- ID:
- ivo://CDS.VizieR/J/AJ/162/238
- Title:
- Radial velocity follow up of Wolf 503
- Short Name:
- J/AJ/162/238
- Date:
- 11 Mar 2022 06:30:07
- Publisher:
- CDS
- Description:
- Using radial-velocity measurements from four instruments, we report the mass and density of a 2.043{+/-}0.069R{Earth} sub-Neptune orbiting the quiet K-dwarf Wolf503 (HIP67285). In addition, we present improved orbital and transit parameters by analyzing previously unused short-cadence K2 campaign 17 photometry and conduct a joint radial-velocity-transit fit to constrain the eccentricity at 0.41{+/-}0.05. The addition of a transit observation by Spitzer also allows us to refine the orbital ephemeris in anticipation of further follow-up. Our mass determination, 6.26_-0.70_^+0.69^M{Earth} , in combination with the updated radius measurements, gives Wolf503b a bulk density of {rho}=2.92_-0.44_^+0.50^g/cm^3^. Using interior composition models, we find this density is consistent with an Earth-like core with either a substantial H_2_O mass fraction (45_-16_^+19^%) or a modest H/He envelope (0.5%{+/-}0.3%). The low H/He mass fraction, along with the old age of Wolf503 (11{+/-}2Gyr), makes this sub-Neptune an opportune subject for testing theories of XUV-driven mass loss while the brightness of its host (J=8.3mag) makes it an attractive target for transmission spectroscopy.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/157/97
- Title:
- Radial velocity measurements of K2-3 & GJ3470
- Short Name:
- J/AJ/157/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report improved masses, radii, and densities for four planets in two bright M-dwarf systems, K2-3 and GJ3470, derived from a combination of new radial velocity and transit observations. Supplementing K2 photometry with follow-up Spitzer transit observations refined the transit ephemerides of K2-3 b, c, and d by over a factor of 10. We analyze ground-based photometry from the Evryscope and Fairborn Observatory to determine the characteristic stellar activity timescales for our Gaussian Process fit, including the stellar rotation period and activity region decay timescale. The stellar rotation signals for both stars are evident in the radial velocity data and is included in our fit using a Gaussian process trained on the photometry. We find the masses of K2-3 b, K2-3 c, and GJ3470 b to be 6.48_-0.93_^+0.99^, 2.14_-1.04_^+1.08^, and 12.58_-1.28_^+1.31^ M_{Earth}_, respectively. K2-3 d was not significantly detected and has a 3{sigma} upper limit of 2.80 M_{Earth}_. These two systems are training cases for future TESS systems; due to the low planet densities ({rho}<3.7 g/cm^-3^) and bright host stars (K<9 mag), they are among the best candidates for transmission spectroscopy in order to characterize the atmospheric compositions of small planets.
- ID:
- ivo://CDS.VizieR/J/AJ/160/114
- Title:
- Radial velocity monitoring of TOI-421
- Short Name:
- J/AJ/160/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-141137, TIC94986319), a bright (V=9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations-comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echelle Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution Echelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements-and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421b, has an orbital period of Pb=5.19672{+/-}0.00049days, a mass of Mb=7.17{+/-}0.66M{Earth}, and a radius of Rb=2.68_-0.18_^+0.19^R{Earth}, whereas the outer warm Neptune, TOI-421c, has a period of Pc=16.06819{+/-}0.00035days, a mass of Mc=16.42_-1.04_^+1.06^M{Earth}, a radius of Rc=5.09_-0.15_^+0.16^R{Earth}, and a density of {rho}c=0.685_-0.072_^+0.080^g/cm^3^. With its characteristics, the outer planet ({rho}c=0.685_-0.072_^+0.080^g/cm^3^) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421b and TOI-421c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Ly{alpha} transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421c if equilibrium chemistry is assumed.
- ID:
- ivo://CDS.VizieR/J/ApJ/648/629
- Title:
- Radio observations of late M, L, and T dwarfs
- Short Name:
- J/ApJ/648/629
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present radio observations of 90 dwarf stars and brown dwarfs of spectral type M5-T8. Three sources exhibit radio activity, in addition to the six objects previously detected in quiescence and outburst, leading to an overall detection rate of ~10% for objects later than M7.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A131
- Title:
- Radio survey of ultracool dwarfs
- Short Name:
- J/A+A/549/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to increase the sample of ultracool dwarfs studied in the radio domain to allow a more statistically significant understanding of the physical conditions associated with these magnetically active objects. We conducted a volume-limited survey at 4.9GHz of 32 nearby ultracool dwarfs with spectral types covering the range M7-T8. A statistical analysis was performed on the combined data from the present survey and previous radio observations of ultracool dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/791/10
- Title:
- Radius distribution of planets around cool stars
- Short Name:
- J/ApJ/791/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We calculate an empirical, non-parametric estimate of the shape of the period-marginalized radius distribution of planets with periods less than 150 days using the small yet well-characterized sample of cool (T_eff_< 4000 K) dwarf stars in the Kepler catalog. In particular, we present and validate a new procedure, based on weighted kernel density estimation, to reconstruct the shape of the planet radius function down to radii smaller than the completeness limit of the survey at the longest periods. Under the assumption that the period distribution of planets does not change dramatically with planet radius, we show that the occurrence of planets around these stars continues to increase to below 1 R_{sun}_, and that there is no strong evidence for a turnover in the planet radius function. In fact, we demonstrate using many iterations of simulated data that a spurious turnover may be inferred from data even when the true distribution continues to rise toward smaller radii. Finally, the sharp rise in the radius distribution below ~3 R_{sun}_ implies that a large number of planets await discovery around cool dwarfs as the sensitivities of ground-based transit surveys increase.
