- ID:
- ivo://CDS.VizieR/J/ApJ/761/162
- Title:
- Tycho-2 stars in Galactic Bulge Survey
- Short Name:
- J/ApJ/761/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify 69 X-ray sources discovered by the Galactic Bulge Survey (GBS) that are coincident with or very close to bright stars in the Tycho-2 catalog. Additionally, two other GBS sources are resolved binary companions to Tycho-2 stars where both components are separately detected in X-rays. Most of these are likely to be real matches, but we identify nine objects with large and significant X-ray-to-optical offsets as either detections of resolved binary companions or chance alignments. We collate known spectral types for these objects, and also examine Two Micron All Sky Survey colors, variability information from the All-Sky Automated Survey, and X-ray hardness ratios for the brightest objects. Nearly a third of the stars are found to be optically variable, divided roughly evenly between irregular variations and periodic modulations. All fall among the softest objects identified by the GBS. The sample forms a very mixed selection, ranging in spectral class from O9 to M3. In some cases, the X-ray emission appears consistent with normal coronal emission from late-type stars, or wind emission from early-types, but the sample also includes one known Algol, one W UMa system, two Be stars, and several X-ray bright objects likely to be coronally active stars or binaries. Surprisingly, a substantial fraction of the spectroscopically classified, non-coincidental sample (12 out of 38 objects) have late B or A type counterparts. Many of these exhibit redder near-IR colors than expected for their spectral type and/or variability, and it is likely that the X-rays originate from a late-type companion star in most or all of these objects.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/389/1871
- Title:
- Type Ia supernovae candidates from SDSS
- Short Name:
- J/MNRAS/389/1871
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the course of the Sloan Digital Sky Survey (SDSS-I), a large fraction of the surveyed area was observed more than once due to field tiling overlap, usually at different epochs. We utilize some of these data to perform a supernova (SN) survey at a mean redshift of z=0.2. Our archival search, in ~5 per cent of the SDSS-I overlap area, produces 29 SN candidates clearly associated with host galaxies. Using the Bayesian photometric classification algorithm of Poznanski et al. (2002PASP..114..833P), and correcting for classification bias, we find 17 of the 29 candidates are likely Type Ia SNe.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/208
- Title:
- Type IIP supernovae from Pan-STARRS1
- Short Name:
- J/ApJ/799/208
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years, wide-field sky surveys providing deep multiband imaging have presented a new path for indirectly characterizing the progenitor populations of core-collapse supernovae (SNe): systematic light-curve studies. We assemble a set of 76 grizy-band Type IIP SN light curves from Pan-STARRS1, obtained over a constant survey program of 4yr and classified using both spectroscopy and machine-learning-based photometric techniques. We develop and apply a new Bayesian model for the full multiband evolution of each light curve in the sample. We find no evidence of a subpopulation of fast-declining explosions (historically referred to as "Type IIL" SNe). However, we identify a highly significant relation between the plateau phase decay rate and peak luminosity among our SNe IIP. These results argue in favor of a single parameter, likely determined by initial stellar mass, predominantly controlling the explosions of red supergiants. This relation could also be applied for SN cosmology, offering a standardizable candle good to an intrinsic scatter of <~0.2mag. We compare each light curve to physical models from hydrodynamic simulations to estimate progenitor initial masses and other properties of the Pan-STARRS1 Type IIP SN sample. We show that correction of systematic discrepancies between modeled and observed SN IIP light-curve properties and an expanded grid of progenitor properties are needed to enable robust progenitor inferences from multiband light-curve samples of this kind. This work will serve as a pathfinder for photometric studies of core-collapse SNe to be conducted through future wide-field transient searches.
- ID:
- ivo://CDS.VizieR/J/AJ/132/1023
- Title:
- U-band dropouts in Hubble Ultra Deep Field
- Short Name:
- J/AJ/132/1023
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine data from the extremely deep Hubble Space Telescope U (F300W) image, obtained using WFPC2 as part of the parallel observations of the Hubble Ultra Deep Field campaign, with BVi images from the Great Observatories Origins Deep Survey to identify a sample of Lyman break galaxies in the redshift range 2.0<=z<=3.5. We use recent stellar population synthesis models with a wide variety of ages, metallicities, redshifts, and dust content, and a detailed representation of the HI cosmic opacity as a function of redshift to model the colors of galaxies in our combination of WFPC2 and ACS filters. Using these models, we derive improved color selection criteria that provide a clean selection of relatively unobscured star-forming galaxies in this redshift range. Our WFPC2 F300W image is the deepest image ever obtained at that wavelength. The 10 limiting magnitude measured over 0.2arcsec^2^ is 27.5mag in the WFPC2 F300W image, about 0.5mag deeper than the F300W image in the Hubble Deep Field (HDF)-North.
- ID:
- ivo://CDS.VizieR/J/MNRAS/306/592
- Title:
- UBVR CCD sequences for wide-field surveys. II.
- Short Name:
- J/MNRAS/306/592
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a continuing campaign to secure deep multi-colour CCD sequences for photoelectric calibration in UK Schmidt fields with galactic latitudes |b|>50{deg}. In this paper, we present UBVR photometry in 12 fields and BR photometry in a further 14 fields observed within UK Schmidt survey fields centered at {delta}=-30{deg}. Our observations were carried out with the 0.9m Telecope at the Cerro-Tololo Inter-American Observatory.
- ID:
- ivo://CDS.VizieR/J/MNRAS/276/33
- Title:
- UBVRI CCD sequences for wide-field surveys. I.
