- ID:
- ivo://CDS.VizieR/J/ApJ/764/25
- Title:
- FUSE spectra analysis of hot subdwarf stars
- Short Name:
- J/ApJ/764/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- When the neutral interstellar medium is exposed to extreme-ultraviolet and soft X-ray radiation, the argon atoms in it are far more susceptible to being ionized than the hydrogen atoms. We make use of this fact to determine the level of ionization in the nearby warm neutral medium. By analyzing Far-Ultraviolet Spectroscopic Explorer observations of ultraviolet spectra of 44 hot subdwarf stars a few hundred parsecs away from the Sun, we can compare column densities of Ar I to those of O I, where the relative ionization of oxygen can be used as a proxy for that of hydrogen. The measured deficiency [ArI/OI]=-0.427+/-0.11dex below the expectation for a fully neutral medium implies that the electron density n(e){approx}0.04/cm3 if n(H)=0.5/cm3. This amount of ionization is considerably larger than what we expect from primary photoionizations resulting from cosmic rays, the diffuse X-ray background, and X-ray emitting sources within the medium, along with the additional ionizations caused by energetic secondary photoelectrons, Auger electrons, and photons from helium recombinations. We favor an explanation that bursts of radiation created by previous, nearby supernova remnants that have faded by now may have elevated the ionization, and the gas has not yet recombined to a quiescent level. A different alternative is that the low-energy portion of the soft X-ray background is poorly shielded by the H I because it is frothy and has internal pockets of very hot, X-ray emitting gases.
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- ID:
- ivo://CDS.VizieR/J/A+A/385/986
- Title:
- FUSE UV spectrum of HR 5223
- Short Name:
- J/A+A/385/986
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New spectra have been obtained for the pole-on Be star HR 5223 (HD 120991) using the Far Ultraviolet Satellite Explorer (FUSE). We give a complete description of the far-UV spectral range (920 to 1180{AA}). The spectra are affected by strong blends with interstellar lines and molecular bands that also significantly lower the energy distribution of the star. We produce a synthetic spectrum of the interstellar medium (ISM) to determine the column densities of several elements (H_2_, H I, N I, O I ...) seen towards HR 5223 and to disentangle the components due to the ISM, the photosphere and/or to the circumstellar envelope.
- ID:
- ivo://CDS.VizieR/J/AJ/162/126
- Title:
- FUV and optical absorption in 47 Tucanae
- Short Name:
- J/AJ/162/126
- Date:
- 14 Mar 2022 08:43:21
- Publisher:
- CDS
- Description:
- The Bright Star in the globular cluster 47Tucanae (NGC104) is a post-asymptotic giant branch (post-AGB) star of spectral type B8III. The ultraviolet spectra of late-B stars exhibit myriad absorption features, many due to species unobservable from the ground. The Bright Star thus represents a unique window into the chemistry of 47Tuc. We have analyzed observations obtained with the Far Ultraviolet Spectroscopic Explorer, the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, and the Magellan Inamori Kyocera Echelle Spectrograph on the Magellan Telescope. By fitting these data with synthetic spectra, we determine various stellar parameters (Teff=10850{+/-}250K, logg=2.20{+/-}0.13) and the photospheric abundances of 26 elements, including Ne, P, Cl, Ga, Pd, In, Sn, Hg, and Pb, which have not previously been published for this cluster. Abundances of intermediate-mass elements (Mg through Ga) generally scale with Fe, while the heaviest elements (Pd through Pb) have roughly solar abundances. Its low C/O ratio indicates that the star did not undergo third dredge-up and suggests that its heavy elements were made by a previous generation of stars. If so, this pattern should be present throughout the cluster, not just in this star. Stellar-evolution models suggest that the Bright Star is powered by a He-burning shell, having left the AGB during or immediately after a thermal pulse. Its mass (0.54{+/-}0.16M{sun}) implies that single stars in 47Tuc lose 0.1-0.2M{sun} on the AGB, only slightly less than they lose on the red giant branch.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A49
- Title:
- Gaia18aen light and velocity curves
- Short Name:
- J/A+A/644/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Besides the astrometric mission of the Gaia satellite, its repeated and high-precision measurements also serve as an all-sky photometric transient survey. The sudden brightenings of the sources are published as Gaia Photometric Science Alerts and are made publicly available, allowing the community to photometrically and spectroscopically follow up on the object. The goal of this paper is to analyze the nature and derive the basic parameters of Gaia18aen, a transient detected at the beginning of 2018. This object coincides with the position of the emission-line star WRAY 15-136. The brightening was classified as a "nova?" on the basis of a subsequent spectroscopic observation. We analyzed two spectra of Gaia18aen and collected the available photometry of the object covering the brightenings in 2018 and also the preceding and following periods of quiescence. Based on this observational data, we derived the parameters of Gaia18aen and discussed the nature of the object. Gaia18aen is the first symbiotic star discovered by Gaia satellite. The system is an S-type symbiotic star and consists of an M giant of a slightly super-solar metallicity, where Teff~3500K, a radius of ~230R_{sun}_, and a high luminosity L~7400L_{sun}_. The hot component is a hot white dwarf. We tentatively determined the orbital period of the system 487d. The main outburst of Gaia18aen in 2018 was accompanied by a decrease in the temperature of the hot component. The first phase of the outburst was characterized by the high luminosity L~27000L_{sun}_, which remained constant for about three weeks after the optical maximum, later followed by the gradual decline of luminosity and increase of temperature. Several re-brightenings have been detected on the timescales of hundreds of days.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/138
