Search

Start Over Capability Type Simple Cone Search
16531. UVES/VLT spectra of white dwarfs
ID:
ivo://CDS.VizieR/J/A+A/505/441
Title:
UVES/VLT spectra of white dwarfs
Short Name:
J/A+A/505/441
Date:
21 Oct 2021
Publisher:
CDS
Description:
The ESO Supernova Ia Progenitor Survey (SPY) took high-resolution spectra of more than 1000 white dwarfs and pre-white dwarfs. About two thirds of the stars observed are hydrogen-dominated DA white dwarfs. Here we present a catalog and detailed spectroscopic analysis of the DA stars in the SPY. Atmospheric parameters effective temperature and surface gravity are determined for normal DAs. Double-degenerate binaries, DAs with magnetic fields or dM companions, are classified and discussed.
16532. UVES/VLT spectroscopy of white dwarfs
ID:
ivo://CDS.VizieR/J/A+A/470/1079
Title:
UVES/VLT spectroscopy of white dwarfs
Short Name:
J/A+A/470/1079
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a detailed spectroscopic analysis of the stars with helium-dominated spectra in the ESO Supernova Ia Progenitor Survey (SPY). Atmospheric parameters, masses, and abundances of trace hydrogen are determined and discussed in the context of spectral evolution of white dwarfs. The spectra are compared with theoretical model atmospheres using a {chi}^2^ fitting technique, leading to determinations of effective temperature, surface gravity, and hydrogen abundance. Our final sample contains 71 objects, of which 6 are new detections and 14 are reclassified from DB to DBA because of the presence of H lines. One is a cool DO with weak HeII lines, 2 are composite DB+dM. 55% of the DB sample show hydrogen and are thus DBA, a significantly higher fraction than found before.
16533. UV-excess quasar candidates
ID:
ivo://CDS.VizieR/J/A+AS/111/169
Title:
UV-excess quasar candidates
Short Name:
J/A+AS/111/169
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have developed a procedure (so called PAPA) for measurement of magnitudes (about 0.1mag accurate) and positions (with accuracy better than 0.5arcsec) of all the objects present on photographic plates digitised with the MAMA machine. This homogeneous procedure was applied to four Schmidt plates - in U, B and twice V - covering the Palomar-Sky-Survey field PS +30deg 13h00m, a 40-square-degree zone at the North Galactic Pole. A general-interest exhaustive tricolour catalogue of 19542 star-like objects down to V=20.0 has been produced and we selected 1681 quasar candidates on the basis of ultraviolet excess and, when possible, absence of any measurable proper motion. The astrometric and photometric catalogue of the candidates is given in electronic form.
16534. UV-excess quasar candidates around NGC 450
ID:
ivo://CDS.VizieR/J/A+AS/123/529
Title:
UV-excess quasar candidates around NGC 450
Short Name:
J/A+AS/123/529
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe the results of a survey for moderately bright quasars performed in a 20.6-square-degree field around the galaxy NGC 450. The quasar candidates we re-selected on the basis of their ultraviolet excess: by comparative visual inspection of the double image of each single object on a U/B dual-exposure Schmidt photographic plate, 95 primary and 45 secondary quasar candidates were selected on the basis of their U image being too bright. The spectroscopic identification of the primary candidates led to the discovery of 59 bona fide quasars (out of which 6 were previously known). The Palomar Schmidt plate was digitised using the MAMA measuring machine and the outcoming data reduced using ad hoc procedures. A photometric calibration allowed us to derive values for the limiting magnitudes and for the U-B index selection threshold of the survey. A catalogue containing 60 quasars is presented with accurate positions, magnitudes and additional information such as redshifts. We studied the spatial distribution of the objects and detected, for the quasars of our sample, a significant deviation from randomness in the form of a propensity to cluster in pairs on the celestial sphere with a typical scale of about 10arcmin. We also formally detected a tendency towards a 3-D clustering, but this result is induced by a single pair of quasars. A forthcoming paper will deal with a similar work performed in a field around NGC 520; the latter field is located directly to the North of the present one and slightly overlaps it.
16535. UV-excess sources from UVEX
ID:
ivo://CDS.VizieR/J/MNRAS/420/1115
Title:
