- ID:
- ivo://CDS.VizieR/J/A+A/506/1469
- Title:
- theta Cyg radial velocity variations
- Short Name:
- J/A+A/506/1469
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the frame of the search for extrasolar planets and brown dwarfs around early-type main-sequence stars, we present the results obtained on the early F-type star theta Cygni. ELODIE and SOPHIE at Observatoire de Haute-Provence (OHP) were used to obtain 91 and 162 spectra, respectively. Our dedicated radial-velocity measurement method was used to monitor the star's radial velocities over five years. We also use complementary, high angular resolution and high-contrast images taken with PUEO at CFHT. We show that theta Cygni radial velocities are quasi-periodically variable, with a ~150-day period. These variations are not due to the ~0.35M_{sun}_ stellar companion that we detected in imaging at more than 46AU from the star. The absence of correlation between the bisector velocity span variations and the radial velocity variations for this 7km/s vsini star, as well as other criteria indicate that the observed radial velocity variations are not due to stellar spots. The observed amplitude of the bisector velocity span variations also seems to rule out stellar pulsations. However, we observe a peak in the bisector velocity span periodogram at the same period as the one found in the radial velocity periodogram, which indicates a probable link between these radial velocity variations and the low amplitude lineshape variations which are of stellar origin. Long-period variations are not expected from this type of star to our knowledge. If a stellar origin (hence of new type) was to be confirmed for these long-period radial velocity variations, this would have several consequences on the search for planets around main-sequence stars, both in terms of observational strategy and data analysis. An alternative explanation for these variable radial velocities is the presence of at least one planet of a few Jupiter masses orbiting at less than 1AU; however this planet alone does not explain all observed features, and the theta Cygni system is obviously more complex than a planetary system with 1 or 2 planets. The available data do not allow to distinguish between these two possible origins. A vigourous follow-up in spectroscopy and photometry is needed to get a comprehensive view of the star intrinsic variability and/or its surrounding planetary system.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/210/5
- Title:
- The twenty-five year Lick planet search
- Short Name:
- J/ApJS/210/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Lick Planet Search program began in 1987 when the first spectrum of {tau} Ceti was taken with an iodine cell and the Hamilton Spectrograph. Upgrades to the instrument improved the Doppler precision from about 10m/s in 1992 to about 3m/s in 1995. The project detected dozens of exoplanets with orbital periods ranging from a few days to several years. The Lick survey identified the first planet in an eccentric orbit (70 Virginis) and the first multi-planet system around a normal main sequence star (Upsilon Andromedae). These discoveries advanced our understanding of planet formation and orbital migration. Data from this project helped to quantify a correlation between host star metallicity and the occurrence rate of gas giant planets. The program also served as a test bed for innovation with testing of a tip-tilt system at the Coud\'e focus and fiber scrambler designs to stabilize illumination of the spectrometer optics. The Lick Planet Search with the Hamilton Spectrograph effectively ended when a heater malfunction compromised the integrity of the iodine cell. Here, we present more than 14000 velocities for 386 stars that were surveyed between 1987 and 2011.
- ID:
- ivo://CDS.VizieR/J/MNRAS/422/1988
- Title:
- Three short-period, transiting exoplanets
- Short Name:
- J/MNRAS/422/1988
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of three extrasolar planets that transit their moderately bright (m_V_=12-13) host stars. WASP-44b is a 0.89-M_Jup_ planet in a 2.42-day orbit around a G8V star. WASP-45b is a 1.03-M_Jup_ planet which passes in front of the limb of its K2V host star every 3.13-days. Weak CaII H&K emission seen in the spectra of WASP-45 suggests that the star is chromospherically active. WASP-46b is a 2.10-M_Jup_ planet in a 1.43-day orbit around a G6V star. Rotational modulation of the light curves of WASP-46 and weak CaII H&K emission in its spectra show the star to be photospherically and chromospherically active.
- ID:
- ivo://CDS.VizieR/J/ApJ/664/1185
- Title:
- Three transits of the exoplanet TrES-2
- Short Name:
- J/ApJ/664/1185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Of the nearby transiting exoplanets that are amenable to detailed study, TrES-2 is both the most massive and the one with the largest impact parameter. We present z-band photometry of three transits of TrES-2. We improve on the estimates of the planetary, stellar, and orbital parameters, in conjunction with the spectroscopic analysis of the host star by Sozzetti and coworkers. We find the planetary radius to be Rp=1.222+/-0.038R_Jup_ and the stellar radius to be R*=1.003+/-0.027R_{sun}_. The quoted uncertainties include the systematic error due to the uncertainty in the stellar mass (M*=0.980+/-0.062 M_{sun}_) The timings of the transits have an accuracy of 25s and are consistent with a uniform period, thus providing a baseline for future observations with the NASA Kepler satellite, whose field of view will include TrES-2.
