- ID:
- ivo://CDS.VizieR/J/ApJ/705/89
- Title:
- IRS spectra of solar-type stars
- Short Name:
- J/ApJ/705/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed 152 nearby solar-type stars with the Infrared Spectrometer (IRS) on the Spitzer Space Telescope. Including stars that met our criteria but were observed in other surveys, we get an overall success rate for finding excesses in the long-wavelength IRS band (30-34um) of 11.8%+/-2.4%. The success rate for excesses in the short-wavelength band (8.5-12um) is ~1% including sources from other surveys. Two stars (HD 40136 and HD 10647) show weak evidence for spectral features; the excess emission in the other systems is featureless. For most stars with excesses, we detect an excess at both IRS and Multiband Imaging Photometer for Spitzer (MIPS) wavelengths. Only three stars in this sample show a MIPS 70um excess with no IRS excess, implying that very cold dust is rare around solar-type stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/597/A52
- Title:
- K and G dwarfs stellar granulation variability
- Short Name:
- J/A+A/597/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In solar-type stars, the attenuation of convective blueshift by stellar magnetic activity dominates the RV (radial velocity) variations over the low amplitude signal induced by low mass planets. Models of stars that differ from the Sun will require a good knowledge of the attenuation of the convective blueshift to estimate its impact on the variations. It is therefore crucial to precisely determine not only the amplitude of the convective blueshift for different types of stars, but also the dependence of this convective blueshift on magnetic activity, as these are key factors in our model producing the RV. We studied a sample of main sequence stars with spectral types from G0 to K2 and focused on their temporally averaged properties: the activity level and a criterion allowing to characterise the amplitude of the convective blueshift. This criterion is derived from the dependence of the convective blueshift with the intensity at the bottom of a large set of selected spectral lines.
- ID:
- ivo://CDS.VizieR/J/MNRAS/499/5004
- Title:
- K2-111, an old system with two planets
- Short Name:
- J/MNRAS/499/5004
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports on the detailed characterisation of the K2-111 planetary system with K2, WASP, and ASAS-SN photometry as well as high-resolution spectroscopic data from HARPS-N and ESPRESSO. The host, K2-111, is confirmed to be a mildly evolved (logg=4.17), iron-poor ([Fe/H]=-0.46), but alpha-enhanced ([{alpha}/Fe]=0.27), chromospherically quiet, very old thick disc G2 star. A global fit, performed by using PyORBIT shows that the transiting planet, K2-111 b, orbits with a period P_b_=5.3518+/-0.0004d, and has a planet radius of 1.82^+0.11^_-0.09_R_{Earth}_ and a mass of 5.29^+0.76^_-0.77_ M_{Earth}_, resulting in a bulk density slightly lower than that of the Earth. The stellar chemical composition and the planet properties are consistent with K2-111 b being a terrestrial planet with an iron core mass fraction lower than the Earth. We announce the existence of a second signal in the radial velocity data that we attribute to a non-transiting planet, K2-111 c, with an orbital period of 15.6785+/-0.0064 days, orbiting in near-3:1 mean-motion resonance with the transiting planet, and a minimum planet mass of 11.3+/-1.1 M_{Earth}_. Both planet signals are independently detected in the HARPS-N and ESPRESSO data when fitted separately. There are potentially more planets in this resonant system, but more well-sampled data are required to confirm their presence and physical parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/157/143
- Title:
- Kepler GK dwarf planet candidate samples
- Short Name:
- J/AJ/157/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We re-examine the statistical confirmation of small long-period Kepler planet candidates in light of recent improvements in our understanding of the occurrence of systematic false alarms in this regime. Using the final Data Release 25 (DR25, Twicken et al. 2016, J/AJ/152/158) Kepler planet candidate catalog statistics, we find that the previously confirmed single-planet system Kepler-452b no longer achieves a 99% confidence in the planetary hypothesis and is not considered statistically validated in agreement with the finding of Mullally et al. (2018AJ....155..210M). For multiple planet systems, we find that the planet prior enhancement for belonging to a multiple-planet system is suppressed relative to previous Kepler catalogs, and we also find that the multiple-planet system member, Kepler-186f, no longer achieves a 99% confidence level in the planetary hypothesis. Because of the numerous confounding factors in the data analysis process that leads to the detection and