- ID:
- ivo://CDS.VizieR/J/AJ/161/149
- Title:
- Vilnius photometry in IC 59 and IC 63
- Short Name:
- J/AJ/161/149
- Date:
- 20 Jan 2022
- Publisher:
- CDS
- Description:
- Optical and infrared continuum polarization from the interstellar medium is driven by radiative processes aligning the grains with the magnetic field. While a quantitative, predictive theory of radiative alignment torques (RATs) exists and has been extensively tested, several parameters of the theory remain to be fully constrained. In a recent paper, Medan & Andersson showed that the polarization efficiency (and therefore grain alignment efficiency) at different locations in the wall of the Local Bubble (LB) could be modeled as proportional to the integrated light intensity from the surrounding stars and OB associations. Here we probe that relationship at high radiation field intensities by studying the extinction and polarization in the two reflection nebulae IC59 and IC63 in the Sh2-185 HII region, illuminated by the B0 IV star {gamma}Cassiopeia. We combine archival visual polarimetry with new seven-band photometry in the Vilnius system, to derive the polarization efficiency from the material. We find that the same linear relationship seen in the LB wall also applies to the Sh2-185 region, strengthening the conclusion from the earlier study.
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- ID:
- ivo://CDS.VizieR/J/ApJS/186/191
- Title:
- VI photometry and spectroscopy in h+{chi} Per
- Short Name:
- J/ApJS/186/191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From photometric observations of ~47000 stars and spectroscopy of ~11000 stars, we describe the first extensive study of the stellar population of the famous Double Cluster, h and {chi} Persei, down to subsolar masses. By analyzing optical spectra and optical/infrared photometry, we constrain the distance moduli (dM), reddening (E(B-V)), and ages for h Persei, {chi} Persei, and the low-density halo population surrounding both cluster cores. With the exception of mass and spatial distribution, the clusters are nearly identical in every measurable way. From these data, we establish the first spectroscopic and photometric membership lists of cluster stars down to early/mid M dwarfs. At minimum, there are ~5000 members within 10' of the cluster centers, while the entire h and {chi} Persei region has at least ~13000 and as many as 20000 members. The Double Cluster contains ~8400M_{sun}_ of stars within 10' of the cluster centers. We estimate a total mass of at least 20000M_{sun}_. We conclude our study by outlining outstanding questions regarding the past and present properties of h and {chi} Persei. From comparing recent work, we compile a list of intrinsic colors and derive a new effective temperature scale for O-M dwarfs, giants, and supergiants.
- ID:
- ivo://CDS.VizieR/J/AJ/153/115
- Title:
- VLT/SINFONI observations of MIPSGAL "bubbles"
- Short Name:
- J/AJ/153/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Very Large Telescope/Spectrograph for INtegral Field Observations in the Near Infrared H- and K-band spectra of potential central stars within the inner 8"-by-8" regions of 55 MIPSGAL "bubbles" (MBs), sub-arcminute circumstellar shells discovered in the mid-IR survey of the Galactic plane with Spitzer/MIPS. At magnitudes brighter than 15, we detect a total of 230 stars in the K band and 179 stars in the H band. We spectrally identify 145 stars in all but three MBs, with average magnitudes of 13.8 and 12.7 respectively, using spectral libraries and previous studies of near-IR stellar spectra. We also use tabulated intrinsic stellar magnitudes and colors to derive distances and extinction values, and to better constrain the classifications of the stars. We reliably identify the central sources for 21 of the 55 MBs, which we classify as follows: one Wolf-Rayet, three luminous blue variable candidates, four early-type (O to F), and 15 late-type (G to M) stars. The 21 central sources are, on average, one magnitude fainter than these in the most recent study of MBs, and we notice a significant drop in the fraction of massive star candidates. For the 34 remaining MBs in our sample, we are unable to identify the central sources due to confusion, low spectroscopic signal-to-noise ratio, and/or lack of detections in the images near the centers of the bubbles. We discuss how our findings compare with previous studies and support the trend, for the most part, between the shells' morphologies in the mid-IR and central sources spectral types.
