- 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.
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- 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/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/
- ID:
- ivo://CDS.VizieR/J/ApJS/119/83
- Title:
- IUE sample of binaries with hot component
- Short Name:
- J/ApJS/119/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained or retrieved IUE spectra for over 100 middle- and late-type giant and supergiant stars whose spectra indicate the presence of a hot component earlier than type F2. The hot companions are classified accurately by temperature class from their far-UV spectra. The interstellar extinction of each system and the relative luminosities of the components are derived from analysis of the UV and optical fluxes, using a grid of UV intrinsic colors for hot dwarfs. We find that there is fair agreement in general between current UV spectral classification and ground-based hot component types, in spite of the difficulties of assigning the latter. There are a few cases in which the cool component optical classifications disagree considerably with the temperature classes inferred from our analysis of UV and optical photometry. The extinction parameter agrees moderately well with other determinations of B-V color excess. Many systems are worthy of further study especially to establish their spectroscopic orbits. Further work is planned to estimate luminosities of the cool components from the data herein; in many cases, these luminosities' accuracies should be comparable to or exceed those of the Hipparcos parallaxes.
- ID:
- ivo://CDS.VizieR/J/A+A/331/633
- Title:
- IUE spectra of lambda Boo stars
- Short Name:
- J/A+A/331/633
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An analysis of the stars included in the catalogue of {lambda} Bootis stars by Paunzen et al. (1997, Cat. <J/A+AS/123/93>) and which also have IUE observations is presented here. Population I A-F type stars as well as field horizontal branch stars were also included in the analysis. Using line-ratios of carbon to heavier elements (Al and Ni) allows us to establish unambiguous membership criteria for the {lambda} Bootis group.
- ID:
- ivo://CDS.VizieR/J/ApJS/93/211
- Title:
- IUE survey of H I Ly{alpha} absorption. I.
- Short Name:
- J/ApJS/93/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure Galactic interstellar neutral hydrogen column densities by analyzing archival interstellar Ly{alpha} absorption line data toward 554 B2 and hotter stars observed at high resolution with the IUE satellite. This study more than doubles the number of lines of sight with measures of N(H I) based on Ly{alpha}. We have included the scattered light background correction algorithm of Bianchi and Bohlin (1984A&A...134...31B) in our data reduction. We use the correlation between the Balmer discontinuity [c_1_] index and the stellar Ly{alpha} absorption in order to assess the effects of stellar Ly alpha contamination. Approximately 40% of the B stars with measured [c_1_] index, exhibit serious stellar Ly{alpha} contamination. Table 1 contains the derived values of the interstellar N(H I) for 393 stars with at most small amounts of stellar contamination. Table 2 lists the observed values of total N(H I) for 161 stars with suspected stellar Ly alpha contamination and/or uncertain stellar parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/160/12
- Title:
- J, Ks, NUV emission of 133 red giant stars
- Short Name:
- J/AJ/160/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Main-sequence stars exhibit a clear rotation-activity relationship, in which rapidly rotating stars drive strong chromospheric/coronal ultraviolet and X-ray emission. While the vast majority of red giant stars are inactive, a few percent exhibit strong ultraviolet emission. Here we use a sample of 133 red giant stars observed by Sloan Digital Sky Survey APOGEE and Galaxy Evolution Explorer to demonstrate an empirical relationship between near-UV (NUV) excess and rotational velocity (vsini). Beyond this simple relationship, we find that NUV excess also correlates with rotation period and with Rossby number in a manner that shares broadly similar trends to those found in M dwarfs, including activity saturation among rapid rotators. Our data also suggest that the most extremely rapidly rotating giants may exhibit so-called supersaturation, which could be caused by centrifugal stripping of these stars rotating at a high fraction of breakup speed. As an example application of our empirical rotation-activity relation, we demonstrate that the NUV emission observed from a recently reported system comprising a red giant with a black hole companion is fully consistent with arising from the rapidly rotating red giant in that system. Most fundamentally, our findings suggest a common origin of chromospheric activity in rotation and convection for cool stars from main sequence to red giant stages of evolution.
