- ID:
- ivo://CDS.VizieR/J/ApJ/898/161
- Title:
- 500days of ASASSN-18pg multiwavelength obs.
- Short Name:
- J/ApJ/898/161
- Date:
- 16 Mar 2022 00:55:51
- Publisher:
- CDS
- Description:
- We present nearly 500 days of observations of the tidal disruption event (TDE) ASASSN-18pg, spanning from 54 days before peak light to 441 days after peak light. Our data set includes X-ray, UV, and optical photometry, optical spectroscopy, radio observations, and the first published spectropolarimetric observations of a TDE. ASASSN-18pg was discovered on 2018 July 11 by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of d=78.6Mpc; with a peak UV magnitude of m~14, it is both one of the nearest and brightest TDEs discovered to-date. The photometric data allow us to track both the rise to peak and the long-term evolution of the TDE. ASASSN-18pg peaked at a luminosity of L~2.4x10^44^erg/s, and its late-time evolution is shallower than a flux {propto}t^-5/3^ power-law model, similar to what has been seen in other TDEs. ASASSN-18pg exhibited Balmer lines and spectroscopic features consistent with Bowen fluorescence prior to peak, which remained detectable for roughly 225days after peak. Analysis of the two-component H{alpha} profile indicates that, if they are the result of reprocessing of emission from the accretion disk, the different spectroscopic lines may be coming from regions between ~10 and ~60 lt-days from the black hole. No X-ray emission is detected from the TDE, and there is no evidence of a jet or strong outflow detected in the radio. Our spectropolarimetric observations indicate that the projected emission region is likely not significantly aspherical, with the projected emission region having an axis ratio of >~0.65.
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- ID:
- ivo://CDS.VizieR/J/A+A/547/A105
- Title:
- D-burning in core accretion objects
- Short Name:
- J/A+A/547/A105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our aim is to study deuterium burning in objects forming according to the core accretion scenario in the hot and cold start assumption and what minimum deuterium burning mass limit is found for these objects. We also study how the burning process influences the structure and luminosity of the objects. Furthermore we want to test and verify our results by comparing them to already existing hot start simulations which did not consider, however, the formation process.
- ID:
- ivo://CDS.VizieR/J/A+A/363/1040
- Title:
- DB white dwarfs from the Hamburg/ESO survey
- Short Name:
- J/A+A/363/1040
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of 40 cool helium-rich white dwarfs found in the Hamburg/ESO survey. They were selected for follow-up spectroscopy because of their U-B colour below -0.18, the absence of strong absorption lines, and a continuum shape similar to that of a quasar. Effective temperatures for individual stars were determined by fitting model atmospheres of nearly pure helium with a small admixture of hydrogen. As a consequence of the selection criteria all but one sample stars have T_eff_ below 20000K. Four stars clearly show helium and hydrogen lines in their spectra. In the spectra of another three, helium, hydrogen, and metal lines can be detected. For these stars hydrogen and metal abundances were also determined by fitting appropriate model atmospheres containing these elements. Seven sample stars most likely have helium-rich atmospheres but do not show any helium lines. They either have featureless spectra or show calcium lines.
- ID:
- ivo://CDS.VizieR/J/other/RAA/19.88
- Title:
- DB white dwarfs from the LAMOST DR5
- Short Name:
- J/other/RAA/19.8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this study, we employ machine learning to build a catalog of DB white dwarfs (DBWDs) from the LAMOST Data Release (DR) 5. Using known DBs from SDSS DR14, we selected samples of high-quality DB spectra from the LAMOST database and applied them to train the machine learning process. Following the recognition procedure, we chose 351 DB spectra of 287 objects, 53 of which were new identifications. We then utilized all the DBWD spectra from both SDSS DR14 and LAMOST DR5 to construct DB templates for LAMOST 1D pipeline reductions. Finally, by applying DB parameter models provided by D. Koester and the distance from Gaia DR2, we calculated the effective temperatures, surface gravities and distributions of the 3D locations and velocities of all DBWDs.
- ID:
- ivo://CDS.VizieR/J/A+A/583/A86
- Title:
- DB white dwarfs in SDSS DR10 and DR12
- Short Name:
- J/A+A/583/A86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- White dwarfs with helium-dominated atmospheres (spectral types DO, DB) comprise approximately 20% of all white dwarfs. There are fewer studies than of their hydrogen-rich counterparts (DA) and thus several questions remain open. Among these are the total masses and the origin of the hydrogen traces observed in a large number and the nature of the deficit of DBs in the range from 30000-45000K. We use the largest-ever sample (by a factor of 10) provided by the Sloan Digital Sky Survey (SDSS) to study these questions. The photometric and spectroscopic data of 1107 helium-rich objects from the SDSS are analyzed using theoretical model atmospheres. Along with the effective temperature and surface gravity, we also determine hydrogen and calcium abundances or upper limits for all objects. The atmosphere models are extended with envelope calculations to determine the extent of the helium convection zones and thus the total amount of hydrogen and calcium present.
