- ID:
- ivo://CDS.VizieR/J/AJ/150/33
- Title:
- Photometry and spectroscopy of HATS-9 and HATS-10
- Short Name:
- J/AJ/150/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of two transiting extrasolar planets by the HATSouth survey. HATS-9b orbits an old (10.8+/-1.5Gyr) V=13.3 G dwarf star with a period p~~1.9153days. The host star has a mass of 1.03M_{sun}_, radius of 1.503R_{sun}_, and effective temperature 5366+/-70K. The planetary companion has a mass of 0.837M_J_ and radius of 1.065R_J_, yielding a mean density of 0.85g/cm^-3^. HATS-10b orbits a V=13.1 G dwarf star with a period p~~3.3128days. The host star has a mass of 1.1M_{sun}_, radius of 1.11R_{sun}_, and effective temperature 5880+/-120K. The planetary companion has a mass of 0.53M_J_ and radius of 0.97R_J_, yielding a mean density of 0.7g/cm3. Both planets are compact in comparison with planets receiving similar irradiation from their host stars and lie in the nominal coordinates of Field 7 of K2, but only HATS-9b falls on working silicon. Future characterization of HATS-9b with the exquisite photometric precision of the Kepler telescope may provide measurements of its reflected light signature.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/156/37
- Title:
- Photometry & Li abund. of cool dwarfs in M35
- Short Name:
- J/AJ/156/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hydra spectra of 85 G-K dwarfs in the young cluster M35 near the Li 6708 {AA} line region are analyzed. From velocities and Gaia astrometry, 78 are likely single-star members that, combined with previous work, produce 108 members with T_eff_ ranging from 6150 to 4000 K as defined by multicolor, broadband photometry, E(B-V)=0.20, and [Fe/H]=-0.15, though there are indications the metallicity may be closer to solar. The Lithium abundance A(Li) follows a well-delineated decline from 3.15 for the hottest stars to upper limits =<1.0 among the coolest dwarfs. Contrary to earlier work, M35 includes single stars at systematically higher A(Li) than the mean cluster relation. This subset exhibits higher V_ROT_ than the more Li-depleted sample and, from photometric rotation periods, is dominated by stars classed as convective (C); all others are interface (I) stars. The cool, high-Li rapid rotators (RRs) are consistent with models that simultaneously consider rapid rotation and radius inflation; RRs hotter than the Sun exhibit excess Li depletion, as predicted by the models. The A(Li) distribution with color and rotation period, when compared to the Hyades/Praesepe and the Pleiades, is consistent with gyrochronological analysis placing M35's age between the older M34 and younger Pleiades. However, the Pleiades display a more excessive range in A(Li) and rotation period than M35 on the low-Li, slow-rotation side of the distribution, with supposedly younger stars at a given T_eff_ in the Pleiades spinning slower, with A(Li) reduced by more than a factor of four compared to M35.
- ID:
- ivo://CDS.VizieR/J/AJ/155/257
- Title:
- Photometry & RV follow-up observations of K2-18
- Short Name:
- J/AJ/155/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- K2-18 is a nearby M2.5 dwarf, located at 34 pc and hosting a transiting planet that was first discovered by the K2 mission and later confirmed with Spitzer Space Telescope observations. With a radius of ~2 R_{Earth}_ and an orbital period of ~33 days, the planet lies in the temperate zone of its host star and receives stellar irradiation similar to that of Earth. Here we perform radial velocity follow-up observations with the visual channel of CARMENES with the goal of determining the mass and density of the planet. We measure a planetary semi-amplitude of K_b_~3.5 m/s and a mass of M_b_~9 M_{Earth}_, yielding a bulk density around {rho}_b_~4 g/cm^3^. This indicates a low-mass planet with a composition consistent with a solid core and a volatile-rich envelope. A signal at 9 days was recently reported using radial velocity measurements taken with the HARPS spectrograph. This was interpreted as being due to a second planet. We see a weaker, time- and wavelength-dependent signal in the CARMENES data set and thus favor stellar activity for its origin. K2-18 b joins the growing group of low-mass planets detected in the temperate zone of M dwarfs. The brightness of the host star in the near-infrared makes the system a good target for detailed atmospheric studies with the James Webb Space Telescope.
- ID:
- ivo://CDS.VizieR/J/A+A/497/497
- Title:
- Physical parameters from JHK flux
- Short Name:
- J/A+A/497/497
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The effective temperature scale of FGK stars, especially at the lowest metallicities remains a major problem in the chemical abundance analysis of metal-poor stars. We present a new implementation of the infrared flux method (IRFM) using the 2MASS catalogue.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A141
- Title:
- Physical parameters of PMS in open clusters
- Short Name:
- J/A+A/531/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our aims are twofold: To determine the physical parameters of PMS members in young open clusters (YOCs), and to check and compare the performances of different model isochrones. We compare UBVRI photometric observations of eleven YOCs to theoretical isochrones in the photometric diagrams. The comparison simultaneously provides membership assignments for MS and PMS stars and estimates for the masses, ages, and spatial distribution of the candidate members. The relations found between the different cluster parameters show that the procedure applied to assign cluster membership, and to measure physical parameters for the selected members, is well founded.