- ID:
- ivo://CDS.VizieR/J/AJ/157/63
- Title:
- Radius relations for low-metallicity M-dwarf stars
- Short Name:
- J/AJ/157/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M subdwarfs are low-metallicity M dwarfs that typically inhabit the halo population of the Galaxy. Metallicity controls the opacity of stellar atmospheres; in metal-poor stars, hydrostatic equilibrium is reached at a smaller radius, leading to smaller radii for a given effective temperature. We compile a sample of 88 stars that span spectral classes K7 to M6 and include stars with metallicity classes from solar-metallicity dwarf stars to the lowest metallicity ultra subdwarfs to test how metallicity changes the stellar radius. We fit models to Palomar Double Spectrograph (DBSP) optical spectra to derive effective temperatures (T_eff_) and we measure bolometric luminosities (L_bol_) by combining broad wavelength-coverage photometry with Gaia parallaxes. Radii are then computed by combining the T_eff_ and L_bol_ using the Stefan-Boltzman law. We find that for a given temperature, ultra subdwarfs can be as much as five times smaller than their solar-metallicity counterparts. We present color-radius and color-surface brightness relations that extend down to [Fe/H] of -2.0 dex, in order to aid the radius determination of M subdwarfs, which will be especially important for the WFIRST exoplanetary microlensing survey.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A49
- Title:
- r- and s- process elements in Milky Way disk
- Short Name:
- J/A+A/586/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Elements heavier than iron are produced through neutron-capture processes in the different phases of stellar evolution. Asymptotic giant branch (AGB) stars are believed to be mainly responsible for elements that form through the slow neutron-capture process, while the elements created in the rapid neutron-capture process have production sites that are less understood. Knowledge of abundance ratios as functions of metallicity can lead to insight into the origin and evolution of our Galaxy and its stellar populations. We aim to trace the chemical evolution of the neutron-capture elements Sr, Zr, La, Ce, Nd, Sm, and Eu in the Milky Way stellar disk. This will allow us to constrain the formation sites of these elements, as well as to probe the evolution of the Galactic thin and thick disks. Using spectra of high resolution (42000<=R<=65000) and high signal-to-noise (S/N>=200) obtained with the MIKE and the FEROS spectrographs, we determine Sr, Zr, La, Ce, Nd, Sm, and Eu abundances for a sample of 593 F and G dwarf stars in the solar neighborhood. The abundance analysis is based on spectral synthesis using one-dimensional, plane-parallel, local thermodynamic equilibrium (LTE) model stellar atmospheres calculated with the MARCS 2012 code.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/2824
- Title:
- Rapid optical variability in ultracool dwarfs
- Short Name:
- J/MNRAS/428/2824
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, a summary of optical time-series photometry of 125 ultracool dwarfs is given. The observing strategy was to monitor each object continuously for 2-3h in order to ascertain whether it was rapidly variable. Many of the targets were observed at multiple epochs, to follow up possible short time-scale variability, or to test for slow brightness changes on longer time-scales. The 353 data sets obtained contain nearly 22000 individual measurements. Optical (I_C_) magnitudes, accurate to roughly 0.1-0.2mag, were derived for 21 objects for which there is no optical photometry in the literature. It is shown that photometry is affected by variable seeing in a large percentage of the time-series observations. Since this could give the appearance of variability intrinsic to the objects, magnitudes are modelled as functions of both time and seeing. Several ultracool dwarfs which had not been monitored before are variable, according to certain model-fitting criteria. A number of objects with multi-epoch observations appear to be variable on longer time-scales. Since testing for variability is far from being straightforward, the time-series data are made available so that interested readers can perform their own analyses.
320. Reference A0V stars
- ID:
- ivo://CDS.VizieR/J/A+AS/137/273
- Title:
- Reference A0V stars
- Short Name:
- J/A+AS/137/273
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hipparcos data for 71 nearby dwarf A0 stars were combined with other data, in particular with high resolution spectra to establish the HR diagram in this temperature range. Almost 30% of unknown binaries were detected and discarded before establishing the M-L relation for bright A0 V field stars. The relationship derived for these single stars is compared to the classical diagram derived from eclipsing binaries. The scatter of the latter is examined and the role of gravity is discussed. A good agreement is found between the evolution-based surface gravity logg_ev_ and the value of logg_ph_ obtained from photometric data.
