- ID:
- ivo://CDS.VizieR/J/ApJ/857/111
- Title:
- Stellar yields of rotating first stars. II.
- Short Name:
- J/ApJ/857/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent theory predicts that first stars are born with a massive initial mass of >~100M_{sun}_. Pair-instability supernova (PISN) is a common fate for such massive stars. Our final goal is to prove the existence of PISNe and thus the high-mass nature of the initial mass function in the early universe by conducting abundance profiling, in which properties of a hypothetical first star is constrained by metal-poor star abundances. In order to determine reliable and useful abundances, we investigate the PISN nucleosynthesis taking both rotating and nonrotating progenitors for the first time. We show that the initial and CO core mass ranges for PISNe depend on the envelope structures: nonmagnetic rotating models developing inflated envelopes have a lower shifted CO mass range of ~70-125_M{sun}_, while nonrotating and magnetic rotating models with deflated envelopes have a range of ~80-135_M{sun}_. However, we find no significant difference in explosive yields from rotating and nonrotating progenitors, except for large nitrogen production in nonmagnetic rotating models. Furthermore, we conduct the first systematic comparison between theoretical yields and a large sample of metal-poor star abundances. We find that the predicted low [Na/Mg]~-1.5 and high [Ca/Mg]~0.5-1.3 abundance ratios are the most important to discriminate PISN signatures from normal metal-poor star abundances, and confirm that no currently observed metal-poor star matches with the PISN abundance. An extensive discussion on the nondetection is presented.
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- ID:
- ivo://CDS.VizieR/J/A+A/593/A123
- Title:
- STELLA-SES Radial Velocities of HD 208472
- Short Name:
- J/A+A/593/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD 208472 is among the most active RS CVn binaries with cool starspots. Decade-long photometry had shown that the spots seem to change their longitudinal appearance with a period of about six years, coherent with brightness variations. Our aim is to spatially resolve the stellar surface of HD 208472 and related the photometric results to the true longitudinal and latitudinal spot appearance. Furthermore, we investigate surface differential rotation pattern of the star. We employ three years of high resolution, high S/N spectroscopic data from the STELLA robotic observatory and determine new and more precise stellar physical parameters. Pre-calculated synthetic spectra are fit to each of these spectra and new spot-corrected orbital elements are given. A sample of 34 absorption lines per spectrum is used to calculate mean line profiles with a S/N of several hundred. A total of 13 temperature Doppler images are reconstructed from these line profiles with the inversion code iMap. Differential rotation is investigated by cross-correlating successive Doppler images in each observing season. Spots on HD 208472 are distributed preferably at high latitudes and less occasionally around mid-to-low latitudes. No polar-cap like structure is seen at any epoch. We observed a flip-flop event between 2009 and 2010, manifested as a flip of the spot activity from phase 0.0 to phase 0.5, while the overall brightness of the star continued to increase and reached an all-time maximum in 2014. Cross-correlation of successive Doppler images suggests a solar-like differential rotation which is ~15 times weaker in strength compared to the Sun.
20873. Stephenson H{alpha} stars
- ID:
- ivo://CDS.VizieR/J/A+A/402/963
- Title:
- Stephenson H{alpha} stars
- Short Name:
- J/A+A/402/963
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of spectroscopic observations for 52 objects from the list of H{alpha} emission stars of Stephenson (1986ApJ...300..779S). Out of six known T Tauri stars observed, five showed H{alpha} in emission and in one (StHa 40), H{alpha} changed from being in absorption to emission over a period of two years, accompanied by photometric and spectral type variability. We confirm the T Tauri nature of one Stephenson object (StHa 48) on the basis of the presence of H{alpha} and H{beta} in emission, Li I {lambda}6708 in absorption, infrared excess and X-ray emission. Among the 52 objects observed, there were other emission line objects: 1 Ke star, 1 BQ[] star, 2 galaxies and 2 Be stars. We present a higher-resolution spectrum of StHa 62 showing permitted and forbidden lines in emission typical of BQ[] stars. Twenty five out of 30 newly observed objects failed to show H{alpha} in emission. We also present 2MASS observations for 112 StHa objects. We suggest three Stephenson objects (StHa 52, 125 and 129) to be YSOs on the basis of 2MASS, IRAS and ROSAT observations. These and all other known YSOs amongst StHa stars are found in regions of star-forming clouds in Taurus, Orion and Ophiuchus. YSOs at high galactic latitudes in other parts of the sky are therefore rare.
