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- ID:
- ivo://CDS.VizieR/J/A+A/614/A122
- Title:
- Radial-velocity of CARMENES M dwarfs
- Short Name:
- J/A+A/614/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from ~1cm/s to ~1km/s, depending on various stellar and activity parameters. We investigate the observed relations between RVs, stellar activity, and stellar parameters of M dwarfs by analyzing CARMENES high-resolution visual-channel spectra (0.5-1um), which were taken within the CARMENES RV planet survey during its first 20 months of operation. During this time, 287 of the CARMENES- sample stars were observed at least five times. From each spectrum we derived a relative RV and a measure of chromospheric Halpha emission. In addition, we estimated the chromatic index (CRX) of each spectrum, which is a measure of the RV wavelength dependence. Despite having a median number of only 11 measurements per star, we show that the RV variations of the stars with RV scatter of >10m/s and a projected rotation velocity vsini>2km/s are caused mainly by activity. We name these stars 'active RV-loud stars' and find their occurrence to increase with spectral type: from ~3% for early-type M dwarfs (M0.0-2.5V) through ~30% for mid-type M dwarfs (M3.0-5.5V) to >50% for late-type M dwarfs (M6.0-9.0V). Their RV-scatter amplitude is found to be correlated mainly with vsini. For about half of the stars, we also find a linear RV-CRX anticorrelation, which indicates that their activity-induced RV scatter is lower at longer wavelengths. For most of them we can exclude a linear correlation between RV and Halpha emission. Our results are in agreement with simulated activity-induced RV variations in M dwarfs. The RV variations of most active RV-loud M dwarfs are likely to be caused by dark spots on their surfaces, which move in and out of view as the stars rotate.
- ID:
- ivo://CDS.VizieR/J/AJ/149/8
- Title:
- Radial velocity of southern visual multiple stars
- Short Name:
- J/AJ/149/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution spectra of visual multiple stars were taken in 2008-2009 to detect or confirm spectroscopic subsystems and to determine their orbits. Radial velocities of 93 late-type stars belonging to visual multiple systems were measured by numerical cross-correlation. We provide the individual velocities, the width, and the amplitude of the Gaussians that approximate the correlations. The new information on the multiple systems resulting from these data is discussed. We discovered double-lined binaries in HD 41742B, HD 56593C, and HD 122613AB, confirmed several other known subsystems, and constrained the existence of subsystems in some visual binaries where both components turned out to have similar velocities. The orbits of double-lined subsystems with periods of 148 and 13 days are computed for HD 104471 Aa,Ab and HD 210349 Aa,Ab, respectively. We estimate individual magnitudes and masses of the components in these triple systems and update the outer orbit of HD 104471 AB.
- ID:
- ivo://CDS.VizieR/J/AJ/162/56
- Title:
- Radial velocity of 240 YSOs with MMT/Hectochelle
- Short Name:
- J/AJ/162/56
- Date:
- 14 Mar 2022 06:56:34
- Publisher:
- CDS
- Description:
- Stellar kinematics is a powerful tool for understanding the formation process of stellar associations. Here, we present a kinematic study of the young stellar population in the Rosette nebula using recent Gaia data and high-resolution spectra. We first isolate member candidates using the published mid-infrared photometric data and the list of X-ray sources. A total of 403 stars with similar parallaxes and proper motions are finally selected as members. The spatial distribution of the members shows that this star-forming region is highly substructured. The young open cluster NGC2244 in the center of the nebula has a pattern of radial expansion and rotation. We discuss its implication on the cluster formation, e.g., monolithic cold collapse or hierarchical assembly. On the other hand, we also investigate three groups located around the border of the HII bubble. The western group seems to be spatially correlated with the adjacent gas structure, but their kinematics is not associated with that of the gas. The southern group does not show any systematic motion relative to NGC2244. These two groups might be spontaneously formed in filaments of a turbulent cloud. The eastern group is spatially and kinematically associated with the gas pillar receding away from NGC2244. This group might be formed by feedback from massive stars in NGC2244. Our results suggest that the stellar population in the Rosette Nebula may form through three different processes: the expansion of stellar clusters, hierarchical star formation in turbulent clouds, and feedback-driven star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/524/A10
- Title:
- Radial Velocity standard stars
- Short Name:
- J/A+A/524/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The calibration of the Radial Velocity Spectrometer (RVS) onboard the ESA Gaia satellite (to be launched in 2012) requires a list of standard stars with a radial velocity (RV) known with an accuracy of at least 300m/s. The IAU commission 30 lists of RV standard stars are too bright and not dense enough. We describe the selection criteria due to the RVS constraints for building an adequate full-sky list of at least 1000 RV standards from catalogues already published in the literature.
