- 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.
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- 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.
- 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.
- 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).
- 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}.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A146
- Title:
- Radial Velocity and BIS measurements of Polaris
- Short Name:
- J/A+A/623/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate temporally changing variability amplitudes and the multi- periodicity of the type-I Cepheid Polaris using 162 high-precision radial velocity (RV) and bisector inverse span (BIS) measurements based on optical spectra recorded using Hermes at the 1.2m Flemish Mercator telescope on La Palma, Canary Islands, Spain. Using an empirical template fitting method, we show that Polaris' RV amplitude has been stable to within ~30m/s between September 2011 and November 2018. We apply the template fitting method to publicly accessible, homogeneous RV data sets from the literature and provide an updated solution of Polaris' eccentric 29.3yr orbit. While the inferred pulsation-induced RV amplitudes differ among individual data sets, we find no evidence for time-variable RV amplitudes in any of the separately considered, homogeneous data sets. Additionally, we find that increasing photometric amplitudes determined using SMEI photometry are likely spurious detections due to as yet ill-understood systematic effects of instrumental origin. Given this confusing situation, further analysis of high-quality homogeneous data sets with well-understood systematics is required to confidently establish whether Polaris' variability amplitude is subject to change over time. We confirm periodic bisector variability periods of 3.97d and 40.22d using Hermes BIS measurements and identify a third signal at a period of 60.17d. Although the 60.17d signal dominates the BIS periodogram, we caution that this signal may not be independent of the 40.22d signal. Finally, we show that the 40.22d signal cannot be explained by stellar rotation. Further long-term, high-quality spectroscopic monitoring is required to unravel the complete set of Polaris' periodic signals, which has the potential to provide unprecedented insights into the evolution of Cepheid variables.
- ID:
- ivo://CDS.VizieR/J/ApJ/903/110
- Title:
- Radial velocity and g-i color in M85 globular clusters
- Short Name:
- J/ApJ/903/110
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- We present a study on the stellar population and kinematics of globular clusters (GCs) in the peculiar galaxy M85. We obtain optical spectra of 89 GCs at 8kpc<R<160kpc using the MMT/Hectospec. We divide them into three groups, blue/green/red GCs (B/G/RGCs), with their (g-i)0 colors. All GC subpopulations have mean ages of about 10Gyr, but showing differences in metallicities. The BGCs and RGCs are the most metal-poor ([Z/H]~-1.49) and metal-rich ([Z/H]~-0.45), respectively, and the GGCs are in between. We find that the inner GC system exhibits a strong overall rotation that is entirely due to a disklike rotation of the RGC system. The BGC system shows little rotation. The GGCs show kinematic properties clearly distinct among the GC subpopulations, having higher mean velocities than the BGCs and RGCs and being aligned along the major axis of M85. This implies that the GGCs have an origin different from the other GC subpopulations. The rotation-corrected velocity dispersion of the RGC system is much lower than that of the BGC system, indicating the truncation of the red halo of M85. The BGCs have a flat velocity dispersion profile out to R=67kpc, reflecting the dark matter extent of M85. Using the velocity dispersion of the BGC system, we estimate the dynamical mass of M85 to be 3.8x1012M{sun}. We infer that M85 has undergone merging events lately, resulting in the peculiar kinematics of the GC system.
- ID:
- ivo://CDS.VizieR/J/AJ/120/2101
- Title:
- Radial Velocity and Photometry of HD 104994
- Short Name:
- J/AJ/120/2101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intense coordinated spectroscopic and photometric monitoring of the suspected Wolf-Rayet binary WR 46 in 1999 reveals clear periodic variations, P=0.329+/-0.013 days, in the radial velocities of the emission lines of highest ionization potential, O VI and N V, found deepest in the Wolf-Rayet wind and thus least likely to be perturbed by a companion. These are accompanied by coherent variability in the profiles of lines with lower ionization/excitation potential and in the continuum flux. Most probably originating from orbital motion of the Wolf-Rayet component of the binary, this periodic radial velocity signal disappears from time to time, thus creating a puzzle yet to be solved. We show that the entangled patterns of the line profile variability are mainly governed by transitions between high and low states of the system's continuum flux. Based in part on observations obtained at the European Southern Observatory, La Silla, Chile (ESO program 62.H-0110).
