- ID:
- ivo://CDS.VizieR/J/AJ/154/123
- Title:
- Radial velocity follow-up of the HD 3167 system
- Short Name:
- J/AJ/154/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD 3167 is a bright (V=8.9 mag) K0 V star observed by NASA's K2 space mission during its Campaign 8. It has recently been found to host two small transiting planets, namely, HD 3167b, an ultra-short-period (0.96 days) super-Earth, and HD 3167c, a mini-Neptune on a relatively long-period orbit (29.85 days). Here we present an intensive radial velocity (RV) follow-up of HD 3167 performed with the FIES@NOT, HARPS@ESO-3.6 m, and HARPS-N@TNG spectrographs. We revise the system parameters and determine radii, masses, and densities of the two transiting planets by combining the K2 photometry with our spectroscopic data. With a mass of 5.69+/-0.44 M_{Earth}_, a radius of 1.574+/-0.054 R_{Earth}_, and a mean density of 8.00_-0.98_^+1.10^ g/cm^3^, HD 3167b joins the small group of ultra-short-period planets known to have rocky terrestrial compositions. HD 3167c has a mass of 8.33_-1.85_^+1.79^ M_{Earth}_ and a radius of 2.740_-0.100_^+0.106^ R_{Earth}_, yielding a mean density of 2.21_-0.53_^+0.56^ g/cm^3^, indicative of a planet with a composition comprising a solid core surrounded by a thick atmospheric envelope. The rather large pressure scale height (~350 km) and the brightness of the host star make HD 3167c an ideal target for atmospheric characterization via transmission spectroscopy across a broad range of wavelengths. We found evidence of additional signals in the RV measurements but the currently available data set does not allow us to draw any firm conclusions on the origin of the observed variation.
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- ID:
- ivo://CDS.VizieR/J/AJ/162/238
- Title:
- Radial velocity follow up of Wolf 503
- Short Name:
- J/AJ/162/238
- Date:
- 11 Mar 2022 06:30:07
- Publisher:
- CDS
- Description:
- Using radial-velocity measurements from four instruments, we report the mass and density of a 2.043{+/-}0.069R{Earth} sub-Neptune orbiting the quiet K-dwarf Wolf503 (HIP67285). In addition, we present improved orbital and transit parameters by analyzing previously unused short-cadence K2 campaign 17 photometry and conduct a joint radial-velocity-transit fit to constrain the eccentricity at 0.41{+/-}0.05. The addition of a transit observation by Spitzer also allows us to refine the orbital ephemeris in anticipation of further follow-up. Our mass determination, 6.26_-0.70_^+0.69^M{Earth} , in combination with the updated radius measurements, gives Wolf503b a bulk density of {rho}=2.92_-0.44_^+0.50^g/cm^3^. Using interior composition models, we find this density is consistent with an Earth-like core with either a substantial H_2_O mass fraction (45_-16_^+19^%) or a modest H/He envelope (0.5%{+/-}0.3%). The low H/He mass fraction, along with the old age of Wolf503 (11{+/-}2Gyr), makes this sub-Neptune an opportune subject for testing theories of XUV-driven mass loss while the brightness of its host (J=8.3mag) makes it an attractive target for transmission spectroscopy.
- ID:
- ivo://CDS.VizieR/J/ApJ/732/39
- Title:
- Rotational velocities of K giant stars
- Short Name:
- J/ApJ/732/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for unusually rapidly rotating giant stars in a large sample of K giants (~1300 stars) that had been spectroscopically monitored as potential targets for the Space Interferometry Mission's Astrometric Grid. The stars in this catalog are much fainter and typically more metal-poor than those of other catalogs of red giant star rotational velocities, but the spectra generally only have signal-to-noise ratio (S/N) of ~20-60, making the measurement of the widths of individual lines difficult. To compensate for this, we have developed a cross-correlation method to derive rotational velocities in moderate S/N echelle spectra to efficiently probe this sample for rapid rotator candidates. We have discovered 28 new red giant rapid rotators as well as one extreme rapid rotator with a vsin i of 86.4km/s. Rapid rotators comprise 2.2% of our sample, which is consistent with other surveys of brighter, more metal-rich K giant stars. Although we find that the temperature distribution of rapid rotators is similar to that of the slow rotators, this may not be the case with the distributions of surface gravity and metallicity. The rapid rotators show a slight overabundance of low-gravity stars and as a group are significantly more metal-poor than the slow rotators, which may indicate that the rotators are tidally locked binaries.
