- ID:
- ivo://CDS.VizieR/J/A+A/410/905
- Title:
- Interstellar reddening parameter measurements
- Short Name:
- J/A+A/410/905
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new measurements of the interstellar reddening parameter R_V_=A_V_/E(B-V) towards 185 O stars, using J, H, Ks photometry from the 2MASS project. The average R_V_ from these is of 3.19+/-0.50. All objects whose R_V_ departs from this value by more than 2 sigma have been recognized. Ten objects have R_V_ higher than this value and two lower. In the Cygnus region R_V_ values follow the behaviour of the general interstellar medium, while in the Carina arm, in spite of the relatively larger distance, local cloud effects prevail. The relatively few stars of our sample whose Hipparcos parallaxes are reliable, are found to have distances systematically smaller than the distances derived by the spectroscopic parallaxes. We argue that this effect is consistent with the recently claimed discovery of grey extinction towards OB stars.
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- ID:
- ivo://CDS.VizieR/J/AJ/158/105
- Title:
- IR photometry of field RR Lyrae variable stars
- Short Name:
- J/AJ/158/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-epoch infrared photometry in the K_s_-band for 74 bright RR Lyrae variable stars tied directly to the Two-Micron All-Sky Survey (2MASS) photometric system. We systematize additional K-band photometry from the literature to the 2MASS system and combine it to obtain photometry for 146 RR Lyrae stars on a consistent, modern system. A set of outlier stars in the literature photometry is identified and discussed. Reddening estimates for each star are gathered from the literature and combined to provide an estimate of the interstellar absorption affecting each star, and we find excellent agreement with another source in the literature. We utilize trigonometric parallaxes from the Second Data Release of the European Space Agency's Gaia astrometric satellite to determine the absolute magnitude, M_Ks_ for each of these stars, and analyze them using the astrometry-based luminosity prescription to obtain a parallax-based calibration of M_K_ (RR). Our period-luminosity-metallicity relationship is M_Ks_=(-2.8+/-0.2)(logP+0.27)+(0.12+/-0.02) ([Fe/H]+1.3)-(0.41+/-0.03) mag. A Gaia global zero-point error of {pi}_zp_=-0.042+/-0.013 mas is determined for this sample of RR Lyrae stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/470/864
- Title:
- JHKL photometry of the Galactic Center
- Short Name:
- J/ApJ/470/864
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- J, H, K, and L photometry for the stars in the central ~2' (~5pc) of the Galaxy are presented. Using the observed J-H, H-K, and K-L colors and assumed intrinsic colors, we determine the interstellar extinction at 2.2mm (A_K_) for approximately 1100 individual stars. The mean A_K_ (=3.3mag) is similar to previous results, but we find that the reddening is highly variable, and some stars are likely to be seen through A_K_>6mag. The dereddened K-band luminosity function points to a significantly brighter component to the stellar population (>1.5mag at K) than found in the stellar population in Baade's window, confirming previous work done at lower spatial resolution. The observed flux of all Galactic center stars with estimated K0 (dereddened magnitude) =<7.0mag is ~25% of the total in the 2'x2' field. The data were obtained in July 11-13 on the 4m telescope at the Cerro Tololo Observatory (CTIO) using the Ohio State Infrared Imager qnd Spectrometer (OSIRIS). Our observations confirm the recent finding that several bright M stars in the Galactic center are variable. Our photometry also establishes the near-infrared variability of the M1-2 supergiant, IRS 7.
- ID:
- ivo://CDS.VizieR/J/AJ/130/496
- Title:
- KISS emission-line galaxy candidates
- Short Name:
- J/AJ/130/496
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic observations for 315 emission-line galaxy (ELG) candidates from the KPNO International Spectroscopic Survey (KISS) have been obtained using the MDM Observatory 2.4m telescope on Kitt Peak. KISS is a wide-field objective-prism survey for extragalactic emission-line objects that has cataloged over 2200 ELG candidates to date. Spectroscopic follow-up observations are being carried out to study the characteristics of the survey objects. The observational data presented here include redshifts, reddening estimates, line equivalent widths, H{alpha} line fluxes, and emission-line ratios. The galaxies have been classified based on their emission-line characteristics.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/28
- Title:
- K2 star parameters from Gaia & LAMOST
- Short Name:
- J/ApJS/247/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous measurements of stellar properties for K2 stars in the Ecliptic Plane Input Catalog (EPIC) largely relied on photometry and proper motion measurements, with some added information from available spectra and parallaxes. Combining Gaia DR2 distances with spectroscopic measurements of effective temperatures, surface gravities, and metallicities from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) DR5, we computed updated stellar radii and masses for 26838 K2 stars. For 195250 targets without a LAMOST spectrum, we derived stellar parameters using random forest regression on photometric colors trained on the LAMOST sample. In total, we measured spectral types, effective temperatures, surface gravities, metallicities, radii, and masses for 222088 A, F, G, K, and M-type K2 stars. With these new stellar radii, we performed a simple reanalysis of 299 confirmed and 517 candidate K2 planet radii from Campaigns 1-13, elucidating a distinct planet radius valley around 1.9R_{Earth}_, a feature thus far only conclusively identified with Kepler planets, and tentatively identified with K2 planets. These updated stellar parameters are a crucial step in the process toward computing K2 planet occurrence rates.
- ID:
- ivo://CDS.VizieR/J/AJ/154/31
- Title:
- {lambda} Bootis stars: the southern survey I.
