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3581. Stellar population synthesis of clumps
ID:
ivo://CDS.VizieR/J/ApJS/234/35
Title:
Stellar population synthesis of clumps
Short Name:
J/ApJS/234/35
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have identified 1027 star-forming complexes in a sample of 46 galaxies from the Spirals, Bridges, and Tails (SB&T) sample of interacting galaxies, and 693 star-forming complexes in a sample of 38 non-interacting spiral (NIS) galaxies in 8{mu}m observations from the Spitzer Infrared Array Camera. We have used archival multi-wavelength UV-to IR observations to fit the observed spectral energy distribution of our clumps with the Code Investigating GALaxy Emission using a double exponentially declined star formation history. We derive the star formation rates (SFRs), stellar masses, ages and fractions of the most recent burst, dust attenuation, and fractional emission due to an active galactic nucleus for these clumps. The resolved star formation main sequence holds on 2.5kpc scales, although it does not hold on 1kpc scales. We analyzed the relation between SFR, stellar mass, and age of the recent burst in the SB&T and NIS samples, and we found that the SFR per stellar mass is higher in the SB&T galaxies, and the clumps are younger in the galaxy pairs. We analyzed the SFR radial profile and found that the SFR is enhanced through the disk and in the tidal features relative to normal spirals.
3582. Stellar properties for M dwarfs in MEarth-South
ID:
ivo://CDS.VizieR/J/AJ/156/217
Title:
Stellar properties for M dwarfs in MEarth-South
Short Name:
J/AJ/156/217
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stellar rotation periods are valuable both for constraining models of angular momentum loss and for understanding how magnetic features impact inferences of exoplanet parameters. Building on our previous work in the northern hemisphere, we have used long-term, ground-based photometric monitoring from the MEarth Observatory to measure 234 rotation periods for nearby, southern hemisphere M dwarfs. Notable examples include the exoplanet hosts GJ 1132, LHS 1140, and Proxima Centauri. We find excellent agreement between our data and K2 photometry for the overlapping subset. Among the sample of stars with the highest quality data sets, we recover periods in 66%; as the length of the data set increases, our recovery rate approaches 100%. The longest rotation periods we detect are around 140 days, which we suggest represent the periods that are reached when M dwarfs are as old as the local thick disk (about 9 Gyr).
3583. Stellar rotation for 71 NGC 6811 members
ID:
ivo://CDS.VizieR/J/ApJ/733/L9
Title:
Stellar rotation for 71 NGC 6811 members
Short Name:
J/ApJ/733/L9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present rotation periods for 71 single dwarf members of the open cluster NGC 6811 determined using photometry from NASA's Kepler mission. The results are the first from The Kepler Cluster Study, which combines Kepler's photometry with ground-based spectroscopy for cluster membership and binarity. The rotation periods delineate a tight sequence in the NGC 6811 color-period diagram from ~1 day at mid-F to ~11 days at early-K spectral type. This result extends to 1Gyr similar prior results in the ~600Myr Hyades and Praesepe clusters, suggesting that rotation periods for cool dwarf stars delineate a well-defined surface in the three-dimensional space of color (mass), rotation, and age. It implies that reliable ages can be derived for field dwarf stars with measured colors and rotation periods, and it promises to enable further understanding of various aspects of stellar rotation and activity for cool stars.
3584. Stellar rotation in Hyades and Praesepe
ID:
ivo://CDS.VizieR/J/MNRAS/413/2218
Title:
Stellar rotation in Hyades and Praesepe
Short Name:
J/MNRAS/413/2218
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of photometric surveys for stellar rotation in the Hyades and in Praesepe, using data obtained as part of the SuperWASP exoplanetary transit-search programme. We determined accurate rotation periods for more than 120 sources whose cluster membership was confirmed by common proper motion and colour-magnitude fits to the clusters' isochrones. This allowed us to determine the effect of magnetic braking on a wide range of spectral types for expected ages of ~600Myr for the Hyades and Praesepe. Both clusters show a tight and nearly linear relation between J-Ks colour and rotation period in the F, G and K spectral range. This confirms that loss of angular momentum was significant enough that stars with strongly different initial rotation rates have converged to the same rotation period for a given mass, by the ages of Hyades and Praesepe.
