- ID:
- ivo://CDS.VizieR/J/MNRAS/353/601
- Title:
- 2dF survey of the Small Magellanic Cloud
- Short Name:
- J/MNRAS/353/601
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of new spectral types for hot, luminous stars in the Small Magellanic Cloud. The catalogue contains 4161 objects, giving an order of magnitude increase in the number of SMC stars with published spectroscopic classifications. The targets are primarily B- and A-type stars (2862 and 853 objects respectively), with 1 Wolf-Rayet, 139 O-type, and 306 FG stars, sampling the main sequence to ~mid-B. The selection and classification criteria are described, and objects of particular interest are discussed, including UV-selected targets from the Ultraviolet Imaging Telescope (UIT) experiment, Be and B[e] stars, `anomalous A supergiants', and composite-spectrum systems. We examine the incidence of Balmer-line emission, and the relationship between H-gamma equivalent width and absolute magnitude for BA stars.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/438/201
- Title:
- DG Leo uvby differential photometry
- Short Name:
- J/A+A/438/201
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multi-site and multi-year differential photometry of the triple star DG Leo reveals a complex frequency spectrum that can be modelled as the combination of at least three {delta} Scuti type frequencies in the range 11.5-13c/d (with semi-amplitudes of 2-7mmag) and a superimposed slow variability of larger amplitude. The period of the slow variation fits very well with half the orbital period of the inner spectroscopic binary indicating the presence of ellipsoidal variations caused by the tidally deformed components in a close configuration. These findings, together with the results of a recent spectroscopic analysis (showing that the system consists of a pair of mild Am stars and one A-type component of normal solar composition), infer that DG Leo is an extremely interesting asteroseismic target. Identification of which component(s) of this multiple system is (or are) pulsating and determination of the excited pulsation modes will both contribute to a much better understanding of the non-trivial link between multiplicity, chemical composition, rotation, and pulsation in the lower part of the classical Cepheid instability strip.
- ID:
- ivo://CDS.VizieR/J/AJ/145/142
- Title:
- Differential BV photometry of {delta} Sco
- Short Name:
- J/AJ/145/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We acquired Johnson BV photometry of the binary Be disk system {delta} Scorpii during its 2009, 2010, 2011, and 2012 observing seasons and used it to probe the innermost regions of the disk. We found that several disk building events have occurred during this time, resulting in an overall brightening in the V band and reddening of the system. In addition to these long-term trends, we found cyclical variability in each observing season on timescales between 60 and 100days. We were able to reproduce the changes in the magnitude and color of {delta} Sco using our theoretical models and found that variable mass-loss rates in the range 2.5-7.0*10^-9^M_{Sun}_/yr over ~35days can reproduce the observed increase in brightness.
- ID:
- ivo://CDS.VizieR/J/AJ/151/40
- Title:
- Differential BV photometry of 5 variables in M79
- Short Name:
- J/AJ/151/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a luminous F-type post-asymptotic-giant-branch (PAGB) star in the Galactic globular cluster (GC) M79 (NGC 1904). At visual apparent and absolute magnitudes of V=12.20 and M_V_=-3.46, this "yellow" PAGB star is by a small margin the visually brightest star known in any GC. It was identified using CCD observations in the uBVI photometric system, which is optimized to detect stars with large Balmer discontinuities, indicative of very low surface gravities. Follow-up observations with the SMARTS 1.3 and 1.5m telescopes show that the star is not variable in light or radial velocity, and that its velocity is consistent with cluster membership. Near- and mid-infrared observations with 2MASS and WISE show no evidence for circumstellar dust. We argue that a sharp upper limit to the luminosity function exists for yellow PAGB stars in old populations, making them excellent candidates for Population II standard candles, which are four magnitudes brighter than RR Lyrae variables. Their luminosities are consistent with the stars being in a PAGB evolutionary phase, with core masses of ~0.53M_{sun}_. We also detected four very hot stars lying above the horizontal branch ("AGB-manque" stars); along with the PAGB star, they are the brightest objects in M79 in the near-ultraviolet. In the Appendix, we give periods and light curves for five variables in M79: three RR Lyrae stars, a Type II Cepheid, and a semiregular variable.
