- ID:
- ivo://CDS.VizieR/J/MNRAS/439/2618
- Title:
- VISTA variables in Sagittarius dSph
- Short Name:
- J/MNRAS/439/2618
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variability is examined in over 2.6 million stars covering 11 square degrees of the core of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) from Visible and Infrared Survey Telescope for Astronomy Z-band observations. Generally, pulsation on the Sgr dSph giant branches appears to be excited by the internal {kappa} mechanism. Pulsation amplitudes appear identical between red and asymptotic (red giant branch/asymptotic giant branch) giant stars, and between unreddened carbon and oxygen-rich stars at the same luminosity. The lack of correlation between infrared excess and variability among oxygen-rich stars indicates that pulsations do not contribute significantly to wind driving in oxygen-rich stars in the Sgr dSph, though the low amplitudes of these stars mean this may not apply elsewhere. The dust-enshrouded carbon stars have the highest amplitudes of the stars we observe. Only in these stars does an external {kappa}-mechanism-driven pulsation seem likely, caused by variations in their more opaque carbon-rich molecules or dust. This may allow pulsation driving of winds to be effective in carbon stars. Variability can be simplified to a power law (A{prop.to}L/T_2_), as in other systems. In total, we identify 3026 variable stars (with rms variability of {delta}Z>~0.015mag), of which 176 are long-period variables associable with the upper giant branches of the Sgr dSph. We also identify 324 candidate RR Lyrae variables in the Sgr dSph and 340 in the outer Galactic bulge.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/146/112
- Title:
- V light curve of RW Aur
- Short Name:
- J/AJ/146/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- RW Aur A is a classical T Tauri star, believed to have undergone a reconfiguration of its circumstellar environment as a consequence of a recent flyby of its stellar companion, RW Aur B. This interaction stripped away part of the circumstellar disk of RW Aur A, leaving a tidally disrupted "arm" and a short truncated circumstellar disk. We present photometric observations of the RW Aur system from the Kilodegree Extremely Little Telescope survey showing a long and deep dimming that occurred from 2010 September until 2011 March. The dimming has a depth of ~2mag, a duration of ~180 days, and was confirmed by archival observations from American Association of Variable Star Observers. We suggest that this event is the result of a portion of the tidally disrupted disk occulting RW Aur A, specifically a fragment of the tidally disrupted arm. The calculated transverse linear velocity of the occulter is in excellent agreement with the measured relative radial velocity of the tidally disrupted arm. Using simple kinematic and geometric arguments, we show that the occulter cannot be a feature of the RW Aur A circumstellar disk, and we consider and discount other hypotheses. We also place constraints on the thickness and semimajor axis of the portion of the arm that occulted the star.
- ID:
- ivo://CDS.VizieR/J/A+A/486/505
- Title:
- V light curve of SDSS J080434.20+510349.2
- Short Name:
- J/A+A/486/505
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed a new cataclysmic variable (CV) SDSS J080434.20+510349.2 to study the origin of long-term variability found in its light curve. Multi-longitude, time-resolved, photometric observations were acquired to analyze this uncommon behavior, which has been found in two newly discovered CVs. This study of SDSS J080434.20+510349.2 concerns primarily the understanding of the nature of the observed, double-humped, light curve and its relation to a cyclic brightening that occurs during quiescence. The observations were obtained early in 2007, when the object was at about V~17.1, about 0.4mag brighter than the pre-outburst magnitude. The light curve shows a sinusoidal variability with an amplitude of about 0.07mag and a periodicity of 42.48min, which is half of the orbital period of the system. We observed in addition two "mini-outbursts" of the system of up to 0.6mag, which have a duration of about 4days each. The "mini-outburst" has a symmetric profile and is repeated in approximately every 32days. Subsequent monitoring of the system shows a cyclical behavior of such "mini-outbursts" with a similar recurrence period. The origin of the double-humped light curve and the periodic brightening is discussed in the light of the evolutionary state of SDSS J080434.20+510349.2.
