- ID:
- ivo://CDS.VizieR/J/ApJ/652/1554
- Title:
- Iron in hot DA white dwarfs
- Short Name:
- J/ApJ/652/1554
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the iron abundance pattern in hot, hydrogen-rich (DA) white dwarfs. The study is based on new and archival far-ultraviolet spectroscopy of a sample of white dwarfs in the temperature range 30000K<=Teff<=64000K. The spectra obtained with the Far Ultraviolet Spectroscopic Explorer, along with spectra obtained with the Hubble Space Telescope Imaging Spectrograph and the International Ultraviolet Explorer, sample FeIII-FeVI absorption lines, enabling a detailed iron abundance analysis over a wider range of effective temperatures than previously afforded.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/826/209
- Title:
- IRX-{beta} relation of HII regions in NGC628
- Short Name:
- J/ApJ/826/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It has been found that the infrared-to-ultraviolet luminosity ratio (IRX) and ultraviolet spectral slope ({beta}) have a tight correlation in starburst galaxies, while in normal galaxies the relation is deviated and has a much larger scatter. Star formation regions are much simpler in both morphology and physical properties than galaxies, so their photometric and spectroscopic properties are more easily and accurately determined. We have used the integral field spectroscopy and multiband photometric images to study the IRX-{beta} relation of HII regions in a nearby galaxy, NGC 628. There are obvious correlations between the D_n_ (4000), stellar population age, star formation rate, especially H{alpha} equivalent width EW(H{alpha}), and deviation distance d_p_ from the starburst IRX-{beta} relation. However, there is little correlation between the Balmer decrement, metallicity, and d_p_. It is much more complicated than expected, so that we cannot introduce a single second parameter to describe the scatter and deviation of the HII region IRX-{beta} relation.
- ID:
- ivo://CDS.VizieR/J/ApJS/136/631
- Title:
- IUE absorption toward 164 early-type stars
- Short Name:
- J/ApJS/136/631
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of Galactic interstellar AlIII, SiIV, and CIV absorption recorded in high-resolution archival ultraviolet spectra of 164 hot early-type stars observed by the International Ultraviolet Explorer (IUE) satellite. The objects studied were drawn from the list of hot stars scheduled to be observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite as part of observing programs designed to investigate absorption by OVI in the Galactic disk and halo. Multiple IUE echelle-mode integrations have been combined to produce a single ultraviolet (1150-1900{AA}) spectrum of each star with a spectral resolution of ~25km/s (FWHM). Selected absorption-line profiles are presented for each star along with plots of the apparent column density per unit velocity for each line of the AlIII, SiIV, and CIV doublets. We report absorption-line equivalent widths, absorption velocities, and integrated column densities based on the apparent optical depth method of examining interstellar absorption lines. We also determine column densities and Doppler parameters from single-component curve-of-growth analyses. The scientific analysis of these observations will be undertaken after the FUSE satellite produces similar measurements for absorption by interstellar OIV, FeIII, SIII, and other ions.
- ID:
- ivo://CDS.VizieR/III/188
- Title:
- IUE Atlas of B-Type Stellar Spectra
- Short Name:
- III/188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The IUE Atlas of B-type Stellar Spectra is an atlas of B-type spectra consisting of short-wavelength, high-resolution data from the International Ultraviolet Explorer archive, designed to complement the widely used O-star atlas from the same source (Walborn, Nichols-Bohlin, & Panek 1985, NASA Reference Publication 1155, catalog <III/115>). The atlas presented here completes the OB natural group, i.e., to spectral type B3 for the main sequence and giants, type B5 at class Ib, and B8 at Ia, which is also the most relevant domain for stellar-wind effects among normal B-type spectra.
- ID:
- ivo://CDS.VizieR/III/115
- Title:
- IUE Atlas of O-Type Stellar Spectra
- Short Name:
- III/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The International Ultraviolet Explorer Atlas of O-Type Spectra From 1200 to 1900 A (Walborn et el. 1985) lists normalized fluxes and flux quality factors, splice points, and identifying information (star name/number, spectral type, SWP number, and name of the principal investigator) on 101 spectrograms of 98 O-type stars. The primary purpose of this work is to investigate the existence of systematic trends in the ultraviolet line spectra of the O stars, including the prominent stellar wind features, and the degree to which they correlate with the optical spectral classifications. A subsidiary objective is to identify ultraviolet features which may themselves prove useful as classifications criteria.
