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4211. Rotational periods in Cygnus OB2
ID:
ivo://CDS.VizieR/J/A+A/603/A106
Title:
Rotational periods in Cygnus OB2
Short Name:
J/A+A/603/A106
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a near-infrared time-series photometry study in the field of Cygnus OB2 association (RA~20.55h, DE~41.2{deg}). Observations were carried out in the JHK bands at the WFCAM/UKIRT telescope over 112 observed nights. We investigated the occurrence of periodicity in the time-series and we found reliable periods for 894 candidate members.
4212. Rotation of field stars from CoRoT data
ID:
ivo://CDS.VizieR/J/MNRAS/424/11
Title:
Rotation of field stars from CoRoT data
Short Name:
J/MNRAS/424/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present period measurements of a large sample of field stars in the solar neighbourhood, observed by the COnvection ROtation and planetary Transits (CoRoT) satellite in two different directions of the Galaxy. The presence of a period was detected using the Lomb-Scargle normalized periodogram technique and the autocorrelation analysis. The assessment of the results has been performed through a consistency verification supported by the folded light-curve analysis. The data analysis procedure has discarded a non-negligible fraction of light curves due to instrumental artefacts; however, it has allowed us to identify pulsators and binaries among a large number of field stars. We measure a wide range of periods, from 0.25 to 100d, most of which are rotation periods. The final catalogue includes 1978 periods, with 1727 of them identified as rotational periods, 169 as pulsations and 82 as orbital periods of binary systems.
4213. Rotation periods and membership in M34
ID:
ivo://CDS.VizieR/J/ApJ/733/115
Title:
Rotation periods and membership in M34
Short Name:
J/ApJ/733/115
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a 5 month photometric time-series survey for stellar rotation periods combined with a 4 year radial-velocity survey for membership and binarity in the 220Myr open cluster M34. We report surface rotation periods for 120 stars, 83 of which are kinematic and photometric late-type cluster members. A comparison to previous work serves to illustrate the importance of high-cadence long baseline photometric observations and membership information. The new M34 periods are less biased against slow rotation and cleaned for non-members. The rotation periods of the cluster members span over more than an order of magnitude from 0.5 days up to 11.5 days, and trace two distinct rotational sequences -fast (C) and moderate-to-slow (I)- in the color-period diagram. The sequences represent two different states (fast and slow) in the rotational evolution of the late-type cluster members. We use the color-period diagrams for M34 and for younger and older clusters to estimate the timescale for the transition from the C to the I sequence and find <~150Myr, ~150-300Myr, and ~300-600 Myr for G, early-mid K, and late K dwarfs, respectively. The small number of stars in the gap between C and I suggests a quick transition. We determine a gyrochronology age of 240Myr for M34.
4214. Rotation periods for 171 Gaia members of NGC 6811
ID:
ivo://CDS.VizieR/J/ApJ/879/49
Title:
Rotation periods for 171 Gaia members of NGC 6811
Short Name:
J/ApJ/879/49
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stellar rotation was proposed as a potential age diagnostic that is precise, simple, and applicable to a broad range of low-mass stars (<=1M_{sun}_). Unfortunately, rotation period (P_rot_) measurements of low-mass members of open clusters have undermined the idea that stars spin down with a common age dependence (i.e., P_rot{propto}age^0.5^): K dwarfs appear to spin down more slowly than F and G dwarfs. Agueros+ (2018, J/ApJ/862/33) interpreted data for the ~1.4Gyr-old cluster NGC 752 differently, proposing that after having converged onto a slow-rotating sequence in their first 600-700Myr (by the age of Praesepe), K dwarf P_rot_ stall on that sequence for an extended period of time. We use data from Gaia DR2 to identify likely single-star members of the ~1Gyr-old cluster NGC 6811 with Kepler light curves. We measure P_rot_ for 171 members, more than doubling the sample relative to the existing catalog and extending the mass limit from ~0.8 to ~0.6M_{sun}_. We then apply a gyrochronology formula calibrated with Praesepe and the Sun to 27 single G dwarfs in NGC 6811 to derive a precise gyrochronological age for the cluster of 1.04+/-0.07Gyr. However, when our new low-mass rotators are included, NGC 6811's color-P_rot_ sequence deviates away from the naive 1Gyr projection down to T_eff_~4295K (K5V, 0.7M_{sun}), where it clearly overlaps with Praesepe's. Combining these data with P_rot_ for other clusters, we conclude that the assumption that mass and age are separable dependencies is invalid. Furthermore, the cluster data show definitively that stars experience a temporary epoch of reduced braking efficiency where P_rot_ stall, and that the duration of this epoch lasts longer for lower-mass stars.