UV-excess sources from UVEX
Short Name:
J/MNRAS/420/1115
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first catalogue of point-source ultraviolet (UV)-excess sources selected from the UV-Excess Survey of the Northern Galactic Plane (UVEX). UVEX images the Northern Galactic Plane in the U, g, r and HeI{lambda}5875 bands in the Galactic latitude range -5<b<+5{deg}. Through an automated algorithm, which works on a field-to-field basis, we select blue UV-excess sources in 211 square degrees from the (U-g) versus (g-r) colour-colour diagram and the g versus (U-g) and g versus (g-r) colour-magnitude diagrams. The UV-excess catalogue covers the magnitude range 14<g<22.5, contains 2170 sources and consists of a mix of white dwarfs, post-common-envelope objects, interacting binaries, quasars and active galactic nuclei. Two other samples of outliers were found during the selection: (i) a "subdwarf" sample, consisting of no less than 9872 candidate metal-poor stars or lightly reddened main-sequence stars, and (ii) a "purple" sample consisting of 803 objects, most likely a mix of reddened late M giants, T Tauri stars, planetary nebulae, symbiotic stars and carbon stars. Cross-matching the selected UV-excess catalogue with other catalogues aids with the first classification of the different populations and shows that more than 99 per cent of our selected sources are unidentified sources.
16536. UVEX sources spectroscopic follow-up
ID:
ivo://CDS.VizieR/J/MNRAS/426/1235
Title:
UVEX sources spectroscopic follow-up
Short Name:
J/MNRAS/426/1235
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of the first spectroscopic follow-up of 132 optically blue ultraviolet (UV)-excess sources selected from the UV-Excess Survey of the Northern Galactic Plane (UVEX). The UV-excess spectra are classified into different populations and grids of model spectra are fitted to determine spectral types, temperatures, surface gravities and reddening. From this initial spectroscopic follow-up 95 per cent of the UV-excess candidates turn out to be genuine UV-excess sources such as white dwarfs, white dwarf binaries, subdwarf types O and B, emission-line stars and quasi stellar objects. The remaining sources are classified as slightly reddened main-sequence stars with spectral types later than A0V. The fraction of DA white dwarfs is 47 per cent with reddening smaller than E(B-V)<=0.7mag. Relations between the different populations and their UVEX photometry, Galactic latitude and reddening are shown. A larger fraction of UVEX white dwarfs is found at magnitudes fainter than g>17 and Galactic latitude smaller than |b|<4 compared to main-sequence stars, blue horizontal branch stars and subdwarfs.
16537. UV/far-IR data of infrared excess sources
ID:
ivo://CDS.VizieR/J/MNRAS/406/420
Title:
UV/far-IR data of infrared excess sources
Short Name:
J/MNRAS/406/420
Date:
21 Oct 2021
Publisher:
CDS
Description:
We explore the nature of Infrared Excess sources (IRX), which are proposed as candidates for luminous [LX(2-10keV)>10^43^erg/s] Compton thick (NH>2x10^24^cm^-2^) QSOs at z~~2. Lower redshift, z~~1, analogues of the distant IRX population are identified by first redshifting to z=2 the spectral energy distributions (SEDs) of all sources with secure spectroscopic redshifts in the AEGIS (6488) and the GOODS-North (1784) surveys and then selecting those that qualify as IRX sources at that redshift. A total of 19 galaxies are selected. The mean redshift of the sample is z~~1. We do not find strong evidence for Compton thick QSOs in the sample. For nine sources with X-ray counterparts, the X-ray spectra are consistent with Compton thin active galactic nucleus (AGN). Only three of them show tentative evidence for Compton thick obscuration. The SEDs of the X-ray undetected population are consistent with starburst activity.
16538. UV-FIR obs. of post-starburst galaxies & dust masses
ID:
ivo://CDS.VizieR/J/ApJ/879/131
Title:
UV-FIR obs. of post-starburst galaxies & dust masses
Short Name:
J/ApJ/879/131
Date:
21 Oct 2021
Publisher:
CDS
Description:
