- ID:
- ivo://CDS.VizieR/J/A+A/643/A22
- Title:
- UVES spectra of Feige 46 and LSIV -14 116
- Short Name:
- J/A+A/643/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hot subdwarf stars of spectral types O and B represent a poorly understood phase in the evolution of low-mass stars, in particular of close compact binaries. A variety of phenomena are observed, which make them important tools for several astronomical disciplines. For instance, the richness of oscillations of many subdwarfs are important for asteroseismology. Furthermore, hot subdwarfs are among the most chemically peculiar stars known. Two intermediate He-rich hot subdwarf stars, LSIV -14 116 and Feige 46, are particularly interesting, because they show extreme enrichments of heavy elements such as Ge, Sr, Y, and Zr, strikingly similar in both stars. In addition, both stars show light oscillations at periods incompatible with standard pulsation theory and form the class of V366 Aqr variables. We investigate whether the similar chemical compositions extend to more complete abundance patterns in both stars and validate the pulsations in Feige 46 using its recent TESS light curve. High-resolution optical and near-ultraviolet spectroscopy are combined with non-local-thermodynamical-equilibrium model atmospheres and synthetic spectra calculated with Tlusty and Synspec to determine detailed metal abundance patterns in both stars consistently. Many previously unidentified lines are identified for the first time with transitions originating from GaIII, GeIII-IV, SeIII, KrIII, SrII-III, YIII, ZrIII-IV, and SnIV, most of which have not been observed so far in any star. The abundance patterns of 19 metals in both stars are almost identical, light metals being only slightly more abundant in Feige 46 while Zr, Sn, and Pb are slightly less enhanced compared to LSIV -14 116. Both abundance patterns are distinctively different from those of normal He-poor hot subdwarfs of similar temperature. The extreme enrichment in heavy metals of more than 4 dex compared to the Sun is likely the result of strong atmospheric diffusion processes that operate similarly in both stars while their similar patterns of C, N, O, and Ne abundances might provide clues to their as yet unclear evolutionary history. Finally, we find that the periods of the pulsation modes in Feige 46 are stable to better than dP/dt~=10^-8^s/s. This is is not compatible with dP/dt predicted for pulsations driven by the epsilon-mechanism and excited by helium-shell flashes in a star which is evolving, for example, onto the extended horizontal branch.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/370/426
- Title:
- UVES Spectrum of APM BR J0307-4945
- Short Name:
- J/A+A/370/426
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first high-resolution (6.2 to 7.7km/s FWHM) spectra of the APM BR J0307-4945 quasar at z_em_=4.73 obtained with UVES on the 8.2m VLT Kueyen telescope. We focus our analysis on a damped Lyman-{alpha} system at z_abs_=4.466, the most distant DLA system known to the present date, observed when the age of the universe was only 1.3Gyr. The following table lists the wavelengths and equivalent widths for all absorption-line features (except the telluric lines) redwards of the quasar Ly-{alpha} emission detected at 4{sigma} in equivalent width. The transition names and approximate redshifts are specified for the features we successfully identified. About 80% of the absorption lines redwards of the quasar Ly-{alpha} emission have been identified, corresponding to 13 metal-line systems.
- ID:
- ivo://CDS.VizieR/J/A+AS/107/385
- Title:
- UV-excess objects Spacelab-1 survey IV.
- Short Name:
- J/A+AS/107/385
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/317/712
- Title:
- UV fluxes and electron density of AG Peg
- Short Name:
- J/A+A/317/712
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we study in detail the variability of the symbiotic nova AG Peg in the IUE range during the period 1978-1995. We find that the luminosity of the hot component decreased steadily from about 1850L_{sun}_ in 1978 to 430L_{sun}_ in 1995 while its effective temperature remained nearly constant, 86500+/-1300K. At the same time, the mass loss rate decreased by a factor of 4-5 although the ejection velocity remained constant. The observed fainting of both the narrow and the broad emission lines is ascribed to the decrease of the luminosity and ionizing flux from the hot source. The narrow emission lines and the long wavelength UV continuum show periodic variations arising from a dense and asymmetric nebular region associated with the cool star. Radial velocity variations of the narrow lines indicate that this region is receding from the center of mass of the system, and support the presence of the ablation tail suggested by Penston and Allen (1985MNRAS.212..939P). No periodic flux variations are seen in the short wavelength ultraviolet continuum and in the broad emission lines, which are both formed in the fast wind from the hot component.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/164
- Title:
- UV galaxies in CANDELS from z=8 to z=4
- Short Name:
- J/ApJ/756/164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the evolution of galaxy rest-frame ultraviolet (UV) colors in the epoch 4<~z<~8. We use new wide-field near-infrared data in the Great Observatories Origins Deep Survey-South field from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, Hubble Ultra Deep Field (HUDF) 2009, and Early Release Science programs to select galaxies via photometric redshift measurements. Our sample consists of 2812 candidate galaxies at z>~3.5, including 113 at z=~7-8. We fit the observed spectral energy distribution to a suite of synthetic stellar population models and measure the value of the UV spectral slope ({beta}) from the best-fit model spectrum. We run simulations to show that this measurement technique results in a smaller scatter on {beta} than other methods, as well as a reduced number of galaxies with catastrophically incorrect {beta} measurements (i.e., {Delta}{beta}>1).
