- ID:
- ivo://CDS.VizieR/J/ApJ/719/890
- Title:
- Keck radial velocities of GJ 876
- Short Name:
- J/ApJ/719/890
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Continued radial velocity (RV) monitoring of the nearby M4V red dwarf star GJ 876 with Keck/High Resolution Echelle Spectrograph has revealed the presence of a Uranus-mass fourth planetary companion in the system. The new planet has a mean period of P_e_=126.6 days (over the 12.6-year baseline of the RV observations), and a minimum mass of m_e_sini_e_=12.9+/-1.7M_{earth}_. The detection of the new planet has been enabled by significant improvements to our RV data set for GJ 876. The data have been augmented by 36 new high-precision measurements taken over the past five years. In addition, the precision of all of the Doppler measurements have been significantly improved by the incorporation of a high signal-to-noise template spectrum for GJ 876 into the analysis pipeline. Implementation of the new template spectrum improves the internal rms errors for the velocity measurements taken during 1998-2005 from 4.1m/s to 2.5m/s.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/469/2907
- Title:
- Kepler-410Ab transit timing variations
- Short Name:
- J/MNRAS/469/2907
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the determination of the individual times of transit we used short- cadence (sampled every 58.8 seconds) de-trended data (PDCSAP_FLUX) from quarters Q1 to Q17, provided by the NASA Exoplanet Archive. As a first step, we extracted parts of the LC around detected transits using the ephemeris given in Van Eylen et al. (2014ApJ...782...14V), where we took an interval 0.2 days around the computed transit time (the interval size is approximately double the transit duration). To remove additional residual trends caused by the stellar activity and instrumental long-term photometric variation, we fitted the out-of-transit part of LC by a second-order polynomial function. Then we subtracted 8% flux contamination from the wide companion Kepler-410B, according to calculations of Van Eylen et al. (2014ApJ...782...14V). All individual parts of the LC with transits were stacked together to obtain the template of the transit. The stacked LC was fitted by our software implementation of Mandel & Agol (2002ApJ...580L.117M) model, where we used theMarkov Chain Monte Carlo (MCMC) simulation method for the determination of transit parameters. This method takes into account individual errors of Kepler observations and gives a realistic and statistically significant estimate of parameter errors. As a starting point for the MCMC fitting, we used the physical parameters of the planet given in Van Eylen et al. (2014ApJ...782...14V). We have adopted a fixed value a=0.1226AU. We have used a quadratic model of limb darkening with starting values of coefficients from Sing (2010, Cat. J/A+A/510/A21). We ran the MCMC simulation with 10^6^ steps. We have repeated the MCMC simulation with the previous solution as the starting point on each of 70 individual transit intervals, and let only the time of transit to update. The new values were used to improve the linear ephemeris and to construct a new O-C diagram. The combined light curve stacked using a linear ephemeris is affected by relatively large amplitude of O-C time shifts. To correct this effect, we used iterative procedure that takes the best-fit O-C values into account. Afterwards, a new stacked light curve was constructed and a new MCMC transit solution was calculated, subsequently a new ephemeris and O-C values were determined. This process was repeated three times until a convergent solution was reached.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A112
- Title:
- Kepler-539 CAFE radial velocity measurements
- Short Name:
- J/A+A/590/A112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We confirm the planetary nature of Kepler-539 b (aka Kepler object of interest K00372.01), a giant transiting exoplanet orbiting a solar-analogue G2V star. The mass of Kepler-539 b was accurately derived thanks to a series of precise radial velocity measurements obtained with the CAFE spectrograph mounted on the CAHA 2.2-m telescope. A simultaneous fit of the radial-velocity data and Kepler photometry revealed that Kepler-539 b is a dense Jupiter-like planet with a mass of Mp=0.97M_Jup_ and a radius of Rp=0.747R_Jup_, making a complete circular revolution around its parent star in 125.6-days. The semi-major axis of the orbit is roughly 0.5au, implying that the planet is at 0.45au from the habitable zone. By analysing the mid-transit times of the 12 transit events of Kepler-539 b recorded by the Kepler spacecraft, we found a clear modulated transit time variation (TTV), which is attributable to the presence of a planet c in a wider orbit. The few timings available do not allow us to precisely estimate the properties of Kepler-539 c and our analysis suggests that it has a mass between 1.2 and 3.6 M_Jup_, revolving on a very eccentric orbit (0.4<e<0.6) with a period larger than 1000-days. The high eccentricity of planet c is the probable cause of the TTV modulation of planet b. The analysis of the CAFE spectra revealed a relatively high photospheric lithium content, A(Li)=2.48dex, which, together with both a gyrochronological and isochronal analysis, suggests that the parent star is relatively young.
