- ID:
- ivo://CDS.VizieR/J/A+A/564/A26
- Title:
- Spectroscopy of HD 86222
- Short Name:
- J/A+A/564/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopic and photometric analysis of the quintuple star HD 86222 with an eclipsing component. Until now three visual components A, B, and C of this multiple star were known. Four components in the A/B pair were detected during the examination of the cross correlation functions obtained from the spectra.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/148/62
- Title:
- Spectroscopy of HD 5980
- Short Name:
- J/AJ/148/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New spectroscopic observations of the LBV/WR multiple system HD 5980 in the Small Magellanic Cloud are used to address the question of the masses and evolutionary status of the two very luminous stars in the 19.3 day eclipsing binary system. Two distinct components of the NV4944{AA} line are detected in emission and their radial velocity variations are used to derive masses of 61 and 66M_{sun}_, under the assumption that binary interaction effects on this atomic transition are negligible. We propose that this binary system is the product of quasi-chemically homogeneous evolution with little or no mass transfer. Thus, both of these binary stars may be candidates for gamma-ray burst progenitors or even pair instability supernovae. Analysis of the photospheric absorption lines belonging to the third-light object in the system confirm that it consists of an O-type star in a 96.56day eccentric orbit (e=0.82) around an unseen companion. The 5:1 period ratio and high eccentricities of the two binaries suggest that they may constitute a hierarchical quadruple system.
- ID:
- ivo://CDS.VizieR/J/AJ/153/248
- Title:
- Spectroscopy of V Tri
- Short Name:
- J/AJ/153/248
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Time-series, multi-color photometry and high-resolution spectra of the short-period eclipsing binary V Tri were obtained through observation. The completely covered light and radial velocity (RV) curves of the binary system are presented. All times of light minima derived from both photoelectric and CCD photometry were used to calculate the orbital period and new ephemerides of the eclipsing system. The analysis of the O-C diagram reveals that the orbital period is 0.58520481 days, decreasing at a rate of dP/dt=-7.80x10^-8^ day/yr. The mass transfer between the two components and the light-time-travel effect due to a third body could be used to explain the period decrease. However, a semi-detached configuration with the lower-mass component filling and the primary nearly filling each of their Roche lobes was derived from the synthesis of the light and RV curves by using the 2015 version of the Wilson-Devinney code. We consider the period decrease to be the nonconservative mass transfer from the secondary component to the primary and the mass loss of the system, which was thought to be an EB type, while it should be an EA type (semi-detached Algol-type) from our study. The masses, radii, and luminosities of the primary and secondary are 1.60+/-0.07M_{sun}_, 1.64+/-0.02R_{sun}_, and 14.14+/-0.73L_{sun}_ and 0.74+/-0.02M_{sun}_, 1.23+/-0.02R_{sun}_, and 1.65+/-0.05L_{sun}_, respectively.
- ID:
- ivo://CDS.VizieR/J/AJ/146/70
- Title:
- Spectroscopy of W UMa-type binary stars
- Short Name:
- J/AJ/146/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study is the first attempt to determine the metallicities of W UMa-type binary stars using spectroscopy. We analyzed about 4500 spectra collected at the David Dunlap Observatory. To circumvent problems caused by the extreme spectral line broadening and blending and by the relatively low quality of the data, all spectra were subject to the same broadening function (BF) processing to determine the combined line strength in the spectral window centered on the Mg I triplet between 5080{AA} and 5285{AA}. All individual integrated BFs were subsequently orbital-phase averaged to derive a single line-strength indicator for each star. The star sample was limited to 90 W UMa-type (EW) binaries with the strict phase-constancy of colors and without spectral contamination by spectroscopic companions. The best defined results were obtained for an F-type sub-sample (0.32<(B-V)_0_<0.62) of 52 binaries for which integrated BF strengths could be interpolated in the model atmosphere predictions. The logarithmic relative metallicities, [M/H], for the F-type sub-sample indicate metal abundances roughly similar to the solar metallicity, but with a large scatter which is partly due to combined random and systematic errors. Because of the occurrence of a systematic color trend resulting from inherent limitations in our approach, we were forced to set the absolute scale of metallicities to correspond to that derived from the m_1_index of the Stromgren uvby photometry for 24 binaries of the F-type sub-sample. The trend-adjusted metallicities [M/H]_1_ are distributed within -0.65<[M/H]_1_<+0.50, with the spread reflecting genuine metallicity differences between stars. One half of the F-sub-sample binaries have [M/H]_1_within -0.37<[M/H]_1_<+0.10, a median of -0.04 and a mean of -0.10, with a tail toward low metallicities, and a possible bias against very high metallicities. A parallel study of kinematic data, utilizing the most reliable and recently obtained proper motion and radial velocity data for 78 binaries of the full sample, shows that the F-type sub-sample binaries (44 stars with both velocities and metallicity determinations) have similar kinematic properties to solar-neighborhood, thin-disk dwarfs with space velocity component dispersions: {sigma}U=33km/s, {sigma}V=23km/s and {sigma}W=14km/s. FU Dra with a large spatial velocity, V_tot_=197km/s and [M/H]_1_=-0.6+/-0.2, appears to be the only thick-disk object in the F-type sub-sample. The kinematic data indicate that the F-type EW binaries are typical, thin-disk population stars with ages about 3-5.5Gyr. The F-type binaries that appear to be older than the rest tend to have systematically smaller mass ratios than most of the EW binaries of the same period.
