- ID:
- ivo://CDS.VizieR/J/ApJ/862/33
- Title:
- Improved & expanded membership catalog for NGC752
- Short Name:
- J/ApJ/862/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nearby open cluster NGC 752 presents a rare opportunity to study stellar properties at ages >1Gyr. However, constructing a membership catalog for it is challenging; most surveys have been limited to identifying its giants and dwarf members earlier than mid-K. We supplement past membership catalogs with candidates selected with updated photometric and proper-motion criteria, generating a list of 258 members, a >50% increase over previous catalogs. Using a Bayesian framework to fit MESA Isochrones & Stellar Tracks evolutionary models to literature photometry and the Tycho-Gaia Astrometric Solution data available for 59 cluster members, we infer the age of and distance to NGC 752: 1.34+/-0.06Gyr and 438_-6_^+8^pc. We also report the results of our optical monitoring of the cluster using the Palomar Transient Factory. We obtain rotation periods for 12 K and M cluster members, the first periods measured for such low-mass stars with a well-constrained age >1Gyr. We compare these new periods to data from the younger clusters Praesepe and NGC 6811, and to a theoretical model for angular momentum loss, to examine stellar spin-down for low-mass stars over their first 1.3Gyr. While on average NGC 752 stars are rotating more slowly than their younger counterparts, the difference is not significant. Finally, we use our spectroscopic observations to measure H{alpha} for cluster stars, finding that members earlier than ~M2 are magnetically inactive, as expected at this age. Forthcoming Gaia data should solidify and extend the membership of NGC 752 to lower masses, thereby increasing its importance for studies of low-mass stars.
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- ID:
- ivo://CDS.VizieR/J/ApJS/230/9
- Title:
- Improved multi-band photometry from SERVS
- Short Name:
- J/ApJS/230/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply The Tractor image modeling code to improve upon existing multi-band photometry for the Spitzer Extragalactic Representative Volume Survey (SERVS). SERVS consists of post-cryogenic Spitzer observations at 3.6 and 4.5{mu}m over five well-studied deep fields spanning 18deg^2^. In concert with data from ground-based near-infrared (NIR) and optical surveys, SERVS aims to provide a census of the properties of massive galaxies out to z~5. To accomplish this, we are using The Tractor to perform "forced photometry." This technique employs prior measurements of source positions and surface brightness profiles from a high-resolution fiducial band from the VISTA Deep Extragalactic Observations survey to model and fit the fluxes at lower-resolution bands. We discuss our implementation of The Tractor over a square-degree test region within the XMM Large Scale Structure field with deep imaging in 12 NIR/optical bands. Our new multi-band source catalogs offer a number of advantages over traditional position-matched catalogs, including (G1) consistent source cross-identification between bands, (2) de-blending of sources that are clearly resolved in the fiducial band but blended in the lower resolution SERVS data, (3) a higher source detection fraction in each band, (4) a larger number of candidate galaxies in the redshift range 5<z<6, and (5) a statistically significant improvement in the photometric redshift accuracy as evidenced by the significant decrease in the fraction of outliers compared to spectroscopic redshifts. Thus, forced photometry using The Tractor offers a means of improving the accuracy of multi-band extragalactic surveys designed for galaxy evolution studies. We will extend our application of this technique to the full SERVS footprint in the future.
- ID:
- ivo://CDS.VizieR/J/AJ/119/1448
- Title:
- Improved properties for cool stars
- Short Name:
- J/AJ/119/1448
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new grids of colors and bolometric corrections for F-K stars having 4000 K {<=} Teff {<=} 6500 K, 0.0 {<=} log(g) {<=} 4.5, and -3.0 {<=} [Fe/H] {<=} 0.0. Colors are tabulated for Johnson U-V and B-V, Cousins V-R and V-I, Johnson-Glass V-K, J-K, and H-K, and CIT/CTIO V-K, J-K, H-K, and CO. We have developed these color-temperature relations by convolving synthetic spectra with the best-determined, photometric filter transmission profiles. The synthetic spectra have been computed with the SSG spectral synthesis code (Bell & Gustafsson 1978; Gustafsson & Bell 1979) using MARCS stellar atmosphere models (Gustafsson et al. 1975; Bell et al. 1976) as input. Both of these codes have been improved substantially, especially at low temperatures, through the incorporation of new opacity data. The resulting synthetic colors have been put onto the observational systems by applying color calibrations derived from models and photometry of field stars that have effective temperatures determined by the infrared flux method. These color calibrations have zero points that change most of the original synthetic colors by less than 0.02 mag, and the corresponding slopes generally alter the colors by less than 5%.
- ID:
- ivo://CDS.VizieR/J/ApJ/842/42
- Title:
- Improved reddenings for 59 Galactic Cepheids
- Short Name:
- J/ApJ/842/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new photometric method by which improved high-precision reddenings and true distance moduli can be determined to individual Galactic Cepheids once distance measurements are available. We illustrate that the relative positioning of stars in the Cepheid period-luminosity (PL) relation (Leavitt law) is preserved as a function of wavelength. This information then provides a powerful constraint for determining reddenings to individual Cepheids, as well as their distances. As a first step, we apply this method to the 59 Cepheids in the compilation of Fouque et al. Updated reddenings, distance moduli (or parallaxes), and absolute magnitudes in seven (optical through near-infrared) bands are given. From these intrinsic quantities, multiwavelength PL and color-color relations are derived. We find that the V-band period-luminosity-color relation has an rms scatter of only 0.06mag, so that individual Cepheid distances can be measured to 3%, compared with dispersions of 6 to 13% for the one-parameter K through B PL relations, respectively. This method will be especially useful in conjunction with the new accurate parallax sample upcoming from Gaia.
