 17 months. The astrometric residuals of 11 epochs have an rms dispersion of 0.4mas, which is larger than the average precision of 0.23mas per epoch and hints towards an additional signal or excess noise. Comparison of the point-spread functions in OSIRIS and FORS2/VLT images reveals no differences critical for high-precision astrometry, despite the GTC's segmented primary mirror. We attribute the excess noise to an unknown effect that may be uncovered with additional data. For 2M1821+14, we measured a relative parallax of 10^6.15^+/-0.18mas and determined a correction of 0.50+/-0.05mas to absolute parallax, leading to a distance of 9.38+/-0.03pc. We excluded at 3{sigma} confidence the presence of a companion to 2M1821+14 down to a mass ratio of 0.1 (~5M_Jupiter_) with a period of 50-1000d and a separation of 0.1-0.7au. The accurate parallax allowed us to estimate the age and mass of 2M1821+14 of 120-700Myr and 0.049^+0.014^_-0.024_M_{sun}_, thus confirming its intermediate age and substellar mass. We complement our study with a parallax and proper motion catalogue of 587 stars (i'=~15.5-22) close to 2M1821+14, used as astrometric references. This study demonstrates submas astrometry with the GTC, a capability applicable for a variety of science cases including the search for extrasolar planets and relevant for future astrometric observations with E-ELT and TMT.
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32. MDFC Version 10
- ID:
- ivo://CDS.VizieR/II/361
- Title:
- MDFC Version 10
- Short Name:
- II/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Mid-infrared stellar Diameters and Fluxes compilation Catalogue (MDFC) dedicated to long-baseline interferometry at mid-infrared wavelengths (3-13um). It gathers data for half a million stars, i.e. nearly all the stars of the Hipparcos-Tycho catalogue whose spectral type is reported in the SIMBAD data base. We cross-match 26 data bases to provide basic information, binarity elements, angular diameter, magnitude and flux in the near and mid-infrared, as well as flags that allow us to identify the potential calibrators. The catalogue covers the entire sky with 465857 stars, mainly dwarfs and giants from B to M spectral types closer than 18kpc. The smallest reported values reach 0.16uJy in L and 0.1uJy in N for the flux, and 2-microarcsec for the angular diameter. We build four lists of calibrator candidates for the L and Nbands suitable with the Very Large Telescope Interferometer (VLTI) sub- and main arrays using the MATISSE instrument. We identify 1621 candidates for L and 44 candidates for N with the Auxiliary Telescopes (ATs), 375 candidates for both bands with the ATs, and 259 candidates for both bands with the Unit Telescopes (UTs). Predominantly cool giants, these sources are small and bright enough to belong to the primary lists of calibrator candidates. In the near future, we plan to measure their angular diameter with 1 per cent accuracy.
- ID:
- ivo://CDS.VizieR/J/PASP/119/994
- Title:
- MIPS 24um calibrators
- Short Name:
- J/PASP/119/994
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the stellar calibrator sample and the conversion from instrumental to physical units for the 24{mu}m channel of the Multiband Imaging Photometer for Spitzer (MIPS). The primary calibrators are A stars, and the calibration factor based on those stars is 4.54x10^-2^MJy/sr/(DN/s), with a nominal uncertainty of 2%. We discuss the data reduction procedures required to attain this accuracy; without these procedures, the calibration factor obtained using the automated pipeline at the Spitzer Science Center is 1.6%+/-0.6% lower. We extend this work to predict 24{mu}m flux densities for a sample of 238 stars that covers a larger range of flux densities and spectral types. We present a total of 348 measurements of 141 stars at 24{mu}m. This sample covers a factor of ~460 in 24{mu}m flux density, from 8.6mJy up to 4.0Jy. We show that the calibration is linear over that range with respect to target flux and background level. The calibration is based on observations made using 3s exposures; a preliminary analysis shows that the calibration factor may be 1% and 2% lower for 10 and 30s exposures, respectively. We also demonstrate that the calibration is very stable: over the course of the mission, repeated measurements of our routine calibrator, HD 159330, show a rms scatter of only 0.4%. Finally, we show that the point-spread function (PSF) is well measured and allows us to calibrate extended sources accurately; Infrared Astronomy Satellite (IRAS) and MIPS measurements of a sample of nearby galaxies are identical within the uncertainties.
