- ID:
- ivo://CDS.VizieR/J/MNRAS/445/4395
- Title:
- Fundamental properties of giant gas planets
- Short Name:
- J/MNRAS/445/4395
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is already stated in the previous studies that the radius of the giant planets is affected by stellar irradiation. The confirmed relation between radius and incident flux depends on planetary mass intervals. In this study, we show that there is a single relation between radius and irradiated energy per gram per second (l-), for all mass intervals. There is an extra increase in radius of planets if l- is higher than 1100 times energy received by the Earth (l_{earth}_). This is likely due to dissociation of molecules. The tidal interaction as a heating mechanism is also considered and found that its maximum effect on the inflation of planets is about 15 percent. We also compute age and heavy element abundances from the properties of host stars, given in the TEPCat catalogue (Southworth). The metallicity given in the literature is as [Fe/H]. However, the most abundant element is oxygen, and there is a reverse relation between the observed abundances [Fe/H] and [O/Fe]. Therefore, we first compute [O/H] from [Fe/H] by using observed abundances, and then find heavy element abundance from [O/H]. We also develop a new method for age determination. Using the ages we find, we analyse variation of both radius and mass of the planets with respect to time, and estimate the initial mass of the planets from the relation we derive for the first time. According to our results, the highly irradiated gas giants lose 5 percent of their mass in every 1Gyr.
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- ID:
- ivo://CDS.VizieR/J/other/RMxAA/53.439
- Title:
- Gaia stars with GALEX NUV excess
- Short Name:
- J/other/RMxAA/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate parallaxes from Gaia DR1 (TGAS) are combined with GALEX visual Nuv magnitudes to produce absolute MNUV magnitudes and an ultraviolet HR diagram for a large sample of astrometric stars. A functional fit is derived of the lower envelope main sequence of the nearest 1403 stars (distance <40pc), which should be reddening-free. Using this empirical fit, 50 nearby stars are selected with significant Nuv excess. These are predominantly late K and early M dwarfs, often associated with X-ray sources, and showing other manifestations of magnetic activity. The sample may include systems with hidden white dwarfs, stars younger than the Pleiades, or, most likely, tight interacting binaries of the BY Dra-type. A separate collection of 40 stars with precise trigonometric parallaxes and Nuv-G colors bluer than 2mag is presented. It includes several known novae, white dwarfs, and binaries with hot subdwarf (sdOB) components, but most remain unexplored.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A116
- Title:
- Galactic Cepheids and RR Lyrae multiplicity. I.
- Short Name:
- J/A+A/623/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Classical Cepheids (CCs) and RR Lyrae stars (RRLs) are important classes of variable stars used as standard candles to estimate galactic and extragalactic distances. Their multiplicity is imperfectly known, particularly for RRLs. Astoundingly, only one RRL is convincingly demonstrated to be a binary as of today, TU UMa, out of tens of thousands of known RRLs. We aim at detecting the binary and multiple stars present in a sample of Milky Way CCs and RRLs. In the present article, we combine the Hipparcos and Gaia DR2 positions to determine the mean proper motion of the targets, and we search for proper motion anomalies (PMa) caused by close-in orbiting companions. We identify 57 CC binaries from PMa out of 254 tested stars, and 75 additional candidates, confirming the high binary fraction of these massive stars. For 28 binary CCs, we determine the companion mass by combining their spectroscopic orbital parameters and astrometric PMa. We detect 13 RRLs showing a significant PMa out of 198 tested stars, and 61 additional candidates. We determine that the binarity fraction of CCs is likely above 80%, while that of RRLs is at least 7%. The newly detected systems will be useful to improve our understanding of their evolutionary states. The discovery of a significant number of RRLs in binary systems also resolves the long-standing mystery of their extremely low apparent binarity fraction.
