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.
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.
We present a catalog of near-infrared (NIR) spectra and associated measurements for 886 nearby M dwarfs. The spectra were obtained with the NASA-Infrared Telescope Facility SpeX Spectrograph during a two-year observing campaign; they have high signal-to-noise ratios (S/N>100-150), span 0.8-2.4{mu}m, and have R~2000. Our catalog of measured values contains useful T_eff_ and composition-sensitive features, empirical stellar parameter measurements, and kinematic, photometric, and astrometric properties compiled from the literature. We focus on measurements of M dwarf abundances ([Fe/H] and [M/H]), capitalizing on the precision of recently published empirical NIR spectroscopic calibrations. We explore systematic differences between different abundance calibrations, and from other similar M dwarf catalogs. We confirm that the M dwarf abundances we measure show the expected inverse dependence with kinematic-, activity-, and color-based age indicators. Finally, we provide updated [Fe/H] and [M/H] for 16 M dwarf planet hosts. This catalog represents the largest published compilation of NIR spectra and associated parameters for M dwarfs. It provides a rich and uniform resource for nearby M dwarfs, and will be especially valuable for measuring Habitable Zone locations and comparative abundances of the M dwarf planet hosts that will be uncovered by upcoming exoplanet surveys.
The location of young sources in the Galaxy suggests a four-armed spiral structure, whereas tangential points of spiral arms observed in the integrated light at infrared and radio wavelengths indicate that only two arms are massive. Variable extinction in the Galactic plane and high light-to-mass ratios of young sources make it difficult to judge the total mass associated with the arms outlined by such tracers. The current objective is to estimate the mass associated with the Sagittarius arm by means of the kinematics of the stars across it. Spectra of 1726 candidate B- and A-type stars within 3{deg} of the Galactic center (GC) were obtained with the FLAMES instrument at the VLT with a resolution of ~6000 in the spectral range of 396-457nm. Radial velocities were derived by least-squares fits of the spectra to synthetic ones. The final sample was limited to 1507 stars with either Gaia DR2 parallaxes or main-sequence B-type stars having reliable spectroscopic distances. The solar peculiar motion in the direction of the GC relative to the local standard of rest (LSR) was estimated to U_{sun}_=10.7+/-1.3km/s. The variation in the median radial velocity relative to the LSR as a function of distance from the sun shows a gradual increase from slightly negative values near the sun to almost 5km/s at a distance of around 4kpc. A sinusoidal function with an amplitude of 3.4+/-1.3km/s and a maximum at 4.0+/-0.6kpc inside the sun is the best fit to the data. A positive median radial velocity relative to the LSR around 1.8kpc, the expected distance to the Sagittarius arm, can be excluded at a 99% level of confidence. A marginal peak detected at this distance may be associated with stellar streams in the star-forming regions, but it is too narrow to be associated with a major arm feature. A comparison with test-particle simulations in a fixed galactic potential with an imposed spiral pattern shows the best agreement with a two-armed spiral potential having the Scutum-Crux arm as the next major inner arm. A relative radial forcing dFr~1.5% and a pattern speed in the range of 20-30km/s/kpc yield the best fit. The lack of a positive velocity perturbation in the region around the Sagittarius arm excludes it from being a major arm. Thus, the main spiral potential of the Galaxy is two-armed, while the Sagittarius arm is an inter-arm feature with only a small mass perturbation associated with it.
We present the analysis of the rotation curves of a sample of 32 spiral galaxies derived from the spectroscopic observations of a sample of 47 galaxies.
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.
We present a resolved star spectroscopic survey of 15 dwarf spheroidal (dSph) satellites of the Andromeda galaxy (M31). We filter foreground contamination from Milky Way (MW) stars, noting that MW substructure is evident in this contaminant sample. We also filter M31 halo field giant stars and identify the remainder as probable dSph members. We then use these members to determine the kinematical properties of the dSphs. For the first time, we confirm that And XVIII, XXI, and XXII show kinematics consistent with bound, dark-matter-dominated galaxies. From the velocity dispersions for the full sample of dSphs we determine masses, which we combine with the size and luminosity of the galaxies to produce mass-size-luminosity scaling relations. With these scalings we determine that the M31 dSphs are fully consistent with the MW dSphs, suggesting that the well-studied MW satellite population provides a fair sample for broader conclusions. We also estimate dark matter halo masses of the satellites and find that there is no sign that the luminosity of these galaxies depends on their dark halo mass, a result consistent with what is seen for MW dwarfs. Two of the M31 dSphs (And XV, XVI) have estimated maximum circular velocities smaller than 12 km/s (to 1{sigma}), which likely places them within the lowest-mass dark matter halos known to host stars (along with Bootes I of the MW). Finally, we use the systemic velocities of the M31 satellites to estimate the mass of the M31 halo, obtaining a virial mass consistent with previous results.
Sp. obs. of rapidly rotating stars in the Pleiades
Short Name:
J/ApJ/901/91
Date:
18 Feb 2022 11:55:29
Publisher:
CDS
Description:
Radial velocities for the early-type stars in the Pleiades cluster have always been challenging to measure because of the significant rotational broadening of the spectral lines. The large scatter in published velocities has led to claims that many are spectroscopic binaries, and in several cases, preliminary orbital solutions have been proposed. To investigate these claims, we obtained and report here velocity measurements for 33 rapidly rotating B, A, and early F stars in the Pleiades region, improving significantly on the precision of the historical velocities for most objects. With one or two exceptions, we do not confirm any of the previous claims of variability, and we also rule out all four of the previously published orbital solutions, for HD 22637, HD 23302, HD 23338, and HD 23410. We do find HD 22637 to be a binary but with a different period (71.8d). HD 23338 is likely a binary as well, with a preliminary 8.7yr period also different from the one published. Additionally, we report a 3635d orbit for HD 24899, another new spectroscopic binary in the cluster. From the 32 bona fide members in our sample, we determine a mean radial velocity for the Pleiades of 5.79+/-0.24km/s, or 5.52+/-0.31km/s when objects with known visual companions are excluded. Adding these astrometric binaries to the new spectroscopic ones, we find a lower limit to the binary fraction among the B and A stars of 37%. In addition to the velocities, we measure vsini for all stars, ranging between 69 and 317km/s.
We have calculated spectra from 1000 to 200000{AA} with a constant resolving power of {lambda}/{Delta}{lambda}=20000 and from 8470 and 8710{AA} (Gaia Radial Velocity Spectrometer - RVS - spectral range) with a constant resolving power of {lambda}/{Delta}{lambda}=300000. This for the Stagger-grid 3D stellar atmosphere models in the ranges: Teff from 4000 to 7000K, logg from 1.5 to 5.0, and [Fe/H], from -4.0 to +0.5. We used synthetic spectra to compute theoretical colours in the Johnson-Cousins UBV(RI)C, SDSS, 2MASS, Gaia, SkyMap- per, Stroemgren systems, and HST-WFC3.
