- ID:
- ivo://CDS.VizieR/J/A+A/624/A38
- Title:
- Radial velocities of K2-36
- Short Name:
- J/A+A/624/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- K2-36 is a K dwarf orbited by two small (R_b_=1.43+/-0.08R_{earth}_ and R_c_=3.2+/-0.3R_{earth}_, close-in (a_b_=0.022AU and a_c_=0.054AU) transiting planets discovered by the Kepler/K2 space observatory. They are representatives of two distinct families of small planets (R_p_<4R_{earth}_) recently emerged from the analysis of Kepler data, with likely a different structure, composition and evolutionary pathways. We revise the fundamental stellar parameters and the sizes of the planets, and provide the first measurement of their masses and bulk densities, which we use to infer their structure and composition. We observed K2-36 with the HARPS-N spectrograph over ~3.5-years, collecting 81 useful radial velocity measurements. The star is active, with evidence for increasing levels of magnetic activity during the observing time span. The radial velocity scatter is ~17m/s due to the stellar activity contribution, which is much larger that the semi-amplitudes of the planetary signals. We tested different methods for mitigating the stellar activity contribution to the radial velocity time variations and measuring the planet masses with good precision. We find that K2-36 is likely a ~1Gyr old system, and by treating the stellar activity through a Gaussian process regression, we measured the planet masses m_b_=3.9+/-1.1M_{earth}_ and m_c_=7.8+/-2.3M_{earth}_. The derived planet bulk densities {rho}_b_=7.2^+2.5^_-2.1_g/cm^3^ and {rho}_c_=1.3^+0.7^_-0.5^g/cm^3^ point out that K2-36b has a rocky, Earth-like composition, and K2-36c is a low-density sub-Neptune. Composed of two planets with similar orbital separations but different densities, K2-36 represents an optimal laboratory for testing the role of the atmospheric escape in driving the evolution of close-in, low-mass planets after ~1Gyr from their formation. Due to their similarities, we performed a preliminary comparative analysis between the systems K2-36 and Kepler-36, which we deem worthy of a more detailed investigation.
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- ID:
- ivo://CDS.VizieR/J/AJ/154/216
- Title:
- Radial velocities of 41 Kepler eclipsing binaries
- Short Name:
- J/AJ/154/216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Eclipsing binaries are vital for directly determining stellar parameters without reliance on models or scaling relations. Spectroscopically derived parameters of detached and semi-detached binaries allow us to determine component masses that can inform theories of stellar and binary evolution. Here we present moderate resolution ground-based spectra of stars in close binary systems with and without (detected) tertiary companions observed by NASA's Kepler mission and analyzed for eclipse timing variations. We obtain radial velocities and spectroscopic orbits for five single-lined and 35 double-lined systems, and confirm one false positive eclipsing binary. For the double-lined spectroscopic binaries, we also determine individual component masses and examine the mass ratio M_2_/M_1_ distribution, which is dominated by binaries with like-mass pairs and semi-detached classical Algol systems that have undergone mass transfer. Finally, we constrain the mass of the tertiary component for five double-lined binaries with previously detected companions.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A116
- Title:
- Radial velocities of K-M dwarfs
- Short Name:
- J/A+A/596/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this paper is to present complete radial-velocity data for the spectroscopically selected McCormick (MCC) sample of nearby K-M dwarfs and, based on these data, to determine the space-velocity distributions of late-type stars in the solar neighborhood.
- ID:
- ivo://CDS.VizieR/J/A+A/576/A88
- Title:
- Radial velocities of 8 KOI eclipsing binaries
- Short Name:
- J/A+A/576/A88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kepler mission has searched for planetary transits in more than two hundred thousand stars by obtaining very accurate photometric data over a long period of time. Among the thousands of detected candidates, the planetary nature of around 15% has been established or validated by different techniques. But additional data are needed to characterize the rest of the candidates and reject other possible configurations. We started a follow-up program to validate, confirm, and characterize some of the planet candidates. In this paper we present the radial velocity analysis of those that present large variations, which are compatible with being eclipsing binaries. We also study those showing high rotational velocities, which prevents us from reaching the necessary precision to detect planetary-like objects. We present new radial velocity results for 13 Kepler objects of interest (KOIs) obtained with the CAFE spectrograph at the Calar Alto Observatory and analyze their high-spatial resolution (lucky) images obtained with AstraLux and the Kepler light curves of some interesting cases. We have found five spectroscopic and eclipsing binaries (group A). Among them, the case of KOI-3853 is of particular interest. This system is a new example of the so-called heartbeat stars, showing dynamic tidal distortions in the Kepler light curve. We have also detected duration and depth variations of the eclipse. We suggest possible scenarios to explain such an effect, including the presence of a third substellar body possibly detected in our radial velocity analysis. We also provide upper mass limits to the transiting companions of six other KOIs with high rotational velocities (group B). This property prevents the radial velocity method from achieving the necessary precision to detect planetary-like masses. Finally, we analyze the large radial velocity variations of two other KOIs, which are incompatible with the presence of planetary-mass objects (group C). These objects are likely to be stellar binaries. However, a longer timespan is needed to complete their characterization.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/1140
- Title:
- Radial velocities of K0 stars
- Short Name:
- J/MNRAS/371/1140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Paper XIII (Griffin, 1986MNRAS.219...95G) of this series presented radial velocities for 406 stars in certain of the Clube Selected Areas, a set of areas systematically arranged in Galactic coordinates. We now complete the survey by providing the radial velocities, mostly obtained at the European Southern Observatory (ESO), of 625 stars in the six southernmost Areas. Each star has been measured at least twice; the mean velocities have standard errors typically of 0.2-0.3km/s. Additional observations made from Haute-Provence of many of the stars that are observable from there have helped to identify, and in some instances to characterize, the ~70 spectroscopic binaries discovered in this programme. The final results of the programme, complementing those given in table 3 of Paper XIII, are summarized in Table 12, which presents the mean velocities and velocity dispersions in the six southern Areas. It is noted that the difference between Paper XIII and this one as regards the provenance of the radial velocities has led to a small difference in zero-points, which is discussed in Section 3 and needs to be taken into account in any analysis of the combined data.