- ID:
- ivo://CDS.VizieR/J/ApJ/707/671
- Title:
- IM Vir BVRI photometry and radial velocities
- Short Name:
- J/ApJ/707/671
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report extensive spectroscopic and differential photometric BVRI observations of the active, detached, 1.309-day double-lined eclipsing binary IM Vir, composed of a G7-type primary and a K7 secondary. With these observations, we derive accurate absolute masses and radii of M1=0.981+/-0.012M_{sun}_, M2=0.6644+/-0.0048M_{sun}_, R1=1.061+/-0.016R_{sun}_, and R2=0.681+/-0.013R_{sun}_ for the primary and secondary, with relative errors under 2%. The effective temperatures are 5570+/-100K and 4250+/-130K, respectively. The significant difference in mass makes this a favorable case for comparison with stellar evolution theory. We find that both stars are larger than the models predict, by 3.7% for the primary and 7.5% for the secondary, as well as cooler than expected, by 100K and 150K, respectively. These discrepancies are in line with previously reported differences in low-mass stars, and are believed to be caused by chromospheric activity, which is not accounted for in current models. The effect is not confined to low-mass stars: the rapidly rotating primary of IM Vir joins the growing list of objects of near-solar mass (but still with convective envelopes) that show similar anomalies. The comparison with the models suggests an age of 2.4Gyr for the system, and a metallicity of [Fe/H]~-0.3 that is consistent with other indications, but requires confirmation.
- ID:
- ivo://CDS.VizieR/II/154
- Title:
- Individual UBV Observations of LSS Stars
- Short Name:
- II/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBV Photometry of Stars from "Luminous Stars in the Southern Milky Way" by J.S. Drilling, Louisiana State University Observatory, 22 July 1989.
- ID:
- ivo://CDS.VizieR/J/PAZh/31/332
- Title:
- Infrared Luminosities of Local Galaxies
- Short Name:
- J/PAZh/31/332
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on data from 2MASS (<II/246>) we analyzed the infrared properties of 451 Local-Volume galaxies at distances D<=10Mpc.
- ID:
- ivo://CDS.VizieR/J/AJ/104/1349
- Title:
- Infrared-luminous giants in M32
- Short Name:
- J/AJ/104/1349
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A previously unknown population of very luminous, red, asymptotic-giant-branch stars has been identified as a result of near-infrared (JHK) imaging in the dwarf elliptical galaxy M32. Situated above the tip of the normal first red giant branch, these stars are intrinsically brighter than the most luminous normal giants in old Galactic globular clusters by approximately 2 bolometric magnitudes. Moreover, they are a full bolometric magnitude brighter than the brightest giants observed in our own Galactic bulge. Several possible explanations for this population are examined, including old long-period variables, binary mergers, supermetallicity, and intermediate-age stars. It is suggested that the simplest explanation at present, is that M32 had a star formation episode less than about 5 billion years ago. These stars would then be the evolved extended asymptotic giant branch population resulting from that event (similar to those stars observed in the intermediate-age clusters in the Magellanic Clouds). This population may be similar to that in the M31 bulge, recently observed by Rich and Mould. The detection of a young component in M32 is of particular interest because historically, M32 has been a fiducial galaxy for population synthesis techniques. An understanding of M32 remains crucial for our understanding of distant and more luminous elliptical galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A100
- Title:
- Infrared massive stellar content of M83
- Short Name:
- J/A+A/578/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of point sources in the field of M83. Sources were first cataloged that were found in both Spitzer IRAC 3.6-micron and 4.5-micron images. These were then supplemented with 5.8 and 8.0-micron photometry. Ground-based near-IR photometry in J and Ks-bands were extracted from imaging from the FourStar camera on the Baade Magellan Telescope at Las Campanas Observatory. Optical photometry was extracted from Hubble Space Telescope Wide Field Camera 3 observations of seven fields covering much of the bright disk region of M83.
- ID:
- ivo://CDS.VizieR/J/AJ/160/268
- Title:
- Infrared photometry of binaries in Orion OB1
- Short Name:
- J/AJ/160/268
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Statistics of low-mass pre-main-sequence binaries in the Orion OB1 association with separations ranging from 0.6" to 20" (220 to 7400au at 370pc) are studied using images from the VISTA Orion mini survey and astrometry from Gaia. The input sample based on the CVSO catalog contains 1137 stars of K and M spectral types (masses between 0.3 and 0.9M{odot}), 1021 of which are considered to be association members. There are 135 physical binary companions to these stars with mass ratios above ~0.13. The average companion fraction is 0.09{+/-}0.01 over 1.2 decades in separation, slightly less than, but still consistent with, the field. We found a difference between the Ori OB1a and OB1b groups, the latter being richer in binaries by a factor of 1.6{+/-}0.3. No overall dependence of the wide- binary frequency on the observed underlying stellar density is found, although in the Ori OB1a off-cloud population, these binaries seem to avoid dense clusters. The multiplicity rates in Ori OB1 and in sparse regions like Taurus differ significantly, hinting that binaries in the field may originate from a mixture of diverse populations.