- ID:
- ivo://CDS.VizieR/J/ApJ/692/L9
- Title:
- Tidal evolution of transiting extrasolar planets
- Short Name:
- J/ApJ/692/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We revisit the tidal stability of extrasolar systems harboring a transiting planet and demonstrate that, independently of any tidal model, none, but one (HAT-P-2b) of these planets has a tidal equilibrium state, which implies ultimately a collision of these objects with their host star. Consequently, conventional circularization and synchronization timescales cannot be defined because the corresponding states do not represent the endpoint of the tidal evolution. Using numerical simulations of the coupled tidal equations for the spin and orbital parameters of each transiting planetary system, we confirm these predictions and show that the orbital eccentricity and the stellar obliquity do not follow the usually assumed exponential relaxation but instead decrease significantly, eventually reaching a zero value only during the final runaway merging of the planet with the star. The only characteristic evolution timescale of all rotational and orbital parameters is the lifetime of the system, which crucially depends on the magnitude of tidal dissipation within the star. These results imply that the nearly circular orbits of transiting planets and the alignment between the stellar spin axis and the planetary orbit are unlikely to be due to tidal dissipation. Other dissipative mechanisms, for instance interactions with the protoplanetary disk, must be invoked to explain these properties.
- ID:
- ivo://CDS.VizieR/J/AJ/154/4
- Title:
- Times of transits and occultations of WASP-12b
- Short Name:
- J/AJ/154/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new transit and occultation times for the hot Jupiter WASP-12b. The data are compatible with a constant period derivative: P.=-29+/-3ms/yr and P/P.=3.2Myr. However, it is difficult to tell whether we have observed orbital decay or a portion of a 14-year apsidal precession cycle. If interpreted as decay, the star's tidal quality parameter Q_star_ is about 2*10^5^. If interpreted as precession, the planet's Love number is 0.44+/-0.10. Orbital decay appears to be the more parsimonious model: it is favored by {Delta}_{chi}^2^_=5.5 despite having two fewer free parameters than the precession model. The decay model implies that WASP-12 was discovered within the final ~0.2% of its existence, which is an unlikely coincidence but harmonizes with independent evidence that the planet is nearing disruption. Precession does not invoke any temporal coincidence, but it does require some mechanism to maintain an eccentricity of {approx}0.002 in the face of rapid tidal circularization. To distinguish unequivocally between decay and precession will probably require a few more years of monitoring. Particularly helpful will be occultation timing in 2019 and thereafter.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A116
- Title:
- Titan middle atmosphere thermal field
- Short Name:
- J/A+A/641/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the seasonal evolution of Titan's thermal field and distributions of haze, C_2_H_2_, C_2_H_4_, C_2_H_6_, CH_3_C_2_H, C_3_H_8_, C_4_H_2_, C_6_H_6_, HCN, and HC_3_N from March 2015 (Ls=66{deg}) to September 2017 (Ls=93{deg}) (i.e., from the last third of northern spring to early summer). We analyzed thermal emission of Titan's atmosphere acquired by the Cassini Composite Infrared Spectrometer (CIRS) with limb and nadir geometry to retrieve the stratospheric and mesospheric temperature and mixing ratios pole-to-pole meridional cross sections from 5mbar to 50ubar (120-650km). The southern stratopause varied in a complex way and showed a global temperature increase from 2015 to 2017 at high-southern latitudes. Stratospheric southern polar temperatures, which were observed to be as low as 120K in early 2015 due to the polar night, showed a 30K increase (at 0.5mbar) from March 2015 to May 2017 due to adiabatic heating in the subsiding branch of the global overturning circulation. All photochemical compounds were enriched at the south pole by this subsidence. Polar cross sections of these enhanced species, which are good tracers of the global dynamics, highlighted changes in the structure of the southern polar vortex. These high enhancements combined with the unusually low temperatures (<120K) of the deep stratosphere resulted in condensation at the south pole between 0.1 and 0.03mbar (240-280km) of HCN, HC_3_N, C_6_H_6_ and possibly C4H2 in March 2015 (Ls=66{deg}). These molecules were observed to condense deeper