- ID:
- ivo://CDS.VizieR/J/A+A/518/A1
- Title:
- Galactic massive stars with AstraLux
- Short Name:
- J/A+A/518/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive stars have high-multiplicity fractions, and many of them have still undetected components, thus hampering the study of their properties. I study a sample of massive stars with high angular resolution to better characterize their multiplicity. I observed 138 fields that include at least one massive star with AstraLux, a lucky imaging camera at the 2.2m Calar Alto telescope. I also used observations of 3 of those fields with ACS/HRC on HST to obtain complementary information and to calibrate the AstraLux data. The results were compared with existing information from the Washington Double Star Catalog, Tycho-2, 2MASS, and other literature results.
- ID:
- ivo://CDS.VizieR/J/MNRAS/487/2474
- Title:
- GALAH unresolved triple Sun-like star
- Short Name:
- J/MNRAS/487/2474
- Date:
- 02 Mar 2022 00:37:36
- Publisher:
- CDS
- Description:
- The latest Gaia data release enables us to accurately identify stars that are more luminous than would be expected on the basis of their spectral type and distance. During an investigation of the 329 best solar twin candidates uncovered among the spectra acquired by the GALAH survey, we identified 64 such overluminous stars. In order to investigate their exact composition, we developed a data-driven methodology that can generate a synthetic photometric signature and spectrum of a single star. By combining multiple such synthetic stars into an unresolved binary or triple system and comparing the results to the actual photometric and spectroscopic observations, we uncovered 6 definitive triple stellar system candidate and an additional 14 potential candidates whose combined spectrum mimics the solar spectrum. Considering the volume correction factor for a magnitude-limited survey, the fraction of probable unresolved triple stars with long orbital periods is 2 per cent. Possible orbital configurations of the candidates were investigated using the selection and observational limits. To validate the discovered multiplicity fraction, the same procedure was used to evaluate the multiplicity fraction of other stellar types.
- ID:
- ivo://CDS.VizieR/J/ApJ/766/9
- Title:
- GALEX observations of exoplanet host stars
- Short Name:
- J/ApJ/766/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the far-UV (FUV) and near-UV (NUV) photometry from the NASA Galaxy Evolution Explorer (GALEX), we searched for evidence of increased stellar activity due to tidal and/or magnetic star-planet interactions (SPI) in the 272 known FGK planetary hosts observed by GALEX. With the increased sensitivity of GALEX, we are able probe systems with lower activity levels and at larger distances than what has been done to date with X-ray satellites. We compared samples of stars with close-in planets (a<0.1AU) to those with far-out planets (a>0.5AU) and looked for correlations of excess activity with other system parameters. This statistical investigation found no clear correlations with a, M_p_, or M_p_/a, in contrast to some X-ray and CaII studies. However, there is tentative evidence (at a level of 1.8{sigma}) that stars with radial-velocity-(RV)-detected close-in planets are more FUV-active than stars with far-out planets, in agreement with several published X-ray and Ca II results. The case is strengthened to a level of significance to 2.3{sigma} when transit-detected close-in planets are included. This is most likely because the RV-selected sample of stars is significantly less active than the field population of comparable stars, while the transit-selected sample is similarly active. Given the factor of 2-3 scatter in fractional FUV luminosity for a given stellar effective temperature, it is necessary to conduct a time-resolved study of the planet hosts in order to better characterize their UV variability and generate a firmer statistical result.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A188
- Title:
- G 264-012 and Gl 393 radial velocity curves
- Short Name:
- J/A+A/650/A188
