- 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.
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Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/A+AS/136/531
- Title:
- Valinhos CCD Meridian Circle radio stars
- Short Name:
- J/A+AS/136/531
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The astrometry of 16 radio stars taken from the list of Wendker (1995, Cat. <II/199>) is presented. The observations were carried out between 1996.3 and 1998.8 at the Valinhos CCD Meridian Circle. The results are given on the Hipparcos/Tycho reference frame. The data obtained relatively to the ACT catalogue is presented here. The ACT reference stars measured on 16 sky strips are listed on the table named tableref. The Table 1 of this paper, is presented, giving the radio star position on each field.
- ID:
- ivo://CDS.VizieR/J/AJ/159/8
- Title:
- Vanishing and appearing sources using USNO data
- Short Name:
- J/AJ/159/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we report the current status of a new research program. The primary goal of the "Vanishing and Appearing Sources during a Century of Observations" project is to search for vanishing and appearing sources using existing survey data to find examples of exceptional astrophysical transients. The implications of finding such objects extend from traditional astrophysics fields to the more exotic searches for evidence of technologically advanced civilizations. In this first paper we present new, deeper observations of the tentative candidate discovered by Villarroel et al. (2016AJ....152...76V). We then perform the first searches for vanishing objects throughout the sky by comparing 600 million objects from the US Naval Observatory Catalogue (USNO) B1.0 (Cat. I/284) down to a limiting magnitude of ~20-21 with the recent Pan-STARRS Data Release-1 (DR1, Cat. II/349) with a limiting magnitude of ~23.4. We find about 150000 preliminary candidates that do not have any Pan-STARRS counterpart within a 30" radius. We show that these objects are redder and have larger proper motions than typical USNO objects. We visually examine the images for a subset of about 24000 candidates, superseding the 2016 study with a sample 10 times larger. We find about 100 point sources visible in only one epoch in the red band of the USNO, which may be of interest in searches for strong M-dwarf flares, high-redshift supernovae, or other categories of unidentified red transients.
- ID:
- ivo://CDS.VizieR/J/MNRAS/268/305
- Title:
- Variability of optically selected quasars
- Short Name:
- J/MNRAS/268/305
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The variability properties of a sample of ~300 optically selected quasars near the South Galactic Pole (SGP) have been studied over a baseline of 16 years using a series of twelve UK Schmidt Telescope B_J_ plates at seven epochs. In this sample there is a correlation between variability and both quasar luminosity and redshift, at greater than the 99 per cent significance level. Quasars of high luminosity show significantly less variability than those with low luminosity, the rms variation ranging from about 0.25mag at M_B_=-23 to 0.1mag at M_B_=-28. The observed trends can be explained by an intrinsic dependence of quasar variability on luminosity combined with the effects of time dilation, and have implications for quasar samples selected by variability or multicolour techniques. The change in the slope of the n(m) relation at the break can be less pronounced in variability-selected samples. Our results can be used to test models for the origin and reprocessing of the continuum emission in quasars.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/73
- Title:
- Variability of RSGs in M31 from the iPTF survey
- Short Name:
- J/ApJ/859/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most massive stars end their lives as red supergiants (RSGs), a short-lived evolutionary phase when they are known to pulsate with varying amplitudes. The RSG period-luminosity (PL) relation has been measured in the Milky Way, the Magellanic Clouds and M33 for about 120 stars in total. Using over 1500 epochs of R-band monitoring from the Palomar Transient Factory survey over a five-year period, we study the variability of 255 spectroscopically cataloged RSGs in M31. We find that all RGSs brighter than M_K_~-10mag (log(L/L_{sun}_)>4.8) are variable at {Delta}m_R_>0.05mag. Our period analysis finds 63 with significant pulsation periods. Using the periods found and the known values of M_K_ for these stars, we derive the RSG PL relation in M31 and show that it is consistent with those derived earlier in other galaxies of different metallicities. We also detect, for the first time, a sequence of likely first-overtone pulsations. Comparison to stellar evolution models from MESA confirms the first-overtone hypothesis and indicates that the variable stars in this sample have 12M_{sun}_<M<24M_{sun}_. As these RSGs are the immediate progenitors to Type II-P core-collapse supernovae (SNe), we also explore the implication of their variability in the initial-mass estimates for SN progenitors based on archival images of the progenitors. We find that this effect is small compared to the present measurement errors.
