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- ID:
- ivo://CDS.VizieR/J/A+A/372/145
- Title:
- Symbiotic stars UBV(RI)c photometry. II.
- Short Name:
- J/A+A/372/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accurate UBV(RI)_C_ photometric sequences for an additional 20 symbiotic stars. As for the 20 targets of Paper I (Henden et al., 2000, Cat. <J/A+AS/143/343>), the sequences extend over wide brightness and color ranges, and are suited to cover both quiescence and outburst phases. The sequences are intended to assist both present time photometry as well as measurement of photographic plates from historical archives.
- ID:
- ivo://CDS.VizieR/J/A+A/458/339
- Title:
- Symbiotic stars UBV(RI)c photometry. III.
- Short Name:
- J/A+A/458/339
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accurate UBV(RI)_C_ photometric sequences and astrometric positions for a final set of 41 symbiotic stars. In a similar manner to the 40 targets of Papers I and II, these sequences extend over wide brightness and color ranges and are suited to covering both quiescence and outburst phases. They are intended to assist both the CCD photometric monitoring of current variability and exploitation of old photographic plates from historical archives.
- ID:
- ivo://CDS.VizieR/J/A+AS/111/57
- Title:
- Synthetic absorption in star forming regions
- Short Name:
- J/A+AS/111/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectral evolutionary calculations have been employed in order to follow the behaviour of absorption lines in single-burst star forming regions. The model calculations are based on theoretical evolutionary tracks and model atmosphere stellar spectra at 5A resolution and they include the pre-main sequence phase. Three different metallicities have been considered; Z=0.001, 0.008 and 0.020, this range covers easily the one occupied by blue compact dwarf galaxies. This analysis focuses on the post-active burst phase and follows the evolution up to 15 million years after the episode of star formation has ceased, using an instantaneous burst of star formation. The absorption lines included are hydrogen, neutral and once ionized helium. Non-LTE absorption line profiles have been implemented to these lines, also at a 5A resolution. The equivalent widths and line profiles are studied as a function of lower and upper mass limits and slope of the mass function as well as the age. It is shown that the equivalent widths of the Balmer lines are increasing during the course of evolution, while the strength of the neutral and ionized helium lines decreases monotonically. Both the hydrogen and helium lines show high sensitivity to variations in the initial mass function (IMF). The Balmer line equivalent widths range from about 1.5 to 6.5A, depending on the IMF parameters used. As anticipated, these numbers are rather insensitive to the metallicity. Contrary to what has been claimed, the Balmer lines are prominent even if the lower mass limit is as high as 10M_{sun}_. It has been proposed that the weak hydrogen lines sometimes seen in starburst galaxies, often interpreted as evidence for a deficiency in low mass stars, could be due to the finite lifetimes of pre-main sequence stars. This analysis shows that it is very much dependent on the slope of the mass function. The equivalent width of the HeI-4471A line never exceeds 0.35A for any choice of the IMF parameters while the equivalent width of the HeII-4686A line reaches at the most 0.20A using the most top-heavy IMF. As expected, these numbers are only slightly dependent on the metallicity in the optical spectral region.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1227
- Title:
- Synthetic Stroemgren photometry
- Short Name:
- J/AJ/127/1227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new grid of theoretical color indices for the Stroemgren uvby photometric system has been derived from MARCS model atmospheres and SSG synthetic spectra for cool dwarf and giant stars having -3.0<=[Fe/H]<=+0.5 and 3000<=T_eff_<=8000K. In the present investigation, we have also analyzed the observed Stroemgren photometry for the classic Population II subdwarfs, compared our "final" (b-y)-Teff relationship with those derived empirically in a number of recent studies and examined in some detail the dependence of the m1 index on [Fe/H].