448. UVILLSS Catalogue
- ID:
- ivo://CDS.VizieR/VI/84
- Title:
- UVILLSS Catalogue
- Short Name:
- VI/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue is an extension in the ultraviolet region (129 to 3903 Angstroems) of the ILLSS catalogue (Coluzzi, 1993; catalog <VI/71>) which lists lines in the optical region. The data are from "Ultraviolet Multiplet Table" (Moore 1950, 1952, 1962) and arranged in two files: the catalogue and the references. There are two versions of each file, one presented in the author's original format, and the second organised as a table. The reference files are arranged by element: for each spectrum the first line contains within parenthesis the Ionization Potential; the grade of analysis; the grade denoting the relative number of classified lines included as compared with the total number classified in the ultraviolet; the date of completion of the manuscript; the limit for three spectra H, He I, He II. The limit in cm-1 has been multiplied by the factor 0.00012345 to obtain the tabulated ionisation potential, which is expressed in electron-Volts. The analysis grades range from A to E, grade A indicating that the analysis is essentially complete ,and grade E that the structure has been recognised, but is limited to a single multiplet or transition. List A, List B, etc., denote the relative numbers of classified lines listed here as compared with the total number classified in the ultraviolet, A denoting that all classified lines in the ultraviolet are listed, and D that only a few of the leading ones are tabulated. The letters on the left, A, B, C, etc. preceding the reference, indicate the source used for the wavelength quoted in the Table. Those papers used only for analysis or intensity follow the ones used for wavelength, and are not preceded by the letters denoting the source. The letters "WL", "I", "T", indicating what was taken from each paper for the Table compilation , denote, respectively, wavelength, intensity, and terms, the last referring to the analysis of the spectrum. These informations are taken from Moore (1950).
- ID:
- ivo://CDS.VizieR/J/ApJS/107/215
- Title:
- UV Images of Nearby Galaxies
- Short Name:
- J/ApJS/107/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The accompanying tables are part of a pictorial atlas of UV (2300A) images, obtained with the Hubble Space Telescope (HST) Faint Object Camera, of the central 22"x22" of 110 galaxies. The observed galaxies are an unbiased selection constituting about one half of a complete sample of all large (D>6') and nearby (V< 2000 km/s) galaxies. This is the first extensive UV imaging survey of normal galaxies. The data are useful for studying star formation, low-level nuclear activity, and UV emission by evolved stellar populations in galaxies. At the HST resolution (0.05"), the images display an assortment of morphologies and UV brightnesses. These include bright nuclear point sources, compact young star clusters scattered in the field or arranged in circumnuclear rings, centrally-peaked diffuse light distributions, and galaxies with weak or undetected UV emission. We measure the integrated 2300A flux in each image, and classify the UV morphology. The UV and optical parameters are given in the tables.
- ID:
- ivo://CDS.VizieR/J/AJ/141/205
- Title:
- UVOT imaging of M81 and Holmberg IX
- Short Name:
- J/AJ/141/205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Swift UV/Optical Telescope (UVOT) imaging of the galaxies M81 and Holmberg IX. We combine UVOT imaging in three near-ultraviolet (NUV) filters (uvw2: 1928{AA}; uvm2: 2246{AA}; uvw1: 2600{AA}) with ground-based optical imaging from the Sloan Digital Sky Survey to constrain the stellar populations of both galaxies. Our analysis consists of three different methods. First, we use the NUV imaging to identify UV star-forming knots and then perform spectral energy distribution (SED) modeling on the UV/optical photometry of these sources. Second, we measure surface brightness profiles of the disk of M81 in the NUV and optical. Lastly, we use SED fitting of individual pixels to map the properties of the two galaxies.