- Title:
- Gaia and LAMOST DR4 M giant members of Sgr stream
- Short Name:
- J/ApJ/874/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use LAMOST DR4 M giants combined with Gaia DR2 proper motions and ALLWISE photometry to obtain an extremely pure sample of Sagittarius (Sgr) stream stars. Using TiO5 and CaH spectral indices as indicators, we selected a large sample of M-giant stars from M-dwarf stars in LAMOST DR4 spectra. Considering the position, distance, proper motion, and angular momentum distribution, we obtained 164 pure Sgr stream stars. We find that the trailing arm has higher energy than the leading arm in the same angular momentum. The trailing arm we detected extends to a heliocentric distance of ~130kpc at {Lambda}_{sun}_~170{deg}, which is consistent with the feature found in RR Lyrae in Sesar+ (2017, J/ApJ/844/L4). Both of these detections of Sgr, in M-giants and in RR Lyrae, imply that the Sgr stream may contain multiple stellar populations with a broad metallicity range.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A17
- Title:
- Gaia 19bld spectroscopic follow-up
- Short Name:
- J/A+A/657/A17
- Date:
- 21 Mar 2022 09:21:49
- Publisher:
- CDS
- Description:
- As the event displayed an increased brightness, spectroscopic follow-up observations were immediately scheduled. Low-resolution spectra (R~500) were obtained using the FLOYDS spectrograph, which is mounted on the Las Cumbres Observatory (LCO) 2-m telescope at Siding Spring Observatory In addition,we used the X-shooter instrument mounted on the ESO Very Large Telescope (VLT) which is a multi-wavelength, medium-resolution spectrograph consisted of three spectroscopic arms allowing for simultaneous observations at three wavelength ranges: UVB (300-559.5nm), VIS (559.5-1024nm), and NIR (1024-2480nm). Spectra used in this publication.
- ID:
- ivo://vopdc.obspm/gepi/gaia
- Title:
- Gaia catalog release 2
- Short Name:
- Gaia
- Date:
- 14 Nov 2018 00:30:00
- Publisher:
- Paris Astronomical Data Centre - GEPI
- Description:
- The second Gaia data release, Gaia DR2, encompasses astrometry, photometry, radial velocities, astrophysical parameters (stellar effective temperature, extinction, reddening, radius, and luminosity), and variability information for up to 1.6 billion stars. Gaia DR2 is based on the first 22 months of the nominal, five-year mission, processed by the Gaia Data Processing and Analysis Consortium (DPAC).
- ID:
- ivo://org.gavo.dc/gaia/s3/ssa
- Title:
- Gaia DR3 MC sampled XP spectra SSA
- Short Name:
- gdr3spec SSAP
- Date:
- 27 Dec 2024 08:31:12
- Publisher:
- The GAVO DC team
- Description:
- This is a re-publication the Gaia DR3 RP/BP spectra in the IVOA Spectral Data Model. It presents the continous spectra in sampled form, using a Monte Carlo scheme to decorrelate errors, elaborated in this resource's reference URL. The underlying tables are also available for querying through TAP, which opens some powerful methods for mass-analysing the data.
- ID:
- ivo://org.gavo.dc/gaia/s3/pub
- Title:
- Gaia DR3 RP/BP (XP) Monte Carlo sampled spectra
- Date:
- 06 Feb 2024 08:59:18
- Publisher:
- The GAVO DC team
- Description:
- This is a re-publication the Gaia DR3 RP/BP spectra in the IVOA Spectral Data Model. It presents the continous spectra in sampled form, using a Monte Carlo scheme to decorrelate errors, elaborated in this resource's reference URL. The underlying tables are also available for querying through TAP, which opens some powerful methods for mass-analysing the data.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A52
- Title:
- Gaia-ESO Survey: H{alpha} emission stars catalogue
- Short Name:
- J/A+A/581/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the properties of H{alpha} emission stars across the sample of 22035 spectra from the Gaia-ESO Survey internal data release, observed with the GIRAFFE instrument and largely belonging to stars in young open clusters. Automated fits using two independent Gaussian profiles and a third component accounting for the nebular emission allow us to discern distinct morphological types of H{alpha} line profiles with the introduction of a simplified classification scheme. Altogether we find 3765 stars with intrinsic emission and sort their spectra into eight distinct morphological categories: single component emission, emission blend, sharp emission peaks, double emission, P-Cygni, inverted P-Cygni, self absorption, and emission in absorption. We have more than one observation for 1430 stars in our sample, thus allowing a quantitative discussion of the degree of variability of H{alpha} emission profiles, which is expected for young, active objects. We present a catalogue of stars with properties of their H{alpha} emission line profiles, morphological classification, analysis of variability with time and the supplementary information from SIMBAD, VizieR and ADS databases. The records in SIMBAD indicate the presence of H{alpha} emission for roughly 25% of all stars in our catalogue while at least 305 of them have already been more thoroughly investigated according to the references in ADS. The most frequently identified morphological categories in our sample of spectra are emission blend (23%), emission in absorption (22%), and self absorption (16%). Objects with repeated observations demonstrate that our classification into discrete categories is generally stable through time while seemingly less stable are categories P-Cygni and Self absorption, which is the consequence of discrete classification rules as well as of the fundamental change in profile shape. Such records of emission stars can be valuable for automatic pipelines in large surveys, where it may prove very useful to pinpoint outliers during calculation of general stellar properties and elemental abundances. They can find use in studies of star formation processes, interacting binaries and other fields of stellar physics.