3696. SZ Her BVRI light curves
- ID:
- ivo://CDS.VizieR/J/AJ/143/34
- Title:
- SZ Her BVRI light curves
- Short Name:
- J/AJ/143/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiband CCD photometric observations of SZ Her were obtained between 2008 February and May. The light curve was completely covered and indicated a significant temperature difference between both components. The light-curve synthesis presented in this paper indicates that the eclipsing binary is a classical Algol-type system with parameters of q=0.472, i=87.57{deg}, and {Delta}(T_1_-T_2_)=2381K; the primary component fills approximately 77% of its limiting lobe and is slightly larger than the lobe-filling secondary component. More than 1100 times of minimum light spanning more than a century were used to study an orbital behavior of the binary system. It was found that the orbital period of SZ Her varied due to a combination of two periodic variations with cycle lengths of P_3_=85.8yr and P_4_=42.5yr and semi-amplitudes of K_3_=0.013days and K_4_=0.007days, respectively. The most reasonable explanation for these variations is a pair of light-time effects driven by the possible existence of two M-type companions with minimum masses of M_3_=0.22M_{sun}_ and M_4_=0.19M_{sun}_ that are located close to the 2:1 mean motion resonance. If two additional bodies exist, then the overall dynamics of the multiple system may provide a significant clue to the formation and evolution of the eclipsing pair.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A138
- Title:
- Taffy system CO(1-0) datacube
- Short Name:
- J/A+A/647/A138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Taffy system (UGC 12914/15) consists of two massive spiral galaxies which had a head-on collision about 20Myr ago. New sensitive, high-resolution CO(1-0) observations of the Taffy system with the IRAM PdBI are presented. About 25% of the total interferometric CO luminosity stems from the bridge region. Assuming a Galactic N(H2)/ICO conversion factor for the galactic disks and a third of this value for the bridge gas, about 10% of the molecular gas mass is located in the bridge region. The giant HII region close to UGC 12915 is located at the northern edge of the high-surface brightness giant molecular cloud association (GMA), which has the highest velocity dispersion among the bridge GMAs. The bridge GMAs are clearly not virialized because of their high velocity dispersion. Three dynamical models are presented and while no single model reproduces all of the observed features, they are all present in at least one of the models. Most of the bridge gas detected in CO does not form stars. We suggest that turbulent adiabatic compression is responsible for the exceptionally high velocity dispersion of the molecular ISM and the suppression of star formation in the Taffy bridge. In this scenario the turbulent velocity dispersion of the largest eddies and turbulent substructures/clouds increase such that giant molecular clouds are no longer in global virial equilibrium. The increase of the virial parameter leads to a decrease of the star formation efficiency. Most of the low-surface density, CO-emitting gas will disperse without forming stars but some of the high-density gas will probably collapse and form dense star clusters, such as the luminous HII region close to UGC 12915. We suggest that globular clusters and super star clusters formed and still form through the gravitational collapse of gas previously compressed by turbulent adiabatic compression during galaxy interactions.
- ID:
- ivo://CDS.VizieR/J/AJ/133/1470
- Title:
- TAROT suspected variable star catalog
- Short Name:
- J/AJ/133/1470
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- TAROT (Telescope a Action Rapide pour les Objets Transitoires) is a robotic observatory designed to observe very early optical transients of gamma-ray bursts (GRBs). As GRBs do not often occur, we use TAROT for various other celestial targets spread over the sky. For every field observed by TAROT, we computed the magnitudes of every star. From this work, we found 1175 new variable stars brighter than 17mag. We selected the best variable star candidates and compiled them in the TSVSC1 (TAROT Suspected Variable Star Catalog, ver. 1), which also contains Fourier-series coefficients that fit the light curves.
- ID:
- ivo://CDS.VizieR/II/230
- Title:
- TASS Mark III photometric survey
- Short Name:
- II/230
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Amateur Sky Survey (TASS) is a loose confederation of amateur and professional astronomers. We describe the design and construction of our Mark III system, a set of wide-field drift-scan CCD cameras which monitor the celestial equator down to 13th magnitude in several passbands. We explain the methods by which images are gathered, processed, and reduced into lists of stellar positions and magnitudes. Over the period 1996 October to 1998 November, we compiled a large database of photometric measurements. One of our results is the tenxcat catalog, which contains measurements on the standard Johnson-Cousins system for 367,241 stars; it contains links to the light curves of these stars as well.
- ID:
- ivo://CDS.VizieR/J/AJ/159/273
- Title:
- Taurus members & nonmembers with K2 data
- Short Name:
- J/AJ/159/273
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of K2 light curves (LCs) from Campaigns 4 and 13 for members of the young (~3Myr) Taurus association, in addition to an older (~30Myr) population of stars that is largely in the foreground of the Taurus molecular clouds. Out of 156 of the highest-confidence Taurus members, we find that 81% are periodic. Our sample of young foreground stars is biased and incomplete, but nearly all stars (37/38) are periodic. The overall distribution of rotation rates as a function of color (a proxy for mass) is similar to that found in other clusters: the slowest rotators are among the early M spectral types, with faster rotation toward both earlier FGK and later M types. The relationship between period and color/mass exhibited by older clusters such as the Pleiades is already in place by Taurus age. The foreground population has very few stars but is consistent with the USco and Pleiades period distributions. As found in other young clusters, stars with disks rotate on average slower, and few with disks are found rotating faster than ~2days. The overall amplitude of the LCs decreases with age, and higher-mass stars have generally lower amplitudes than lower-mass stars. Stars with disks have on average larger amplitudes than stars without disks, though the physical mechanisms driving the variability and the resulting LC morphologies are also different between these two classes.