characterization of a signal, it is difficult to determine whether any one planetary candidate achieves a strict criterion for confirmation relative to systematic false alarms. For instance, when taking into account a simplified model of processing variations, the additional single-planet systems Kepler-443b, Kepler-441b, Kepler-1633b, Kepler-1178b, and Kepler-1653b have a non-negligible probability of falling below 99% confidence in the planetary hypothesis. The systematic false alarm hypothesis must be taken into account when employing statistical validation techniques in order to confirm planet candidates that approach the detection threshold of a survey. We encourage those performing transit searches of K2, TESS, and other similar data sets to quantify their systematic false alarm rates. Alternatively, independent photometric detection of the transit signal or radial velocity measurements can eliminate the false alarm hypothesis.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A67
- Title:
- Kepler solar-type stars modeling
- Short Name:
- J/A+A/601/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kepler space telescope yielded unprecedented data for the study of solar-like oscillations in other stars. The large samples of multi-year observations posed an enormous data analysis challenge that has only recently been surmounted. Asteroseismic modeling has become more sophisticated over time, with better methods gradually developing alongside the extended observations and improved data analysis techniques. We apply the latest version of the Asteroseismic Modeling Portal (AMP) to the full-length Kepler data sets for 57 stars, comprising planetary hosts, binaries, solar-analogs, active stars, and for validation purposes, the Sun. From an analysis of the derived stellar properties for the full sample, we identify a variation of the mixing-length parameter with atmospheric properties. We also derive a linear relation between the stellar age and a characteristic frequency separation ratio. In addition, we find that the empirical correction for surface effects suggested by Kjeldsen and coworkers is adequate for solar-type stars that are not much hotter (Teff<~6200K) or significantly more evolved (logg>~4.2, <{Delta}{nu}> >~80uHz80) than the Sun. Precise parallaxes from the Gaia mission and future observations from TESS and PLATO promise to improve the reliability of stellar properties derived from asteroseismology.
- ID:
- ivo://CDS.VizieR/J/AJ/105/2299
- Title:
- Li abundance of solar-type stars. II.
- Short Name:
- J/AJ/105/2299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We draw upon a recent study of the membership of the Ursa Major Group (UMaG) to examine lithium among 0.3 Gyr old solar-type stars. For most G and K dwarfs, Li confirms the conclusions about membership in UMaG reached on the basis of kinematics and chromospheric activity. G and K dwarfs in UMaG have less Li than comparable stars in the Pleiades. This indicates that G and K dwarfs undergo Li depletion while they are on the main sequence, in addition to any pre-main-sequence depletion they may have experienced. Moreover, the Li abundances of the Pleiades K dwarfs cannot be attributed to main-sequence depletion alone, demonstrating that pre-main-sequence depletion of Li also takes place. The Sun's Li abundance implies that the main-sequence mechanism becomes less effective with age, otherwise the Sun would have even less Li than it does. The hottest stars in the UMaG (T(eff) >~ 6800K) have Li abundances like those of hot stars in the Pleiades and Hyades and in T Tauris, and the two genuine UMaG members with temperatures near Boesgaard's Li chasm have Li abundances consistent with that chasm developing fully by 0.3 Gyr for stars with UMaG's metallicity ([Fe/H] = -0.08 +/- 0.09). We see differences in the abundance of Li between UMaG members of the same spectral types, indicating that a real spread in the lithium abundance exists within this group.
- ID:
- ivo://CDS.VizieR/J/A+A/515/A93
- Title:
- Li abundances in solar-analog stars. II.
- Short Name:
- J/A+A/515/A93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We previously attempted to ascertain why the LiI 6708 line-strengths of Sun-like stars differ so significantly despite the superficial similarities of stellar parameters. We carried out a comprehensive analysis of 118 solar analogs and reported that a close connection exists between the Li abundance (A_Li_) and the line-broadening width (v_r+m_) mainly contributed by rotational effect), which led us to conclude that stellar rotation may be the primary control of the surface Li content. To examine our claim in more detail, we study whether the degree of stellar activity exhibits a similar correlation with the Li abundance, which is expected because of the widely believed close connection between rotation and activity.