- Short Name:
- J/AJ/154/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The {lambda} Boo stars are a class of chemically peculiar Population I A-type stars characterized by under-abundances of the refractory elements, but near-solar abundances of carbon, nitrogen, oxygen, and sulfur. There is some evidence that {lambda} Boo stars have higher frequencies of "bright" debris disks than normal A-type stars. The discovery of four exoplanets orbiting HR8799, a {lambda} Boo star with a resolved debris disk, suggests that the {lambda} Boo phenomenon may be related to the presence of a dynamic debris disk, perhaps perturbed by migrating planets. However, only 64 {lambda} Boo stars are known, and those stars were discovered with different techniques, making it problematic to use that sample for statistical purposes, including determining the frequency of debris disks. The purpose of this paper is to derive a new sample of {lambda} Boo stars using a technique that does not lead to biases with respect to the presence of infrared excesses. Through spectroscopic observations in the southern hemisphere, we have discovered 33 {lambda} Boo stars and have confirmed 12 others. As a step toward determining the proportion of {lambda} Boo stars with infrared excesses, we have used WISE data to examine the infrared properties of this sample out to 22{mu}m. On this basis, we cannot conclude that {lambda} Boo stars have a greater tendency than normal A-type stars to show infrared excesses. However, observing this sample at longer wavelengths may change that conclusion, as many {lambda} Boo debris disks are cool and do not radiate strongly at 22{mu}m.
- ID:
- ivo://CDS.VizieR/J/AJ/152/45
- Title:
- LAMOST survey of star clusters in M31. II.
- Short Name:
- J/AJ/152/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We select from Paper I a sample of 306 massive star clusters observed with the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) in the vicinity fields of M31 and M33, and determine their metallicities, ages, and masses. Metallicities and ages are estimated by fitting the observed integrated spectra with stellar synthesis population (SSP) models with a pixel-to-pixel spectral fitting technique. Ages for most young clusters are also derived by fitting the multi-band photometric measurements with model spectral energy distributions (SEDs). The estimated cluster ages span a wide range, from several million years to the age of the universe. The numbers of clusters younger and older than 1Gyr are, respectively, 46 and 260. With ages and metallicities determined, cluster masses are then estimated by comparing the multi-band photometric measurements with SSP model SEDs. The derived masses range from ~10^3^ to ~10^7^M_{Sun}_, peaking at ~10^4.3^ and ~10^5.7^M_{Sun}_ for young (<1Gyr) and old (>1Gyr) clusters, respectively. Our estimated metallicities, ages, and masses are in good agreement with available literature values. Old clusters richer than [Fe/H]~-0.7dex have a wide range of ages. Those poorer than [Fe/H]~-0.7dex seem to be composed of two groups, as previously found for Galactic globular clusters-one of the oldest ages with all values of metallicity down to ~-2dex and another with metallicity increasing with decreasing age. The old clusters in the inner disk of M31 (0-30kpc) show a clear metallicity gradient measured at -0.038+/-0.023dex/kpc.
- ID:
- ivo://CDS.VizieR/J/ApJ/595/247
- Title:
- Line intensities in the planetary nebula NGC 5307
- Short Name:
- J/ApJ/595/247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Echelle spectrophotometry of the planetary nebula NGC 5307 is presented. The data consist of Very Large Telescope Ultraviolet Visual Echelle Spectrograph observations in the 3100-10360{AA} range. Electron temperatures and densities have been determined using different line intensity ratios. We determine the H, He, C, and O abundances based on recombination lines; these abundances are almost independent of the temperature structure of the nebula. We also determine the N, O, Ne, S, Cl, and Ar abundances based on collisionally excited lines; the ratios of these abundances relative to that of H depend strongly on the temperature structure of the nebula.
- ID:
- ivo://CDS.VizieR/J/AJ/144/134
- Title:
- LITTLE THINGS survey of nearby dwarf galaxies
- Short Name:
- J/AJ/144/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes, The HI Nearby Galaxy Survey), which is aimed at determining what drives star formation in dwarf galaxies. This is a multi-wavelength survey of 37 dwarf irregular and 4 blue compact dwarf galaxies that is centered around HI-line data obtained with the National Radio Astronomy Observatory (NRAO) Very Large Array (VLA). The HI-line data are characterized by high sensitivity ({<=}1.1mJy/beam per channel), high spectral resolution ({<=}2.6km/s), and high angular resolution (~6"). The LITTLE THINGS sample contains dwarf galaxies that are relatively nearby ({<=}10.3Mpc; 6" is {<=}300pc), that were known to contain atomic hydrogen, the fuel for star formation, and that cover a large range in dwarf galactic properties. We describe our VLA data acquisition, calibration, and mapping procedures, as well as HI map characteristics, and show channel maps, moment maps, velocity-flux profiles, and surface gas density profiles. In addition to the HI data we have GALEX UV and ground-based UBV and H{alpha} images for most of the galaxies, and JHK images for some. Spitzer mid-IR images are available for many of the galaxies as well. These data sets are available online.
- ID:
- ivo://CDS.VizieR/J/AJ/157/22
- Title:
- Luminous and variable stars in NGC 2403 and M81
- Short Name:
- J/AJ/157/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of spectroscopy and multi-wavelength photometry of luminous and variable star candidates in the nearby spiral galaxies NGC 2403 and M81. We discuss specific classes of stars, the Luminous Blue Variables (LBVs), B[e] supergiants (sgB[e]), and the high-luminosity yellow hypergiants. We identify two new LBV candidates, and three sgB[e] stars in M81. We also find that some stars that were previously considered LBV candidates are actually field stars. The confirmed and candidate LBVs and sgB[e] stars together with the other confirmed members are shown on the HR Diagrams for their respective galaxies. We also present the HR Diagrams for the two "SN impostors", V37 (SN2002kg) and V12 (SN1954J) in NGC 2403 and the stars in their immediate environments.
