- ID:
- ivo://CDS.VizieR/J/A+A/631/A34
- Title:
- KELT-9b radial velocity curve
- Short Name:
- J/A+A/631/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the framework of the GAPS project, we observed the planet-hosting star KELT-9 (A-type star, vsini~110km/s) with the HARPS-N spectrograph at the Telescopio Nazionale Galileo. In this work we analyse the spectra and the extracted radial velocities, to constrain the physical parameters of the system and to detect the planetary atmosphere of KELT-9b. We extracted from the high-resolution optical spectra the mean stellar line profiles with an analysis based on the Least Square Deconvolution technique. Then, we computed the stellar radial velocities with a method optimized for fast rotators, by fitting the mean stellar line profile with a purely rotational profile instead of using a Gaussian function. The new spectra and analysis led us to update the orbital and physical parameters of the system, improving in particular the value of the planetary mass to Mp=2.88+/-0.35M_Jup_. We discovered an anomalous in-transit radial velocity deviation from the theoretical Rossiter- McLaughlin effect solution, calculated from the projected spin-orbit angle {lambda}=-85.78+/-0.46 degrees measured with Doppler tomography. We prove that this deviation is caused by the planetary atmosphere of KELT-9b, thus we name this effect Atmospheric Rossiter-McLaughlin effect. By analysing the magnitude of the radial velocity anomaly, we obtained information on the extension of the planetary atmosphere as weighted by the model used to retrieve the stellar mean line profiles, which is up to 1.22+/-0.02Rp. The Atmospheric Rossiter-McLaughlin effect will be observable for other exo- planets whose atmosphere has non-negligible correlation with the stellar mask used to retrieve the radial velocities, in particular ultra-hot Jupiters with iron in their atmosphere. The duration and amplitude of the effect will depend not only on the extension of the atmosphere, but also on the in-transit planetary radial velocities and on the projected rotational velocity of the parent star.
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- ID:
- ivo://CDS.VizieR/J/A+A/634/A29
- Title:
- Kepler-278 and Kepler-391 spectra
- Short Name:
- J/A+A/634/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kepler-278 and Kepler-391 are two of the three evolved stars on the red giant branch (RGB) known to date, to host multiple short-period transiting planets. Moreover, these planets are among the smallest discovered around RGB stars. Here, we present a detailed stellar and planetary characterization of these remarkable systems. Methods. Based on high-quality spectra from Gemini-GRACES of Kepler-278 and Kepler-391, we obtained refined stellar parameters and precise chemical abundances of 25 elements. Nine of these elements and the carbon isotopic ratios, ^12^C/^13^C, were not previously measured. Also, combining our new stellar parameters with a photodynamical analysis of the Kepler light curves, we determined accurate planetary properties of both systems. Results. Our revised stellar parameters agree reasonably well with most of the previous results, although we find that Kepler-278 is ~15% less massive than previously reported. The abundances of C, N, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, and Ce, in both stars, are consistent with those of evolved nearby thin disk stars. Kepler-391 presents a relatively high abundance of lithium (A(Li)NLTE=1.29+/-0.09dex), which is likely a remnant from the main-sequence phase. The precise spectroscopic parameters of Kepler-278 and Kepler-391 along with their high 12 C/13 C ratios show that both stars are just starting their ascent on the RGB. The planets Kepler-278b, Kepler-278c, and Kepler-391c are warm sub-Neptunes, whilst Kepler-391b is a hot sub-Neptune that falls in the Hot Super-Earth desert and therefore it might be undergoing photo-evaporation of its outer envelope. The high-precision obtained in the transit times allowed us not only to confirm Kepler-278c's TTV signal but also to find evidence of a previously undetected TTV signal for the inner planet Kepler-278b. From the presence of gravitational interaction between these bodies we constrain, for the first time, the mass of Kepler-278b (Mp=56M_Earth_) and Kepler-278c (Mp=35M_Earth_). The mass limits, coupled with our precise determinations of the planetary radii, suggest that their bulk compositions are consistent with a significant amount of water content and the presence of H2 gaseous envelopes. Finally, our photodynamical analysis also shows that the orbits of both planets around Kepler-278 are highly eccentric (e~0.7) and, surprisingly, coplanar. Further observations (e.g., precise radial velocities) of this system are needed to confirm the eccentricity values presented here.
- ID:
- ivo://CDS.VizieR/J/ApJ/861/149
- Title:
- Kepler Follow-up Observation Program. II. Spectro.
- Short Name:
- J/ApJ/861/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from spectroscopic follow-up observations of stars identified in the Kepler field and carried out by teams of the Kepler Follow-up Observation Program. Two samples of stars were observed over 6yr (2009-2015): 614 standard stars (divided into "platinum" and "gold" categories) selected based on their asteroseismic detections and 2667 host stars of Kepler Objects of Interest (KOIs), most of them planet candidates. Four data analysis pipelines were used to derive stellar parameters for the observed stars. We compare the Teff, log(g), and [Fe/H] values derived for the same stars by different pipelines; from the average of the standard deviations of the differences in these parameter values, we derive error floors of ~100K, 0.2dex, and 0.1dex for Teff, log(g), and [Fe/H], respectively. Noticeable disagreements are seen mostly at the largest and smallest parameter values (e.g., in the giant star regime). Most of the log(g) values derived from spectra for the platinum stars agree on average within 0.025dex (but with a spread of 0.1-0.2dex) with the asteroseismic log(g) values. Compared to the Kepler Input Catalog (KIC), the spectroscopically derived stellar parameters agree within the uncertainties of the KIC but are more precise and thus an important contribution toward deriving more reliable planetary radii.