3585. Stellar rotation in M35
ID:
ivo://CDS.VizieR/J/ApJ/695/679
Title:
Stellar rotation in M35
Short Name:
J/ApJ/695/679
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a five month photometric time-series survey for stellar rotation over a 40'x40' field centered on the 150Myr open cluster M35 (=NGC 2168). We report rotation periods for 441 stars within this field and determine their cluster membership and binarity based on a decade-long radial velocity survey, proper-motion measurements, and multiband photometric observations. We find that 310 of the stars with measured rotation periods are late-type members of M35. The distribution of rotation periods for cluster members span more than 2 orders of magnitude from ~0.1 to 15 days, not constrained by the sampling frequency and the timespan of the survey. With an age between the zero-age main sequence and the Hyades, and with ~6 times more rotation periods than measured in the Pleiades, M35 permit detailed studies of early rotational evolution of late-type stars. Nearly 80% of the 310 rotators lie on two distinct sequences in the color-period plane, and define clear relations between stellar rotation period and color (mass). The M35 color-period diagram enables us to determine timescales for the transition between the two rotational states, of ~60Myr and ~140Myr for G and K dwarfs, respectively.
3586. Stellar SEDs in SDSS and 2MASS filters
ID:
ivo://CDS.VizieR/J/AJ/134/2398
Title:
Stellar SEDs in SDSS and 2MASS filters
Short Name:
J/AJ/134/2398
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Sloan Digital Sky Survey (SDSS) and Two Micron All Sky Survey (2MASS) are rich resources for studying stellar astrophysics and the structure and formation history of the Galaxy. As new surveys and instruments adopt similar filter sets, it is increasingly important to understand the properties of the ugrizJHKs stellar locus, both to inform studies of "normal" main-sequence stars and enable robust searches for point sources with unusual colors. Using a sample of ~600000 point sources detected by SDSS and 2MASS, we tabulate the position and width of the ugrizJHKs stellar locus as a function of g-i color, and provide accurate polynomial fits. We map the Morgan-Keenan spectral type sequence to the median stellar locus by using synthetic photometry of spectral standards and by analyzing 3000 SDSS stellar spectra with a custom spectral typing pipeline, described in the Appendix to this paper. We develop an algorithm to calculate a point source's minimum separation from the stellar locus in a seven-dimensional color space, and use it to robustly identify objects with unusual colors, as well as spurious SDSS/2MASS matches.
3587. Stellar streams in Andromeda (M31)
ID:
ivo://CDS.VizieR/J/MNRAS/390/1437
Title:
Stellar streams in Andromeda (M31)
Short Name:
J/MNRAS/390/1437
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectroscopic analysis of five stellar streams ("A", "B", "Cr", "Cp" and "D") as well as the extended star cluster, EC4, which lies within Stream "C", all discovered in the halo of M31 from our Canada-France-Hawaii Telescope/MegaCam survey. These spectroscopic results were initially serendipitous, making use of our existing observations from the DEep Imaging Multi-Object Spectrograph mounted on the Keck II telescope, and thereby emphasizing the ubiquity of tidal streams that account for ~70 per cent of the M31 halo stars in the targeted fields. Subsequent spectroscopy was then procured in Stream "C" and Stream "D" to trace the velocity gradient along the streams. Nine metal-rich ([Fe/H]~-0.7) stars at v_hel_=-349.5km/s, {sigma}_v,corr_~5.1+/-2.5km/s are proposed as a serendipitous detection of Stream "Cr", with follow-up kinematic identification at a further point along the stream. Seven metal-poor ([Fe/H]~-1.3) stars confined to a narrow, 15km/s velocity bin centred at v_hel_=-285.6, {sigma}_v,corr_=4.3^+1.7^_-1.4_km/s represent a kinematic detection of Stream "Cp", again with follow-up kinematic identification further along the stream. For the cluster EC4, candidate member stars with average [Fe/H]~-1.4, are found at v_hel_=-282 suggesting it could be related to Stream "Cp". No similarly obvious cold kinematic candidate is found for Stream "D", although candidates are proposed in both of two spectroscopic pointings along the stream (both at ~-400km/s). Spectroscopy near the edge of Stream "B" suggests a likely kinematic detection at v_hel_~-330, {sigma}_v,corr_~6.9km/s, while a candidate kinematic detection of Stream "A" is found (plausibly associated to M33 rather than M31) with v_hel_~-170, {sigma}_v,corr_=12.5km/s. The low dispersion of the streams in kinematics, physical thickness and metallicity makes it hard to reconcile with a scenario whereby these stream structures as an ensemble are related to the giant southern stream. We conclude that the M31 stellar halo is largely made up of multiple kinematically cold streams.