- ID:
- ivo://CDS.VizieR/J/AJ/146/146
- Title:
- Differential BV photometry of VV Crv
- Short Name:
- J/AJ/146/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained red-wavelength spectroscopy and Johnson B and V differential photoelectric photometry of the eclipsing binary VV Crv=HR 4821. The system is the secondary of the common proper motion double star ADS 8627, which has a separation of 5.2". VV Crv has an orbital period of 3.144536 days and a low but non-zero eccentricity of 0.085. With the Wilson-Devinney program we have determined a simultaneous solution of our spectroscopic and photometric observations. Those orbital elements produce masses of M_1_=1.978+/-0.010M_{sun}_ and M_2_=1.513+/-0.008M_{sun}_, and radii of R_1_=3.375+/-0.010R_{sun}_ and R_2_=1.650+/-0.008R_{sun}_for the primary and secondary, respectively. The effective temperatures of the two components are 6500K (fixed) and 6638K, so the star we call the primary is the more massive but cooler and larger component. A comparison with evolutionary tracks indicates that the components are metal rich with [Fe/H]=0.3, and the system has an age of 1.2Gyr. The primary is near the end of its main-sequence lifetime and is rotating significantly faster than its pseudosynchronous velocity. The secondary is still well ensconced on the main sequence and is rotating more slowly than its pseudosynchronous rate.
- ID:
- ivo://CDS.VizieR/J/AJ/145/39
- Title:
- Differential BV(RI)c light curves of PY Vir
- Short Name:
- J/AJ/145/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Complete CCD photometric light curves in BV(RI)_c_ bands obtained in 2012 for the short-period close binary system PY Virginis are presented. A new photometric analysis with the Wilson-Van Hamme code shows that PY Vir is an A-type marginal contact binary system. The absolute parameters of PY Vir are derived using spectroscopic and photometric solutions. Combining new determined times of minimum light with others published in the literature, the O-C diagram of the binary star is investigated. A periodic variation, with a period of 5.22(+/-0.05)years and an amplitude of 0.0075(+/-0.0004)days, was discovered. Since the spectrum of a third component has been detected by Rucinski et al. (2008, cat. J/AJ/136/586), we consider this cyclic period oscillation to be the result of the light-time effect due to the presence of a third body. This third component may also be a binary itself. Therefore, PY Vir should be a quadruple system composed of two cool-type binary systems. This system is a good astrophysical laboratory to study the formation and evolution of close binaries and multiple systems.
- ID:
- ivo://CDS.VizieR/J/AJ/147/50
- Title:
- Differential BVRI light curves of DV Psc
- Short Name:
- J/AJ/147/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present six new BVR_c_I_c_ CCD light curves of a short-period RS CVn binary DV Psc obtained in 2010-2012. The light curve distortions change on both short and long timescales, which is explained by two starspots on the primary component. Moreover, five new flare events were detected and the flare ratio of DV Psc is about 0.082 flares per hour. There is a possible relation between the phases (longitude) of the flares and starspots for all of the available data of late-type binaries, which implies a correlation of the stellar activity of the spots and flares. The cyclic oscillation, with a period of 4.9+/-0.4yr, may result from the magnetic activity cycle, identified by the variability of Max.I-Max.II. Until now, there were no spectroscopic studies of chromospheric activity indicators of the H_{beta}_and H_{gamma}_lines for DV Psc. Our observations of these indicators show that DV Psc is active, with excess emissions. The updated O-C diagram with an observing time span of about 15yr shows an upward parabola, which indicates a secular increase in the orbital period of DV Psc. The orbital period secularly increases at a rate of dP/dt=2.0x10^-7^days/yr, which might be explained by the angular momentum exchanges or mass transfer from the secondary to primary component.
