The characterization of exoplanets relies on that of their host star. However, stellar evolution models cannot always be used to derive the mass and radius of individual stars, because many stellar ...internal parameters are poorly constrained. Here, we use the probability density functions (PDFs) of directly measured parameters to derive the joint PDF of the stellar and planetary mass and radius. Because combining the density and radius of the star is our most reliable way of determining its mass, we find that the stellar (respectively planetary) mass and radius are strongly (respectively moderately) correlated. We then use a generalized Bayesian inference analysis to characterize the possible interiors of 55 Cnc e. We quantify how our ability to constrain the interior improves by accounting for correlation. The information content of the mass-radius correlation is also compared with refractory element abundance constraints. We provide posterior distributions for all interior parameters of interest. Given all available data, we find that the radius of the gaseous envelope is . A stronger correlation between the planetary mass and radius (potentially provided by a better estimate of the transit depth) would significantly improve interior characterization and reduce drastically the uncertainty on the gas envelope properties.
Abstract
The analysis of the available Transiting Exoplanet Survey Satellite (TESS) light curves of
α
Sex (HD 87887) reveals low-frequency pulsations with a period of about 9.1 hr in this ...spectroscopic A0 III standard star. The IUE observations in 1992 December reveal large flux variations both in the far-UV and in the mid-UV, which are accompanied by variations of the brightness in the
V
band recorded by the the Fine Error Sensor on board IUE. The ultraviolet variability could be due to an eclipse by an hitherto undetected companion of smaller radius, possibly 2.5
R
⊙
, but this needs confirmation by further monitoring possibly with TESS. An abundance determination yields solar abundances for most elements. Only carbon and strontium are underabundant and titanium, vanadium, and baryum mildly overabundant. Identification is provided for most of the lines absorbing more than 2% in the optical spectrum of
α
Sex. Stellar evolution modeling shows that
α
Sex is near the terminal-age main sequence, and its mass, radius, and age are estimated to be
M
= 2.57 ± 0.32
M
⊙
,
R
= 3.07 ± 0.90
R
⊙
,
A
= 385 ± 77 Myr, respectively.
The advent of space-based missions like Kepler has revolutionized the study of solar-type stars, particularly through the measurement and modeling of their resonant modes of oscillation. Here we ...analyze a sample of 66 Kepler main-sequence stars showing solar-like oscillations as part of the Kepler seismic LEGACY project. We use Kepler short-cadence data, of which each star has at least 12 months, to create frequency-power spectra optimized for asteroseismology. For each star, we identify its modes of oscillation and extract parameters such as frequency, amplitude, and line width using a Bayesian Markov chain Monte Carlo "peak-bagging" approach. We report the extracted mode parameters for all 66 stars, as well as derived quantities such as frequency difference ratios, the large and small separations and the behavior of line widths with frequency and line widths at with , for which we derive parametrizations; and behavior of mode visibilities. These average properties can be applied in future peak-bagging exercises to better constrain the parameters of the stellar oscillation spectra. The frequencies and frequency ratios can tightly constrain the fundamental parameters of these solar-type stars, and mode line widths and amplitudes can test models of mode damping and excitation.
Abstract
We report on a detailed abundance study of six bright, mostly southern, slowly rotating late B-stars: HD 1279 (B8III), HD 99803 (B9V), HD 123445 (B9V), HD 147550 (B9V), HD 171961 (B8III), ...and HD 202671 (B5II/III), hitherto reported as normal stars. We compare them to the two classical HgMn stars
μ
Lep and
β
Scl, and to the superficially normal star
ν
Cap. In the spectra of the six stars, the Hg
ii
line at 3984 Å line is clearly seen and numerous lines of P, Ti, Mn, Fe, Ga, Sr, Y, and Zr appear to be strong absorbers. A comparison of newly acquired and archival spectra of these objects with a grid of synthetic spectra for selected unblended lines reveals large overabundances of P, Ti, Cr, Mn, Sr, Y, Zr, Ba, Pt, and Hg, and underabundances of He, Mg, Sc, and Ni. The effective temperatures, surface gravities, low projected rotational velocities, and the peculiar abundance patterns of the six investigated stars show that they are new chemically peculiar stars, mostly new HgMn stars, and are reclassified as such. The evolutionary status of these stars has been inferred, and their ages and masses estimated. The two most massive objects, HD 1279 and HD 202671, might have evolved away from the main sequence recently, the other stars are main-sequence objects. HD 99803A is a sharp lined HgMn star with grazing eclipses. From TESS and MASCARA photometry, we determine an orbital period of
P
orb
= 26.12022 ± 0.00004 day.