- ID:
- ivo://CDS.VizieR/J/AJ/156/64
- Title:
- RV measurements for 6 K giants in the SENS program
- Short Name:
- J/AJ/156/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of long-period radial velocity (RV) variations in six intermediate-mass K-giant stars using precise RV measurements. These discoveries are part of the Search for Exoplanets around Northern Circumpolar Stars (SENS) survey being conducted at the Bohyunsan Optical Astronomy Observatory. The nature of the RV variations was investigated by looking for photometric and line shape variations. We can find no variability with the RV period in these quantities and conclude that RV variations are most likely due to unseen sub-stellar companions. Orbital solutions for the six stars yield orbital periods in the range 418-1065 days and minimum masses in the range 1.9-8.5 M_J_. These properties are typical on planets around intermediate-mass stars. Our SENS survey so far has about an 8% confirmed planet occurrence rate, and it will provide better statistics on planets around giant stars when the survey is completed.
- ID:
- ivo://CDS.VizieR/J/AJ/155/120
- Title:
- RV variability of the K-giant {gamma} Draconis
- Short Name:
- J/AJ/155/120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present precise stellar radial velocity (RV) measurements of {gamma} Dra taken from 2003 to 2017. The data from 2003 to 2011 show coherent, long-lived variations with a period of 702 days. These variations are consistent with the presence of a planetary companion having m sin i=10.7 M_Jup_ whose orbital properties are typical for giant planets found around evolved stars. An analysis of the Hipparcos photometry, Ca II S-index measurements, and measurements of the spectral line shapes during this time show no variations with the RV of the planet, which seems to "confirm" the presence of the planet. However, RV measurements taken from 2011-2017 seem to refute this. From 2011-2013, the RV variations virtually disappear, only to return in 2014 but with a noticeable phase shift. The total RV variations are consistent either with amplitude variations on timescales of ~10.6 year, or the beating effect between two periods of 666 and 801 days. It seems unlikely that both these signals stem from a two-planet system. A simple dynamical analysis indicates that there is only a 1%-2% chance that the two-planet system is stable. Rather, we suggest that this multi-periodic behavior may represent a new form of stellar variability, possibly related to oscillatory convective modes. If such intrinsic stellar variability is common around K giant stars and is attributed to planetary companions, then the planet occurrence rate among these stars may be significantly lower than thought.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/154
- Title:
- Sgr stream K- & M-giants and BHB stars
- Short Name:
- J/ApJ/886/154
- Date:
- 07 Dec 2021 13:01:04
- Publisher:
- CDS
- Description:
- We characterize the kinematic and chemical properties of ~3000 Sagittarius (Sgr) stream stars, including K-giants, M-giants, and blue horizontal branch stars (BHBs), selected from SEGUE-2, Large Sky Area Multi-Object Fibre Spectroscopic Telescope, and Sloan Digital Sky Survey separately in Integrals-of-Motion space. The orbit of the Sgr stream is quite clear from the velocity vector in the X-Z plane. Stars traced by K-giants and M-giants show that the apogalacticon of the trailing steam is ~100kpc. The metallicity distributions of Sgr K-giants, M-giants, and BHBs indicate that the M-giants are on average the most metal-rich population, followed by K-giants and BHBs. All of the K-giants, M-giants, and BHBs indicate that the trailing arm is on average more metal-rich than the leading arm, and the K-giants show that the Sgr debris is the most metal-poor part. The {alpha}-abundance of Sgr stars exhibits a similar trend with the Galactic halo stars at lower metallicity ([Fe/H]<~-1.0dex), and then evolve down to lower [{alpha}/Fe] than disk stars at higher metallicity, which is close to the evolution pattern of the {alpha}-element of Milky Way dwarf galaxies. We find that VY and metallicity of K-giants have gradients along the direction of the line of sight from the Galactic center in the X-Z plane, and the K-giants show that VY increases with metallicity at [Fe/H]>~-1.5dex. After dividing the Sgr stream into bright and faint streams according to their locations in equatorial coordinates, the K-giants and BHBs show that the bright and faint streams present different VY and metallicities, the bright stream is on average higher in VY and metallicity than the faint stream.