- ID:
- ivo://CDS.VizieR/J/AJ/152/105
- Title:
- Kepler-80 transit timing observations
- Short Name:
- J/AJ/152/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kepler has discovered hundreds of systems with multiple transiting exoplanets which hold tremendous potential both individually and collectively for understanding the formation and evolution of planetary systems. Many of these systems consist of multiple small planets with periods less than ~50 days known as Systems with Tightly spaced Inner Planets, or STIPs. One especially intriguing STIP, Kepler-80 (KOI-500), contains five transiting planets: f, d, e, b, and c with periods of 1.0, 3.1, 4.6, 7.1, and 9.5 days, respectively. We provide measurements of transit times and a transit timing variation (TTV) dynamical analysis. We find that TTVs cannot reliably detect eccentricities for this system, though mass estimates are not affected. Restricting the eccentricity to a reasonable range, we infer masses for the outer four planets (d, e, b, and c) to be 6.75_-0.51_^+0.69^, 4.13_-0.95_^+0.81^, 6.93_-0.70_^+1.05^, and 6.74_-0.86_^+1.23^ Earth masses, respectively. The similar masses but different radii are consistent with terrestrial compositions for d and e and ~2% H/He envelopes for b and c. We confirm that the outer four planets are in a rare dynamical configuration with four interconnected three-body resonances that are librating with few degree amplitudes. We present a formation model that can reproduce the observed configuration by starting with a multi-resonant chain and introducing dissipation. Overall, the information-rich Kepler-80 planets provide an important perspective into exoplanetary systems.
- ID:
- ivo://CDS.VizieR/J/A+A/589/A21
- Title:
- K-H_2_ line shapes for cool brown dwarfs spectra
- Short Name:
- J/A+A/589/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of cooler and cooler brown dwarfs show that the contribution from broadening at many bars pressure is becoming important. The opacity in the red optical to near-IR region under these conditions is dominated by the extremely pressure-broadened wings of the alkali resonance lines, in particular, the KI resonance doublet at 0.77um. Collisions with H_2_ are preponderant in brown dwarf atmospheres at an effective temperature of about 1000K; the H_2_ perturber densities reach several 10^19^ even in Jupiter-mass planets and exceed 10^20^ for super-Jupiters and older Y dwarfs. As a consequence, it appears that when the far wing absorption due to alkali atoms in a dense H_2_ atmosphere is significant, accurate pressure broadened profiles that are valid at high densities of H_2_ should be incorporated into spectral models.
- ID:
- ivo://CDS.VizieR/J/A+A/569/A15
- Title:
- KIC 10553698A asteroseismology
- Short Name:
- J/A+A/569/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The subdwarf-B pulsator, KIC10553698A, is one of 16 such objects observed with one-minute sampling for most of the duration of the Kepler Mission. Like most of these stars, it displays a rich g-mode pulsation spectrum with several clear multiplets that maintain regular frequency splitting. We identify these pulsation modes as components of rotationally split multiplets in a star rotating with a period of ~41d. From 162 clearly significant periodicities, we are able to identify 156 as likely components of l=1 or l=2 multiplets. For the first time we are able to detect l=1 modes that interpose in the asymptotic period sequences and that provide a clear indication of mode trapping in a stratified envelope, as predicted by theoretical models. A clear signal is also present in the Kepler photometry at 3.387d. Spectroscopic observations reveal a radial-velocity amplitude of 64.8km/s. We find that the radial-velocity variations and the photometric signal have phase and amplitude that are perfectly consistent with a Doppler-beaming effect and conclude that the unseen companion, KIC10553698B, must be a white dwarf most likely with a mass close to 0.6M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/3809
- Title:
- KIC 10670103 frequency spectrum
- Short Name:
- J/MNRAS/440/3809
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse 2.75yr of Kepler spacecraft observations of the pulsating subdwarf B star KIC 10670103. These 1.4 million measurements have an impressive duty cycle of 93.8 per cent, a frequency resolution of 0.017{mu}Hz, and a 5{sigma} detection limit of 0.1 parts-per-thousand (ppt). We detect 278 periodicities, making KIC 10670103 the richest pulsating subdwarf B star to date. Frequencies range from 23 to 673{mu}Hz (0.4 and 11.8h), with amplitudes from the detection limit up to 14 ppt. Follow-up spectroscopic data were obtained from which it was determined that KIC 10670103 does not show significant radial velocity variations. Updated atmospheric model fits determined T_eff_=21485+/-540K, logg=5.14+/-0.05, and logN(He)/N(H) =-2.60+/-0.04. We identify pulsation modes using asymptotic period spacings and frequency multiplets. The frequency multiplets indicate a spin period of 88+/-8d. Of the 278 periodicities detected in KIC 10670103, 163 (59 per cent) have been associated with low-degree (l<=2) pulsation modes, providing tight constraints for model fitting. While the data are exquisite, amplitudes (and some frequencies) are not stable over the course of the observations, requiring tools which are non-standard for compact pulsators such as sliding Fourier transforms and Lorentzian fitting. Using the 163 identified pulsation modes, it is possible to make detailed examinations of the pulsation structure; including where the pulsation power is concentrated in radial order, over what frequency range mode trapping is inefficient, and how power switches between multiplet members.