Oscillations of the Sun have been used to understand its interior structure. The extension of similar studies to more distant stars has raised many difficulties despite the strong efforts of the ...international community over the past decades. The CoRoT (Convection Rotation and Planetary Transits) satellite, launched in December 2006, has now measured oscillations and the stellar granulation signature in three main sequence stars that are noticeably hotter than the sun. The oscillation amplitudes are about 1.5 times as large as those in the Sun; the stellar granulation is up to three times as high. The stellar amplitudes are about 25% below the theoretic values, providing a measurement of the nonadiabaticity of the process ruling the oscillations in the outer layers of the stars.
Imaging at high angular resolution (HRA) is a flourishing discipline. High performance instruments like the spectro-polarimeter SPHERE at VLT/ESO has recently been implemented. A harvest of splendid ...results is continuously coming from interferometry with PIONIER, MATISSE, and now GRAVITY (all at VLTI/ESO), VEGA and JouFlu (CHARA), and at longer wavelengths with ALMA at VLTI/ESO and NOEMA/IRAM. The future is already underway with the very close launch of JWST/NASA, and the development of ELT at ESO. HRA provides a unique way to study regions of stellar formation, proto- planetary discs as well as the surfaces of stars and their environments. This volume offers lectures given by world experts in the field during the EvrySchatzman School on Stellar Physics (EES 2017) held in Roscoff, France. The addressed topics include a course of introduction to optical/IR interferometry covering the history and basic principles, a course on diffraction-dominated observational astronomy, and a course presenting the principles and instrumentation of optical long baseline interferometry. This book will be a valuable reference for researchers and students in the coming years.
Gaia Data Release 2 Andrae, René; Fouesneau, Morgan; Creevey, Orlagh ...
Astronomy and astrophysics (Berlin),
08/2018, Letnik:
616
Journal Article
Recenzirano
Odprti dostop
The second Gaia data release (Gaia DR2) contains, beyond the astrometry, three-band photometry for 1.38 billion sources. One band is the G band, the other two were obtained by integrating the Gaia ...prism spectra (BP and RP). We have used these three broad photometric bands to infer stellar effective temperatures, Teff, for all sources brighter than G = 17 mag with Teff in the range 3000–10 000 K (some 161 million sources). Using in addition the parallaxes, we infer the line-of-sight extinction, AG, and the reddening, E(BP − RP), for 88 million sources. Together with a bolometric correction we derive luminosity and radius for 77 million sources. These quantities as well as their estimated uncertainties are part of Gaia DR2. Here we describe the procedures by which these quantities were obtained, including the underlying assumptions, comparison with literature estimates, and the limitations of our results. Typical accuracies are of order 324 K (Teff), 0.46 mag (AG), 0.23 mag (E(BP − RP)), 15% (luminosity), and 10% (radius). Being based on only a small number of observable quantities and limited training data, our results are necessarily subject to some extreme assumptions that can lead to strong systematics in some cases (not included in the aforementioned accuracy estimates). One aspect is the non-negativity contraint of our estimates, in particular extinction, which we discuss. Yet in several regions of parameter space our results show very good performance, for example for red clump stars and solar analogues. Large uncertainties render the extinctions less useful at the individual star level, but they show good performance for ensemble estimates. We identify regimes in which our parameters should and should not be used and we define a “clean” sample. Despite the limitations, this is the largest catalogue of uniformly-inferred stellar parameters to date. More precise and detailed astrophysical parameters based on the full BP/RP spectrophotometry are planned as part of the third Gaia data release.
