- ID:
- ivo://CDS.VizieR/J/AJ/162/174
- Title:
- HARPS radial velocity follow up of GJ 1214
- Short Name:
- J/AJ/162/174
- Date:
- 21 Mar 2022 00:16:00
- Publisher:
- CDS
- Description:
- We present an intensive effort to refine the mass and orbit of the enveloped terrestrial planet GJ1214b using 165 radial velocity (RV) measurements taken with the HARPS spectrograph over a period of 10years. We conduct a joint analysis of the RVs with archival Spitzer/IRAC transits and measure a planetary mass and radius of 8.17{+/-}0.43M{Earth} and 2.742-_0.053_^+0.050^R{Earth}. Assuming that GJ1214b is an Earth-like core surrounded by a H/He envelope, we measure an envelope mass fraction of X_env_=5.24_-0.29_^+0.30^%. GJ1214b remains a prime target for secondary eclipse observations of an enveloped terrestrial, the scheduling of which benefits from our constraint on the orbital eccentricity of <0.063 at 95% confidence, which narrows the secondary eclipse window to 2.8hr. By combining GJ1214 with other mid-M-dwarf transiting systems with intensive RV follow up, we calculate the frequency of mid-M-dwarf planetary systems with multiple small planets and find that 90_-21_^+5^% of mid-M dwarfs with a known planet with mass [1,10]M{Earth} and orbital period [0.5,50]days, will host at least one additional planet. We rule out additional planets around GJ1214 down to 3M{Earth} within 10days, such that GJ1214 is a single-planet system within these limits. This result has a 44_-5_^+9^ probability given the prevalence of multiplanet systems around mid-M dwarfs. We also investigate mid-M-dwarf RV systems and show that the probability that all reported RV planet candidates are real planets is <12% at 99% confidence, although this statistical argument is unable to identify the probable false positives.
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- ID:
- ivo://CDS.VizieR/J/AJ/162/79
- Title:
- HARPS radial velocity follow up of TOI-1634
- Short Name:
- J/AJ/162/79
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- Studies of close-in planets orbiting M dwarfs have suggested that the M-dwarf radius valley may be well explained by distinct formation timescales between enveloped terrestrials and rocky planets that form at late times in a gas-depleted environment. This scenario is at odds with the picture that close-in rocky planets form with a primordial gaseous envelope that is subsequently stripped away by some thermally driven mass-loss process. These two physical scenarios make unique predictions of the rocky/enveloped transition's dependence on orbital separation such that studying the compositions of planets within the M-dwarf radius valley may be able to establish the dominant physics. Here, we present the discovery of one such keystone planet: the ultra-short-period planet TOI-1634b (P=0.989days, F=121F{Earth}, r_p_=1.790_-0.081_^+0.080^R{Earth}) orbiting a nearby M2 dwarf (K_s_=8.7, R_s_=0.450R{sun}, M_s_=0.502M{sun}) and whose size and orbital period sit within the M-dwarf radius valley. We confirm the TESS-discovered planet candidate using extensive ground-based follow-up campaigns, including a set of 32 precise radial velocity measurements from HARPS-N. We measure a planetary mass of 4.91_-0.70_^+0.68^M{Earth}, which makes TOI-1634b inconsistent with an Earth-like composition at 5.9{sigma} and thus requires either an extended gaseous envelope, a large volatile-rich layer, or a rocky composition that is not dominated by iron and silicates to explain its mass and radius. The discovery that the bulk composition of TOI-1634b is inconsistent with that of Earth supports the gas-depleted formation mechanism to explain the emergence of the radius valley around M dwarfs with M_s_<~0.5M{sun}.
- ID:
- ivo://CDS.VizieR/J/A+A/523/A15
- Title:
- HARPS XXIII: RV data for the 8 targets
- Short Name:
- J/A+A/523/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present our HARPS radial-velocity data for eight low-activity solar-type stars belonging to the HARPS volume-limited sample: HD6718, HD8535, HD28254, HD290327, HD43197, HD44219, HD148156, and HD156411. Keplerian fits to these data reveal the presence of low-mass companions around these targets. With minimum masses ranging from 0.58 to 2.54M_{Jup}_, these companions are in the planetary mass domain. The orbital periods of these planets range from slightly less than one to almost seven years. The eight orbits presented in this paper exhibit a wide variety of eccentricities: from 0.08 to above 0.8.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A109
- Title:
- HARPS XXXI. The M-dwarf sample
- Short Name:
- J/A+A/549/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Searching for planets around stars with different masses helps us to assess the outcome of planetary formation for different initial conditions. The low-mass M dwarfs are also the most frequent stars in our Galaxy and potentially therefore, the most frequent planet hosts. We present observations of 102 southern nearby M dwarfs, using a fraction of our guaranteed time on the ESO/HARPS spectrograph. We observed for 460 h and gathered 1965 precise (~1-3m/s) radial velocities (RVs), spanning the period from Feb. 11, 2003 to Apr. 1, 2009.