4215. Rotation periods for NGC 3532
ID:
ivo://CDS.VizieR/J/A+A/652/A60
Title:
Rotation periods for NGC 3532
Short Name:
J/A+A/652/A60
Date:
22 Feb 2022
Publisher:
CDS
Description:
A very rich cluster intermediate in age between the Pleiades (150Myr) and the Hyades (600Myr) is needed to probe the rotational evolution, especially the transition between fast and slow rotation that occurs between the two ages. We study the rich 300Myr-old open cluster NGC 3532 to probe this important transition and to provide constraints on angular momentum loss. Measuring the rotation periods builds on our prior work of providing spectroscopic membership information for the cluster, and it supports the chromospheric activity measurements of cluster stars that we provide in a companion paper. Using 42d-long photometric time series observations obtained with the Yale 1m telescope at CTIO, we measured rotation periods for members of NGC 3532 and compared them with the predictions of angular momentum evolution models. We directly measured 176 photometric rotation periods for the cluster members. An additional 113 photometric rotation periods were identified using activity information, described fully in the companion paper, resulting in a total sample containing 279 rotation periods for FGKM stars in NGC 3532. The colour-period diagram constructed from this rich data set shows a well-populated and structured slow rotator sequence, and a fast rotator sequence evolved beyond zero-age main sequence age whose stars are in transition from fast to slow rotation. The slow rotator sequence itself is split into slightly slower and faster rotators, a feature we trace to photometric binary status. We also identify an extended slow rotator sequence extending to P~32d, apparently the analogue of the one we previously identified in NGC 2516. We compare our period distribution to rotational isochrones in colour-period space and find that all considered models have certain shortcomings. Using more detailed spin-down models, we evolve the rotation periods of the younger NGC 2516 forward in time and find that the spindown of the models is too aggressive with respect to the slow rotators. In contrast, stars on the evolved fast rotator sequence are not spun down strongly enough by these models. Our observations suggest a shorter crossing time for the rotational gap, one we estimate to be ~80Myr for early-K dwarfs.
4216. Rotation periods of 97 solar-like stars
ID:
ivo://CDS.VizieR/J/A+A/634/L9
Title:
Rotation periods of 97 solar-like stars
Short Name:
J/A+A/634/L9
Date:
21 Oct 2021
Publisher:
CDS
Description:
The accurate determination of stellar rotation periods is important for estimating stellar ages and for understanding stellar activity and evolution. While rotation periods can be determined for about thirty thousand stars in the Kepler field, there are over one hundred thousand stars, especially with low photometric variability and irregular pattern of variations, for which rotational periods are unknown. Here we investigate the effect of metallicity on the detectability of rotation periods. This is done by synthesising light curves of hypothetical stars that are identical to our Sun with the exception of the metallicity. These light curves are then used as an input to the period determination algorithms. We find that the success rate for recovering the rotation signal has a minimum close to the solar metallicity value. This can be explained by the compensation effect of facular and spot contributions. In addition, selecting solar-like stars with near-solar effective temperature and photometric variability, and with metallicity between M/H=-0.35 and M/H=0.35 from the Kepler sample, we analyse the fraction of stars for which rotational periods have been detected as a function of metallicity. In agreement with our theoretical estimate we find a local minimum for the detection fraction close to the solar metallicity. We further report rotation periods of 87 solar-like Kepler stars for the first time.
4217. r' photometry of Abell 1367 and Coma
ID:
ivo://CDS.VizieR/J/A+A/397/421
Title:
r' photometry of Abell 1367 and Coma
Short Name:
J/A+A/397/421
Date:
21 Oct 2021
Publisher:
CDS
Description:
We provide the total r'-band galaxy counts corresponding to our observed fields of the clusters of galaxies Abell 1367 and Coma, as well as the r'-band background counts from Yasuda et al. (2001AJ....122.1104Y). We also provide some basic properties of the galaxies detected in our r'-band survey of the clusters of galaxies Abell 1367 and Coma: coordinates, r'-band magnitudes and surface brightness, position angles, recession velocities and ellipticities are provided. The observations were carried out with the Wide Field Camera (WFC) attached to the Prime Focus of the INT 2.5m located at Observatorio de El Roque de los Muchachos, on 26 and 28 April 2000, under photometric conditions, excepting the last half of the second night.
