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1101. Radial velocity curves of 3 Cepheids
ID:
ivo://CDS.VizieR/J/MNRAS/434/870
Title:
Radial velocity curves of 3 Cepheids
Short Name:
J/MNRAS/434/870
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of spectroscopic radial velocity and photometric data of three bright Galactic Cepheids: LR Trianguli Australis (LR TrA), RZ Velorum (RZ Vel) and BG Velorum (BG Vel). Based on new radial velocity data, these Cepheids have been found to be members of spectroscopic binary systems. The ratio of the peak-to-peak radial velocity amplitude to photometric amplitude indicates the presence of a companion for LR TrA and BG Vel. IUE spectra indicate that the companions of RZ Vel and BG Vel cannot be hot stars. The analysis of all available photometric data revealed that the pulsation period of RZ Vel and BG Vel varies monotonically, due to stellar evolution. Moreover, the longest period Cepheid in this sample, RZ Vel, shows period fluctuations superimposed on the monotonic period increase. The light-time effect interpretation of the observed pattern needs long-term photometric monitoring of this Cepheid. The pulsation period of LR TrA has remained constant since the discovery of its brightness variation. Using statistical data, it is also shown that a large number of spectroscopic binaries still remain to be discovered among bright classical Cepheids.
1102. Radial velocity curves of 7 KIC
ID:
ivo://CDS.VizieR/J/MNRAS/469/2089
Title:
Radial velocity curves of 7 KIC
Short Name:
J/MNRAS/469/2089
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, we present high- and middle-resolution spectral observations of seven heartbeat (HB), highly eccentric, Kepler binaries: four of them (KIC 3230227, KIC 03547874, KIC 03749404, KIC 07672068) are SB2 stars and the remaining three (KIC 04949194, KIC 05960989, KIC 10092506) are SB1 stars. The flux amplitudes of their HB signals are from 0.001 to 0.01. Five targets of the sample with eccentricity above 0.64 show tidally induced oscillations, which are harmonics of the orbital period. The orbital and global parameters of all targets were determined as a result of simultaneous modelling of our spectral observations and Kepler photometric data. They exhibit that the masses and radii of some target components do not obey the temperature-mass-radius relation of main-sequence stars. Although our targets do not obey precisely the theoretical period-eccentricity relation, they confirm the previous conclusion that HB stars draw the upper envelope of the eccentricity-period distribution. We did not find simple empirical dependences of the amplitude of the HB signal on the orbital and global parameters of the targets.
1103. Radial velocity curves of 11 UMa and HD 32518
ID:
ivo://CDS.VizieR/J/A+A/505/1311
Title:
Radial velocity curves of 11 UMa and HD 32518
Short Name:
J/A+A/505/1311
Date:
21 Oct 2021
Publisher:
CDS
Description:
11 UMi and HD 32518 belong to a sample of 62 K giant stars that has been observed since February 2004 using the 2m Alfred Jensch telescope of the Thueringer Landessternwarte (TLS) to measure precise radial velocities (RVs). The aim of this survey is to investigate the dependence of planet formation on the mass of the host star by searching for planetary companions around intermediate-mass giants.
1104. Radial velocity for 19 RR Lyrae
ID:
ivo://CDS.VizieR/J/AJ/162/117
Title:
Radial velocity for 19 RR Lyrae
Short Name:
J/AJ/162/117
Date:
21 Mar 2022 00:54:18
Publisher:
CDS
Description:
We report 272 radial velocities for 19 RR-Lyrae variables. For most of the stars we have radial velocities for the complete pulsation cycle. These data are used to determine robust center-of-mass radial velocities that have been compared to values from the literature in a search for evidence of binary systems. Center-of-mass velocities were determined for each star using Fourier Series and template fits to the radial velocities. Our center-of-mass velocities have uncertainties from {+/-}0.16km/s to {+/-}2.5km/s, with a mean uncertainty of {+/-}0.92km/s. We combined our center-of-mass velocities with values from the literature to look for deviations from the mean center-of-mass velocity of each star. Fifteen RR-Lyrae show no evidence of binary motion (BK And, CI And, Z CVn, DM Cyg, BK Dra, RR Gem, XX Hya, SZ Leo, BX Leo, TT Lyn, CN Lyr, TU Per, U Tri, RV UMa, and AV Vir). In most cases this conclusion is reached due to the sporadic sampling of the center-of-mass velocities over time. Three RR Lyrae show suspicious variation in the center-of-mass velocities that may indicate binary motion but do not prove it (SS Leo, ST Leo, and AO Peg). TU UMa was observed by us near a predicted periastron passage (at 0.14 in orbital phase) but the absence of additional center-of-mass velocities near periastron makes the binary detection, based on radial velocities alone, uncertain. Two stars in our sample show H{gamma} emission in phases 0.9-1.0: SS Leo and TU UMa.
