- ID:
- ivo://CDS.VizieR/J/AJ/159/282
- Title:
- Membership in Ophiuchus & Upper Scorpius complex
- Short Name:
- J/AJ/159/282
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a survey for new members of the Ophiuchus cloud complex using high-precision astrometry from the second data release of Gaia, proper motions measured with multi-epoch images from the Spitzer Space Telescope, and color-magnitude diagrams constructed with photometry from various sources. Through spectroscopy of candidates selected with those data, we have identified 155 new young stars. Based on available measurements of kinematics, we classify 102, 47, and 6 of those stars as members of Ophiuchus, Upper Sco, and other populations in Sco-Cen, respectively. We have also assessed the membership of all other stars in the vicinity of Ophiuchus that have spectroscopic evidence of youth from previous studies, arriving at a catalog of 373 adopted members of the cloud complex. For those adopted members, we have compiled mid-infrared photometry from Spitzer and the Wide-field Infrared Survey Explorer and have used mid-infrared colors to identify and classify circumstellar disks. We find that 210 of the members show evidence of disks, including 48 disks that are in advanced stages of evolution. Finally, we have estimated the relative median ages of the populations near the Ophiuchus clouds and the surrounding Upper Sco association using absolute K-band magnitudes (MK) based on Gaia parallaxes. If we adopt an age 10Myr for Upper Sco, then the relative values of MK imply median ages of ~2Myr for L1689 and embedded stars in L1688, 3-4Myr for low-extinction stars near L1688, and ~6Myr for the group containing {rho}Oph.
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- ID:
- ivo://CDS.VizieR/J/AJ/159/166
- Title:
- Membership & properties of moving groups with Gaia
- Short Name:
- J/AJ/159/166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the membership probability of young stars belonging to nearby moving groups with Gaia DR2 data. The sample of 1429 stars was identified from "The Catalog of Suspected Nearby Young Moving Group Stars" (CSNYMGS; see Riedel+, J/AJ/153/95). Good-quality parallax and proper motion values were retrieved for 890 stars from the Gaia DR2 database. The analysis for membership probability is performed in the framework of the LACEwING algorithm (Riedel 2016IAUS..314...33R). From the analysis it is confirmed that 279 stars do not belong to any of the known moving groups. We estimated the U, V, W space velocity values for 250 moving group members, which were found to be more accurate than previous values listed in the literature. The velocity ellipses of all the moving groups are well constrained within the "good box," a widely used criterion to identify moving group members. The age of moving group members are uniformly estimated from the analysis of the Gaia color-magnitude diagram with MIST isochrones. We found a spread in the age distribution of stars belonging to some moving groups, which needs to be understood from further studies.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/87
- Title:
- Members of the young open cluster IC 2395
- Short Name:
- J/ApJ/832/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new deep UBVRI images and high-resolution multi-object optical spectroscopy of the young (~6-10Myr old), relatively nearby (800pc) open cluster IC 2395. We identify nearly 300 cluster members and use the photometry to estimate their spectral types, which extend from early B to middle M. We also present an infrared imaging survey of the central region using the IRAC and MIPS instruments on board the Spitzer Space Telescope, covering the wavelength range from 3.6 to 24{mu}m. Our infrared observations allow us to detect dust in circumstellar disks originating over a typical range of radii from ~0.1 to ~10 au from the central star. We identify 18 Class II, 8 transitional disk, and 23 debris disk candidates, respectively, 6.5%, 2.9%, and 8.3% of the cluster members with appropriate data. We apply the same criteria for transitional disk identification to 19 other stellar clusters and associations spanning ages from ~1 to ~18Myr. We find that the number of disks in the transitional phase as a fraction of the total with strong 24{mu}m excesses ([8]-[24]>=1.5) increases from (8.4+/-1.3)% at ~3Myr to (46+/-5)% at ~10Myr. Alternative definitions of transitional disks will yield different percentages but should show the same trend.
- ID:
- ivo://CDS.VizieR/J/ApJ/871/151
- Title:
- METAL Hubble program. I. Initial results
- Short Name:
- J/ApJ/871/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Metal Evolution, Transport, and Abundance in the Large Magellanic Cloud (METAL) is a large cycle 24 program on the Hubble Space Telescope aimed at measuring dust extinction properties and interstellar depletions in the Large Magellanic Cloud (LMC) at half-solar metallicity. The 101-orbit program is composed of Cosmic Origins Spectrograph (COS) and Space Telescope Imaging Spectrograph (STIS) spectroscopy toward 33 LMC massive stars between 1150 and 3180{AA} and parallel Wide Field Camera 3 (WFC3) imaging in seven near-UV to near-IR filters. The fraction of silicon in the gas phase (depletion) obtained from the spectroscopy decreases with increasing hydrogen column density. Depletion patterns for silicon differ between the Milky Way, LMC, and Small Magellanic Cloud (SMC), with the silicon depletion level offsetting almost exactly the metallicity differences, leading to constant gas-phase abundances in those galaxies for a given hydrogen column density. The silicon depletion correlates linearly with the absolute-to-selective extinction, RV, indicating a link between gas depletion and dust grain size. Extinction maps are derived from the resolved stellar photometry in the parallel imaging, which can be compared to far-IR images from Herschel and Spitzer to estimate the emissivity of dust at LMC metallicity. The full METAL sample of depletions, UV extinction curves, and extinction maps will inform the abundance, size, composition, and optical properties of dust grains in the LMC, comprehensively improve our understanding of dust properties, and improve the accuracy with which dust-based gas masses, star formation rates, and star formation histories in nearby and high-redshift galaxies are estimated. This overview paper describes the goals, design, data reduction, and initial results of the METAL survey.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/1627
- Title:
- Mid-IR photometry of cold brown dwarfs
- Short Name:
- J/ApJ/710/1627
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new Spitzer Infrared Array Camera (IRAC) photometry of 12 very late-type T dwarfs: nine have [3.6], [4.5], [5.8], and [8.0] photometry and three have [3.6] and [4.5] photometry only. Combining this with previously published photometry, we investigate trends with type and color that are useful for both the planning and interpretation of infrared surveys designed to discover the coldest T or Y dwarfs. The online appendix provides a collation of MKO-system YJHKL'M' and IRAC photometry for a sample of M, L, and T dwarfs. There are 12 dwarfs currently known with H-[4.5]>3.0, and 500K<~T_eff_<~800K, which we examine in detail. The ages of the dwarfs in the sample range from very young (0.1-1.0Gyr) to relatively old (3-12Gyr). The mass range is possibly as low as 5 Jupiter masses to up to 70 Jupiter masses, i.e., near the hydrogen burning limit. The metallicities also span a large range, from [m/H]=-0.3 to [m/H]=+0.3.