- ID:
- ivo://CDS.VizieR/J/MNRAS/420/757
- Title:
- STEREO magnetic chemically peculiar stars
- Short Name:
- J/MNRAS/420/757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- About 10% of upper main-sequence stars are characterized by the presence of chemical peculiarities, often found together with a structured magnetic field. The atmospheres of most of those chemically peculiar stars present surface spots, leading to photometric variability caused by rotational modulation. The study of the light curves of those stars therefore permits a precise measurement of their rotational period, which is important to study stellar evolution and to plan further detailed observations. We analysed the light curves of 1028 chemically peculiar stars obtained with the STEREO spacecraft. We present here the results obtained for the 337 magnetic chemically peculiar stars in our sample.
- ID:
- ivo://CDS.VizieR/J/MNRAS/429/119
- Title:
- STEREO non-magnetic chemically peculiar stars
- Short Name:
- J/MNRAS/429/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analysed the photometric data obtained with the STEREO spacecraft for 558 non-magnetic chemically peculiar (CP) stars to search for rotational and pulsational variability. Applying the Lomb-Scargle and the phase dispersion minimization methods, we have detected photometric variability for 44 objects from which 35 were previously unknown. The new objects are all bright stars on the ecliptic plane (magnitude range 4.7<V<11.7) and will therefore be of great interest to studies of stellar structure and evolution. In particular, several show multiple signals consistent with hybrid {delta} Scuti and {gamma} Doradus pulsation, with different periodicities allowing very different regions of the stellar interior to be studied. There are two subgroups of stars in our sample: the cool metallic line Am (CP1) and the hot HgMn (CP3) stars. These objects fall well inside the classical instability strip where {delta} Scuti, {gamma} Doradus and slowly pulsating B-type stars are located. We also expect to find periods correlated to the orbital period for CP1 objects as they are mostly members of binary systems. For CP3 stars, rotationally induced variability is still a matter of debate. Although surface spots were detected, they are believed to produce only marginal photometric amplitudes. So, periods from several hours to a few days were expected for these two star groups. The STEREO/HI-1 data are well matched to studies of this frequency domain, owing to the cadence of approximately 40-min and multiple epochs over four and a half years. The remaining 514 stars are likely to be constant in the investigated range from 0.1 to 10d. In some cases, the presence of blending or systematic effects prevented us from detecting any reliable variability and in those cases we classified the star as constant. We discuss our results in comparison to already published ones and find a very good agreement. Finally, we have calibrated the variable stars in terms of the effective temperature and luminosity in order to estimate masses and ages. For this purpose, we used specifically developed calibrations for CP stars and, when available, Hipparcos parallaxes. All but two objects cover the stellar mass range from 1.5 to 5M_{sun}_ and are located between the zero- and terminal-age main sequence.