- ID:
- ivo://CDS.VizieR/J/other/IBVS/6121
- Title:
- Spectrosocopy of the multiple star HT Vir
- Short Name:
- J/other/IBVS/612
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectra of HT Virginis were collected at 0.5m Newtonian telescope (PST1) equipped with echelle spectrograph (R=40 000). The focal length of the telescope is 2.25m. The data set was obtained between 6 May 2011 and 21 May 2011. The signal-to-noise ratio is from 10 to 85. The collected data covered spectral range from 4288 to 7517{AA}. The continuum of the spectra was normalised to 1 while the wave length scale was not corrected to the heliocentric values. The spectra contain light from the eclipsing pair B and component A which is SBI type (A/B separation is 0.56 arcsec).
- ID:
- ivo://CDS.VizieR/J/ApJ/786/2
- Title:
- Spitzer photometric time series of HD 97658
- Short Name:
- J/ApJ/786/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Super-Earths transiting nearby bright stars are key objects that simultaneously allow for accurate measurements of both their mass and radius, providing essential constraints on their internal composition. We present here the confirmation, based on Spitzer transit observations, that the super-Earth HD 97658 b transits its host star. HD 97658 is a low-mass (M_*_=0.77+/-0.05 M_{sun}_) K1 dwarf, as determined from the Hipparcos parallax and stellar evolution modeling. To constrain the planet parameters, we carry out Bayesian global analyses of Keck-High Resolution Echelle Spectrometer (Keck-HIRES) radial velocities and Microvariability and Oscillations of STars (MOST) and Spitzer photometry. HD 97658 b is a massive (M_p_=7.55_-0.79_^+0.83^ M_{earth}_) and large (R_p_=2.247_0.095_^+0.098^ R_{earth}_ at 4.5 {mu}m) super-Earth. We investigate the possible internal compositions for HD 97658 b. Our results indicate a large rocky component, of at least 60% by mass, and very little H-He components, at most 2% by mass. We also discuss how future asteroseismic observations can improve the knowledge of the HD 97658 system, in particular by constraining its age. Orbiting a bright host star, HD 97658 b will be a key target for upcoming space missions such as the Transiting Exoplanet Survey Satellite (TESS), the Characterizing Exoplanet Satellite (CHEOPS), the Planetary Transits and Oscillations of stars (PLATO), and the James Webb Space Telescope to characterize thoroughly its structure and atmosphere.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A117
- Title:
- Spitzer search for 19 planets
- Short Name:
- J/A+A/601/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Short-period super-Earths and Neptunes are now known to be very frequent around solar-type stars. Improving our understanding of these mysterious planets requires the detection of a significant sample of objects suitable for detailed characterization. Searching for the transits of the low-mass planets detected by Doppler surveys is a straightforward way to achieve this goal. Indeed, Doppler surveys target the most nearby main-sequence stars, they regularly detect close-in low-mass planets with significant transit probability, and their radial velocity data constrain strongly the ephemeris of possible transits. In this context, we initiated in 2010 an ambitious Spitzer multi-Cycle transit search project that targeted 25 low-mass planets detected by radial velocity, focusing mainly on the shortest-period planets detected by the HARPS spectrograph. We report here null results for 19 targets of the project. For 16 planets out of 19, a transiting configuration is strongly disfavored or firmly rejected by our data for most planetary compositions.We derive a posterior probability of 83% that none of the probed 19 planets transits (for a prior probability of 22%), which still leaves a significant probability of 17% that at least one of them does transit. Globally, our Spitzer project revealed or confirmed transits for three of its 25 targeted planets, and discarded or disfavored the transiting nature of 20 of them. Our light curves demonstrate for Warm Spitzer excellent photometric precisions: for 14 targets out of 19, we were able to reach standard deviations that were better than 50ppm per 30 min intervals. Combined with its Earth-trailing orbit, which makes it capable of pointing any star in the sky and to monitor it continuously for days, this work confirms Spitzer as an optimal instrument to detect sub-mmag-deep transits on the bright nearby stars targeted by Doppler surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/170
- Title:
- Spots parameters for LCs of the EB star KIC 6048106
- Short Name:
- J/ApJ/833/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Kepler photometry of KIC 6048106, which is exhibiting the O'Connell effect and multiperiodic pulsations. Including a starspot on either of the components, light-curve synthesis indicates that this system is a semi-detached Algol with a mass ratio of 0.211, an orbital inclination of 73.9{deg}, and a large temperature difference of 2534K. To examine in detail both the spot variations and pulsations, we separately analyzed the Kepler time-series data at the interval of an orbital period in an iterative way. The results reveal that the variable asymmetries of the light maxima can be interpreted as the changes with time of a magnetic cool spot on the secondary component. Multiple frequency analyses were performed in the outside-eclipse light residuals after removal of the binarity effects from the observed Kepler data. We detected 30 frequencies with signal to noise amplitude ratios larger than 4.0, of which six (f_2_-f_6_ and f_10_) can be identified as high-order (17<=n<=25) low-degree (l=2) gravity-mode pulsations that were stable during the observing run of 200 days. In contrast, the other frequencies may be harmonic and combination terms. For the six frequencies, the pulsation periods and pulsation constants are in the ranges of 0.352-0.506 days and 0.232-0.333 days, respectively. These values and the position on the Hertzsprung-Russell diagram demonstrate that the primary star is a {gamma} Dor variable. The evolutionary status and the pulsation nature of KIC 6048106 are discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A31
- Title:
- Statistical test on binary stars non-coevality
- Short Name:
- J/A+A/587/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop a statistical test on the expected difference in age estimates of two coeval stars in detached double-lined eclipsing binary systems that are only caused by observational uncertainties. We focus on stars in the mass range [0.8; 1.6] Msun, with an initial metallicity [Fe/H] from -0.55 to 0.55dex, and on stars in the main-sequence phase. The ages were obtained by means of the SCEPtER technique, a maximum-likelihood procedure relying on a pre-computed grid of stellar models. The observational constraints used in the recovery procedure are stellar mass, radius, effective temperature, and metallicity [Fe/H]. To check the effect of the uncertainties affecting observations on the (non-)coevality assessment, the chosen observational constraints were subjected to a Gaussian perturbation before applying the SCEPtER code. We defined the statistic W computed as the ratio of the absolute difference of estimated ages for the two stars over the age of the older one. We determined the critical values of this statistics above which coevality can be rejected in dependence on the mass of the two stars, on the initial metallicity [Fe/H], and on the evolutionary stage of the primary star. The median expected difference in the reconstructed age between the coeval stars of a binary system - caused alone by the observational uncertainties - shows a strong dependence on the evolutionary stage. This ranges from about 20% for an evolved primary star to about 75% for a near ZAMS primary. The median difference also shows an increase with the mass of the primary star from 20% for 0.8M_{sun}_ stars to about 50% for 1.6M_{sun}_ stars. The reliability of these results was checked by repeating the process with a grid of stellar models computed by a different evolutionary code; the median difference in the critical values was only 0.01. We show that the W test is much more sensible to age differences in the binary system components than the alternative approach of comparing the confidence interval of the age of the two stars. We also found that the distribution of W is, for almost all the examined cases, well approximated by beta distributions. The proposed method improves upon the techniques that are commonly adopted for judging the coevality of an observed system. It also provides a result founded on reliable statistics that simultaneously accounts for all the observational uncertainties.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A21
- Title:
- Stellar Limb-Darkening Coefficients
- Short Name:
- J/A+A/510/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transiting exoplanets provide unparalleled access to the fundamental parameters of both extrasolar planets and their host stars. We present limb-darkening coefficients (LDCs) for the exoplanet hunting CoRot and Kepler missions. The LDCs are calculated with ATLAS stellar atmospheric model grids and span a wide range of T_eff_, logg, and metallically [M/H]. Both CoRot and Kepler use wide nonstandard photometric filters, and are producing a large inventory of high- quality transiting lightcurves, sensitive to stellar limb darkening. Comparing the stellar model limb darkening to results from the first seven CoRot planets, we find better fits are found when two model intensities at the limb are excluded in the coefficient calculations. This calculation method can help to avoid a major deficiency present at the limbs of the 1D stellar models.