1105. Radial velocity of gamma Pegasi
ID:
ivo://CDS.VizieR/J/A+A/448/697
Title:
Radial velocity of gamma Pegasi
Short Name:
J/A+A/448/697
Date:
21 Oct 2021
Publisher:
CDS
Description:
High resolution and high signal to noise ratio spectroscopic observations of the classical {beta} Cephei star {gamma} Peg were obtained between 1991 and 2005. The analysis of these data combined with previously published results shows that {gamma} Peg is a spectroscopic binary with an orbital period of 370.5d. We discovered three new frequencies in addition to the well-known 6.5897d^-1^ (0.15175d) one. That at 6.01d^-1^ is a typical Cephei frequency. The two others at 0.68 and 0.87d^-1^ are similar to the high degree g-mode frequencies found in SPB stars. Thus, {gamma} Peg is a hybrid {beta} Cephei-SPB star. Its position in the HR diagram is compatible with such a status. In addition, a small increase of the main period has been detected between the 1995 and 2005 observations.
1106. Radial velocity studies of close binary stars
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.
1107. Radial velocity time series of EK Eridani
ID:
ivo://CDS.VizieR/J/A+A/628/A106
Title:
Radial velocity time series of EK Eridani
Short Name:
J/A+A/628/A106
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present further evidence of acoustic oscillations in the slowly rotating overactive G8 sub-giant EK Eri. This star was observed with the 1m Hertzsprung SONG telescope at the Observatorio del Teide for two different runs of 8 and 13 nights, respectively, that were separated by about a year. We determined a significant excess of power around {nu}_max_=253+/-3uHz in the first observing run and were able to determine a large separation, {Delta}_{nu}_=16.430+/-22uHz. No significant excess of power was instead detected in a subsequent SONG observing season, as also supported by our analysis of the simultaneous TESS photometric observations. We propose a new amplitude-luminosity relation in order to account for the missing power in the power spectrum. Based on the evolutionary stage of this object, we argue that a standard {alpha}^2^{OMEGA} dynamo cannot be excluded as the possible origin for the observed magnetic field.
1108. Radial velocity variable stars from LAMOST DR4
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.
1109. Radii of 22 galactic Cepheids
ID:
ivo://CDS.VizieR/J/A+AS/140/79
Title:
Radii of 22 galactic Cepheids
Short Name:
J/A+AS/140/79
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present radial velocity data for 22 galactic Cepheid stars obtained with Coravel spectrometer. Continuous observation over several years has enabled us to obtain 852 individual velocities covering all the phases of the pulsation. The mean number of measurements per star is 39, ranging from 20 to 113. For each star radial velocity versus phase diagrams have been fitted by analytical relation, and the stellar radius variation has been derived by integration of this relation over the whole period. Using recent ubv photometry of the literature and velocity curves, we have calculated the radii of the stars using a method based on the Baade-Wesselink concept. For these 22 Cepheids we give a linear logarithmic period-radius relation with a range of 2,4 to 45 days.
1110. Radio emission from stars at 250GHz
ID:
ivo://CDS.VizieR/J/A+A/281/161
Title:
Radio emission from stars at 250GHz
Short Name:
J/A+A/281/161
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used the IRAM 30 m-telescope together with the Max Planck Institute for Radio Astronomy (MPIfR) bolometer to survey nearly 270 stars of different types for 250GHz continuum emission. We compare these data with their low frequency (cm-range) properties. Early type stars show very often a deviation from the uniformly expanding wind model which we tentatively attribute to temperature and/or density fluctuations in their deeper atmospheric layers. For WR stars this deviation seems to depend on the effective temperature. Pre-main sequence stars usually seem to be surrounded by a shell of warm dust making a substantial contribution to the 250 GHz flux density value. We have found especially for nearby giants and supergiants that a layer at the transition from photosphere to chromosphere emits ample 250 GHz radiation. We show that the present data can still be explained by a simple uniformly illuminated disk model with the known stellar radius. Optically variable stars are not very strong emitters at 250 GHz. We preferentially detected the more exotic ones, a few Beta Lyr-type and symbiotic stars. Comments on many individual objects are given in the appropriate sections.