- ID:
- ivo://CDS.VizieR/J/AJ/157/116
- Title:
- Radial velocities of K2-291 with HIRES & HARPS-N
- Short Name:
- J/AJ/157/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- K2-291 is a solar-type star with a radius of R_*_=0.899+/-0.034 R_{sun}_ and mass of M_*_=0.934+/-0.038 M_{sun}_. From the K2 C13 data, we found one super-Earth planet (R_p_=1.589_-0.072_^+0.095^ R_{Earth}_) transiting this star on a short period orbit (P=2.225177_-6.8e-5_^+6.6e-5^ days). We followed this system up with adaptive-optic imaging and spectroscopy to derive stellar parameters, search for stellar companions, and determine a planet mass. From our 75 radial velocity measurements using High Resolution Echelle Spectrometer on Keck I and High Accuracy Radial velocity Planet Searcher in the northern hemisphere on Telescopio Nazionale Galileo, we constrained the mass of K2-291 b to M_p_=6.49+/-1.16 M_{Earth}_. We found it necessary to model correlated stellar activity radial velocity signals with a Gaussian process (GP) in order to more accurately model the effect of stellar noise on our data; the addition of the GP also improved the precision of this mass measurement. With a bulk density of {rho}=8.84_-2.03_^+2.50^ g/cm^3^, the planet is consistent with an Earth-like rock/iron composition and no substantial gaseous envelope. Such an envelope, if it existed in the past, was likely eroded away by photoevaporation during the first billion years of the star's lifetime.
- ID:
- ivo://CDS.VizieR/J/A+A/448/155
- Title:
- Radial velocities of Leo I globular clusters
- Short Name:
- J/A+A/448/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- VLT/FLAMES radial velocities for 50 Globular Clusters (GCs), 37 field stars and 21 unclassified objects around the Leo I group galaxies NGC 3379 and NGC 3384 are presented. Object Id and BVR photometry are from Rhode & Zepf (2004AJ....127..302R). Positions (J2000.0) should be accurate to ~0"2 or better w.r.t. the GSC2.1 catalogue. Heliocentric radial velocities and their errors were estimated by fitting the peak (see the width, heigh, and Tonry & Davies (1979AJ.....84.1511T) coefficient) of the cross-correlation function (CCF) with the IRAF/RV package task FXCOR, using simulatenous and ELODIE library stellar templates. Objects have been assigned three quality class, class A being the most secure velocity determination, and class C the least secure; the latter objects require confirmation, and such GCs were not considered for the dynamical analysis presented in the paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/663/960
- Title:
- Radial velocities of Leo I stars
- Short Name:
- J/ApJ/663/960
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a wide-field (4.5deg^2^) photometric and spectroscopic survey of the Leo I dwarf spheroidal (dSph) galaxy to explore its extended morphology and dynamics. To select Leo I red giant branch star candidates we exploit M, T2, and DDO51 filter photometry; this yields 100% pure Leo I stars among more than 100 M<21.5 Leo I giant candidates having previous or new Keck spectroscopy.
- ID:
- ivo://CDS.VizieR/J/PASP/117/1
- Title:
- Radial velocities of 166 LHS stars
- Short Name:
- J/PASP/117/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 178 radial velocity measurements for 166 late-type stars selected from the Luyten Half-Second (LHS) proper motion catalog (Cat. <I/87>). Space velocities are given for all but two of them. Most of the stars lie within 25pc of the Sun, but the list includes a handful of high-velocity transients from the halo population.
- ID:
- ivo://CDS.VizieR/J/A+A/460/459
- Title:
- Radial velocities of LMC RR Lyrae
- Short Name:
- J/A+A/460/459
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- All galaxies that have been adequately examined so far have shown an extended stellar halo. To search for such a halo in the LMC we have obtained low-resolution spectra for 100 LMC RR Lyrae stars, of which 87 are in the field and 13 in the clusters NGC 1835 and NGC 2019. We measured radial velocities for 87 LMC RR Lyrae stars, and metallicities for 78 RR Lyrae stars, nearly tripling the previous sample. These targets are located in 10 fields covering a wide range of distances, out to 2.5 degrees from the center of the LMC.