- ID:
- ivo://CDS.VizieR/J/AJ/155/114
- Title:
- HAT-TR-318-007: a double-lined M dwarf binary
- Short Name:
- J/AJ/155/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery by the HATNet survey of HAT-TR-318-007, a P=3.34395390+/-0.00000020 day period detached double-lined M dwarf binary with total secondary eclipses. We combine radial velocity (RV) measurements from TRES/FLWO 1.5 m and time-series photometry from HATNet, FLWO 1.2 m, BOS 0.8 m, and NASA K2 Campaign 5, to determine the masses and radii of the component stars: M_A_=0.448+/-0.011 M_{sun}_^N^, M_B_=0.2721_-0.0042_^+0.0041^ M_{sun}_^N^, R_A_=0.4548_-0.0036_^+0.0035^ R_{sun}_^N^, and R_B_=0.2913_-0.0024_^+0.0023^ R_{sun}_^N^. We obtained a FIRE/Magellan near-infrared spectrum of the primary star during a total secondary eclipse, and we use this to obtain disentangled spectra of both components. We determine spectral types of ST_A_=M3.71+/-0.69 and ST_B_=M5.01+/-0.73 and effective temperatures of T_eff,A_=3190+/-110 K and T_eff,B_=3100+/-110 K for the primary and secondary star, respectively. We also measure a metallicity of [Fe/H]=+0.298+/-0.080 for the system. We find that the system has a small, but significant, nonzero eccentricity of 0.0136+/-0.0026. The K2 light curve shows a coherent variation at a period of 3.41315_-0.00032_^+0.00030^ days, which is slightly longer than the orbital period, and which we demonstrate comes from the primary star. We interpret this as the rotation period of the primary. We perform a quantitative comparison between the Dartmouth stellar evolution models and the seven systems, including HAT-TR-318-007, that contain M dwarfs with 0.2 M_{sun}_^N^<M<0.5 M_{sun}_^N^, have metallicity measurements, and have masses and radii determined to better than 5% precision. Discrepancies between the predicted and observed masses and radii are found for three of the systems.
- ID:
- ivo://CDS.VizieR/J/AJ/154/67
- Title:
- HAZMAT. II. Low-mass stars with GALEX UV observations
- Short Name:
- J/AJ/154/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ultraviolet (UV) light from a host star influences a planet's atmospheric photochemistry and will affect interpretations of exoplanetary spectra from future missions like the James Webb Space Telescope. These effects will be particularly critical in the study of planetary atmospheres around M dwarfs, including Earth-sized planets in the habitable zone. Given the higher activity levels of M dwarfs compared to Sun-like stars, time-resolved UV data are needed for more accurate input conditions for exoplanet atmospheric modeling. The Galaxy Evolution Explorer (GALEX) provides multi-epoch photometric observations in two UV bands: near-ultraviolet (NUV; 1771-2831{AA}) and far-ultraviolet (FUV; 1344-1786{AA}). Within 30pc of Earth, there are 357 and 303 M dwarfs in the NUV and FUV bands, respectively, with multiple GALEX observations. Simultaneous NUV and FUV detections exist for 145 stars in both GALEX bands. Our analyses of these data show that low-mass stars are typically more variable in the FUV than the NUV. Median variability increases with later spectral types in the NUV with no clear trend in the FUV. We find evidence that flares increase the FUV flux density far more than the NUV flux density, leading to variable FUV to NUV flux density ratios in the GALEX bandpasses.The ratio of FUV to NUV flux is important for interpreting the presence of atmospheric molecules in planetary atmospheres such as oxygen and methane as a high FUV to NUV ratio may cause false-positive biosignature detections. This ratio of flux density in the GALEX bands spans three orders of magnitude in our sample, from 0.008 to 4.6, and is 1 to 2 orders of magnitude higher than for G dwarfs like the Sun. These results characterize the UV behavior for the largest set of low-mass stars to date.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A41
- Title:
- HD 176986 HARPS + HARPS-N data
- Short Name:
- J/A+A/612/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a system of two super-Earths orbiting the moderately active K-dwarf HD 176986. This work is part of the RoPES RV program of G- and K-type stars that combines radial velocity from both HARPS and HARPS-N spectrograph to search for short-period terrestrial planets. HD 176986 b and c are super-Earth mass planets with masses of 5.74 and 9.18 Me, with orbital periods of 6.49 and 16.82 days, at a distances of 0.063 and 0.119AU, in orbits that are consistent with circular. The host star is a K2.5 dwarf, and in spite of its modest level of chromospheric activity log(R'hk)=-4.90+/-0.04, shows a complex activity pattern. Along with the discovery of the planets we study the magnetic cycle and rotation of the star. HD 176986 proves to be suitable to test the available techniques of RV analysis and our understanding of stellar activity.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/147
- Title:
- Herschel observations stars in THA
- Short Name:
- J/ApJ/753/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Herschel PACS photometry of 17 B- to M-type stars in the 30Myr old Tucana-Horologium Association. This work is part of the Herschel Open Time Key Programme "Gas in Protoplanetary Systems" (GASPS). 6 of the 17 targets were found to have infrared excesses significantly greater than the expected stellar IR fluxes, including a previously unknown disk around HD30051. These six debris disks were fitted with single-temperature blackbody models to estimate the temperatures and abundances of the dust in the systems. For the five stars that show excess emission in the Herschel PACS photometry and also have Spitzer IRS spectra, we fit the data with models of optically thin debris disks with realistic grain properties in order to better estimate the disk parameters. The model is determined by a set of six parameters: surface density index, grain size distribution index, minimum and maximum grain sizes, and the inner and outer radii of the disk. The best-fitting parameters give us constraints on the geometry of the dust in these systems, as well as lower limits to the total dust masses. The HD105 disk was further constrained by fitting marginally resolved PACS 70{mu}m imaging.
- ID:
- ivo://CDS.VizieR/J/AJ/159/30
- Title:
- High proper-motion M-type stars spectroscopic obs.
- Short Name:
- J/AJ/159/30
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- Large numbers of low-to-medium-resolution spectra of M-type dwarf stars from both the local Galactic disk and halo are available from various surveys. In order to fully exploit these data, we develop a template-fit method using a set of empirically assembled M dwarf/subdwarf classification templates, based on the measurements of the TiO and CaH molecular bands near 7000{AA}, which are used to classify M dwarfs/subdwarfs by spectral type and metallicity class. We further present a pipeline to automatically determine the effective temperature Teff, metallicity [M/H], {alpha}-element to iron abundance ratio [{alpha}/Fe], and surface gravity logg of M dwarfs/subdwarfs using the latest version of BT-Settl model atmospheres. We apply these methods to a set of low-to-medium-resolution spectra of 1544 high proper-motion ({mu}>=0.4"/yr) M dwarfs/subdwarfs, collected at the MDM observatory, Lick Observatory, Kitt-Peak National Observatory, and Cerro-Tololo Interamerican Observatory.
- ID:
- ivo://CDS.VizieR/J/MNRAS/318/1206
- Title:
- High proper motion stars in SA 94
- Short Name:
- J/MNRAS/318/1206
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have applied the astrometric techniques devised by Murray (1986MNRAS.223..649M) for analysis of 48-inch Schmidt photographic data to SuperCOSMOS scans of UK Schmidt plates centred on Kapteyn's Selected Area 94 (RA=2h53m, DE=0{deg}). In this preliminary study, we combine astrometric data from four short-exposure V-band plates, taken in 1987 August (2 plates) and 1993 August (2 plates), with BVRI photometry from sky-limited plate material, to identify stars with proper motions exceeding 0.1"/yr. This paper discusses the completeness of the resulting sample and presents spectroscopy of 30 stars with {mu}>0.2"/yr. Based on the latter observations and the distribution in the [H_V_, (V-I)] reduced proper-motion diagram, we have classified stars in the complete sample as candidate white dwarfs, main-sequence dwarfs and halo subdwarfs, and derived estimates of the disc and halo luminosity functions.