Gaia Data Release 2 Andrae, René; Fouesneau, Morgan; Creevey, Orlagh ...
Astronomy and astrophysics (Berlin),
8/2018, Letnik:
616
Journal Article
Recenzirano
Odprti dostop
The second
Gaia
data release (
Gaia
DR2) contains, beyond the astrometry, three-band photometry for 1.38 billion sources. One band is the
G
band, the other two were obtained by integrating the
Gaia
...prism spectra (BP and RP). We have used these three broad photometric bands to infer stellar effective temperatures,
T
eff
, for all sources brighter than
G
= 17 mag with
T
eff
in the range 3000–10 000 K (some 161 million sources). Using in addition the parallaxes, we infer the line-of-sight extinction,
A
G
, and the reddening,
E
(BP − RP), for 88 million sources. Together with a bolometric correction we derive luminosity and radius for 77 million sources. These quantities as well as their estimated uncertainties are part of
Gaia
DR2. Here we describe the procedures by which these quantities were obtained, including the underlying assumptions, comparison with literature estimates, and the limitations of our results. Typical accuracies are of order 324 K (
T
eff
), 0.46 mag (
A
G
), 0.23 mag (
E
(BP − RP)), 15% (luminosity), and 10% (radius). Being based on only a small number of observable quantities and limited training data, our results are necessarily subject to some extreme assumptions that can lead to strong systematics in some cases (not included in the aforementioned accuracy estimates). One aspect is the non-negativity contraint of our estimates, in particular extinction, which we discuss. Yet in several regions of parameter space our results show very good performance, for example for red clump stars and solar analogues. Large uncertainties render the extinctions less useful at the individual star level, but they show good performance for ensemble estimates. We identify regimes in which our parameters should and should not be used and we define a “clean” sample. Despite the limitations, this is the largest catalogue of uniformly-inferred stellar parameters to date. More precise and detailed astrophysical parameters based on the full BP/RP spectrophotometry are planned as part of the third
Gaia
data release.
First stellar parameters from Apsis Andrae, Rene; Fouesneau, Morgan; Creevey, Orlagh ...
Astronomy and astrophysics (Berlin),
08/2018, Letnik:
616
Journal Article
Recenzirano
Odprti dostop
The second Gaia data release (Gaia DR2) contains, beyond the astrometry, three-band photometry for 1.38 billion sources. One band is the G band, the other two were obtained by integrating the Gaia ...prism spectra (BP and RP). We have used these three broad photometric bands to infer stellar effective temperatures, T-eff, for all sources brighter than G = 17 mag with T-eff in the range 3000-10 000K (some 161 million sources). Using in addition the parallaxes, we infer the line-of-sight extinction, A(G), and the reddening, E(BP-RP), for 88 million sources. Together with a bolometric correction we derive luminosity and radius for 77 million sources. These quantities as well as their estimated uncertainties are part of Gaia DR2. Here we describe the procedures by which these quantities were obtained, including the underlying assumptions, comparison with literature estimates, and the limitations of our results. Typical accuracies are of order 324K (T-eff), 0.46 mag (A(G)), 0.23 mag (E(BP-RP)), 15% (luminosity), and 10% (radius). Being based on only a small number of observable quantities and limited training data, our results are necessarily subject to some extreme assumptions that can lead to strong systematics in some cases (not included in the aforementioned accuracy estimates). One aspect is the non-negativity contraint of our estimates, in particular extinction, which we discuss. Yet in several regions of parameter space our results show very good performance, for example for red clump stars and solar analogues. Large uncertainties render the extinctions less useful at the individual star level, but they show good performance for ensemble estimates. We identify regimes in which our parameters should and should not be used and we define a "clean" sample. Despite the limitations, this is the largest catalogue of uniformly-inferred stellar parameters to date. More precise and detailed astrophysical parameters based on the full BP/RP spectrophotometry are planned as part of the third Gaia data release.
PDF