We derive dust masses (M_dust_) from the spectral energy distributions of 58 post-starburst galaxies (PSBs). There is an anticorrelation between specific dust mass (M_dust_/M_*_) and the time elapsed since the starburst ended, indicating that dust was either destroyed, expelled, or rendered undetectable over the ~1Gyr after the burst. The M_dust_/M_*_ depletion timescale, 205_-37_^+58^Myr, is consistent with that of the CO-traced M_H2_/M_*_, suggesting that dust and gas are altered via the same process. Extrapolating these trends leads to the M_dust_/M_*_ and M_H2_/M_*_ values of early-type galaxies (ETGs) within 1-2Gyr, a timescale consistent with the evolution of other PSB properties into ETGs. Comparing Mdust and M_H2_ for PSBs yields a calibration, log M_H2_=0.45logM_dust_+6.02, that allows us to place 33 PSBs on the Kennicutt-Schmidt (KS) plane, {Sigma}SFR-{Sigma}M_H2_. Over the first ~200-300Myr, the PSBs evolve down and off of the KS relation, as their star formation rate (SFR) decreases more rapidly than M_H2_. Afterwards, M_H2_ continues to decline whereas the SFR levels off. These trends suggest that the star formation efficiency bottoms out at 10^-11^/yr and will rise to ETG levels within 0.5-1.1Gyr afterwards. The SFR decline after the burst is likely due to the absence of gas denser than the CO-traced H2. The mechanism of the M_dust_/M_*_ and M_H2_/M_*_ decline, whose timescale suggests active galactic nucleus/low-ionization nuclear emission-line region feedback, may also be preventing the large CO-traced molecular gas reservoirs from collapsing and forming denser star-forming clouds.
16539. UV-FIR SED results of SDSS QSOs and their hosts
ID:
ivo://CDS.VizieR/J/ApJ/824/70
Title:
UV-FIR SED results of SDSS QSOs and their hosts
Short Name:
J/ApJ/824/70
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this work, we present a study of 207 quasars selected from the Sloan Digital Sky Survey quasar catalogs and the Herschel Stripe 82 survey. Quasars within this sample are high-luminosity quasars with a mean bolometric luminosity of 10^46.4^erg/s. The redshift range of this sample is within z Herschel-SPIRE bands, the quasar sample is complete yet highly biased. Based on the multi-wavelength photometric observation data, we conducted a spectral energy distribution (SED) fitting through UV to FIR. Parameters such as active galactic nucleus (AGN) luminosity, far-IR (FIR) luminosity, stellar mass, as well as many other AGN and galaxy properties are deduced from the SED fitting results. The mean star formation rate (SFR) of the sample is 419M_{sun}_/yr and the mean gas mass is ~10^11.3^M_{sun}_. All of these results point to an IR luminous quasar system. Compared with star formation main sequence (MS) galaxies, at least 80 out of 207 quasars are hosted by starburst galaxies. This supports the statement that luminous AGNs are more likely to be associated with major mergers. The SFR increases with the redshift up to z=2. It is correlated with the AGN bolometric luminosity, where L_FIR_{propto}L_Bol_^0.46+/-0.03^. The AGN bolometric luminosity is also correlated with the host galaxy mass and gas mass. Yet the correlation between L_FIR_ and L_Bol_ has higher significant level, implies that the link between AGN accretion and the SFR is more primal. The M_BH_/M_*_ ratio of our sample is 0.02, higher than the value 0.005 in the local universe. It might indicate an evolutionary trend of the M_BH_/M_*_ scaling relation.
16540. UV Flux distributions of gamma Dor stars
ID:
ivo://CDS.VizieR/J/A+A/472/241
Title:
UV Flux distributions of gamma Dor stars
Short Name:
J/A+A/472/241
Date:
21 Oct 2021
Publisher:
CDS
Description:
It seems that the recently identified class of pulsating stars, the gamma Dor type-variables, includes objects with different metal abundances and a large percentage of binaries. We looked for indicators of metal abundance peculiarities and stellar binarity in a sample of 40 confirmed gamma Dor stars. Absolute magnitudes from Hipparcos parallaxes and UV magnitudes, from the S2/S68 experiment on board the TD1 satellite, are retrieved from databases and compared with predicted values. A set of non variable normal stars is used to check the consistency of this analysis and also serve as reference stars. Twenty-nine stars of the gamma Dor star sample, which is 73% of it, are discovered having abnormal UV fluxes constantly showing UV flux excesses compared to those computed with the atmospheric parameters (Teff, logg, and metallicity) determined from calibration of the uvbyBeta indices. The reason for this UV excess of flux at 196.5nm and at 236.5nm, which was previously known only for HD 209295, cannot be ascribed to binarity alone. An extra source of UV flux or less UV absorption - yet unknown - must be present.

Limit your search

more »

more »

more »

more »

more »

more »