- ID:
- ivo://CDS.VizieR/J/A+A/485/41
- Title:
- VLT spectroscopy of blue massive stars in NGC55
- Short Name:
- J/A+A/485/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first paper of a series devoted to studying the population of blue massive stars in NGC 55, a galaxy of the Sculptor group at a distance of about 2Mpc. We have obtained optical (3300-6210{AA}), low-resolution spectra of approximately 200 blue massive stars with VLT-FORS2, which we have classified with the aid of Milky Way and Magellanic Cloud standard stars.
- ID:
- ivo://CDS.VizieR/J/AJ/161/42
- Title:
- Volume-limited sample of cool dwarfs. I. L0-T8 dwarfs
- Short Name:
- J/AJ/161/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new volume-limited sample of L0-T8 dwarfs out to 25pc defined entirely by parallaxes, using our recent measurements from UKIRT/WFCAM along with Gaia DR2 and literature parallaxes. With 369 members, our sample is the largest parallax-defined volume-limited sample of L and T dwarfs to date, yielding the most precise space densities for such objects. We find the local L0-T8 dwarf population includes 5.5%{+/-}1.2% young objects (<~200Myr) and 2.6%{+/-}1.6% subdwarfs, as expected from recent studies favoring representative ages <~4Gyr for the ultracool field population. This is also the first volume-limited sample to comprehensively map the transition from L to T dwarfs (spectral types ~L8-T4). After removing binaries, we identify a previously unrecognized, statistically significant (>4.4{sigma}) gap ~0.5mag wide in (J-K)_MKO_ colors in the L/T transition, i.e., a lack of such objects in our volume-limited sample, implying a rapid phase of atmospheric evolution. In contrast, the most successful models of the L/T transition to date-the "hybrid" models of Saumon & Marley-predict a pileup of objects at the same colors where we find a deficit, demonstrating the challenge of modeling the atmospheres of cooling brown dwarfs. Our sample illustrates the insights to come from even larger parallax-selected samples from the upcoming Legacy Survey of Space and Time by the Vera Rubin Obsevatory.
- ID:
- ivo://CDS.VizieR/J/AJ/149/200
- Title:
- VRI photometry in NGC 7129
- Short Name:
- J/AJ/149/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC7129 is a bright reflection nebula located in the molecular cloud complex near l=105.4{deg}, b=+9.9{deg}, about 1.15kpc distant. Embedded within the reflection nebula is a young cluster dominated by a compact grouping of four early-type stars: BD+65{deg}1638 (B3V), BD+65{deg}1637 (B3e), SVS 13 (B5e), and LkH{alpha} 234 (B8e). About 80 H{alpha} emission sources brighter than V~23 are identified in the region, many of which are presumably T Tauri star members of the cluster. We also present deep (V~23), optical (VR_C_I_C_) photometry of a field centered on the reflection nebula and spectral types for more than 130 sources determined from low dispersion, optical spectroscopy. The narrow pre-main sequence evident in the color-magnitude diagram suggests that star formation was rapid and coeval. A median age of about 1.8Myr is inferred for the H{alpha} and literature-identified X-ray emission sources having established spectral types, using pre-main sequence evolutionary models. Our interpretation of the structure of the molecular cloud and the distribution of young stellar objects is that BD+65{deg}1638 is primarily responsible for evacuating the blister-like cavity within the molecular cloud. LkH{alpha} 234 and several embedded sources evident in near-infrared adaptive optics imaging have formed recently within the ridge of compressed molecular gas. The compact cluster of low-mass stars formed concurrently with the early-type members, concentrated within a central radius of ~0.7pc. Star formation is simultaneously occurring in a semi-circular arc some ~3pc in radius that outlines remaining dense regions of molecular gas. High dispersion, optical spectra are presented for BD+65{deg}1638, BD+65{deg}1637, SVS 13, LkH{alpha} 234, and V350 Cep. These spectra are discussed in the context of the circumstellar environments inferred for these stars.
- ID:
- ivo://CDS.VizieR/III/13
- Title:
- Vyssotsky's Catalogues 1950.0
- Short Name:
- III/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog includes the results of a complete survey of the McCormick objective prism plates for M dwarf stars. catalog.dat includes identifications, magnitudes, proper motions in RA and Dec, spectral types and parallaxes.