- ID:
- ivo://CDS.VizieR/J/MNRAS/456/2636
- Title:
- Kepler-10 chemical composition
- Short Name:
- J/MNRAS/456/2636
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemical abundance studies of the Sun and solar twins have demonstrated that the solar composition of refractory elements is depleted when compared to volatile elements, which could be due to the formation of terrestrial planets. In order to further examine this scenario, we conducted a line-by-line differential chemical abundance analysis of the terrestrial planet host Kepler-10 and 14 of its stellar twins. Stellar parameters and elemental abundances of Kepler-10 and its stellar twins were obtained with very high precision using a strictly differential analysis of high quality Canada-France-Hawaii Telescope, Hobby-Eberly Telescope and Magellan spectra. When compared to the majority of thick disc twins, Kepler-10 shows a depletion in the refractory elements relative to the volatile elements, which could be due to the formation of terrestrial planets in the Kepler-10 system. The average abundance pattern corresponds to ~13 Earth masses, while the two known planets in Kepler-10 system have a combined ~20 Earth masses. For two of the eight thick disc twins, however, no depletion patterns are found. Although our results demonstrate that several factors [e.g. planet signature, stellar age, stellar birth location and Galactic chemical evolution (GCE)] could lead to or affect abundance trends with condensation temperature, we find that the trends give further support for the planetary signature hypothesis.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/3561
- Title:
- Kepler eclipsing binary stars. K2 Campaign 0
- Short Name:
- J/MNRAS/452/3561
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The original Kepler mission observed and characterized over 2400 eclipsing binaries (EBs) in addition to its prolific exoplanet detections. Despite the mechanical malfunction and subsequent non-recovery of two reaction wheels used to stabilize the instrument, the Kepler satellite continues collecting data in its repurposed K2 mission surveying a series of fields along the ecliptic plane. Here, we present an analysis of the first full baseline K2 data release: the Campaign 0 data set. In the 7761 light curves we have identified a total of 207 EBs. Of these, 97 are new discoveries that were not previously identified. Our pixel-level analysis of these objects has also resulted in identification of several false positives (observed targets contaminated by neighbouring EBs), as well as the serendipitous discovery of two short-period exoplanet candidates. We provide catalogue cross-matched source identifications, orbital periods, morphologies and ephemerides for these eclipsing systems. We also describe the incorporation of the K2 sample into the Kepler Eclipsing Binary Catalog, present spectroscopic follow-up observations for a limited selection of nine systems and discuss prospects for upcoming K2 campaigns.
- ID:
- ivo://CDS.VizieR/J/AJ/153/71
- Title:
- Kepler follow-up observation program. I. Imaging
- Short Name:
- J/AJ/153/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from high-resolution, optical to near-IR imaging of host stars of Kepler Objects of Interest (KOIs), identified in the original Kepler field. Part of the data were obtained under the Kepler imaging follow-up observation program over six years (2009-2015). Almost 90% of stars that are hosts to planet candidates or confirmed planets were observed. We combine measurements of companions to KOI host stars from different bands to create a comprehensive catalog of projected separations, position angles, and magnitude differences for all detected companion stars (some of which may not be bound). Our compilation includes 2297 companions around 1903 primary stars. From high-resolution imaging, we find that ~10% (~30%) of the observed stars have at least one companion detected within 1'' (4''). The true fraction of systems with close (<~4'') companions is larger than the observed one due to the limited sensitivities of the imaging data. We derive correction factors for planet radii caused by the dilution of the transit depth: assuming that planets orbit the primary stars or the brightest companion stars, the average correction factors are 1.06 and 3.09, respectively. The true effect of transit dilution lies in between these two cases and varies with each system. Applying these factors to planet radii decreases the number of KOI planets with radii smaller than 2R_{Earth}_ by ~2%-23% and thus affects planet occurrence rates. This effect will also be important for the yield of small planets from future transit missions such as TESS.