- ID:
- ivo://CDS.VizieR/J/ApJ/882/106
- Title:
- DB white dwarfs with SDSS and Gaia data
- Short Name:
- J/ApJ/882/106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive analysis of DB white dwarfs drawn from the Sloan Digital Sky Survey, based on model fits to ugriz photometry and medium-resolution spectroscopy from the Sloan Digital Sky Survey. We also take advantage of the exquisite trigonometric parallax measurements recently obtained by the Gaia mission. Using the so-called photometric and spectroscopic techniques, we measure the atmospheric and physical parameters of each object in our sample (Teff, logg, H/He, Ca/He, R, M), and compare the values obtained from both techniques in order to assess the precision and accuracy of each method. We then explore in great detail the surface gravity, stellar mass, and hydrogen abundance distributions of DB white dwarfs as a function of effective temperature. We present some clear evidence for a large population of unresolved double-degenerate binaries composed of DB+DB and even DB+DA white dwarfs. In the light of our results, we finally discuss the spectral evolution of DB white dwarfs, in particular the evolution of the DB-to-DA ratio as a function of Teff, and we revisit the question of the origin of hydrogen in DBA white dwarfs.
- ID:
- ivo://CDS.VizieR/II/130
- Title:
- 2-D Classification, Vilnius Photometry M56 Region
- Short Name:
- II/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue gives the seven-color photometry in the Vilnius system stars and two-dimensional classification of 752 stars. Photographically determined magnitudes obtained by COSMOS (MacGillivray and Stobie 1984) on the Schmidt plates were input into software described by Smriglio et al. (1986) as a method of automated two-dimensional stellar classification in the Vilnius seven-color intermediate band photometric system (Straizys and Zdanavicius 1970). A region of approximately two square degrees in Lyra centered on RA(1950) = 19h14.6min, DE(1950) = 30deg05' in the direction of the globular cluster M56 was studied and the two-dimensional classification of 752 stars in the magnitude range V = 11 to 15 mag was studied. The photometric system, the method of reduction, the classification procedure and errors were described by Smriglio et al. (1986). The number of stars for which all the six color indices in the Vilnius system are available is close to 3000, but the number of stars which have received two dimensional classification is 752. The success rate of classification appears to be high for stars brighter than V = 15.0 mag for which photometric accuracy is better than +-5%.
- ID:
- ivo://CDS.VizieR/J/A+A/463/1029
- Title:
- DCld303-14.8 & Thumbprint Nebula JHKs phot.
- Short Name:
- J/A+A/463/1029
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of radial density structure of the star forming globule, DCld303.8-14.2 (DC303), and a non-star forming globule, Thumbprint Nebula (TPN), using near-infrared data taken with the ISAAC instrument on the Very Large Telescope. We derive the extinction through the globules using the color excess technique and examine the radial density distribution using Bonnor-Ebert and power-law models.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A79
- Title:
- 400d Cluster Survey Weak Lensing Programme II
- Short Name:
- J/A+A/546/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Evolution in the mass function of galaxy clusters sensitively traces both the expansion history of the Universe and cosmological structure formation. Robust cluster mass determinations are a key ingredient for a reliable measurement of this evolution, especially at high redshift. Weak gravitational lensing is a promising tool for, on average, unbiased mass estimates. This weak lensing project aims at measuring reliable weak lensing masses for a complete X-ray selected sample of 36 high redshift (0.35<z<0.9) clusters. The goal of this paper is to demonstrate the robustness of the methodology against commonly encountered problems, including pure instrumental effects, the presence of bright (8-9mag) stars close to the cluster centre, ground based measurements of high-z (z~0.8) clusters, and the presence of massive unrelated structures along the line-sight.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A44
- Title:
- 3D-corrected oxygen abundances for halo stars
- Short Name:
- J/A+A/624/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Measurable amounts of Be could have been synthesised primordially if the Universe were non-homogeneous or in the presence of late decaying relic particles. We investigate the Be abundance in the extremely metal-poor star 2MASS J1808-5104 ([Fe/H]=-3.84) with the aim of constraining inhomogeneities or the presence of late decaying particles. High resolution, high signal-to-noise ratio (S/N) UV spectra were acquired at ESO with the Kueyen 8.2m telescope and the UVES spectrograph. Abundances were derived using several model atmospheres and spectral synthesis code. We measured log(Be/H)=-14.3 from a spectrum synthesis of the region of the Be line. Using a conservative approach, however we adopted an upper limit two times higher, i.e. log(Be/H)<-14.0. We measured the O abundance from UV-OH lines and find [O/H]=-3.46 after a 3D correction. Our observation reinforces the existing upper limit on primordial Be. There is no observational indication for a primordial production of 9Be. This places strong constraints on the properties of putative relic particles. This result also supports the hypothesis of a homogeneous Universe, at the time of nucleosynthesis. Surprisingly, our upper limit of the Be abundance is well below the Be measurements in stars of similar [O/H]. This may be evidence that the Be-O relation breaks down in the early Galaxy, perhaps due to the escape of spallation products from the gas clouds in which stars such as 2MASS J1808-5104 have formed.