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2101. Radial velocities of 12 Psc and HD 159062
ID:
ivo://CDS.VizieR/J/AJ/161/106
Title:
Radial velocities of 12 Psc and HD 159062
Short Name:
J/AJ/161/106
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of a white dwarf companion to the G1 V star 12Psc found as part of a Keck adaptive optics imaging survey of long-term accelerating stars from the McDonald Observatory Planet Search Program. Twenty years of precise radial-velocity monitoring of 12Psc with the Tull Spectrograph at the Harlan J. Smith telescope reveals a moderate radial acceleration (~10m/s/yr), which together with relative astrometry from Keck/NIRC2 and the astrometric acceleration between Hipparcos and Gaia DR2 yields a dynamical mass of M_B_=0.605_-0.022_^+0.021^M{sun} for 12PscB, a semimajor axis of 40_-4_^+2^au, and an eccentricity of 0.84{+/-}0.08. We also report an updated orbital fit of the white dwarf companion to the metal-poor (but barium-rich) G9 V dwarf HD159062 based on new radial velocity observations from the High-Resolution Spectrograph at the Hobby-Eberly Telescope and astrometry from Keck/NIRC2. A joint fit of the available relative astrometry, radial velocities, and tangential astrometric acceleration yields a dynamical mass of M_B_=0.609_-0.011_^+0.010^M{sun} for HD159062B, a semimajor axis of 60_-7_^+5^au, and preference for circular orbits (e<0.42 at 95% confidence). 12PscB and HD159062B join a small list of resolved Sirius-like benchmark white dwarfs with precise dynamical mass measurements which serve as valuable tests of white dwarf mass-radius cooling models and probes of AGB wind accretion onto their main-sequence companions.
2102. Radial velocities of 14 southern Cepheids
ID:
ivo://CDS.VizieR/J/MNRAS/362/1167
Title:
Radial velocities of 14 southern Cepheids
Short Name:
J/MNRAS/362/1167
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present high-resolution spectroscopic observations and species-by-species radial velocities of a number of southern Cepheids. The stars (BP Cir, V350 Sgr, AX Cir, V636 Sco, W Sgr, S Mus, {beta} Dor, TT Aql, Y Oph, YZ Car, SW Vel, X Pup, T Mon and l Car) were observed as part of a long-term programme at Mt John University Observatory. Radial velocities were determined with the line bisector technique, and have a precision of ~300m/s. Velocity differences as large as 30km/s were found for H and Ca II when referenced to the metallic line velocity curves, but more subtle variations (of 12km/s) were also detected in many other species. Pulsational phase anticorrelations are found between lines of Si II and Ba II, confirming the propagation time delay between line-forming layers producing these two species. We find that the amplitude and phase differences between the various species increase with period.
2103. Radial velocities of stars in the Galactic Center
ID:
ivo://CDS.VizieR/J/ApJ/681/1254
Title:
Radial velocities of stars in the Galactic Center
Short Name:
J/ApJ/681/1254
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from K-band slit scan observations of a ~20"x20" region of the Galactic center (GC) in two separate epochs more than 5 years apart. The high-resolution (R={lamda}/{Delta}{lambda}>=14000) observations allow the most accurate radial velocity and acceleration measurements of the stars in the central parsec of the Galaxy. Detected stars can be divided into three groups based on the CO absorption band heads at ~2.2935um and the HeII lines at ~2.0581 and ~2.112, 2.113um: cool, narrow-line hot, and broad-line hot. The radial velocities of the cool, late-type stars have approximately a symmetrical distribution with its center at ~-7.8+/-10.3km/s and a standard deviation ~113.7+/-10.3km/s. Although our statistics are dominated by the brightest stars, we estimate a central black hole mass of (3.9+/-1.1)x10^6^M_{sun}_, consistent with current estimates from complete orbits of individual stars. Our surface density profile and the velocity dispersion of the late-type stars support the existence of a low-density region at the Galactic center suggested by earlier observations.