- ID:
- ivo://CDS.VizieR/J/AJ/146/79
- Title:
- Differential BVRI light curves of EP And
- Short Name:
- J/AJ/146/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New multi-color CCD photometric light curves of the eclipsing binary EP And were obtained over six nights in 2006, 2011, and 2012. Using the Wilson-Devinney code, we computed the photometric elements of this system. It was discovered that EP And is a W-type W UMa contact binary system with a mass ratio of q=2.685 and a degree of contact factor f=24.9%, rather than an A-type system. Combining 28 newly determined times of minimum light derived from 1999 to 2012 with others collected from the literature, a long-term increase (dP/dt=+5.22x10^-8^days/yr) with a sinusoidal variation (A=0.0109days; T=40.89yr) in the orbital period was found. The orbital period secular increases may be interpreted as conservative mass transfer from the less massive component to the more massive one, and cyclic variations of the orbital period may be caused by the light-travel time effect through the presence of a third body. The evolutionary status and the age of the system are also discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/145/16
- Title:
- Differential BVRI light curves of NSVS 02502726
- Short Name:
- J/AJ/145/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NSVS 02502726 has been known as a double-lined, detached eclipsing binary that consists of two low-mass stars. We obtained BVRI photometric follow-up observations in 2009 and 2011 to measure improved physical properties of the binary star. Each set of light curves, including the 2008 data given by Cakirli et al., was simultaneously analyzed with the previously published radial velocity curves using the Wilson-Devinney binary code. The conspicuous seasonal light variations of the system are satisfactorily modeled by a two-spot model with one starspot on each component and by changes of the spot parameters with time. Based on 23 eclipse timings calculated from the synthetic model and one ephemeris epoch, an orbital period study of NSVS 02502726 reveals that the period has experienced a continuous decrease of -5.9x10^-7^day/yr or a sinusoidal variation with a period and semi-amplitude of 2.51yr and 0.0011days, respectively. The timing variations could be interpreted as either the light-travel-time effect due to the presence of an unseen third body, or as the combination of this effect and angular momentum loss via magnetic stellar wind braking. Individual masses and radii of both components are determined to be M_1_=0.689+/-0.016M_{sun}_, M_2_=0.341+/-0.009M_{sun}_, R_1_=0.707+/-0.007R_{sun}_, and R_2_=0.657+/-0.008R_{sun}_. The results are very different from those of Cakirli et al. with the primary's radius (0.674+/-0.006R_{sun}_) smaller the secondary's (0.763+/-0.007R_{sun}_). We compared the physical parameters presented in this paper with current low-mass stellar models and found that the measured values of the primary star are best fitted to a 79Myr isochrone. The primary is in good agreement with the empirical mass-radius relation from low-mass binaries, but the secondary is oversized by about 85%.
- ID:
- ivo://CDS.VizieR/J/AJ/146/157
- Title:
- Differential BVRI photometry of FI Boo
- Short Name:
- J/AJ/146/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the interesting W UMa binary FI Boo in view of the spectroscopic signature of a third body through photometry, period variation, and a thorough investigation of solution uniqueness. We obtained new BVR_c_I_c_ photometric data that, when combined with spectroscopic data, enable us to analyze the system FI Boo and determine its basic orbital and physical properties through PHOEBE, as well as the period variation by studying the times of the minima. This combined approach allows us to study the long-term period changes in the system for the first time in order to investigate the presence of a third body and to check extensively the solution uniqueness and the uncertainties of derived parameters. Our modeling indicates that FI Boo is a W-type moderate (f=50.15%+/-8.10%) overcontact binary with component masses of M_h_=0.40+/-0.05M_{sun}_ and M_c_=1.07+/-0.05M_{sun}_, temperatures of T_h_=5746+/-33K and T_c_=5420+/-56K, and a third body, which may play an important role in the formation and evolution. The results were tested by heuristic scanning and parameter kicking to provide the consistent and reliable set of parameters that was used to obtain the initial masses of the progenitors (1.71+/-0.10M_{sun}_ and 0.63+/-0.01M_{sun}_, respectively). We also investigated the evolutionary status of massive components with several sets of widely used isochrones.