- ID:
- ivo://CDS.VizieR/J/ApJ/861/149
- Title:
- Kepler Follow-up Observation Program. II. Spectro.
- Short Name:
- J/ApJ/861/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from spectroscopic follow-up observations of stars identified in the Kepler field and carried out by teams of the Kepler Follow-up Observation Program. Two samples of stars were observed over 6yr (2009-2015): 614 standard stars (divided into "platinum" and "gold" categories) selected based on their asteroseismic detections and 2667 host stars of Kepler Objects of Interest (KOIs), most of them planet candidates. Four data analysis pipelines were used to derive stellar parameters for the observed stars. We compare the Teff, log(g), and [Fe/H] values derived for the same stars by different pipelines; from the average of the standard deviations of the differences in these parameter values, we derive error floors of ~100K, 0.2dex, and 0.1dex for Teff, log(g), and [Fe/H], respectively. Noticeable disagreements are seen mostly at the largest and smallest parameter values (e.g., in the giant star regime). Most of the log(g) values derived from spectra for the platinum stars agree on average within 0.025dex (but with a spread of 0.1-0.2dex) with the asteroseismic log(g) values. Compared to the Kepler Input Catalog (KIC), the spectroscopically derived stellar parameters agree within the uncertainties of the KIC but are more precise and thus an important contribution toward deriving more reliable planetary radii.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A124
- Title:
- Kepler-117 (KOI-209) transit-timing variations
- Short Name:
- J/A+A/573/A124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of our follow-up campaign of Kepler planets, we observed Kepler-117 with the SOPHIE spectrograph at the Observatoire de Haute-Provence. This F8-type star hosts two transiting planets in non-resonant orbits. The planets, Kepler-117 b and c, have orbital periods ~=18.8 and ~=50.8-days, and show transit-timing variations (TTVs) of several minutes. We performed a combined Markov chain Monte Carlo (MCMC) fit on transits, radial velocities, and stellar parameters to constrain the characteristics of the system. We included the fit of the TTVs in theMCMCby modeling them with dynamical simulations. In this way, consistent posterior distributions were drawn for the system parameters. According to our analysis, planets b and c have notably different masses (0.094+/-0.033 and 1.84+/-0.18M_J_) and low orbital eccentricities (0.0493+/-0.0062 and 0.0323+/-0.0033). The uncertainties on the derived parameters are strongly reduced if the fit of the TTVs is included in the combined MCMC. The TTVs allow measuring the mass of planet b, although its radial velocity amplitude is poorly constrained. Finally, we checked that the best solution is dynamically stable.
- ID:
- ivo://CDS.VizieR/J/ApJ/774/L12
- Title:
- Kepler multiplanet systems analysis (Q1-Q8)
- Short Name:
- J/ApJ/774/L12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Many Kepler multiplanet systems have planet pairs near low-order, mean-motion resonances. In addition, many Kepler multiplanet systems have planets with orbital periods less than a few days. With the exception of Kepler-42, however, there are no examples of systems with both short orbital periods and nearby companion planets while our statistical analysis predicts ~17 such pairs. For orbital periods of the inner planet that are less than three days, the minimum period ratio of adjacent planet pairs follows the rough constraint P=P_2_/P_1_>~2.3(P_1_/day)^-2/3^ (equation (1)). This absence is not due to a lack of planets with short orbital periods. We also show a statistically significant excess of small, single-candidate systems with orbital periods below three days over the number of multiple candidate systems with similar periods--perhaps a small-planet counterpart to the hot Jupiters.
- ID:
- ivo://CDS.VizieR/J/ApJ/763/41
- Title:
- Kepler multiple-candidate systems radii
- Short Name:
- J/ApJ/763/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the relative sizes of planets within the multiple-candidate systems discovered with the Kepler mission (Burke+, 2014, J/ApJS/210/29). We have compared the size of each planet to the size of every other planet within a given planetary system after correcting the sample for detection and geometric biases. We find that for planet pairs for which one or both objects are approximately Neptune-sized or larger, the larger planet is most often the planet with the longer period. No such size-location correlation is seen for pairs of planets when both planets are smaller than Neptune. Specifically, if at least one planet in a planet pair has a radius of >~3R_{oplus}_, 68%+/-6% of the planet pairs have the inner planet smaller than the outer planet, while no preferred sequential ordering of the planets is observed if both planets in a pair are smaller than <~3R_{oplus}_.