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We report the discovery of two planetary systems, namely G 264-012, an M4.0 dwarf with two terrestrial planets (M_b_sini=2.50^+0.29^_-0.30_M_{sun}_ and M_c_sini=3.75^+0.48^_-0.47_M_{sun}_), and Gl 393, a bright M2.0 dwarf with one terrestrial planet (M_b_sini=1.71+/-0.24M_{sun}_). Although both stars were proposed to belong to young stellar kinematic groups, we estimate their ages to be older than about 700Ma. The two planets around G 264-012 were discovered using only radial-velocity (RV) data from the CARMENES exoplanet survey, with estimated orbital periods of 2.30d and 8.05d, respectively. Photometric monitoring and analysis of activity indicators reveal a third signal present in the RV measurements, at about 100d, caused by stellar rotation. The planet Gl 393b was discovered in the RV data from the HARPS, CARMENES, and HIRES instruments. Its identification was only possible after modelling, with a Gaussian process (GP), the variability produced by the magnetic activity of the star. For the earliest observations, this variability produced a forest of peaks in the periodogram of the RVs at around the 34d rotation period determined from Kepler data, which disappeared in the latest epochs. After correcting for them with this GP model, a significant signal showed at a period of 7.03d. No significant signals in any of our spectral activity indicators or contemporaneous photometry were found at any of the planetary periods. Given the orbital and stellar properties, the equilibrium temperatures of the three planets are all higher than that for Earth. Current planet formation theories suggest that these two systems represent a common type of architecture. This is consistent with formation following the core accretion paradigm.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A111
- Title:
- GAPS V: Global analysis of the XO-2 system
- Short Name:
- J/A+A/575/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- XO-2 is the first confirmed wide stellar binary system where the almost twin components XO-2N and XO-2S have planets, and it is a peculiar laboratory in which to investigate the diversity of planetary systems. This stimulated a detailed characterization study of the stellar and planetary components based on new observations. We collected high-resolution spectra with the HARPS-N spectrograph and multi-band light curves. Spectral analysis led to an accurate determination of the stellar atmospheric parameters and characterization of the stellar activity, and high-precision radial velocities of XO-2N were measured. We collected 14 transit light curves of XO-2Nb used to improve the transit parameters. Photometry provided accurate magnitude differences between the stars and a measure of their rotation periods.
- ID:
- ivo://CDS.VizieR/J/ApJ/670/1367
- Title:
- Gemini Deep Planet Survey
- Short Name:
- J/ApJ/670/1367
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the Gemini Deep Planet Survey, a near-infrared adaptive optics search for giant planets and brown dwarfs around 85 nearby young stars. The observations were obtained with the Altair adaptive optics system at the Gemini North telescope, and angular differential imaging was used to suppress the speckle noise of the central star. Typically, the observations are sensitive to angular separations beyond 0.5" with 5{sigma} contrast sensitivities in magnitude difference at 1.6um of 9.5 at 0.5", 12.9 at 1", 15.0 at 2", and 16.5 at 5". These sensitivities are sufficient to detect planets more massive than 2M_{Jup}_ with a projected separation in the range 40-200AU around a typical target. Second-epoch observations of 48 stars with candidates (out of 54) have confirmed that all candidates are unrelated background stars. A detailed statistical analysis of the survey results is presented.
- ID:
- ivo://CDS.VizieR/J/A+A/659/L4
- Title:
- Geometric albedo of HD 209458 b
- Short Name:
- J/A+A/659/L4
- Date:
- 02 Mar 2022 07:55:13
- Publisher:
- CDS
- Description:
- We report the detection of the secondary eclipse of the hot Jupiter HD 209458 b in optical/visible light using the CHEOPS space telescope. Our measurement of 20.4^+3.2^_3.3_ parts per million (ppm) translates into a geometric albedo of Ag=0.096+/-0.016. The previously estimated dayside temperature of about 1500K implies that our geometric albedo measurement consists predominantly of reflected starlight and is largely uncontaminated by thermal emission. This makes the present result one of the most robust measurements of Ag for any exoplanet, critical for understanding the atmosphere. Our calculations of the bandpass-integrated geometric albedo demonstrate that the measured value of Ag is consistent with a cloud-free atmosphere, where starlight is reflected via Rayleigh scattering by hydrogen molecules, with water and sodium abundances consistent with stellar metallicity. We predict that the bandpass-integrated TESS geometric albedo is too faint to detect and that a phase curve of HD 209458 b observed by CHEOPS would have a distinct shape associated with Rayleigh scattering if the atmosphere is indeed cloud-free.
