- ID:
- ivo://CDS.VizieR/J/ApJ/771/107
- Title:
- Spectroscopy of faint KOI stars
- Short Name:
- J/ApJ/771/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar properties are measured for a large set of Kepler mission exoplanet candidate host stars. Most of these stars are fainter than 14th magnitude, in contrast to other spectroscopic follow-up studies. This sample includes many high-priority Earth-sized candidate planets. A set of model spectra are fitted to R~3000 optical spectra of 268 stars to improve estimates of T_eff_, log(g), and [Fe/H] for the dwarfs in the range 4750<=T_eff_<=7200K. These stellar properties are used to find new stellar radii and, in turn, new radius estimates for the candidate planets. The result of improved stellar characteristics is a more accurate representation of this Kepler exoplanet sample and identification of promising candidates for more detailed study. This stellar sample, particularly among stars with T_eff_>~5200K, includes a greater number of relatively evolved stars with larger radii than assumed by the mission on the basis of multi-color broadband photometry. About 26% of the modeled stars require radii to be revised upward by a factor of 1.35 or greater, and modeling of 87% of the stars suggest some increase in radius. The sample presented here also exhibits a change in the incidence of planets larger than 3-4R_{Earth}_ as a function of metallicity. Once [Fe/H] increases to >=-0.05, large planets suddenly appear in the sample while smaller planets are found orbiting stars with a wider range of metallicity.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/152/142
- Title:
- Spitzer and WISE light curves of Neptune
- Short Name:
- J/AJ/152/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Spitzer Space Telescope in 2016 February to obtain high cadence, high signal-to-noise, 17hr duration light curves of Neptune at 3.6 and 4.5{mu}m. The light curve duration was chosen to correspond to the rotation period of Neptune. Both light curves are slowly varying with time, with full amplitudes of 1.1mag at 3.6{mu}m and 0.6mag at 4.5{mu}m. We have also extracted sparsely sampled 18hr light curves of Neptune at W1 (3.4{mu}m) and W2 (4.6{mu}m) from the Wide-feld Infrared Survey Explorer (WISE)/NEOWISE archive at six epochs in 2010-2015. These light curves all show similar shapes and amplitudes compared to the Spitzer light curves but with considerable variation from epoch to epoch. These amplitudes are much larger than those observed with Kepler/K2 in the visible (amplitude ~0.02mag) or at 845nm with the Hubble Space Telescope (HST) in 2015 and at 763nm in 2016 (amplitude ~0.2mag). We interpret the Spitzer and WISE light curves as arising entirely from reflected solar photons, from higher levels in Neptune's atmosphere than for K2. Methane gas is the dominant opacity source in Neptune's atmosphere, and methane absorption bands are present in the HST 763 and 845nm, WISE W1, and Spitzer 3.6{mu}m filters.
- ID:
- ivo://CDS.VizieR/J/ApJ/755/9
- Title:
- Spitzer/IRAC light curves of GJ 436 system
- Short Name:
- J/ApJ/755/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of UCF-1.01, a strong exoplanet candidate with a radius 0.66+/-0.04 times that of Earth (R_{oplus}_). This sub-Earth sized planet transits the nearby M-dwarf star GJ 436 with a period of 1.365862+/-8x10^-6^ days. We also report evidence of a 0.65+/-0.06R_{Earth}_ exoplanet candidate (labeled UCF-1.02) orbiting the same star with an undetermined period. Using the Spitzer Space Telescope, we measure the dimming of light as the planets pass in front of their parent star to assess their sizes and orbital parameters. If confirmed today, UCF-1.01 and UCF-1.02 would be designated GJ 436c and GJ 436d, respectively, and would be part of the first multiple-transiting-planet system outside of the Kepler field. Assuming Earth-like densities of 5.515g/cm3, we predict both candidates to have similar masses (~0.28M_{oplus}_, 2.6 Mars-masses) and surface gravities of ~0.65g (where g is the gravity on Earth). UCF-1.01's equilibrium temperature (T_eq_, where emitted and absorbed radiation balance for an equivalent blackbody) is 860K, making the planet unlikely to harbor life as on Earth. Its weak gravitational field and close proximity to its host star imply that UCF-1.01 is unlikely to have retained its original atmosphere; however, a transient atmosphere is possible if recent impacts or tidal heating were to supply volatiles to the surface. We also present additional observations of GJ 436b during secondary eclipse. The 3.6{mu}m light curve shows indications of stellar activity, making a reliable secondary eclipse measurement impossible. A second non-detection at 4.5{mu}m supports our previous work in which we find a methane-deficient and carbon monoxide-rich dayside atmosphere.
