- 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.
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- 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.
- ID:
- ivo://CDS.VizieR/III/150A
- Title:
- Perkins Revised MK Types for the Cooler Stars
- Short Name:
- III/150A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The original catalog of standard stars classified on the Revised MK system published in 1989 contains 1054 standard stars of spectral types G0 and later (G, K, M, and a few S stars) classified at the Perkins Observatory. The present version of the catalog takes into account the revisions (before 14h of RA) presented by Philip C. Keenan and Gerald H. Newsom at the Department of Astronomy of the Ohio State University (http://www-astronomy.mps.ohio-state.edu/MKCool) dated 2000 January; the Sun (G2V star) has been omitted from the catalog. Accurate positions were added in 2003. The revised MK system is described by Keenan (1987PASP...99..713K). The spectrograms used for the classification were taken at four different observatories; hence, extensive comparisons have been made to ensure consistency between the Northern and Southern Hemispheres. The list provides a consistent set of standards in most parts of the sky and over a considerable range in magnitude, for stars later than G0. The catalog is not a survey complete to any magnitude and is not intended for statistical studies.
- ID:
- ivo://CDS.VizieR/II/50
- Title:
- Photometric Standard Stars
- Short Name:
- II/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The non-variable stars brighter than 5.0 mag in the equatorial zone between declinations +10{deg} and -10{deg} were adopted by IAU Commission 25 in 1970 as primary standards for the Johnson and Morgan UBV system of 1966. Fainter HR stars in the same zone were chosen as secondary standards. Data for the primary standards are taken from a Cape Royal Observatory Mimeogram and are presented in table2.dat. It gives the weighted mean V magnitudes and B-V colors based upon the best series available up to the end of 1966. The table is believed to provide a consistent UBV system over the southern sky. Most of the secondary standard star data, given in table4.dat, were published in Mon. Notes Astron. Soc. S. Afr. (22,23).
- ID:
- ivo://CDS.VizieR/J/A+A/458/225
- Title:
- Photometric standard stars in the field of GR 290
- Short Name:
- J/A+A/458/225
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Understanding the origin of the instabilities of LBVs is important for shedding light on the late evolutionary stages of massive stars and on the chemical evolution of galaxies. To investigate the physical nature of variable stars in the upper H-R diagram, we performed a spectrophotometric study of the Romano's star GR 290 and the Hubble-Sandage variables A, B, and C in the close galaxy M 33. New spectroscopic and photometric data were employed in conjunction with already published data of these stars in order to derive spectral types, energy distribution and bolometric luminosities.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A108
- Title:
- Photometry of Kepler-82b and c transits
- Short Name:
- J/A+A/628/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From the Kepler mission four planets were detected and confirmed in the Kepler-82 system. The two inner ones (d and e) show no transit timing variations (TTVs) and are dynamically independent from the two outer ones (b and c), which are showing TTVs. A dynamical analysis of the Kepler-82b/c system delivered a very high, hardly to explain, density ratio of about ten between the planets. A chopping component in the TTVs of the outer planet (Kepler-82b) is not explained by the two-planet model. This chopping component hints on another outer planet near the 3:2 or 3:1 resonance to planet c. The time span of Kepler observations are too short for distinguishing between the two models, the dynamical cycle is not fully covered. The completion of the dynamical cycle of this and other Kepler Objects of Interest (KOIs) showing TTVs is the aim of the KOINet. Within the network follow-up observations with ground-based telescopes are organized. These follow-up observations of Kepler-82b/c transits helped to distinguish between the two models, resulting is the detection of a new planet near the 3:2 resonance to Kepler-82d in the system. A detailed photodynamical modelling of the system was carried out to fully characterise the system parameters. The inclusion of the new planet also lead to a more reasonable density ratio of planet b to c of about two.
