- ID:
- ivo://CDS.VizieR/J/AJ/124/1670
- Title:
- Post-T Tauri Stars in Sco-Cen Association
- Short Name:
- J/AJ/124/1670
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a spectroscopic survey of X-ray and proper-motion-selected samples of late-type stars in the Lower Centaurus-Crux (LCC) and Upper Centaurus-Lupus (UCL) subgroups of the nearest OB association: Scorpius-Centaurus. The primary goals of the survey are to determine the star formation history of the OB subgroups and to assess the frequency of accreting stars in a sample dominated by "post-T Tauri" pre-main-sequence (PMS) stars. We investigate two samples: (1) proper-motion candidates from the ACT Catalog (<I/246>) and Tycho Reference Catalog (TRC, <I/250>) with X-ray counterparts in the ROSAT All-Sky Survey (RASS) Bright Source Catalog and (2) G- and K-type stars in the Hipparcos catalog found to be candidate members by de Zeeuw et al. (1999, Cat. <J/AJ/117/354>). We obtained optical spectra of 130 candidates with the Siding Spring 2.3m dual-beam spectrograph.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/442/2081
- Title:
- Praesepe members light curves
- Short Name:
- J/MNRAS/442/2081
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By using the dense coverage of the extrasolar planet survey project HATNet (Hungarian-made Automated Telescope Network), we Fourier analyse 381 high-probability members of the nearby open cluster Praesepe (Beehive/M44/NGC 2632). In addition to the detection of 10 variables (of delta Scuti and other types), we identify 180 rotational variables (including the two known planet hosts). This sample increases the number of known rotational variables in this cluster for spectral classes earlier than M by more than a factor of 3. These stars closely follow a colour/magnitude - period relation from early F to late K stars. We approximate this relation by polynomials for an easier reference to the rotational characteristics in different colours. The total (peak-to-peak) amplitudes of the large majority (94%) of these variables span the range of 0.005-0.04mag. The periods cover a range from 2.5 to 15d. These data strongly confirm that Praesepe and the Hyades have the same gyrochronological ages. Regarding the two planet hosts, Pr0211 (the one with the shorter orbital period) has a rotational period that is ~2d shorter than the one expected from the main rotational pattern in this cluster. This, together with other examples discussed in the paper, may hint that star-planet interaction via tidal dissipation can be significant in some cases in the rotational evolution of stars hosting hot Jupiters.
- ID:
- ivo://CDS.VizieR/J/ApJ/842/83
- Title:
- Praesepe members rotational periods from K2 LCs
- Short Name:
- J/ApJ/842/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze K2 light curves for 794 low-mass (1>~M_*_>~0.1M_{sun}_) members of the ~650Myr old open cluster Praesepe and measure rotation periods (P_rot_) for 677 of these stars. We find that half of the rapidly rotating >~0.3M_{sun}_ stars are confirmed or candidate binary systems. The remaining >~0.3M_{sun}_ fast rotators have not been searched for companions, and are therefore not confirmed single stars. We previously found that nearly all rapidly rotating 0.3M_{sun}_ stars in the Hyades are binaries, but we require deeper binary searches in Praesepe to confirm whether binaries in these two co-eval clusters have different P_rot_ distributions. We also compare the observed P_rot_ distribution in Praesepe to that predicted by models of angular-momentum evolution. We do not observe the clear bimodal P_rot_ distribution predicted by Brown (2014ApJ...789..101B) for >0.5M_{sun}_ stars at the age of Praesepe, but 0.25-0.5M_{sun}_ stars do show stronger bimodality. In addition, we find that >60% of early M dwarfs in Praesepe rotate more slowly than predicted at 650Myr by Matt+ (2015ApJ...799L..23M), which suggests an increase in braking efficiency for these stars relative to solar-type stars and fully convective stars. The incompleteness of surveys for binaries in open clusters likely impacts our comparison with these models since the models only attempt to describe the evolution of isolated single stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/347/101
- Title:
- Precision colour-magnitude diagram of M67
- Short Name:
- J/MNRAS/347/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have calibrated and combined an extensive set of BVI observations of M67 to produce a colour-magnitude diagram of stars measured with high relative precision. We have selected stars that are most likely to be single-star members of the cluster using proper motion, radial velocity, and variability information from the literature, and an examination of the most probable colour-magnitude diagram locations of unresolved stellar blends. We have made detailed comparisons of our photometry of the selected stars with theoretical models, and discuss the most notable discrepancies. Observations of M67 turn-off stars are a severe test of algorithms attempting to describe convective cores in the limit of small extent, and we find strong evidence of a 'hook' just fainter than the turn-off gap. The stars in M67 support assertions that the degree of convective core overshooting decreases to zero for stars with masses in the range 1.0<(M/M_{sun}_)<=1.5, but that the degree of overshoot is smaller than currently used in published isochrones. We also verify that all current theoretical models for the lower main sequence (with the exception of Baraffe et al., 1998, Cat. J/A+A/337/403) are too blue for MV>~6, even when the sequences are shifted to match M67 near the MV of the Sun, probably due to a combination of problems with colour-Teff transformations and realistic surface boundary conditions for models. Finally, we identify a subset of cluster members with unusual photometry (candidate red giant binaries, blue straggler stars, and triple systems) deserving of further study.