3588. Stellar twins in RAVE with Gaia
ID:
ivo://CDS.VizieR/J/MNRAS/472/2517
Title:
Stellar twins in RAVE with Gaia
Short Name:
J/MNRAS/472/2517
Date:
21 Oct 2021
Publisher:
CDS
Description:
We apply the twin method to determine parallaxes to 232 545 stars of the RAVE survey using the parallaxes of Gaia DR1 as a reference. To search for twins in this large data set, we apply the t-student stochastic neighbour embedding projection that distributes the data according to their spectral morphology on a two-dimensional map. From this map, we choose the twin candidates for which we calculate a {chi}^2^ to select the best sets of twins. Our results show a competitive performance when compared to other model-dependent methods relying on stellar parameters and isochrones. The power of the method is shown by finding that the accuracy of our results is not significantly affected if the stars are normal or peculiar since the method is model free. We find twins for 60 per cent of the RAVE sample that are not contained in Tycho-Gaia Astrometric Solution (TGAS) or that have TGAS uncertainties that are larger than 20 per cent. We could determine parallaxes with typical errors of 28 per cent. We provide a complementary data set for the RAVE stars not covered by TGAS, or that have TGAS uncertainties which are larger than 20 per cent, with model-free parallaxes scaled to the Gaia measurements.
3589. Stellar variability in field stars
ID:
ivo://CDS.VizieR/J/PASP/114/656
Title:
Stellar variability in field stars
Short Name:
J/PASP/114/656
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from a 5 night wide-field time-series photometric survey that detects variable field stars. We find that the fraction of stars whose light curves show variations depends on color and magnitude, reaching 17% for the brightest stars in this survey (V~4) for which the photometric precision is best. The fraction of stars found to be variable is relatively high at colors bluer than the Sun and relatively low at colors similar to the Sun and increases again for stars redder than the Sun. We present light curves for a sample of the pulsating and eclipsing variables. Most of the stars identified as pulsating variables have low amplitudes ({Delta}V=0.01-0.05), relatively blue colors, and multiple periods. There are 13 stars we identify as either SX Phoenicis or {delta} Scuti stars. These classes represent a significant contribution to the total number of blue variables found in this survey. Another 17 stars are identified as eclipsing variables, which have a wide range in color, magnitude, and amplitude. Two variable giants are observed, and both show night-to-night ~1% variations. We present data for 222 variables in total, most of which are not classified. Implications of surveys for stellar variability and interferometry are briefly discussed. On 2000 March 16-20 UT we observed a time series of images in V and one or two images each in UBRI toward two 59'x59' fields using the NOAO Mosaic Camera at the Kitt Peak 0.9 m telescope.
3590. Stellar X-ray sources in the COSMOS survey
ID:
ivo://CDS.VizieR/J/ApJ/725/480
Title:
Stellar X-ray sources in the COSMOS survey
Short Name:
J/ApJ/725/480
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of the X-ray properties of a sample of solar- and late-type field stars identified in the Chandra Cosmic Evolution Survey (COSMOS), a deep (160ks) and wide (~0.9deg^2^) extragalactic survey. The sample of 60 sources was identified using both morphological and photometric star/galaxy separation methods. We determine X-ray count rates, extract spectra and light curves, and perform spectral fits to determine fluxes and plasma temperatures. Complementary optical and near-IR photometry is also presented and combined with spectroscopy for 48 of the sources to determine spectral types and distances for the sample. We find distances ranging from 30pc to ~12kpc, including a number of the most distant and highly active stellar X-ray sources ever detected. Overall the sample is typically more luminous than the active Sun, representing the high-luminosity end of the disk and halo X-ray luminosity functions. The halo population appears to include both low-activity spectrally hard sources that may be emitting through thermal bremsstrahlung, as well as a number of highly active sources in close binaries.