- ID:
- ivo://CDS.VizieR/J/A+A/553/A126
- Title:
- Far-UV spectra of PN central stars
- Short Name:
- J/A+A/553/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The occurrence of stellar wind in the central star of a planetary nebula (CSPN) can be revealed by the presence of P Cygni profiles of high-excitation lines overimposed on its stellar continuum. We have examined the entire Far-Ultraviolet Spectroscopic Explorer FUSE archive and merged all useful spectroscopic observations of CSPNe to produce the highest quality spectra that can be used to assess the occurrence of stellar winds. Furthermore, the individual spectra of each CSPN have been compared to search for variability in the P Cygni profile. P Cygni profiles of high-excitation lines have been found in 44 CSPNe, with a clear correlation between the ionization potential of the lines and the effective temperature of the star.
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- ID:
- ivo://CDS.VizieR/J/ApJS/186/175
- Title:
- Far-UV spectroscopic atlas of B stars
- Short Name:
- J/ApJS/186/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have constructed a detailed spectral atlas covering the wavelength region 930-1225{AA} for 10 sharp-lined B0-B9 stars near the main sequence. Most of the spectra we assembled are from the archives of the Far Ultraviolet Spectroscopic Explorer satellite, but for nine stars, wavelength coverage above 1188{AA} was taken from high-resolution International Ultraviolet Explorer or echelle Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra. To represent the tenth star at type B0.2V, we used the Copernicus atlas of tau Sco. We made extensive line identifications in the region 949-1225{AA} of all atomic features having published oscillator strengths at types B0, B2, and B8. These are provided as a supplementary data product-hence the term detailed atlas. Our list of found features totals 2288, 1612, and 2469 lines, respectively. We were able to identify 92%, 98%, and 98% of these features with known atomic transitions with varying degrees of certainty in these spectra. The remaining lines do not have published oscillator strengths. Photospheric lines account for 94%, 87%, and 91%, respectively, of all our identifications, with the remainder being due to interstellar (usually molecular H2) lines. We also discuss the numbers of lines with respect to the distributions of various ions for these three most studied spectral subtypes. A table is also given of 162 least blended lines that can be used as possible diagnostics of physical conditions in B star atmospheres.
- ID:
- ivo://CDS.VizieR/J/ApJ/744/121
- Title:
- Far-UV spectroscopy of T Tau stars
- Short Name:
- J/ApJ/744/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a far-ultraviolet (FUV) spectral atlas consisting of spectra of 91 pre-main-sequence stars. Most stars in this sample were observed with the Space Telescope Imaging Spectrograph and Advanced Camera for Surveys on the Hubble Space Telescope (HST). A few archival spectra from the International Ultraviolet Explorer and the Goddard High Resolution Spectrograph on HST are included for completeness. We find strong correlations among the OI{lambda}1304 triplet, the SiIV {lambda}{lambda}1394/1403 doublet, the CIV{lambda}1549 doublet, and the HeII {lambda}1640 line luminosities. For classical T Tauri stars (CTTSs), we also find strong correlations between these lines and the accretion luminosity, suggesting that these lines form in processes related to accretion. These FUV line fluxes and X-ray luminosity correlate loosely with large scatters. The FUV emission also correlates well with H{alpha}, H{beta}, and CaII K line luminosities. These correlations between FUV and optical diagnostics can be used to obtain rough estimates of FUV line fluxes from optical observations. Molecular hydrogen (H_2_) emission is generally present in the spectra of actively accreting CTTSs but not the weak-lined T Tauri stars that are not accreting. The presence of H_2_ emission in the spectrum of HD 98800N suggests that the disk should be classified as actively accreting rather than a debris disk.
- ID:
- ivo://CDS.VizieR/J/MNRAS/313/641
- Title:
- FAUST observations in 4th Galactic Quadrant
- Short Name:
- J/MNRAS/313/641
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UV observations of FAUST are analysed in four sky fields (Dor, Cen, M81 and Tel), located in the general direction of the Fourth Galactic Quadrant, where 777 UV sources are detected, about 50% more than detected originally by Bowyer et al. (1993ApJ...415..875B). Ground-based objective-prism information for two of the fields were used to select the best-matching optical objects with which to identify the UV sources. Using this, and correlations with existing catalogues, reliable identifications are presented for about 75% of the sources. Most of the remaining sources have assigned optical counterparts but, lacking additional information, we offer only plausible identifications. FAUST is a wide-field telescope (7.6{deg} diameter) designed to image diffuse and point sources in the wavelength range 140-180nm. The experiment, the mission and the data are described in a previous paper by Bowyer et al., 1993ApJ...415..875B .
- ID:
- ivo://CDS.VizieR/J/MNRAS/332/441
- Title:
- FAUST UV sources towards Ophiuchus
- Short Name:
- J/MNRAS/332/441
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of an analysis of a UV image in the direction of Ophiuchus, obtained with the FAUST instrument. The image contains 228 UV sources. Most of these are identified as normal early-type stars through correlations with catalogued objects. For the first time in this project we identify UV sources as such stars by selecting suitable candidates in crowded fields as the bluest objects in colour-colour diagrams using observations from the Wise Observatory. These candidates are then studied using low-resolution spectroscopy, which allows the determination of spectral types to an accuracy of about one-half class, for 60 stars. Synthetic photometry of spectral data is performed in order to predict the expected UV emission, on the basis of the photometric information. These results are used along with the Hipparcos/Tycho (<I/239>) information, to search for subluminous stars. The comparison of the predicted emission with the FAUST measured magnitudes allows us to select 12 stars as highly probable evolved hot stars. High signal-to-noise spectra are obtained for nine of these stars, and Balmer line profiles are compared with the prediction of atmosphere models and with the spectrum of real stellar atmospheres. Among the nine candidates, six are classified as previously unrecognized sdB stars, and two as white dwarfs. Our result indicates that indeed more bright subluminous stars are still unrecognized in the existing samples.