4218. RRab stars toward Baade's window with Blanco/DECam
ID:
ivo://CDS.VizieR/J/ApJ/874/30
Title:
RRab stars toward Baade's window with Blanco/DECam
Short Name:
J/ApJ/874/30
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained repeated images of six fields toward the Galactic bulge in five passbands (u, g, r, i, z) with the DECam imager on the Blanco 4m telescope at CTIO. From more than 1.6 billion individual photometric measurements in the field centered on Baade's window, we have detected 4877 putative variable stars. A total of 474 of these have been confirmed as fundamental mode RR Lyrae stars, whose colors at minimum light yield line-of-sight reddening determinations, as well as a reddenning law toward the Galactic Bulge, which differs significantly from the standard R_V_=3.1 formulation. Assuming that the stellar mix is invariant over the 3 square-degree field, we are able to derive a line-of-sight reddening map with sub-arcminute resolution, enabling us to obtain de-reddened and extinction corrected color-magnitude diagrams (CMDs) of this bulge field using up to 2.5 million well-measured stars. The corrected CMDs show unprecedented detail and expose sparsely populated sequences: for example, delineation of the very wide red giant branch, structure within the red giant clump, the full extent of the horizontal branch, and a surprising bright feature that is likely due to stars with ages younger than 1Gyr. We use the RR Lyrae stars to trace the spatial structure of the ancient stars and find an exponential decline in density with Galactocentric distance. We discuss ways in which our data products can be used to explore the age and metallicity properties of the bulge, and how our larger list of all variables is useful for learning to interpret future LSST alerts.
4219. RRLs in globulars. IV. UBVRI photometry in Omega Cen
ID:
ivo://CDS.VizieR/J/AJ/152/170
Title:
RRLs in globulars. IV. UBVRI photometry in Omega Cen
Short Name:
J/AJ/152/170
Date:
21 Oct 2021
Publisher:
CDS
Description:
New accurate and homogeneous optical UBVRI photometry has been obtained for variable stars in the Galactic globular cluster {omega} Cen (NGC 5139). We secured 8202 CCD images covering a time interval of 24 years and a sky area of 84x48arcmin. The current data were complemented with data available in the literature and provided new, homogeneous pulsation parameters (mean magnitudes, luminosity amplitudes, periods) for 187 candidate {omega} Cen RR Lyrae (RRLs). Among them we have 101 RRc (first overtone) and 85 RRab (fundamental) variables, and a single candidate RRd (double-mode) variable. Candidate Blazhko RRLs show periods and colors that are intermediate between the RRc and RRab variables, suggesting that they are transitional objects. A comparison of the period distribution and the Bailey diagram indicates that RRLs in {omega} Cen show a long-period tail not present in typical Oosterhoff II (OoII) globulars. The RRLs in dwarf spheroidals and in ultra-faint dwarfs have properties between Oosterhoff intermediate and OoII clusters. Metallicity plays a key role in shaping the above evidence. These findings do not support the hypothesis that {omega} Cen is the core remnant of a spoiled dwarf galaxy. Using optical period-Wesenheit relations that are reddening-free and minimally dependent on metallicity we find a mean distance to {omega} Cen of 13.71+/-0.08+/-0.01mag (semi-empirical and theoretical calibrations). Finally, we invert the I-band period-luminosity-metallicity relation to estimate individual RRLs' metal abundances. The metallicity distribution agrees quite well with spectroscopic and photometric metallicity estimates available in the literature.
4220. RRLs in globulars. V.{omega} Centauri NIR photometry
ID:
ivo://CDS.VizieR/J/AJ/155/137
Title:
RRLs in globulars. V.{omega} Centauri NIR photometry
Short Name:
J/AJ/155/137
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new complete near-infrared (NIR, JHK_s_) census of RR Lyrae stars (RRLs) in the globular {omega} Cen (NGC 5139). We collected 15472 JHK_s_ images with 4-8 m class telescopes over 15 years (2000-2015) covering a sky area around the cluster center of 60x34 arcmin^2^. These images provided calibrated photometry for 182 out of the 198 cluster RRL candidates with 10 to 60 measurements per band. We also provide new homogeneous estimates of the photometric amplitude for 180 (J), 176 (H) and 174 (K_s_) RRLs. These data were supplemented with single-epoch JK_s_ magnitudes from VHS (Mcmahon et al. 2013Msngr.154...35M) and with single-epoch H magnitudes from 2MASS (Cat. VII/233). Using proprietary optical and NIR data together with new optical light curves (ASAS-SN) we also updated pulsation periods for 59 candidate RRLs. As a whole, we provide JHK_s_ magnitudes for 90 RRab (fundamentals), 103 RRc (first overtones) and one RRd (mixed-mode pulsator). We found that NIR/optical photometric amplitude ratios increase when moving from first overtone to fundamental and to long-period (P>0.7 days) fundamental RRLs. Using predicted period-luminosity-metallicity relations, we derive a true distance modulus of 13.674+/-0.008+/-0.038 mag (statistical error and standard deviation of the median) based on spectroscopic iron abundances, and of 13.698+/-0.004+/-0.048 mag based on photometric iron abundances. We also found evidence of possible systematics at the 5%-10% level in the zero-point of the period-luminosity relations based on the five calibrating RRLs whose parallaxes had been determined with the HST.