- ID:
- ivo://CDS.VizieR/J/MNRAS/407/2269
- Title:
- Polarisation of a sample of late M dwarfs
- Short Name:
- J/MNRAS/407/2269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present here the final results of the first spectropolarimetric survey of a small sample of active M dwarfs, aimed at providing observational constraints on dynamo action on both sides of the full-convection threshold (spectral type M4). Our two previous studies (Donati et al. 2008. Cat. J/MNRAS/390/545; Morin et al., 2008, Cat. J/MNRAS/384/77) were focused on early and mid M dwarfs. The present paper examines 11 fully convective late M dwarfs (spectral types M5-M8). Tomographic imaging techniques were applied to time-series of circularly polarised profiles of 6 stars, in order to infer their large-scale magnetic topologies. For 3 other stars we could not produce such magnetic maps, because of low variability of the Stokes V signatures, but were able to derive some properties of the magnetic fields. We find 2 distinct categories of magnetic topologies: on the one hand strong axisymmetric dipolar fields (similar to mid M dwarfs), and on the other hand weak fields generally featuring a significant non-axisymmetric component, and sometimes a significant toroidal one. Comparison with unsigned magnetic fluxes demonstrates that the second category of magnetic fields shows less organization (less energy in the large scales), similarly to partly convective early M dwarfs. Stars in both categories have similar stellar parameters, our data do not evidence a separation between these 2 categories in the mass-rotation plane. We also report marginal detection of a large-scale magnetic field on the M8 star VB 10 featuring a significant toroidal axisymmetric component, whereas no field is detectable on VB 8 (M7).
- ID:
- ivo://CDS.VizieR/J/ApJ/775/84
- Title:
- Polarization from stars behind IC63 nebula
- Short Name:
- J/ApJ/775/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the interstellar medium (ISM), molecular hydrogen is expected to form almost exclusively on the surfaces of dust grains. Due to that molecule's large formation energy (-4.5eV), several dynamical effects are likely associated with the process, including the alignment of asymmetric dust grains with the ambient magnetic field. Such aligned dust grains are, in turn, believed to cause the broadband optical/infrared polarization observed in the ISM. Here, we present the first observational evidence for grain alignment driven by H_2_ formation, by showing that the polarization of the light from stars behind the reflection nebula IC 63 appears to correlate with the intensity of H_2_ fluorescence. While our results strongly suggest a role for "Purcell rockets" in grain alignment, additional observations are needed to conclusively confirm their role. By showing a direct connection between H_2_ formation and a probe of the dust characteristics, these results also provide one of the first direct confirmations of the grain-surface formation of H_2_. We compare our observations to ab initio modeling based on Radiative Torque Alignment (RAT) theory.
- ID:
- ivo://CDS.VizieR/J/A+A/513/L7
- Title:
- Post common envelope binaries from SDSS. VIII
- Short Name:
- J/A+A/513/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a large survey of post common envelope binaries (PCEBs) among white dwarf/main sequence (WDMS) binaries from the SDSS that allows to determine the fraction of PCEBs as a function of secondary star mass and therewith to ultimately test the disrupted magnetic braking hypothesis. We obtained multiple spectroscopic observations spread over at least two nights of 589 WDMS binaries. Using mostly the NaI 8183.27,8194.81 absorption doublet we determined the corresponding radial velocities.
- ID:
- ivo://CDS.VizieR/J/A+A/427/933
- Title:
- Precise temperature of F-K field dwarfs
- Short Name:
- J/A+A/427/933
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Highly precise temperatures (sigma=10-15K) have been determined from line depth ratios for a set of 248 F-K field dwarfs of about solar metallicity (-0.5<[Fe/H]<+0.4), based on high resolution (R=42000), high S/N echelle spectra. A new gap has been discovered in the distribution of stars on the Main Sequence in the temperature range 5560 to 5610K. This gap coincides with a jump in the microturbulent velocity Vt and the well-known Li depression near 5600K in field dwarfs and open clusters. As the principal cause of the observed discontinuities in stellar properties we propose the penetration of the convective zone into the inner layers of stars slightly less massive than the Sun and related to it, a change in the temperature gradient.
- ID:
- ivo://CDS.VizieR/J/AJ/137/1
- Title:
- Proper motions and astrometry of late-type dwarfs
- Short Name:
- J/AJ/137/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report proper-motion measurements for 427 late-type M, L, and T dwarfs, 332 of which have been measured for the first time. Combining these new proper motions with previously published measurements yields a sample of 841 M7-T8 dwarfs. We combined parallax measurements or calculated spectrophotometric distances, and computed tangential velocities for the entire sample.