- ID:
- ivo://CDS.VizieR/J/AJ/154/118
- Title:
- WD+dMs from the SUPERBLINK proper motion survey
- Short Name:
- J/AJ/154/118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an activity and kinematic analysis of high proper motion white dwarf-M dwarf binaries (WD+dMs) found in the SUPERBLINK survey, 178 of which are new identifications. To identify WD+dMs, we developed a UV-optical-IR color criterion and conducted a spectroscopic survey to confirm each candidate binary. For the newly identified systems, we fit the two components using model white dwarf spectra and M dwarf template spectra to determine physical parameters. We use H{alpha} chromospheric emission to examine the magnetic activity of the M dwarf in each system, and investigate how its activity is affected by the presence of a white dwarf companion. We find that the fraction of WD+dM binaries with active M dwarfs is significantly higher than their single M dwarf counterparts at early and mid-spectral types. We corroborate previous studies that find high activity fractions at both close and intermediate separations. At more distant separations, the binary fraction appears to approach the activity fraction for single M dwarfs. Using derived radial velocities and the proper motions, we calculate 3D space velocities for the WD+dMs in SUPERBLINK. For the entire SUPERBLINK WD+dMs, we find a large vertical velocity dispersion, indicating a dynamically hotter population compared to high proper motion samples of single M dwarfs. We compare the kinematics for systems with active M dwarfs and those with inactive M dwarfs, and find signatures of asymmetric drift in the inactive sample, indicating that they are drawn from an older population.
- ID:
- ivo://CDS.VizieR/J/AJ/138/1681
- Title:
- WD within 20pc of the Sun
- Short Name:
- J/AJ/138/1681
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the kinematical properties, distribution of spectroscopic subtypes, and stellar population subcomponents of the white dwarfs within 20pc of the Sun. We find no convincing evidence of halo white dwarfs in the total 20pc sample of 129 white dwarfs nor is there convincing evidence of genuine thick disk subcomponent members within 20 parsecs. Virtually, the entire 20pc sample likely belongs to the thin disk. The total DA to non-DA ratio of the 20pc sample is 1.6, a manifestation of deepening envelope convection which transforms DA stars with sufficiently thin H surface layers into non-DAs. The addition of five new stars to the 20pc sample yields a revised local space density of white dwarfs of (4.9+/-0.5)x10^-3^pc^-3^ and a corresponding mass density of (3.3+/-0.3)x10^-3^M_{sun}_pc^-3^. We find that at least 15% of the white dwarfs within 20 parsecs of the Sun (the DAZ and DZ stars) have photospheric metals that possibly originate from accretion of circumstellar material (debris disks) around them. If this interpretation is correct, this suggests the possibility that the same percentage have planets or asteroid-like bodies orbiting them.
- ID:
- ivo://CDS.VizieR/J/ApJ/867/62
- Title:
- White dwarf population of Messier 67
- Short Name:
- J/ApJ/867/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- White dwarfs (WDs) are excellent forensic tools for studying end-of-life issues surrounding low- and intermediate-mass stars, and the old, solar metallicity open star cluster Messier 67 is a proven laboratory for the study of stellar evolution for solar-type stars. In this paper, we present a detailed spectroscopic study of brighter (M_g_<=12.4) WDs in Messier 67, and in combination with previously published proper motion membership determinations, we identify a clean, representative sample of cluster WDs, including 13 members with hydrogen-dominated atmospheres, at least one of which is a candidate double degenerate, and 5 members with helium-dominated atmospheres. Using this sample we test multiple predictions surrounding the final stages of stellar evolution in solar-type stars. In particular, the stochasticity of the integrated mass lost by ~1.5 solar mass stars is less than 7% of the WD remnant mass. We identify WDs likely resulting from binary evolution, including at least one blue straggler remnant and two helium-core WDs. We observe no evidence of a significant population of helium-core WDs formed by enhanced mass loss on the red giant branch of the cluster. The distribution of WD atmospheric compositions is fully consistent with that in the field, limiting proposed mechanisms for the suppression of helium atmosphere WD formation in star clusters. In short, the WD population of Messier 67 is fully consistent with basic predictions of single- and multiple-star stellar evolution theories for solar metallicity stars.