- ID:
- ivo://CDS.VizieR/J/ApJ/696/1950
- Title:
- Sloan iz light curves of HAT-P-10
- Short Name:
- J/ApJ/696/1950
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the discovery of HAT-P-10b, one of the lowest mass (0.487+/-0.018M_J_) transiting extrasolar planets (TEPs) discovered to date by transit searches. HAT-P-10b orbits the moderately bright V=11.89 K dwarf GSC 02340-01714, with a period P=3.7224747+/-0.0000065d, transit epoch T_c_=2454759.68683+/-0.00016(BJD), and duration 0.1090+/-0.0008d. HAT-P-10b has a radius of 1.005^+0.032^_-0.027_R_J_ yielding a mean density of 0.594+/-0.052g/cm^3^. Comparing these observations with recent theoretical models we find that HAT-P-10b is consistent with a ~4.5Gyr, almost pure hydrogen and helium gas giant planet with a 10M_{earth}_ core. With an equilibrium temperature of T_eq_=1020+/-17K, HAT-P-10b is one of the coldest TEPs. Curiously, its Safronov number {Theta}=0.053+/-0.002 falls close to the dividing line between the two suggested TEP populations.
- ID:
- ivo://CDS.VizieR/J/ApJ/763/L26
- Title:
- SMARTS observations of eps Eridani
- Short Name:
- J/ApJ/763/L26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The active K2 dwarf {epsilon} Eri has been extensively characterized both as a young solar analog and more recently as an exoplanet host star. As one of the nearest and brightest stars in the sky, it provides an unparalleled opportunity to constrain stellar dynamo theory beyond the Sun. We confirm and document the 3-year magnetic activity cycle in {epsilon} Eri originally reported by Hatzes and coworkers (2000ApJ...544L.145H), and we examine the archival data from previous observations spanning 45 years. The data show coexisting 3-year and 13-year periods leading into a broad activity minimum that resembles a Maunder minimum-like state, followed by the resurgence of a coherent 3-year cycle. The nearly continuous activity record suggests the simultaneous operation of two stellar dynamos with cycle periods of 2.95+/-0.03yr and 12.7+/-0.3 years, which, by analogy with the solar case, suggests a revised identification of the dynamo mechanisms that are responsible for the so-called "active" and "inactive" sequences as proposed by B\"ohm-Vitense (2007ApJ...657..486B). Finally, based on the observed properties of {epsilon} Eri, we argue that the rotational history of the Sun is what makes it an outlier in the context of magnetic cycles observed in other stars (as also suggested by its Li depletion), and that a Jovian-mass companion cannot be the universal explanation for the solar peculiarities.
- ID:
- ivo://CDS.VizieR/J/AJ/162/41
- Title:
- Speckle interferometry at SOAR in 2020
- Short Name:
- J/AJ/162/41
- Date:
- 14 Mar 2022 06:54:42
- Publisher:
- CDS
- Description:
- The results of speckle interferometric observations at the 4.1m Southern Astrophysical Research Telescope in 2020, as well as earlier unpublished data, are given, totaling 1735 measurements of 1288 resolved pairs and nonresolutions of 1177 targets. We resolved for the first time 59 new pairs or subsystems in known binaries, mostly among nearby dwarf stars. This work continues our long-term speckle program. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and Hipparcos pairs in the solar neighborhood. We also report observations of 892 members of young moving groups and associations, where we resolved 103 new pairs.
- ID:
- ivo://CDS.VizieR/J/A+A/282/831
- Title:
- Spectroscopic orbits of three K dwarf stars
- Short Name:
- J/A+A/282/831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectroscopic orbits of single-lined binary dwarfs HD 23439B, HD 237287 and HD 217580 are derived from the radial velocities measured with two correlation radial-velocity spectrometers: correlation radial velocity (CORAVEL) at the 1m Swiss telescope of Observatoire de Haute-Provence, and radial velocity meters (RVM) used on several telescopes. The mutual agreement of these two data sets is analyzed and found to be quite good. The estimated minimum mass of secondary component corresponds to that of M-type dwarf for the first 2 systems and is equal to 0.06 solar mass for HD 217580.