- ID:
- ivo://CDS.VizieR/J/AJ/158/75
- Title:
- Mid-type M dwarfs planet occurrence rates
- Short Name:
- J/AJ/158/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous studies of planet occurrence rates largely relied on photometric stellar characterizations. In this paper, we present planet occurrence rates for mid-type M dwarfs using spectroscopy, parallaxes, and photometry to determine stellar characteristics. Our spectroscopic observations have allowed us to constrain spectral type, temperatures, and, in some cases, metallicities for 337 out of 561 probable mid-type M dwarfs in the primary Kepler field. We use a random forest classifier to assign a spectral type to the remaining 224 stars. Combining our data with Gaia parallaxes, we compute precise (~3%) stellar radii and masses, which we use to update planet parameters and occurrence rates for Kepler mid-type M dwarfs. Within the Kepler field, there are seven M3 V to M5 V stars that host 13 confirmed planets between 0.5 and 2.5 Earth radii and at orbital periods between 0.5 and 10 days. For this population, we compute a planet occurrence rate of 1.19_-0.49_^+0.70^ planets per star. For M3 V, M4 V, and M5 V, we compute planet occurrence rates of 0.86_-0.68_^+1.32^, 1.36_-1.02_^+2.30^, and 3.07_-2.49_^+5.49^ planets per star, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJS/232/16
- Title:
- Mira stars discovered in LAMOST DR4
- Short Name:
- J/ApJS/232/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on an extensive spectral study of a photometrically confirmed sample of Mira variables, we find a relationship between the relative Balmer emission-line strengths and spectral temperatures of O-rich Mira stars. The F_H{delta}_/F_H{gamma}_ flux ratio increases from less than unity to five as stars cool down from M0 to M10, which is likely driven by increasing TiO absorption above the deepest shock-emitting regions. We also discuss the relationship between the equivalent widths of the Balmer emission lines and the photometric luminosity phase of our Mira sample stars. Using our 291 Mira spectra as templates for reference, 191 Mira candidates are newly identified from the LAMOST DR4 catalog. We summarize the criteria adopted to select Mira candidates based on emission-line indices and molecular absorption bands. This enlarged spectral sample of Mira variables has the potential to contribute significantly to our knowledge of the optical properties of Mira stars and will facilitate further studies of these late-type, long-period variables.
- ID:
- ivo://CDS.VizieR/III/23B
- Title:
- MK Classification for OB Stars
- Short Name:
- III/23B
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog is a compilation of MK spectral types published in the paper, "The kinematics of the Gould Belt: An Expanding Group?" (Rountree Lesh 1968). Spectral types were determined for 464 stars of Henry Draper type B5 and earlier, brighter than 6.5 visual magnitude and higher than -20 degrees in declination. The spectra were classified by the author using plates taken with the Yerkes 40-inch refractor and MK spectrograph. The catalog contains HR, HD numbers, MK types with temperature classes, subclasses, luminosity classes and peculiarities, and remarks.
- ID:
- ivo://CDS.VizieR/J/ApJS/176/216
- Title:
- MK spectral types of Visual Multiples
- Short Name:
- J/ApJS/176/216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this third of three parts of MK classifications of the components brighter than about B=8mag in Aitken's Catalogue (ADS, 1932) new classifications are given for 546 stars. Included in this section are 15 Ap stars, 33 Am stars, 18 stars with composite spectra, three stars with shell spectra, and two SB2s.
200. MK Standard Stars
- ID:
- ivo://CDS.VizieR/III/149
- Title:
- MK Standard Stars
- Short Name:
- III/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The purpose of the present work is to provide a complete list of MK standard stars, selected from the main papers related to this subject, according to the recommendations of both authors of the MK system. The catalogue provides a list of 963 standard stars, with their spectral type, luminosity, equatorial coordinates, magnitudes, colour index (B-V), and references. The magnitude and colours were taken from Mermillod (1986) UBV Photoelectric Photometry Catalogue (catalog <II/122>). In the cases without observations with the UBV catalogue, the apparent magnitude was taken from the SIMBAD data-base (SIMBAD is described at <http://cdsweb.u-strasbg.fr/Simbad.html>)
