- ID:
- ivo://CDS.VizieR/J/A+A/535/A55
- Title:
- 4 stars with long-period planets
- Short Name:
- J/A+A/535/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of four new long-period planets within the HARPS high-precision sample: HD137388b (Msini=0.22M_Jup_), HD204941b (Msini=0.27M_Jup_), HD7199b (Msini=0.29M_Jup_), HD7449b (Msini=1.04M_Jup_). A long-period companion, probably a second planet, is also found orbiting HD7449. Planets around HD137388, HD204941, and HD7199 have rather low eccentricities (less than 0.4) relative to the 0.82 eccentricity of HD7449b. All these planets were discovered even though their hosting stars have clear signs of activity.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/825/62
- Title:
- Stars with M_p_sin(i)>0.1M_Jup_ hot Jupiter
- Short Name:
- J/ApJ/825/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin of Jupiter-mass planets with orbital periods of only a few days is still uncertain. It is widely believed that these planets formed near the water-ice line of the protoplanetary disk, and subsequently migrated into much smaller orbits. Most of the proposed migration mechanisms can be classified either as disk-driven migration, or as excitation of a very high eccentricity followed by tidal circularization. In the latter scenario, the giant planet that is destined to become a hot Jupiter spends billions of years on a highly eccentric orbit, with apastron near the water-ice line. Eventually, tidal dissipation at periastron shrinks and circularizes the orbit. If this is correct, then it should be especially rare for hot Jupiters to be accompanied by another giant planet interior to the water-ice line. Using the current sample of giant planets discovered with the Doppler technique, we find that hot Jupiters with P_orb_<10d are no more or less likely to have exterior Jupiter-mass companions than longer-period giant planets with P_orb_>=10d. This result holds for exterior companions both inside and outside of the approximate location of the water-ice line. These results are difficult to reconcile with the high-eccentricity migration scenario for hot Jupiter formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/159
- Title:
- Statistical analysis of exoplanet surveys
- Short Name:
- J/ApJ/794/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conduct a statistical analysis of a combined sample of direct imaging data, totalling nearly 250 stars. The stars cover a wide range of ages and spectral types, and include five detections ({kappa} And b, two ~60 M_J_ brown dwarf companions in the Pleiades, PZ Tel B, and CD-35 2722B). For some analyses we add a currently unpublished set of SEEDS observations, including the detections GJ 504b and GJ 758B. We conduct a uniform, Bayesian analysis of all stellar ages using both membership in a kinematic moving group and activity/rotation age indicators. We then present a new statistical method for computing the likelihood of a substellar distribution function. By performing most of the integrals analytically, we achieve an enormous speedup over brute-force Monte Carlo. We use this method to place upper limits on the maximum semimajor axis of the distribution function derived from radial-velocity planets, finding model-dependent values of ~30-100 AU. Finally, we model the entire substellar sample, from massive brown dwarfs to a theoretically motivated cutoff at ~5 M_J_, with a single power-law distribution. We find that p(M,a){prop.to}M^-0.65+/-0.60^a^-0.85+/-0.39^ (1{sigma} errors) provides an adequate fit to our data, with 1.0%-3.1% (68% confidence) of stars hosting 5-70 M_J_ companions between 10 and 100 AU. This suggests that many of the directly imaged exoplanets known, including most (if not all) of the low-mass companions in our sample, formed by fragmentation in a cloud or disk, and represent the low-mass tail of the brown dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/25
- Title:
- Stellar and planet properties for K2 candidates
- Short Name:
- J/ApJ/809/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The extended Kepler mission, K2, is now providing photometry of new fields every three months in a search for transiting planets. In a recent study, Foreman-Mackey and collaborators presented a list of 36 planet candidates orbiting 31 stars in K2 Campaign 1. In this contribution, we present stellar and planetary properties for all systems. We combine ground-based seeing-limited survey data and adaptive optics imaging with an automated transit analysis scheme to validate 21 candidates as planets, 17 for the first time, and identify 6 candidates as likely false positives. Of particular interest is K2-18 (EPIC 201912552), a bright (K=8.9) M2.8 dwarf hosting a 2.23+/-0.25 R_{earth}_ planet with T_eq_=272+/-15 K and an orbital period of 33 days. We also present two new open-source software packages which enable this analysis. The first, isochrones, is a flexible tool for fitting theoretical stellar models to observational data to determine stellar properties using a nested sampling scheme to capture the multimodal nature of the posterior distributions of the physical parameters of stars that may plausibly be evolved. The second is vespa, a new general-purpose procedure to calculate false positive probabilities and statistically validate transiting exoplanets.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/2498
- Title:
- Stellar companions of exoplanet host stars
- Short Name:
- J/MNRAS/421/2498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To understand the influence of additional wide stellar companions on planet formation, it is necessary to determine the fraction of multiple stellar systems amongst the known extrasolar planet population. We target recently discovered radial velocity exoplanetary systems observable from the Northern hemisphere and with sufficiently high proper motion to detect stellar companions via direct imaging. We utilize the Calar Alto 2.2-m telescope in combination with its lucky imaging camera AstraLux. 71 planet host stars have been observed so far, yielding one new low-mass (0.239+/-0.022M_{sun}_) stellar companion, 4.5-arcsec (227 au of projected separation) north-east of the planet host star HD 185269, detected via astrometry with AstraLux. We also present follow-up astrometry on three previously discovered stellar companions, showing for the first time common proper motion of the 0.5-arcsec companion to HD 126614. Additionally, we determined the achieved detection limits for all targets, which allow us to characterize the detection space of possible further companions of these stars.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A21
- Title:
- Stellar Limb-Darkening Coefficients
- Short Name:
- J/A+A/510/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transiting exoplanets provide unparalleled access to the fundamental parameters of both extrasolar planets and their host stars. We present limb-darkening coefficients (LDCs) for the exoplanet hunting CoRot and Kepler missions. The LDCs are calculated with ATLAS stellar atmospheric model grids and span a wide range of T_eff_, logg, and metallically [M/H]. Both CoRot and Kepler use wide nonstandard photometric filters, and are producing a large inventory of high- quality transiting lightcurves, sensitive to stellar limb darkening. Comparing the stellar model limb darkening to results from the first seven CoRot planets, we find better fits are found when two model intensities at the limb are excluded in the coefficient calculations. This calculation method can help to avoid a major deficiency present at the limbs of the 1D stellar models.