2104. Radial velocities of the Be star HR 2142
ID:
ivo://CDS.VizieR/J/ApJ/828/47
Title:
Radial velocities of the Be star HR 2142
Short Name:
J/ApJ/828/47
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectroscopic investigation of the Be+sdO binary system HR 2142 that is based upon large sets of ultraviolet observations from the International Ultraviolet Explorer (IUE) and ground-based H{alpha} observations. We measured radial velocities for the Be star component from these spectra and computed a revised orbit. In order to search for the spectral signature of the hot subdwarf, we cross-correlated the short wavelength end of each IUE spectrum with a model hot star spectrum, and then we used the predicted Doppler shifts of the subdwarf to shift-and-add all the cross-correlation functions to the frame of the subdwarf. This merged function shows the weak signal from the spectral lines of the hot star, and a best fit is obtained with a mass ratio M_2_/M_1_=0.07+/-0.02, companion temperature T_eff_>=43+/-5kK, projected rotational velocity Vsini<30km/s, and a monochromatic flux ratio near 1170{AA} of f_2_/f_1_>0.009+/-0.001. This hot subdwarf creates a one-armed spiral, tidal wake in the disk of the Be star, and we present a circumbinary disk model that can explain the occurrence of shell absorption lines by gas enhancements that occur where gas crossing the gap created by the subdwarf strikes the disk boundaries. The faint companion of HR 2142 may be representative of a significant fraction of Be stars with undetected former mass donor companion stars.
2105. Radial velocities of the EB M-dwarf YYGem
ID:
ivo://CDS.VizieR/J/ApJ/873/69
Title:
Radial velocities of the EB M-dwarf YYGem
Short Name:
J/ApJ/873/69
Date:
21 Oct 2021
Publisher:
CDS
Description:
YY Gem is a short-period eclipsing binary system containing two nearly identical, rapidly rotating, very active early M dwarfs. This binary represents an important benchmark system for calibrating empirical relations between fundamental properties of low-mass stars and for testing theories of interior structure and evolution of these objects. Both components of YY Gem exhibit inflated radii, which has been attributed to poorly understood magnetic activity effects. Despite a long history of magnetic activity studies of this system, no direct magnetic field measurements have been made for it. Here we present a comprehensive characterization of the surface magnetic field in both components of YY Gem. We reconstructed the global field topologies with the help of a tomographic inversion technique applied to high-resolution spectropolarimetric data. This analysis revealed moderately complex global fields with a typical strength of 200-300G and anti-aligned dipolar components. A complementary Zeeman intensification analysis of the disentangled intensity spectra showed that the total mean field strength reaches 3.2-3.4kG in both components of YY Gem. We used these results together with other recent magnetic field measurements of M dwarfs to investigate the relation between the global and small-scale fields in these stars. We also assessed predictions of competing magnetoconvection interior structure models developed for YY Gem, finding that only one of them anticipated the surface field strength compatible with our observations. Results of our starspot mapping of YY Gem do not support the alternative family of theoretical stellar models, which attempts to explain the radius inflation by postulating a large spot filling factor.
2106. Radial velocities of the HgMn star HD 11733
ID:
ivo://CDS.VizieR/J/A+A/553/A27
Title:
Radial velocities of the HgMn star HD 11733
Short Name:
J/A+A/553/A27
Date:
21 Oct 2021
Publisher:
CDS
Description:
Time series of high-resolution spectra of the late B-type star HD 11753 exhibiting HgMn chemical peculiarity are used to study the surface distribution of different chemical elements and their temporal evolution. High-resolution and high signal-to-noise ratio spectra were obtained using the CORALIE spectrograph at La Silla in 2000, 2009, and 2010. Surface maps of YII, SrII, TiII, and CrII were calculated using the Doppler imaging technique. The results were also compared to equivalent width measurements. The evolution of chemical spots both on short and long time scales were investigated. We determine the binary orbit of HD 11753 and fine-tune the rotation period of the primary. The earlier discovered fast evolution of the chemical spots is confirmed by an analysis using both the chemical spot maps and equivalent width measurements. In addition, a long-term decrease in the overall YII and SrII abundances is discovered. A detailed analysis of the chemical spot configurations reveals some possible evidence that a very weak differential rotation is operating in HD 11753.
2107. Radial velocities of the semi-detached Algol W UMi
ID:
ivo://CDS.VizieR/J/AJ/155/133
Title:
Radial velocities of the semi-detached Algol W UMi
Short Name:
J/AJ/155/133
Date:
21 Oct 2021
Publisher:
CDS
Description:
Double-lined eclipsing binaries allow accurate and direct determination of fundamental parameters such as mass and radius for each component, and they provide important constraints on the stellar structure and evolution models. In this study, we aim to determine a unique set of binary parameters for the Algol system W UMi and to examine its evolutionary status. New high-resolution time-series spectroscopic observations were carried out during 14 nights from 2008 April to 2011 March, and a total of 37 spectra were obtained using the Bohyunsan Optical Echelle Spectrograph. We measured the radial velocities (RVs) for both components, and the effective temperature of the primary star was found to be T_eff,1_=9310+/-90K by a comparison of the observed spectra and the Kurucz models. The physical parameters of W UMi were derived by an analysis of our RV data together with the multi-band light curves of Devinney et al. The individual masses, radii, and luminosities of both components are M1=3.68+/-0.10M_{sun}_ and M2=1.47+/-0.04M_{sun}_, R1=3.88+/-0.03R_{sun}_ and R2=3.13+/-0.03R_{sun}_, and L1=102+/-1L_{sun}_ and L2=7.3+/-0.1L_{sun}_, respectively. A comparison of these parameters with theoretical stellar models showed that the primary component lies in the main-sequence band, while the less massive secondary is noticeably evolved. The results indicate that the initially more massive star became the present secondary by losing most of its own mass via mass transfer to the companion (present primary).