- ID:
- ivo://CDS.VizieR/J/MNRAS/487/4285
- Title:
- Variable AGN candidates catalog
- Short Name:
- J/MNRAS/487/4285
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Identifying active galactic nuclei (AGNs) through their X-ray emission is efficient, but necessarily biased against X-ray-faint objects. We aim to characterize this bias by comparing X-ray-selected AGNs to the ones identified through optical variability and mid-infrared (mid-IR) colours. We present a catalogue of AGNs selected through optical variability using all publicly available z-band Hubble Space Telescope images in the GOODS-South field. For all objects in the catalogue, we compute X-ray upper limits or discuss detections in the deepest available ~7 Ms Chandra Deep Field South images and present the Spitzer/Infrared Array Camera (IRAC) mid-IR colours. For the variability study, we consider only sources observed over at least five epochs and over a time baseline of up to 10yr. We adopt the elevated median absolute deviation as a variability indicator robust against individual outlier measurements and identify 113 variability-selected AGN candidates. Among these, 26 have an X-ray counterpart and lie within the conventional AGN area in the FX/Fopt diagram. The candidates with X-ray upper limits are on average optically fainter, have higher redshifts compared to the X-ray-detected ones and are consistent with low-luminosity AGNs. Out of 41 variable optical sources with IR detections, 13 fulfill the IR AGN colour selection criteria. Our work emphasizes the importance of optical variability surveys for constructing complete samples of AGNs including the ones that remain undetected even by the deepest X-ray and IR surveys.
- ID:
- ivo://CDS.VizieR/J/A+AS/123/115
- Title:
- Variables stars in Palomar-Groningen field 3
- Short Name:
- J/A+AS/123/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalogue is presented with variable (RR Lyrae, semiregular and Mira) stars located inside field #3 (PG3) of the Palomar-Groningen Survey at the outer edge of the Sagittarius dwarf galaxy. One of the semiregular variables is a carbon star, comparable with those found by Azzopardi et al. (1991A&AS...88..265A). Serendipity provides the suggestion, that their carbon stars might not be located inside, but behind the bulge on the Sagittarius dwarf galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/844/40
- Title:
- Variable stars in M31 and M33. V. HR diagram
- Short Name:
- J/ApJ/844/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present HR diagrams for the massive star populations in M31 and M33, including several different types of emission-line stars: the confirmed luminous blue variables (LBVs), candidate LBVs, B[e] supergiants, and the warm hypergiants. We estimate their apparent temperatures and luminosities for comparison with their respective massive star populations and evaluate the possible relationships of these different classes of evolved, massive stars, and their evolutionary state. Several of the LBV candidates lie near the LBV/S Dor instability strip that supports their classification. Most of the B[e] supergiants, however, are less luminous than the LBVs. Many are very dusty with the infrared flux contributing one-third or more to their total flux. They are also relatively isolated from other luminous OB stars. Overall, their spatial distribution suggests a more evolved state. Some may be post-RSGs (red supergiants) like the warm hypergiants, and there may be more than one path to becoming a B[e] star. There are sufficient differences in the spectra, luminosities, spatial distribution, and the presence or lack of dust between the LBVs and B[e] supergiants to conclude that one group does not evolve into the other.
- ID:
- ivo://CDS.VizieR/J/ApJ/691/228
- Title:
- Velocities of PNe in NGC 4697
- Short Name:
- J/ApJ/691/228
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the implementation of slitless radial velocity measurements of extragalactic planetary nebulae (PNs) with the 8.2m Subaru telescope and its Cassegrain imaging spectrograph, Faint Object Camera and Spectrograph (FOCAS). As a first application, we have extended a previous search for PNs in NGC 4697 to larger angular distances from its center. A total of 218 PNs were detected, and their radial velocities were measured. We have added 56 new PN detections to the existing sample of 535, observed previously with the ESO VLT + FORS imaging spectrograph; 36 of these new 56 PNs are located at angular distances larger than 230 arcsec from the center of NGC 4697. We compare the new FOCAS velocities with the earlier FORS velocities, for 158 of the 162 reobserved sources, finding good agreement. We now have kinematic information extending out to five effective radii from the center.