- ID:
- ivo://CDS.VizieR/J/AJ/141/11
- Title:
- Spitzer observations of planet-host stars
- Short Name:
- J/AJ/141/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since giant planets scatter planetesimals within a few tidal radii of their orbits, the locations of existing planetesimal belts indicate regions where giant planet formation failed in bygone protostellar disks. Infrared observations of circumstellar dust produced by colliding planetesimals are therefore powerful probes of the formation histories of known planets. Here we present new Spitzer infrared spectrograph (IRS) spectrophotometry of 111 solar-type stars, including 105 planet hosts. Our observations reveal 11 debris disks, including two previously undetected debris disks orbiting HD 108874 and HD 130322. Combining the 32um spectrophotometry with previously published MIPS photometry, we find that the majority of debris disks around solar-type stars have temperatures in the range 60<~T_dust_<~100K. Assuming a dust temperature T_dust_=70K, which is representative of the nine debris disks detected by both IRS and MIPS, debris rings surrounding Sun-like stars orbit between 15 and 240AU depending on the mean particle size. Our observations imply that the planets detected by radial-velocity searches formed within 240AU of their parent stars. If any of the debris disks studied here have mostly large, blackbody emitting grains, their companion giant planets must have formed in a narrow region between the ice line and 15AU.
- ID:
- ivo://CDS.VizieR/J/A+A/471/L51
- Title:
- Spitzer observations of the hot Neptune GJ 436b
- Short Name:
- J/A+A/471/L51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer Space Telescope infrared photometry of a primary transit of the hot Neptune GJ 436b. The observations were obtained using the 8{mu}m band of the InfraRed Array Camera (IRAC).
- ID:
- ivo://CDS.VizieR/J/ApJ/786/2
- Title:
- Spitzer photometric time series of HD 97658
- Short Name:
- J/ApJ/786/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Super-Earths transiting nearby bright stars are key objects that simultaneously allow for accurate measurements of both their mass and radius, providing essential constraints on their internal composition. We present here the confirmation, based on Spitzer transit observations, that the super-Earth HD 97658 b transits its host star. HD 97658 is a low-mass (M_*_=0.77+/-0.05 M_{sun}_) K1 dwarf, as determined from the Hipparcos parallax and stellar evolution modeling. To constrain the planet parameters, we carry out Bayesian global analyses of Keck-High Resolution Echelle Spectrometer (Keck-HIRES) radial velocities and Microvariability and Oscillations of STars (MOST) and Spitzer photometry. HD 97658 b is a massive (M_p_=7.55_-0.79_^+0.83^ M_{earth}_) and large (R_p_=2.247_0.095_^+0.098^ R_{earth}_ at 4.5 {mu}m) super-Earth. We investigate the possible internal compositions for HD 97658 b. Our results indicate a large rocky component, of at least 60% by mass, and very little H-He components, at most 2% by mass. We also discuss how future asteroseismic observations can improve the knowledge of the HD 97658 system, in particular by constraining its age. Orbiting a bright host star, HD 97658 b will be a key target for upcoming space missions such as the Transiting Exoplanet Survey Satellite (TESS), the Characterizing Exoplanet Satellite (CHEOPS), the Planetary Transits and Oscillations of stars (PLATO), and the James Webb Space Telescope to characterize thoroughly its structure and atmosphere.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A117
- Title:
- Spitzer search for 19 planets
- Short Name:
- J/A+A/601/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Short-period super-Earths and Neptunes are now known to be very frequent around solar-type stars. Improving our understanding of these mysterious planets requires the detection of a significant sample of objects suitable for detailed characterization. Searching for the transits of the low-mass planets detected by Doppler surveys is a straightforward way to achieve this goal. Indeed, Doppler surveys target the most nearby main-sequence stars, they regularly detect close-in low-mass planets with significant transit probability, and their radial velocity data constrain strongly the ephemeris of possible transits. In this context, we initiated in 2010 an ambitious Spitzer multi-Cycle transit search project that targeted 25 low-mass planets detected by radial velocity, focusing mainly on the shortest-period planets detected by the HARPS spectrograph. We report here null results for 19 targets of the project. For 16 planets out of 19, a transiting configuration is strongly disfavored or firmly rejected by our data for most planetary compositions.We derive a posterior probability of 83% that none of the probed 19 planets transits (for a prior probability of 22%), which still