- ID:
- ivo://CDS.VizieR/J/AJ/160/221
- Title:
- Predicted planetary yields of gap transitional disks
- Short Name:
- J/AJ/160/221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a massive accreting gap planet model that ensures large gaps in transitional disks are kept dust free by the scattering action of three coplanar quasi-circular planets in a 1:2:4 mean motion resonance (MMR). This model uses the constraint of the observed gap size, and the dust-free nature of the gap, to determine within ~10% the possible orbits for three massive planets in an MMR. Calculated orbits are consistent with the observed orbits and H{alpha} emission (the brightest line to observe these planets) for LkCa15b, PDS70b, and PDS70c within observational errors. Moreover, the model suggests that the scarcity of detected H{alpha} planets is likely a selection effect of the current limitations of non-coronagraphic, low (<10%) Strehl, H{alpha} imaging with adaptive optics (AO) systems used in past H{alpha} surveys. We predict that as higher Strehl AO systems (with high- performance custom coronagraphs; like the 6.5m Magellan Telescope MagAO-X system) are utilized at H{alpha}, the number of detected gap planets will substantially increase by more than tenfold. For example, we show that >25{+/-}5 new H{alpha} "gap planets" are potentially discoverable by a survey of the best 19 transitional disks with MagAO-X. Detections of these accreting protoplanets will significantly improve our understanding of planet formation, planet growth and accretion, solar system architectures, and planet-disk interactions.
- ID:
- ivo://CDS.VizieR/J/AJ/140/925
- Title:
- Pre-eruption light curves for Nova U Sco
- Short Name:
- J/AJ/140/925
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery by B.G. Harris and S. Dvorak on JD 2455224.9385 (2010 January 28.4385 UT) of the predicted eruption of the recurrent nova U Scorpii (U Sco). We also report 815 magnitudes (and 16 useful limits) on the pre-eruption light curve in the UBVRI and Sloan r' and i' bands from 2000.4 up to 9hr before the peak of the 2010 January eruption.
- ID:
- ivo://CDS.VizieR/J/ApJ/658/480
- Title:
- Pre-main-sequence stars in Lupus association
- Short Name:
- J/ApJ/658/480
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kinematical analysis of spectroscopically identified pre-main-sequence stars associated with the Lupus dark cloud reveals a streamlike motion of low internal velocity dispersion (<=1.3km/s). A statistically significant mismatch between the convergent point radial velocity and the spectroscopic radial velocity from the literature indicates a moderate degree of expansion. The rate of expansion is too low to account for the present extent of the association if one assumes that the spatially dispersed population was formed in the dense molecular cores observed today. Therefore, it is unlikely that the outlying weak-lined T Tauri members were born in the same star-forming cores as the more compactly located classical T Tauri stars, despite the kinematic integrity of the association. Distances inferred from the classical moving-cluster method show a large depth of the association (~80pc) along the line of sight. A color-magnitude diagram of the association in the near-IR colors corrected for the distribution of distances shows a clear gap separating the older (5-27Myr) and the younger (~1Myr) generations of stars. Half of the identified 1Myr old stars lie in the tight group of mostly classical T Tauri stars associated with the Lupus 3 dark filament. This nest of very young stars appears to be 25pc farther from the Sun than the center of the greater Lupus association.
- ID:
- ivo://CDS.VizieR/J/ApJ/800/120
- Title:
- Profiles of z<0.5 galaxies with Pan-STARRS1
- Short Name:
- J/ApJ/800/120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an analysis of Pan-STARRS1 Medium Deep Survey multi-band (grizy) images of a sample of 698 low-redshift disk galaxies that span broad ranges in stellar mass, star-formation rate, and bulge/disk ratio. We use population synthesis spectral energy distribution fitting techniques to explore the radial distribution of the light, color, surface mass density, mass/light ratio, and age of the stellar populations. We characterize the structure and stellar content of the galaxy disks out to radii of about twice Petrosian r_90_, beyond which the halo light becomes significant. We measure normalized radial profiles for sub-samples of galaxies in three bins each of stellar mass and concentration. We also fit radial profiles to each galaxy. The majority of galaxies have down-bending radial surface brightness profiles in the bluer bands with a break radius at roughly r_90_. However, they typically show single unbroken exponentials in the reddest bands and in the stellar surface mass density. We find that the mass/light ratio and stellar age radial profiles have a characteristic "U" shape. There is a good correlation between the amplitude of the down-bend in the surface brightness profile and the rate of the increase in the M/L ratio in the outer disk. As we move from late- to early-type galaxies, the amplitude of the down-bend and the radial gradient in M/L both decrease. Our results imply a combination of stellar radial migration and suppression of recent star formation can account for the stellar populations of the outer disk.
- ID:
- ivo://CDS.VizieR/J/A+A/451/901
- Title:
- Proper motion and BV photometry in Trumpler 2
- Short Name:
- J/A+A/451/901
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a complex study of the galactic open cluster Trumpler 2 are presented. In order to obtain the proper motions, the positions of approximately 3000 stars up to the limit magnitude B~16.25mag in the area 80'x80' around the cluster were measured on 6 plates with a maximal epoch difference of 63-years. The root-mean error of the relative proper motions is 4.2mas/yr. The catalogue of BV magnitudes of all the stars in the investigated area was compiled. The selection of the cluster members within the region of R<16 arcmin from the center of the cluster was made. Altogether, 148 stars were considered to be cluster members by both astrometrical and photometrical criteria. We present the estimated age (8.91E+07) and physical parameters of the cluster and append the catalogues of the proper motions and of the photometry of the stars.
- ID:
- ivo://CDS.VizieR/J/AJ/129/2420
- Title:
- Proper motion derivatives of binaries
- Short Name:
- J/AJ/129/2420
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Useful constraints on the orbits and mass ratios of astrometric binaries in the Hipparcos catalog are derived from the measured proper motion differences of Hipparcos and Tycho-2 ({Delta}{mu}), accelerations of proper motions (d{mu}/dt) and second derivatives of proper motions (d^2^{mu}/dt^2^). It is shown how, in some cases, statistical bounds can be estimated for the masses of the secondary components. Two catalogs of astrometric binaries are generated, one of binaries with significant proper motion differences and the other of binaries with significant accelerations of their proper motions.