- ID:
- ivo://CDS.VizieR/III/149
- Title:
- MK Standard Stars
- Short Name:
- III/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The purpose of the present work is to provide a complete list of MK standard stars, selected from the main papers related to this subject, according to the recommendations of both authors of the MK system. The catalogue provides a list of 963 standard stars, with their spectral type, luminosity, equatorial coordinates, magnitudes, colour index (B-V), and references. The magnitude and colours were taken from Mermillod (1986) UBV Photoelectric Photometry Catalogue (catalog <II/122>). In the cases without observations with the UBV catalogue, the apparent magnitude was taken from the SIMBAD data-base (SIMBAD is described at <http://cdsweb.u-strasbg.fr/Simbad.html>)
- ID:
- ivo://CDS.VizieR/J/AJ/156/90
- Title:
- New catalog of APOGEE radial velocity standard stars
- Short Name:
- J/AJ/156/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalog of 18080 radial velocity (RV) standard stars selected from the APOGEE data. These RV standard stars are observed at least three times and have a median stability (3{sigma}_RV_) around 240 m/s over a time baseline longer than 200 days. They are largely distributed in the northern sky and could be extended to the southern sky by the future APOGEE-2 survey. Most of the stars are red giants (J-K_s_>=0.5) owing to the APOGEE target selection criteria. Only about 10 per cent of them are main-sequence stars. The H-band magnitude range of the stars is 7-12.5 mag with the faint limit much fainter than the magnitudes of previous RV standard stars. As an application, we show the new set of standard stars to determine the RV zero points of the RAVE, the LAMOST, and the Gaia-RVS Galactic spectroscopic surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/568/A9
- Title:
- 300-2500nm flux calibration reference spectra
- Short Name:
- J/A+A/568/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- While the near-infrared wavelength regime is becoming more and more important for astrophysics there is a marked lack of spectrophotometric standard star data that allow to flux calibrate such data. Furthermore flux calibrating medium to high resolution echelle spectroscopy data is challenging even in the optical wavelength range, because the available flux standard data are often too coarsely sampled. We will provide standard star reference data that allow users to derive response curves from 300nm to 2500nm for spectroscopic data of medium to high resolution, including those taken with echelle spectrographs. In addition we describe a method to correct for moderate telluric absorption without the need of observing telluric standard stars. As reference data for the flux standard we use theoretical spectra derived from stellar model atmospheres. We verify that they provide an appropriate description of the observed standard star spectra by checking for residuals in line cores and line overlap regions in the ratios of observed (X-shooter) spectra to model spectra. The finally selected model spectra are then corrected for remaining mismatches and photometrically calibrated using independent observations. The correction of telluric absorption is performed with the help of telluric model spectra. We provide new, finely sampled reference spectra without telluric absorption for six southern flux standard stars that allow the users to flux calibrate their data from 300nm to 2500nm, and a method to correct for telluric absorption using atmospheric models.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/74.55
- Title:
- Ori OB1 CP stars magnetic fields. III.
- Short Name:
- J/other/AstBu/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper presents results of magnetic field measurements of 10 chemically peculiar stars of subgroup (a) in the Orion OB1 association: HD33917, HD34859, HD35008, HD35039, HD35177, HD35575, HD35730, HD36549, HD38912, and HD294046. Observations were carried out with the circular polarization analyzer at the Main Stellar Spectrograph at the 6-m SAO RAS telescope.Magnetic fields were detected in four stars, six stars have magnetic fields below the detection threshold.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/76.163
- Title:
- Ori OB1 CP stars magnetic fields. V.
- Short Name:
- J/other/AstBu/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper presents the results of magnetic field measurements of 27 chemically peculiar stars in subgroups (c) and (d) of the Orion OB1 association. In total, more than 140 circularly polarized spectra were obtained and measured in the period from 2013 to 2020. An analysis of the results showed that 13 out of 24 CP stars in subgroup (c) have a magnetic field. At the same time, no field of a significant strength was found in any of the three CP stars in subgroup (d). We found that the occurrence of magnetic stars in subgroup (c), whose average age is approximately 5Myr, lies in the middle between the occurrence of magnetic stars in subgroups (a) with an age of 10 Myr and (b), whose age is about 2Myr. Our results indicate a sharp decrease in the occurrence of magnetic CP stars and a simultaneous decrease in their magnetic field with age. The data obtained with the example of the Orion OB1 association generally support the theory of the fossil origin of the magnetic field of chemically peculiar stars; however, the process of the field formation itself can have a number of features manifesting observationally.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/76.39
- Title:
- Ori OB1 CP stars magnetic fields. V.
- Short Name:
- J/other/AstBu/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper presents magnetic field measurements for 15 chemically peculiar (CP) stars of subgroup 1b in the Orion OB1 association. We have found that the proportion of stars with strong magnetic fields among these 15 CP stars is almost twice as large as in subgroup 1a. Along with this, the age of subgroup 1b is estimated as 2Myr, and the age of subgroup 1a is in the order of 10Myr. The average root-mean-square magnetic field <Be> (all) for stars in subgroup 1b is 2.3 times higher than that for stars in subgroup 1a. The conclusions obtained fall within the concept of the fossil origin of large-scale magnetic fields in B and A stars, but the rate of field weakening with age appears anomalously high. We present our results as an important observational test for calibrating the theory of stellar magnetic field formation and evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A95
- Title:
- PCA approach to stellar effective temperatures
- Short Name:
- J/A+A/553/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The derivation of the effective temperature of a star is a critical first step in order to perform a detailed spectroscopic analysis. Spectroscopic methods suffer from systematic errors related to model simplifications. Photometric methods may be more robust, but are exposed to distortions caused by interstellar reddening. Direct methods are difficult to apply, since fundamental data of high accuracy are hard to obtain. We explore a new approach in which the spectrum is used to characterize a star's effective temperature based on a calibration established by a small set of standard stars. We perform Principal Component Analysis on homogeneous libraries of stellar spectra, then calibrate a relationship between the principal components and the effective temperature using a set of stars with reliable effective temperatures. We find that our procedure gives excellent consistency when spectra from a homogeneous set of observations are used. Systematic offsets may appear when combining observations from different sources. Using as reference the spectra of stars with high-quality spectroscopic temperatures in the Elodie library, we define a temperature scale for FG-type disk dwarfs with an internal consistency of about 50K, in excellent agreement with temperatures from direct determinations, but distinct from widely-used scales based in the infrared flux method.