leaves a significant probability of 17% that at least one of them does transit. Globally, our Spitzer project revealed or confirmed transits for three of its 25 targeted planets, and discarded or disfavored the transiting nature of 20 of them. Our light curves demonstrate for Warm Spitzer excellent photometric precisions: for 14 targets out of 19, we were able to reach standard deviations that were better than 50ppm per 30 min intervals. Combined with its Earth-trailing orbit, which makes it capable of pointing any star in the sky and to monitor it continuously for days, this work confirms Spitzer as an optimal instrument to detect sub-mmag-deep transits on the bright nearby stars targeted by Doppler surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A55
- Title:
- Spitzer secondary eclipses of Qatar-1b
- Short Name:
- J/A+A/610/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous secondary eclipse observations of the hot Jupiter Qatar-1b in the Ks band suggest that it may have an unusually high day side temperature, indicative of minimal heat redistribution. There have also been indications that the orbit may be slightly eccentric, possibly forced by another planet in the system. We investigate the day side temperature and orbital eccentricity using secondary eclipse observations with Spitzer. We observed the secondary eclipse with Spitzer/IRAC in subarray mode, in both 3.6 and 4.5um wavelengths. We used pixel-level decorrelation to correct for Spitzer's intra-pixel sensitivity variations and thereby obtain accurate eclipse depths and central phases.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A38
- Title:
- SPOTS II. Planets Orbiting Two Stars
- Short Name:
- J/A+A/593/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A large number of direct imaging surveys for exoplanets have been performed in recent years, yielding the first directly imaged planets and providing constraints on the prevalence and distribution of wide planetary systems. However, like most of the radial velocity ones, these generally focus on single stars, hence binaries and higher-order multiples have not been studied to the same level of scrutiny. This motivated the Search for Planets Orbiting Two Stars (SPOTS) survey, which is an ongoing direct imaging study of a large sample of close binaries, started with VLT/NACO and now continuing with VLT/SPHERE. To complement this survey, we have identified the close binary targets in 24 published direct imaging surveys. Here we present our statistical analysis of this combined body of data. We analysed a sample of 117 tight binary systems, using a combined Monte Carlo and Bayesian approach to derive the expected values of the frequency of companions, for different values of the companion's semi-major axis. Our analysis suggest that the frequency of sub-stellar companions in wide orbit is moderately low (=>13% with a best value of 6% at 95% confidence level) and not significantly different between single stars and tight binaries. One implication of this result is that the very high frequency of circumbinary planets in wide orbits around post-common envelope binaries, implied by eclipse timing, cannot be uniquely due to planets formed before the common-envelope phase (first generation planets), supporting instead the second generation planet formation or a non-Keplerian origin of the timing variations.
- ID:
- ivo://CDS.VizieR/J/ApJ/716/1336
- Title:
- Stability analysis of single-planet
- Short Name:
- J/ApJ/716/1336
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the dynamical stability of planetary systems consisting of one hypothetical terrestrial-mass planet (1 or 10M_{earth}_) and one massive planet (10M{earth}-10M_jup_). We consider masses and orbits that cover the range of observed planetary system architectures (including non-zero initial eccentricities), determine the stability limit through N-body simulations, and compare it to the analytic Hill stability boundary. We show that for given masses and orbits of a two-planet system, a single parameter, which can be calculated analytically, describes the Lagrange stability boundary (no ejections or exchanges) but diverges significantly from the Hill stability boundary. However, we do find that the actual boundary is fractal, and therefore we also identify a second parameter which demarcates the transition from stable to unstable evolution. We show the portions of the habitable zones (HZs) of {rho} CrB, HD 164922, GJ 674, and HD 7924 that can support a terrestrial planet. These analyses clarify the stability boundaries in exoplanetary systems and demonstrate that, for most exoplanetary systems, numerical simulations of the stability of potentially habitable planets are only necessary over a narrow region of the parameter space. Finally, we also identify and provide a catalog of known systems that can host terrestrial planets in their HZs.