with increasing distance from the south pole. At high-northern latitudes, stratospheric enrichments remaining from the winter were observed below 300km between 2015 and May 2017 (Ls=90{deg}) for all chemical compounds and up to September 2017 (Ls=93{deg}) for C_2_H_2_, C_2_H_4_, CH_3_C_2_H, C_3_H_8_, and C_4_H_2_. In September 2017, these local enhancements were less pronounced than earlier for C_2_H_2_, C_4_H_2_, CH_3_C_2_H, HC_3_N, and HCN, and were no longer observed for C_2_H_6_ and C_6_H_6_, which suggests a change in the northern polar dynamics near the summer solstice. These enhancements observed during the entire spring may be due to confinement of this enriched air by a small remaining winter circulation cell that persisted in the low stratosphere up to the northern summer solstice, according to predictions of the Institut Pierre Simon Laplace Titan Global Climate Model (IPSL Titan GCM). In the mesosphere we derived a depleted layer in C_2_H_2_, HCN, and C_2_H_6_ from the north pole to mid-southern latitudes, while C_4_H_2_, C_3_H_4_, C_2_H_4_, and HC_3_N seem to have been enriched in the same region. In the deep stratosphere, all molecules except C_2_H_4_ were depleted due to their condensation sink located deeper than 5mbar outside the southern polar vortex. HCN, C_4_H_2_, and CH_3_C_2_H volume mixing ratio (VMR) cross section contours showed steep slopes near the mid-latitudes or close to the equator, which can be explained by upwelling air in this region. Upwelling is also supported by the cross section of the C_2_H_4_ (the only molecule not condensing among those studied here) volume mixing ratio observed in the northern hemisphere. We derived the zonal wind velocity up to mesospheric levels from the retrieved thermal field. We show that zonal winds were faster and more confined around the south pole in 2015 (Ls=67-72{deg}) than later. In 2016, the polar zonal wind speed decreased while the fastest winds had migrated toward low-southern latitudes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/3608
- Title:
- Titius-Bode-based exoplanet predictions
- Short Name:
- J/MNRAS/448/3608
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse a sample of multiple-exoplanet systems which contain at least three transiting planets detected by the Kepler mission ('Kepler multiples'). We use a generalized Titius-Bode relation to predict the periods of 228 additional planets in 151 of these Kepler multiples. These Titius-Bode-based predictions suggest that there are, on average, 2+/-1 planets in the habitable zone of each star. We estimate the inclination of the invariable plane for each system and prioritize our planet predictions by their geometric probability to transit. We highlight a short list of 77 predicted planets in 40 systems with a high geometric probability to transit, resulting in an expected detection rate of ~15%, ~3 times higher than the detection rate of our previous Titius-Bode-based predictions.
- ID:
- ivo://CDS.VizieR/J/A+A/507/1649
- Title:
- Tohoku-Hiroshima-Nagoya planetary spectra library
- Short Name:
- J/A+A/507/1649
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A comprehensive framework for comparing spectral data from different planets has yet to be established. This framework is needed for the study of extrasolar planets and objects within the solar system. We completed observations to compile a library of planet spectra for all planets, some moons, and some dwarf planets in the solar system to study their general spectroscopic and photometric natures. During May and November of 2008, we acquired spectra for the planets using TRISPEC, which is capable of simultaneous three-band spectroscopy across a wide wavelength range of 0.45-2.5um with low resolving power ({lambda}{Delta}{lambda}~140-360).
- ID:
- ivo://CDS.VizieR/J/AJ/153/258
- Title:
- 2007.5 to 2010.4 HST astrometry of HD 202206
- Short Name:
- J/AJ/153/258
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Hubble Space Telescope Fine Guidance Sensor astrometry and previously published radial velocity measures, we explore the exoplanetary system HD202206. Our modeling results in a parallax, {pi}_abs_=21.96+/-0.12 milliseconds of arc, a mass for HD202206B of M_B_=0.089_-0.006_^+0.007M_{Sun}_, and a mass for HD202206c of M_c_=17.9_-1.8_^+2.9^M_Jup_. HD202206 is a nearly face-on G + M binary orbited by a brown dwarf. The system architecture that we determine supports past assertions that stability requires a 5:1 mean motion resonance (we find a period ratio, P_c_/P_B_=4.92+/-0.04) and coplanarity (we find a mutual inclination, {Phi}=6{deg}+/-2{deg}).