- ID:
- ivo://CDS.VizieR/J/AJ/103/983
- Title:
- Stellar occultation candidates of Saturn
- Short Name:
- J/AJ/103/983
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a list of 203 potential occultations by Saturn and its rings of stars from the Hubble Space Telescope Guide Star Catalog (GSC), during the years 1991-1999. Because the GSC is not a complete catalog, this is not an exhaustive list of Saturn occultations. In particular, stars brighter than magnitude 8 are not included. However, this list does include many fainter candidates than do current occultation candidate lists for Saturn; these fainter stars also can provide a high signal-to-noise ratio if observed with a large telescope or in the infrared where Saturn and its rings have absorption bands. We list the occultation circumstances, as well as star information found in the GSC.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A141
- Title:
- Stellar parameters for 582 HARPS FGK stars
- Short Name:
- J/A+A/533/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To understand the formation and evolution of solar-type stars and planets in the solar neighborhood, we need to obtain their stellar parameters with high precision. We present a catalog of precise stellar parameters for low-activity FGK single stars in a volume-limited sample followed by the HARPS spectrograph in the quest to identify extra-solar planets. The spectroscopic analysis was completed assuming LTE with a grid of Kurucz atmosphere models and using the ARES code to perform an automatic measurement of the line equivalent widths. The results are compared with different independent methods and also with other values found in the literature for common stars. Both comparisons are consistent and illustrate the homogeneity of the parameters derived by our team. The derived metallicities of this sample reveal a somewhat different distribution for the present planet hosts, but still indicates the already known higher frequency of planets observed for the more metal-rich stars. We combine the results derived in this sample with the one from the CORALIE survey to present the largest homogeneous spectroscopic study of the metallicity-giant-planet relation using a total of 1830 stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/90
- Title:
- Stellar parameters of K5 and later type Kepler stars
- Short Name:
- J/ApJ/753/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We estimate the stellar parameters of late K- and early M-type Kepler target stars. We obtain medium-resolution visible spectra of 382 stars with K_P_-J>2 (=~K5 and later spectral type). We determine luminosity class by comparing the strength of gravity-sensitive indices (CaH, K I, Ca II, and Na I) to their strength in a sample of stars of known luminosity class. We find that giants constitute 96%+/-1% of the bright (K_P_<14) Kepler target stars, and 7%+/-3% of dim (K_P_>14) stars, significantly higher than fractions based on the stellar parameters quoted in the Kepler Input Catalog (KIC). The KIC effective temperatures are systematically (110^+15^_-35_K) higher than temperatures we determine from fitting our spectra to PHOENIX stellar models. Through Monte Carlo simulations of the Kepler exoplanet candidate population, we find a planet occurrence of 0.36+/-0.08 when giant stars are properly removed, somewhat higher than when a KIC log g>4 criterion is used (0.27+/-0.05). Last, we show that there is no significant difference in g-r color (a probe of metallicity) between late-type Kepler stars with transiting Earth-to-Neptune-size exoplanet candidates and dwarf stars with no detected transits. We show that a previous claimed offset between these two populations is most likely an artifact of including a large number of misidentified giants.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/L9
- Title:
- Stellar parameters of KIC planet-host stars
- Short Name:
- J/ApJ/788/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most extrasolar planets have been detected by their influence on their parent star, typically either gravitationally (the Doppler method) or by the small dip in brightness as the planet blocks a portion of the star (the transit method). Therefore, the accuracy with which we know the masses and radii of extrasolar planets depends directly on how well we know those of the stars, the latter usually determined from the measured stellar surface gravity, log g. Recent work has demonstrated that the short-timescale brightness variations ("flicker") of stars can be used to measure log g to a high accuracy of ~0.1-0.2 dex. Here, we use flicker measurements of 289 bright (Kepmag<13) candidate planet-hosting stars with T_eff_=4500-6650 K to re-assess the stellar parameters and determine the resulting impact on derived planet properties. This re-assessment reveals that for the brightest planet-host stars, Malmquist bias contaminates the stellar sample with evolved stars: nearly 50% of the bright planet-host stars are subgiants. As a result, the stellar radii, and hence the radii of the planets orbiting these stars, are on average 20%-30% larger than previous measurements had suggested.