- ID:
- ivo://CDS.VizieR/J/AJ/130/767
- Title:
- Radial velocity studies of close binary stars
- Short Name:
- J/AJ/130/767
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocity measurements and sine-curve fits to orbital velocity variations are presented for the ninth set of 10 close binary systems: V395 And, HS Aqr, V449 Aur, FP Boo, SW Lac, KS Peg, IW Per, V592 Per, TU UMi, and FO Vir. The first three are very close, possibly detached, early-type binaries, and all three require further investigation. Particularly interesting is V395 And, whose spectral type is as early as B7/8 for a 0.685 day orbit binary. KS Peg and IW Per are single-line binaries, with the former probably hosting a very low mass star. We have detected a low-mass secondary in an important semidetached system, FO Vir, at q=0.125+/-0.005. The contact binary FP Boo is also a very small mass ratio system, q=0.106+/-0.005. The other contact binaries in this group are V592 Per, TU UMi, and the well-known SW Lac. V592 Per and TU UMi have bright tertiary companions; for these binaries, and for V395 And, we used a novel technique of arranging the broadening functions into a two-dimensional image in phase. The case of TU UMi turned out to be intractable even using this approach, and we have not been able to derive a firm radial velocity orbit for this binary. Three systems of this group were observed spectroscopically before: HS Aqr, SW Lac, and KS Peg.
- ID:
- ivo://CDS.VizieR/J/ApJ/664/1102
- Title:
- Radial velocity survey of Cyg OB2 association
- Short Name:
- J/ApJ/664/1102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a radial velocity survey of the Cyg OB2 association over a 6yr (1999-2005) time interval to search for massive close binaries. During this time we obtained 1139 spectra on 146 OB stars to measure mean systemic radial velocities and radial velocity variations. We spectroscopically identify 73 new OB stars for the first time, the majority of which are likely to be association members.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A5
- Title:
- Radial velocity survey of low-mass binaries
- Short Name:
- J/A+A/618/A5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The identification and characterisation of low-mass binaries is of importance for a range of astrophysical investigations. Low-mass binaries in young (~10-100Myr) moving groups (YMGs) in the solar neighborhood are of particular significance as they provide unique opportunities to calibrate stellar models and evaluate the ages and coevality of the groups themselves. Low-mass M-dwarfs have pre-main sequence life times on the order of ~100Myr and therefore are continually evolving along a mass-luminosity track throughout the YMG phase, providing ideal laboratories for precise isochronal dating, if a model-independent dynamical mass can be measured. AstraLux lucky imaging multiplicity surveys have recently identified hundreds of new YMG low-mass binaries, where a subsample of M-dwarf multiples have estimated orbital periods less than 50 years. We have conducted a radial velocity survey of a sample of 29 such targets to complement the astrometric data. This will allow enhanced orbital determinations and precise dynamical masses to be derived in a shorter timeframe than possible with astrometric monitoring alone, and allow for a more reliable isochronal analysis. Here we present radial velocity measurements derived for our sample over several epochs. We report the detection of the three-component spectroscopic multiple 2MASS J05301858-5358483, for which the C component is a new discovery, and forms a tight pair with the B component. Originally identified as a YMG member, we find that this system is a likely old field interloper, whose high chromospheric activity level is caused by tidal spin-up of the tight BC pair. Two other triple systems with a tight pair exist in the sample, 2MASS J04244260-0647313 (previously known) and 2MASS J20163382-0711456, but for the rest of the targets we find that additional tidally synchronized companions are highly unlikely, providing further evidence that their high chromospheric activity levels are generally signatures of youth.
- ID:
- ivo://CDS.VizieR/J/A+A/535/A39
- Title:
- Radial velocity survey toward NGC 6253
- Short Name:
- J/A+A/535/A39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the most metal-rich open cluster of the Galaxy, NGC 6253 is a target of special interest in the search for extrasolar planets, the study of stellar populations, and the chemical/dynamical evolution of the Galactic disk. We present the results of two photometric campaigns and a VLT multi-epoch radial velocity survey toward the open cluster NGC 6253. We complement our analysis with photometric, proper motion, and radial velocity data available from previous studies of this cluster, and analyze three planetary candidates found in the field of NGC 6253.
- ID:
- ivo://CDS.VizieR/J/ApJS/249/22
- Title:
- Radial velocity variable stars from LAMOST DR4
- Short Name:
- J/ApJS/249/22
- Date:
- 25 Oct 2021 00:46:50
- Publisher:
- CDS
- Description:
- Radial velocity (RV) variable stars are important in astrophysics. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic survey has provided ~6.5 million stellar spectra in its Data Release 4 (DR4). During the survey ~4.7 million unique sources were targeted and ~1 million stars observed repeatedly. The probabilities of stars being RV variables are estimated by comparing the observed RV variations with simulated ones. We build a catalog of 80702 RV variable candidates with probability greater than 0.60 by analyzing the multi-epoch sources covered by LAMOST DR4. Simulations and cross-identifications show that the purity of the catalog is higher than 80%. The catalog consists of 77% binary systems and 7% pulsating stars as well as 16% pollution by single stars. 3138 RV variables are classified through cross-identifications with published results in literatures. By using the 3138 sources common in both LAMOST and a collection of published RV variable catalogs, we are able to analyze LAMOST's RV variable detection rate. The efficiency of the method adopted in this work relies not only on the sampling frequency of observations but also periods and amplitudes of RV variables. With the progress of LAMOST, Gaia, and other surveys, more and more RV variables will be confirmed and classified.