- ID:
- ivo://CDS.VizieR/J/ApJ/736/86
- Title:
- FeII emission in SDSS type 1 AGNs
- Short Name:
- J/ApJ/736/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used a large, homogeneous sample of 4178 z<=0.8 Seyfert 1 galaxies and QSOs selected from the Sloan Digital Sky Survey to investigate the strength of FeII emission and its correlation with other emission lines and physical parameters of active galactic nuclei. We find that the strongest correlations of almost all the emission-line intensity ratios and equivalent widths (EWs) are with the Eddington ratio (L/L_Edd_), rather than with the continuum luminosity at 5100{AA} (L_5100_) or black hole mass (M_BH_); the only exception is the EW of ultraviolet FeII emission, which does not correlate at all with broad-line width, L_5100_, M_BH_, or L/L_Edd_. By contrast, the intensity ratios of both the ultraviolet and optical FeII emission to MgII{lambda}2800 correlate quite strongly with L/L_Edd_. Interestingly, among all the emission lines in the near-UV and optical studied in this paper (including MgII{lambda}2800, H{beta}, and [OIII]{lambda}5007), the EW of narrow optical FeII emission has the strongest correlation with L/L_Edd_. We hypothesize that the variation of the emission-line strength in active galaxies is regulated by L/L_Edd_ because it governs the global distribution of the hydrogen column density of the clouds gravitationally bound in the line-emitting region, as well as its overall gas supply. The systematic dependence on L/L_Edd_ must be corrected when using the FeII/MgII intensity ratio as a measure of the Fe/Mg abundance ratio to study the history of chemical evolution in QSO environments.
- ID:
- ivo://CDS.VizieR/J/A+A/370/1071
- Title:
- Fe XII UV line intensity ratios
- Short Name:
- J/A+A/370/1071
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new set of radiative and electron collisional data for Fe XII was presented in two earlier papers. In the present work, we derive level populations and theoretical line intensities for a range of plasma densities and temperatures. Observations of Fe XII lines obtained with the Solar EUV Rocket Telescope and Spectrograph are analysed both as a check on the quality of the new atomic data and to determine the electron density in active regions and the quiet Sun. The discrepancy between the electron density values determined from Fe XII line intensity ratios and those obtained from other ions is investigated.
- ID:
- ivo://CDS.VizieR/VI/110
- Title:
- Final Merged Log of IUE Observations
- Short Name:
- VI/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The log contains a summary of all IUE Newly Extracted Spectra (INES), which resulted from a post-processing effort at Vilspa. It was constructed by using verified data from the IUE Final Archive Master Catalogue. The observations cover the whole life of the satellite, from March 1978 to September 1996.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A59
- Title:
- Fluctuations of UV background from GALEX
- Short Name:
- J/A+A/631/A59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The all sky survey run by the Galaxy Evolution Explorer (GALEX AIS) mapped about 85 % of the Galaxy at ultraviolet (UV) wavelengths and detected the diffuse UV background produced by the scattering of the radiation from OBA stars by interstellar dust grains. Against this background, diffuse weak structures are detected as well as the UV counterparts to nebulae and molecular clouds. To make full profit of the survey, unsupervised and semi-supervised procedures need to be implemented. The main objective of this work is to implement and analyze the results of the method developed by us for the blind detection of ISM features in the GALEX AIS. Most ISM features are detected at very low signal levels (dark filaments, globules) against the already faint UV background. We have defined an index the UV background fluctuations index (or UBF index) to identify areas of the sky where these fluctuations are detected. The algorithm is applied to the images obtained in the FUV (1344-1786{AA}) band since this is less polluted by stellar sources, facilitating the automated detection. The UBF index is shown to be sensitive to the main star forming regions within the Gould's Belt, as well as to some prominent loops like Loop I or the Eridanus and Monogem areas. The catalogue with the UBF index values is made available on-line to the community.
- ID:
- ivo://CDS.VizieR/J/AJ/152/102
- Title:
- Flux conversion factors for the Swift/UVOT filters
- Short Name:
- J/AJ/152/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the transformation of observed photometry into flux for the creation of spectral energy distributions (SED) and the computation of bolometric luminosities. We do this in the context of supernova studies, particularly as observed with the Swift spacecraft, but the concepts and techniques should be applicable to many other types of sources and wavelength regimes. Traditional methods of converting observed magnitudes to flux densities are not very accurate when applied to UV photometry. Common methods for extinction and the integration of pseudo-bolometric fluxes can also lead to inaccurate results. The sources of inaccuracy, though, also apply to other wavelengths. Because of the complicated nature of translating broadband photometry into monochromatic flux densities, comparison between observed photometry and a spectroscopic model is best done by forward modeling the spectrum into the count rates or magnitudes of the observations. We recommend that integrated flux measurements be made using a spectrum or SED which is consistent with the multi-band photometry rather than converting individual photometric measurements to flux densities, linearly interpolating between the points, and integrating. We also highlight some specific areas where the UV flux can be mischaracterized.