2108. Radial velocities & orbital data, 5 triple stars
ID:
ivo://CDS.VizieR/J/AJ/160/251
Title:
Radial velocities & orbital data, 5 triple stars
Short Name:
J/AJ/160/251
Date:
21 Oct 2021
Publisher:
CDS
Description:
Joint analysis of radial velocities and position measurements of five hierarchical stellar systems is undertaken to determine elements of their inner and outer orbits and, whenever possible, their mutual inclinations. The inner and outer periods are 12.9 and 345yr for HD12376 (ADS1613), 1.14 and ~1500yr for HD19971 (ADS2390), 8.3 and 475yr for HD89795 (ADS7338), 1.11 and 40yr for HD152027, 0.69 and 7.4yr for HD190412. The latter system with its coplanar and quasi-circular orbits belongs to the family of compact planetary-like hierarchies, while the orbits in HD12376 have a mutual inclination of 131{deg}.
2109. Radial velocities & photometry of the K dwarf HD26965
ID:
ivo://CDS.VizieR/J/AJ/155/126
Title:
Radial velocities & photometry of the K dwarf HD26965
Short Name:
J/AJ/155/126
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of a radial velocity signal that can be interpreted as a planetary-mass candidate orbiting the K dwarf HD 26965, with an orbital period of 42.364+/-0.015 days, or alternatively, as the presence of residual, uncorrected rotational activity in the data. Observations include data from HIRES, PFS, CHIRON, and HARPS, where 1111 measurements were made over 16 years. Our best solution for HD 26965 b is consistent with a super-Earth that has a minimum mass of 6.92+/-0.79 M_{Earth}_ orbiting at a distance of 0.215+/-0.008 au from its host star. We have analyzed the correlation between spectral activity indicators and the radial velocities from each instrument, showing moderate correlations that we include in our model. From this analysis, we recover a ~38-day signal, which matches some literature values of the stellar rotation period. However, from independent Mt. Wilson HK data for this star, we find evidence for a significant 42-day signal after subtraction of longer period magnetic cycles, casting doubt on the planetary hypothesis for this period. Although our statistical model strongly suggests that the 42-day signal is Doppler in origin, we conclude that the residual effects of stellar rotation are difficult to fully model and remove from this data set, highlighting the difficulties to disentangle small planetary signals and photospheric noise, particularly when the orbital periods are close to the rotation period of the star. This study serves as an excellent test case for future works that aim to detect small planets orbiting "Sun-like" stars using radial velocity measurements.
2110. Radial velocity and activity measurements of HAT-P-11
ID:
ivo://CDS.VizieR/J/AJ/155/255
Title:
Radial velocity and activity measurements of HAT-P-11
Short Name:
J/AJ/155/255
Date:
21 Oct 2021
Publisher:
CDS
Description:
HAT-P-11 is a mid-K dwarf that hosts one of the first Neptune-sized planets found outside the solar system. The orbit of HAT-P-11b is misaligned with the star's spin-one of the few known cases of a misaligned planet orbiting a star less massive than the Sun. We find an additional planet in the system based on a decade of precision radial velocity (RV) measurements from Keck/High Resolution Echelle Spectrometer. HAT-P-11c is similar to Jupiter in its mass (M_P_sin i=1.6+/-0.1 M_J_) and orbital period (P=9.3_-0.5_^+1.0^ year), but has a much more eccentric orbit (e=0.60+/-0.03). In our joint modeling of RV and stellar activity, we found an activity-induced RV signal of ~7 m/s, consistent with other active K dwarfs, but significantly smaller than the 31 m/s reflex motion due to HAT-P-11c. We investigated the dynamical coupling between HAT-P-11b and c as a possible explanation for HAT-P-11b's misaligned orbit, finding that planet-planet Kozai interactions cannot tilt planet b's orbit due to general relativistic precession; however, nodal precession operating on million year timescales is a viable mechanism to explain HAT-P-11b's high obliquity. This leaves open the question of why HAT-P-11c may have such a tilted orbit. At a distance of 38 pc, the HAT-P-11 system offers rich opportunities for further exoplanet characterization through astrometry and direct imaging.

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