1288. KIC 8462852 GTC spectra
- ID:
- ivo://CDS.VizieR/J/A+A/610/L12
- Title:
- KIC 8462852 GTC spectra
- Short Name:
- J/A+A/610/L12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report ground-based spectrophotometry of KIC 8462852, during its first dimming events since the end of the Kepler mission. The dimmings show a clear colour-signature, and are deeper in visual blue wavelengths than in red ones. The flux loss' wavelength dependency can be described with an absorption Angstroem coefficient of 2.19+/-0.45, which is compatible with absorption by optically thin dust with particle sizes on the order of 0.0015 to 0.15um. These particles would be smaller than is required to be resistant against blow-out by radiation pressure when close to the star. During occultation events, these particles must be replenished on time-scales of days. If dust is indeed the source of KIC 8462852's dimming events, deeper dimming events should show more neutral colours, as is expected from optically thick absorbers.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A94
- Title:
- KIC red giants radial modes amplitude & lifetime
- Short Name:
- J/A+A/616/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The space-borne missions CoRoT and Kepler have provided photometric observations of unprecedented quality. The study of solar-like oscillations observed in red giant stars by these satellites allows a better understanding of the different physical processes occurring in their interiors. In particular, the study of the mode excitation and damping is a promising way to improve our understanding of stellar physics that has, so far, been performed only on a limited number of targets. The recent asteroseismic characterization of the evolutionary status for a large number of red giants allows us to study the physical processes acting in the interior of red giants and how they are modified during stellar evolution. In this work, we aim to obtain information on the excitation and damping of pressure modes through the measurement of the stars' pressure mode widths and amplitudes and to analyze how they are modified with stellar evolution. The objective is to bring observational constraints on the modeling of the physical processes behind mode excitation and damping. We fit the frequency spectra of red giants with well-defined evolutionary status using Lorentzian functions to derive the pressure mode widths and amplitudes. To strengthen our conclusions, we used two different fitting techniques. Pressure mode widths and amplitudes were determined for more than 5000 red giants. With a stellar sample two orders of magnitude larger than previous results, we confirmed that the mode width depends on stellar evolution and varies with stellar effective temperature. In addition, we discovered that the mode width depends on stellar mass. We also confirmed observationally the influence of the stellar metallicity on the mode amplitudes, as predicted by models.
- ID:
- ivo://CDS.VizieR/J/A+A/598/A62
- Title:
- KIC red giants showing depressed mixed modes
- Short Name:
- J/A+A/598/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Seismic observations with the space-borne Kepler mission have shown that a number of evolved stars exhibit low-amplitude dipole modes, which is referred to as depressed modes. Recently, these low amplitudes have been attributed to the presence of a strong magnetic field in the stellar core of those stars. Subsequently, and based on this scenario, the prevalence of high magnetic fields in evolved stars has been inferred. It should be noted, however, that this conclusion remains indirect. We intend to study the properties of mode depression in evolved stars, which is a necessary condition before reaching conclusions about the physical nature of the mechanism responsible for the reduction of the dipole mode amplitudes. We perform a thorough characterization of the global seismic parameters of depressed dipole modes and show that these modes have a mixed character. The observation of stars showing dipole mixed modes that are depressed is especially useful for deriving model-independent conclusions on the dipole mode damping. We use a simple model to explain how mode visibilities are connected to the extra damping seen in depressed modes. Results. Observations prove that depressed dipole modes in red giants are not pure pressure modes but mixed modes. This result, observed in more than 90% of the bright stars (m_V_<=11), invalidates the hypothesis that depressed dipole modes result from the suppression of the oscillation in the radiative core of the stars. Observations also show that, except for visibility, seismic properties of the stars with depressed modes are equivalent to those of normal stars. The measurement of the extra damping that is responsible for the reduction of mode amplitudes, without any prior on its physical nature, potentially provides an efficient tool for elucidating the mechanism responsible for the mode depression. The mixed nature of the depressed modes in red giants and their unperturbed global seismic parameters carry strong constraints on the physical mechanism responsible for the damping of the oscillation in the core. This mechanism is able to damp the oscillation in the core but cannot fully suppress it. Moreover, it cannot modify the radiative cavity probed by the gravity component of the mixed modes. The recent mechanism involving high magnetic fields proposed for explaining depressed modes is not compliant with the observations and cannot be used to infer the strength and prevalence of high magnetic fields in red giants.
