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101. ExoMol line lists for SiO
ID:
ivo://CDS.VizieR/J/MNRAS/434/1469
Title:
ExoMol line lists for SiO
Short Name:
J/MNRAS/434/1469
Date:
21 Oct 2021
Publisher:
CDS
Description:
Accurate rotation-vibration line lists are calculated for silicon monoxide. Line lists are presented for the main isotopologue, ^28^Si^16^O, and four monosubstituted isotopologues ^29^Si^16^O, ^30^Si^16^O, ^28^Si^17^O and ^28^Si^18^O, in their ground electronic states. These line lists are suitable for high temperatures (up to 9000K) including those relevant to exoplanetary atmospheres and cool stars. A combination of empirical and ab initio methods is used: the potential energy curves are determined to high accuracy by fitting to extensive data from analysis of both laboratory and sunspot spectra; a high quality ab initio dipole moment curve is calculated at the large basis set, multi-reference configuration interaction (MRCI) level. A partition function plus full line lists of rotation-vibration transitions are made available in an electronic form as supplementary data to this article and at www.exomol.com.
102. Far-UV excess object survey
ID:
ivo://CDS.VizieR/J/A+A/250/370
Title:
Far-UV excess object survey
Short Name:
J/A+A/250/370
Date:
21 Oct 2021
Publisher:
CDS
Description:
Optical spectra have been obtained for a selection of objects included in a catalog of far ultraviolet bright, high galactic latitude objects detected with a balloon-borne survey telescope. The observed objects provide a sample of subdwarf O and B stars, white dwarfs, and binary systems including a hot sub-luminous member. Model atmospheres analysis of the sub-dwarf sample is used to determine the temperature, gravity, and helium to hydrogen ratio of the individual objects. A smooth distribution of objects is found on the gravity versus temperature diagram near the theoretical location of the extended horizontal branch. A break between the helium rich and helium poor objects occurs at 40000K. Suspected binary objects were found and analyzed to determine the temperature and gravity of the hot subluminous member in each system. The number of subdwarf stars contained in binaries is determined to be from 65% to 100%. The number versus ultraviolet magnitude distribution of the subdwarf B sample is modeled to obtain a midplane density of 3.3x10^-6^pc^-3^ and a population scale height of 240pc. The proportion of white dwarfs that experience the subdwarf phase of evolution is found to be 0.94%.
103. Far-UV spectral atlas of O-type stars
ID:
ivo://CDS.VizieR/J/ApJS/202/17
Title:
Far-UV spectral atlas of O-type stars
Short Name:
J/ApJS/202/17
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, we present a spectral atlas covering the wavelength interval 930-1188{AA} for O2-O9.5 stars using Far-Ultraviolet Spectroscopic Explorer archival data. The stars selected for the atlas were drawn from three populations: Galactic main-sequence (classes III-V) stars, supergiants, and main-sequence stars in the Magellanic Clouds, which have low metallicities. For several of these stars, we have prepared FITS files comprised of pairs of merged spectra for user access via the Multimission Archive at Space Telescope (MAST). We chose spectra from the first population with spectral types O4, O5, O6, O7, O8, and O9.5 and used them to compile tables and figures with identifications of all possible atmospheric and interstellar medium lines in the region 949-1188{AA}. Our identified line totals for these six representative spectra are 821 (500), 992 (663), 1077 (749), 1178 (847), 1359 (1001), and 1798 (1392) lines, respectively, where the numbers in parentheses are the totals of lines formed in the atmospheres, according to spectral synthesis models. The total number of unique atmospheric identifications for the six main-sequence O-star template spectra is 1792, whereas the number of atmospheric lines in common to these spectra is 300. The number of identified lines decreases toward earlier types (increasing effective temperature), while the percentages of "missed" features (unknown lines not predicted from our spectral syntheses) drop from a high of 8% at type B0.2, from our recently published B-star far-UV atlas (Cat. J/ApJS/186/175), to 1%-3% for type O spectra. The percentages of overpredicted lines are similar, despite their being much higher for B-star spectra.
104. Far-UV spectra of Galactic corona sight lines
ID:
ivo://CDS.VizieR/J/ApJ/749/157
Title:
Far-UV spectra of Galactic corona sight lines
Short Name:
J/ApJ/749/157
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of the properties of the transition temperature (T~10^5^K) gas in the Milky Way corona, based on the measurements of OVI, NV, CIV, SiIV, and FeIII absorption lines seen in the far-ultraviolet spectra of 58 sight lines to extragalactic targets, obtained with the Far-Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph. In many sight lines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly ionized atoms are distributed irregularly in a layer with a scale height of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60km/s. On average the integrated column densities are logN(OVI)=14.3, logN(NV)=13.5, logN(CIV)=14.2, logN(SiIV)=13.6, and logN(FeIII)=14.2, with a dispersion of just 0.2 dex in each case. In sight lines around the Galactic center and Galactic north pole, all column densities are enhanced by a factor ~2, while at intermediate latitudes in the southern sky there is a deficit in N(O VI) of about a factor of two, but no deficit for the other ions.
105. Far-UV spectra of PN central stars
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.
106. Far-UV spectroscopic atlas of B stars
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.
107. Far-UV spectroscopy of T Tau stars
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.
108. FAUST observations in 4th Galactic Quadrant
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 .
109. FAUST UV sources towards Ophiuchus
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.
110. FeII emission in SDSS type 1 AGNs
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.