- Short Name:
- J/MNRAS/276/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a campaign to secure deep UBVRI CCD photometric calibration in all UK Schmidt equatorial fields with galactic latitudes |b|<~50{deg}. In this paper we provide information on deep BVRI sequences (B<22mag) in 14 UK Schmidt survey fields centred at declination=0{deg}. Deep U sequences have been obtained for 11 of these fields.
- ID:
- ivo://CDS.VizieR/J/AJ/159/214
- Title:
- UBVRI linear polarisation in Wolf-Rayet winds
- Short Name:
- J/AJ/159/214
- Date:
- 09 Dec 2021
- Publisher:
- CDS
- Description:
- Wolf-Rayet (WR) stars have strong, hot winds, with mass-loss rates at least a factor of 10 greater than their O-star progenitors, although their terminal wind speeds are similar. In this paper, we use the technique of multiband linear polarimetry to extract information on the global asymmetry of the wind in a sample of 47 bright Galactic WR stars. Our observations also include time-dependent observations of 17 stars in the sample. The path to our goal includes removing the dominating component of wavelength-dependent InterStellar Polarization (ISP), which normally follows the well-known Serkowski law. We include a wavelength-dependent ISP position angle parameter in our ISP law and find that 15 stars show significant results for this parameter. We detect a significant component of wavelength-independent polarization due to electron scattering in the wind for 10 cases, with most WR stars showing none at the ~0.05% level precision of our data. The intrinsically polarized stars can be explained with binary interaction, large-scale wind structure, and clumping. We also found that 5 stars out of 19 observed with the Stromgren b filter (probing the complex {lambda}4600-4700{AA} emission-line region) have significant residuals from the ISP law and propose that this is due to wind asymmetries. We provide a useful catalog of ISP for 47 bright Galactic WR stars and upper limits on the possible level of intrinsic polarization.
- ID:
- ivo://CDS.VizieR/J/AJ/133/2393
- Title:
- UBVRI phot. in seven Local Group dwarfs galaxies
- Short Name:
- J/AJ/133/2393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained UBVRI images with the Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory 4m telescopes and Mosaic cameras of seven dwarfs in (or near) the Local Group, all of which have known evidence of recent star formation: IC 10, NGC 6822, WLM, Sextans B, Sextans A, Pegasus, and Phoenix. We construct color-magnitude diagrams (CMDs) of these systems, as well as neighboring regions that can be used to evaluate the degree of foreground contamination by stars in the Milky Way.
2019. UCAC2 Catalogue
- ID:
- ivo://CDS.VizieR/I/289
- Title:
- UCAC2 Catalogue
- Short Name:
- I/289
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UCAC2 is the second release of the ongoing UCAC project, designed to observe the entire sky for R magnitudes of about 7.5 to 16. The observed positional errors are about 20 mas for the stars in the 10-14 magnitude range, and about 70 mas at the limiting magnitude of R~16. For up-to-date information on the project, see the UCAC web page at http://ad.usno.navy.mil/ucac/ . This web page will also serve as the location that the UCAC team will post addenda to the UCAC2 catalog. The UCAC2 is a high density, highly accurate, astrometric catalog of 48,330,571 stars covering the sky from -90 to +40 degrees in declination and going up to +52 degrees in some areas. The northern limit is a function of right ascension. Proper motions and photometry are provided for all stars. Positions and proper motions are on the ICRS (International Celestial Reference System) and given at the epoch J2000.0. The UCAC2 has a number of major differences with respect to UCAC1. These differences include: - much larger sky coverage - reduced systematic errors of CCD observations - positions given at a standard epoch (J2000.0) - the addition of several new catalogs for improved proper motions - photometry in the J, H, and K_s bands from the 2MASS project Additional details of the data are found in Sections 3, 4, and 5 of the "readme.txt" file. UCAC2 is the last intermediate data release before the final, all sky catalog will be constructed. Observations will end around mid 2004; the final catalog is expected out in 2005. The UCAC project, observations, and first data release are described in detail in the paper Zacharias et al. AJ 120, 2131 (2000). Versions of that and other related papers are placed on the UCAC Web page (http://ad.usno.navy.mil/ucac/). The paper describing UCAC2 is in preparation (AJ, 2003); some further details can be found in the "readme.txt" file.
2020. UCAC1 Catalogue
- ID:
- ivo://CDS.VizieR/I/268
- Title:
- UCAC1 Catalogue
- Short Name:
- I/268
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UCAC1 is a high density, highly accurate, astrometric catalog of over 27 million stars in the Southern Hemisphere in the magnitude range of about 8 to 16. This version is the first release of an ongoing project to observe the entire sky; for up-to-date information see the Web page at http://ad.usno.navy.mil/ad/ucac/ . The UCAC1 is a preliminary catalog. By avoiding all "problem cases" (see details in the "intro.txt" file) it is not complete. Positions, proper motions and errors are provided, together with approximate magnitudes in the 579-642nm range. The positional precision is about 20 mas for 9 to 14 mag and 70 mas at 16th mag. The errors of the proper motions are very heterogeneous, ranging from 1 to 35 mas/yr. The UCAC is an observational program using the U.S. Naval Observatory Twin Astrograph and a 4kx4k CCD camera, covering just over 1 square degree per frame with a scale of 0.9"/pixel. Observations started in January 1998 at Cerro Tololo Interamerican Observatory (CTIO) and are continuing. This first catalog contains data observed through 07 November 1999 at which time about 80% of the Southern Hemisphere was completed. Full sky coverage is expected by early 2003 after a re-location of the instrument to the Northern Hemisphere planned for early 2001. The UCAC1 is also available on CD-ROM from the US Naval Observatory. Direct request to nz@pisces.usno.navy.mil with UCAC1 in the subject string.