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/2477
- Title:
- STEREO observations of variable stars
- Short Name:
- J/MNRAS/416/2477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The feasibility of using data from the NASA STEREO mission for variable star and asteroseismology studies has been examined. A data analysis pipeline has been developed that is able to apply selected algorithms to the entire database of nearly a million stars to search for signs of variability. An analysis limited to stars of magnitude 10.5 has been carried out, which has resulted in the extraction of 263 eclipsing binaries (EBs), of which 122 are not recorded as such in the SIMBAD online database. The characteristics of the STEREO observations are shown to be extremely well-suited to variable star studies with the ability to provide continuous phase coverage for extended periods as well as repeated visits that allow both short and long term variability to be observed. This will greatly inform studies of particular stars, such as the pre-cataclysmic variable V471 Tau, as well as entire classes of stars, including many forms of rotational variability. The high-precision photometry has also revealed a potentially substellar companion to a bright (R=7.5mag) nearby star (HD 213597), detected with 5 sigma significance. This would provide a significant contribution to exoplanet research if follow-up observations ascertain the mass to be within the planetary domain. Some particularly unusual EBs from the recovered sample are discussed, including a possible reclassification of a well-known star as an EB rather than a rotational variable (HR 7355) and several particularly eccentric systems, including very long-period EBs.
- ID:
- ivo://astronet.ru/cas/registry
- Title:
- Sternberg Astronomical Institute Catalog Access Services Publishing Registry
- Short Name:
- SAI CAS
- Date:
- 17 Jun 2006 18:44:05
- Publisher:
- Sternberg Astronomical Institute Virtual Observatory Project
- Description:
- SAI CAS publishing registry
- ID:
- ivo://nasa.heasarc/saisncat
- Title:
- Sternberg Astronomical Institute Catalog of Supernovae
- Short Name:
- SAISN
- Date:
- 09 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table comprises the Sternberg Astronomical Institute (SAI) Catalog of Supernovae. This version contains data on 2991 extragalactic supernovae (SNe) which were discovered from 1885 until December 12, 2004 and on their host galaxies. Data for host galaxies were compiled from the following catalogues: (1) RC3 (de Vaucouleurs et al. 1991, Cat. <VII/155>); (2) UGC (Nilson 1973. Cat. <VII/26>); (3) PGC (Paturel et al. 1989, Cat. <VII/119>); (4) MCG (Vorontsov-Velyaminov et al. 1962-1968, Cat. <VII/62>, <VII/100>); (5) ESO (Lauberts 1982, Cat. <VII/34>); (6) CfA (Huchra et al. 1994, see Cat <VII/193>), and (7) from van den Bergh (1994, Cat. <J/ApJS/92/219>). The main source of morphological types, major diameters and axial ratios was the RC3; the data from other sources were reduced to the system of RC3. Photographic magnitudes of galaxies were adopted from the UGC and the PGC together with individual data from the literature. The sources of recession velocities or cz values were the RC3, the CfA, the PGC and IAU Circulars. Position angles were taken from the RC3, UGC and the ESO catalogues, and inclination angles were mainly derived from data in RC3 according to Holmberg (1958MeLu2.136....1H). Some data for SNe and host galaxies were adopted from the GCVS (Samus et al. 1995, Cat. <II/205>). This table was created by the HEASARC in June 2005 based on CDS table II/256/sn.dat. Notice that the number of entries (2991) is more than the number of 2780 mentioned in the published reference: this is apparently due to the fact that the CDS table contains supernovae as recent as December 12, 2004, while the latter is complete only until January 6, 2004. This is a service provided by NASA HEASARC .
- ID:
- ivo://voxastro.org/org
- Title:
- Sternberg Astronomical Institute, Moscow State University
- Date:
- 06 Feb 2017 00:33:18
- Publisher:
- Virtual Observatory for Extragalactic Astrophysics
- Description:
- Sternberg Astronomical Institute is a research unit within Moscow State University, Russia
- ID:
- ivo://astronet.ru
- Title:
- Sternberg Astronomical Institute Virtual Observatory Project
- Short Name:
- SAI VO
- Date:
- 01 Jan 2006
- Publisher:
- Sternberg Astronomical Institute Virtual Observatory Project
- Description:
- Virtual Observatory project at the Sternberg Astronomical Institute provides public access to the growing set of astronomical services developed by the SAI RVO in accordance with the Virtual Observatory standards.