- ID:
- ivo://CDS.VizieR/J/AJ/157/191
- Title:
- Light curve & radial velocities for TOI-172
- Short Name:
- J/AJ/157/191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of TOI-172 b from the Transiting Exoplanet Survey Satellite (TESS) mission, a massive hot Jupiter transiting a slightly evolved G star with a 9.48-day orbital period. This is the first planet to be confirmed from analysis of only the TESS full frame images, because the host star was not chosen as a two-minute cadence target. From a global analysis of the TESS photometry and follow-up observations carried out by the TESS Follow-up Observing Program Working Group, TOI-172 (TIC 29857954) is a slightly evolved star with an effective temperature of T_eff_=5645+/-50 K, a mass of M_*_=1.128_-0.061_^+0.065^ M_{sun}_, radius of R_*_=1.777_-0.044_^+0.047^ R_{sun}_, a surface gravity of log g_*_=3.993_-0.028_^+0.027^, and an age of 7.4_-1.5_^+1.6^ Gyr. Its planetary companion (TOI-172 b) has a radius of R_P_=0.965_-0.029_^+0.032^ R_J_, a mass of M_P_=5.42_-0.20_^+0.22^ M_J_, and is on an eccentric orbit (e=0.3806_-0.0090_^+0.0093^). TOI-172 b is one of the few known massive giant planets on a highly eccentric short-period orbit. Future study of the atmosphere of this planet and its system architecture offer opportunities to understand the formation and evolution of similar systems.
- ID:
- ivo://CDS.VizieR/J/A+A/633/L9
- Title:
- Linear regression fit coefficients
- Short Name:
- J/A+A/633/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The physical processes driving chemical evolution in the Milky Way can be probed using the distribution of abundances in low-mass FGK type stars in space phase at different times. During their final stages of evolution, stars experience nucleosynthesis several times, each at different timescales and producing different chemical elements. Finding abundance ratios that have simple variations across cosmic times therefore remains a challenge. Using the sample of 80 solar twins for which ages and abundances of 30 elements have been measured with high precision, we searched for all possible abundance ratio combinations that show linear trends with age. We found 55 such ratios, all combining an n-capture element and another element produced by different nucleosynthesis channels. We recovered the ratios of [Y/Mg], [Ba/Mg], and [Al/Y] that have been reported previously in the literature, and found that [C/Ba] depends most strongly on age, with a slope of 0.049+/-0.003dex/Gyr. This imposes constraints on the magnitude of the time dependency of abundance ratios in solar twins. Our results suggest that s-process elements, in lieu of Fe, should be used as a reference for constraining chemical evolution models of the solar neighbourhood. Our study illustrates that a wide variety of chemical elements measured in high-resolution spectra is key to meeting the current challenges in understanding the formation and evolution of our Galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/4368
- Title:
- Lithium abundance of solar-like stars
- Short Name:
- J/MNRAS/451/4368
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the determination of the lithium abundance [A(Li)] of 52 solar-like stars. For 41 objects the A(Li) here presented corresponds to the first measurement. We have measured the equivalent widths of the 6708 {AA} lithium feature in high-resolution spectroscopic images (R~80000), obtained at the Observatorio Astrofisico Guillermo Haro (Sonora, Mexico), as part of the first scientific observations of the revitalized Lunar and Planetary Laboratory (LPL) Echelle Spectrograph, now known as the Cananea High-resolution Spectrograph (CanHiS). Lithium abundances were derived with the Fortran code MOOG, using as fundamental input a set of atmospheric parameters recently obtained by our group. With the help of an additional small sample with previous A(Li) determinations, we demonstrate that our lithium abundances are in agreement, to within uncertainties, with other works. Two target objects stand out from the rest of the sample. The star BD+47 3218 (T_eff_=6050+/-52 K, A(Li)=1.86+/-0.07 dex) lies inside the so-called lithium desert in the A(Li)-T_eff_ plane. The other object, BD+28 4515, has an A(Li)=3.05+/-0.07 dex, which is the highest of our sample and compatible with the expected abundances of relatively young stars.