- ID:
- ivo://CDS.VizieR/J/ApJS/147/305
- Title:
- IUE atlas of pre-main-sequence stars
- Short Name:
- J/ApJS/147/305
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identified 137 T Tauri stars (TTS) and 97 Herbig Ae/Be (HAEBE) stars observed by IUE in the wavelength interval 1900-3200{AA}. Each low-resolution (R~6{AA}) spectrum was visually inspected for source contamination and data quality, and then all usable spectra were combined to form a single time averaged spectrum for each star. For sources with multiple observations, we characterized variability and compared with previously published amplitudes at shorter wavelengths. We combined several co-added spectra of diskless TTS to produce a pair of intrinsic stellar spectra unaffected by accretion. We then fitted spectra of TTS with the reddened sum of an intrinsic spectrum and a schematic veiling continuum, measuring emission line fluxes from the residuals. We used extinction and distance estimates from the literature to convert measured Mg II line fluxes into intrinsic line luminosities, noting that the IUE detection limit introduces a sample bias such that intrinsic line luminosity is correlated with extinction. This sample bias complicates any physical interpretation of TTS intrinsic luminosities. We measured extinction toward HAEBE stars by fitting our co-added IUE spectra with reddened spectra of main-sequence stars and also from V band minus 3000{AA} color excess. We measured excess line emission and absorption in spectra of HAEBE stars divided by fitted spectra of main-sequence stars, noting that HAEBE stars with an infrared excess indicating circumstellar material typically also have anomalous UV line strengths. In the latter situation, Mg II is usually shallower than in a main-sequence star of the same spectral class, whereas Fe II lines are equally likely to be deeper or shallower. Our co-added spectra of TTS, HAEBE stars, and main-sequence templates are available electronically, in FITS and ASCCI format, at http://archive.stsci.edu/prepds/iuepms/ .
- ID:
- ivo://CDS.VizieR/J/A+A/602/A71
- Title:
- IUE continuum fluxes of SY Mus
- Short Name:
- J/A+A/602/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Light curves (LCs) of some symbiotic stars show a different slope of the ascending and descending branch of their minimum profile. The origin of this asymmetry is not well understood. We explain this effect in the ultraviolet LCs of the symbiotic binary SY Mus. We model the continuum fluxes in the spectra obtained by the International Ultraviolet Explorer at ten wavelengths, from 1280 to 3080{AA}. We consider that the white dwarf radiation is attenuated by H^0^ atoms, H^-^ ions, and free electrons in the red giant wind. Variation in the nebular component is approximated by a sine wave along the orbit as suggested by spectral energy distribution models. The model includes asymmetric wind velocity distribution and the corresponding ionization structure of the binary. We determined distribution of the H^0^ and H^+^, as well as upper limits of H^-^ and H^0^ column densities in the neutral and ionized region at the selected wavelengths as functions of the orbital phase. Corresponding models of the LCs match well the observed continuum fluxes. In this way, we suggested the main UV continuum absorbing (scattering) processes in the circumbinary environment of S-type symbiotic stars. The asymmetric profile of the ultraviolet LCs of SY Mus is caused by the asymmetric distribution of the circumstellar matter at the near-orbital-plane area.
- ID:
- ivo://CDS.VizieR/J/ApJS/119/207
- Title:
- IUE echelle spectra of hot white dwarfs
- Short Name:
- J/ApJS/119/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper summarizes the results obtained from a comprehensive analysis of all of the SWP echelle spectra of the white dwarf stars contained in the IUE Final Archive. A total of 209 NEWSIPS spectra of 55 degenerate stars of various types have been systematically reduced and analyzed. These include, in addition to conventional white dwarfs, several examples of the hot planetary nebula central stars such as NGC 246, which represent the initial stages of He-rich degenerate evolution. A representative summary of the stellar, circumstellar, and interstellar features found to be present in these spectra is presented. For 33 of the 55 stars, multiple spectra of sufficient quality exist so that co-added spectra with improved signal-to-noise ratio can be constructed. Much previously unrecognized detail and many new features are evident in these data. In addition, it was found necessary to apply several corrections to the NEWSIPS extracted spectra. These corrections, involving the wavelength scale and flux uncertainty vector, are described.
- ID:
- ivo://CDS.VizieR/III/83
- Title:
- IUE Low-Dispersion Reference Atlas I, Normal Stars
- Short Name:
- III/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The atlas contains the fluxes (2 angstroms/step) of 229 low-dispersion stellar spectra collected by the International Ultraviolet Explorer (IUE) satellite, compiled for the purpose of establishing reference spectral sequences in the ultraviolet range. The sequences have been constructed and the standard stars selected directly from the ultraviolet material, staying as far as possible within the general MK frame. The catalog is essentially composed of stars exhibiting normal behaviour in the ultraviolet. A few peculiar objects have, however, been included as an illustration of typical abnormalities. This work clearly pointed out the dangers of extrapolating a spectral classification based on a given wavelength range to another one, and, in particular, of using the MK spectral type alone outside its definition range.
- ID:
- ivo://CDS.VizieR/J/ApJS/147/145
- Title:
- IUE low-dispersion spectra of white dwarfs
- Short Name:
- J/ApJS/147/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have produced an archive of the ultraviolet low-dispersion spectra for the full set of white dwarf stars observed with the International Ultraviolet Explorer (IUE) satellite over the course of its 18-yr mission. This archive contains the spectra of 322 individual degenerate stars which have been processed to optimize the signal-to- noise for each star. In particular, all spectra have been corrected for residual temporal and thermal effects and placed on the Hubble Space Telescope Faint Object Spectrograph absolute flux scale using procedures described by Massa & Fitzpatrick (2000ApJS..126..517M). Wherever possible, multiple observations of individual stars have been co-added to further enhance signal-to-noise and have been combined into a single spectrum including the full 1150 to 3150{AA} wavelength region observed by IUE. The contents of this spectral archive are described and the details of data reduction procedures are provided. The electronic files of the processed spectra are available, in FITS and ASCII formats, with the associated log file, at http://vega.lpl.arizona.edu/newsips/low/