- ID:
- ivo://CDS.VizieR/J/A+A/394/943
- Title:
- V light curve of V567 Oph
- Short Name:
- J/A+A/394/943
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present differential CCD photometry for the high-amplitude delta Scuti star V567 Ophiuchi obtained in the Johnson V-band. It was observed on 15 nights in two consecutive years in order to resolve the long-standing ambiguity related to its secondary period. A frequency analysis of almost 5000 individual single-filtered measurements resulted in two independent frequencies (f_1_=6.6879c/d and f_2_=11.8266c/d) with a ratio of f_1_/f_2_=0.565. The presented photometric data are differential magnitudes relative to the comparison star C_1_ (GSC 00417-01714) from Powell et al. (1990PASP..102.1131P)
- ID:
- ivo://CDS.VizieR/J/A+A/506/1269
- Title:
- V light curve of WR29
- Short Name:
- J/A+A/506/1269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- WR 29 is a known WN7h+O double-lined binary system with a rather short period (3.164-days). We search for light variations to determine the inclination of the system and thus the absolute masses of both components. We observed photometrically the field of WR 29 between December, 2002 and February, 2006. We find that the V light of WR 29 varies in phase with the spectroscopic period of 3.16412-days, presenting two minima corresponding to the conjunctions of the binary components. Numerical models fitted to the light curve indicate an orbital inclination of about 44{deg}, and masses of 53M_{sun}_ and 42M_{sun}_ for the O- and WN-type components, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/440/735
- Title:
- V light curves of EK Dra
- Short Name:
- J/A+A/440/735
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse photometric observations of the young active dwarf EK Dra, spanning altogether 21 years, and including previously unpublished data. The data in Table 2 was observed at the Fairbourn Observatory in southern Arizona using Amadeus, a 0.75m automatic photoelectric telescope (APT) of the University of Vienna. Amadeus is optimised for red wavelengths with an EMI-9828 tube and Johnson-Cousins V(RI)_C_ filters. Differential V magnitudes are variable (EK Dra) - comparison (HD 129390) and check (HD 129798) - comparison (HD 129390). HD 129390 Vmag=7.567
- ID:
- ivo://CDS.VizieR/J/A+A/471/515
- Title:
- V light curves of NGC 6791 variable stars
- Short Name:
- J/A+A/471/515
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work presents a high-precision variability survey in the field of the old, super metal-rich open cluster NGC 6791. The data sample consists of more than 75,000 high-precision CCD time series measurements in the V band obtained mainly at the Canada-France-Hawaii Telescope, with additional data from S. Pedro Martir and Loiano observatories, over a time span of ten nights. The field covers an area of 42x28arcmin^2^. We have discovered 260 new variables and re-determined periods and amplitudes of 70 known variable stars. By means of a photometric evaluation of the membership in NGC 6791, and a preliminary membership based on the proper motions, we give a full description of the variable content of the cluster and surrounding field in the range 16<V<23.5. Accurate periods can be given for the variables with P<4.0d, while for ones with longer periods the limited time-baseline hampered precise determinations. We categorized the entire sample as follows: 6 pulsating, 3 irregular, 3 cataclysmic, 89 rotational variables and 61 eclipsing systems; moreover, we detected 168 candidate variables for which we cannot give a variability class since their periods are much longer than our time baseline. On the basis of photometric considerations, and of the positions of the stars with respect to the center of the cluster, we inferred that 11 new variable stars are likely members of the cluster, for 22 stars the membership is doubtful and 137 are likely non-members. We also detected an outburst of about 3 mag in the light curve of a very faint blue star belonging to the cluster and we suggest that this star could be a new U Gem (dwarf nova) cataclysmic variable.
- ID:
- ivo://CDS.VizieR/J/ApJ/102/17
- Title:
- V light curves of variable stars in NGC 6229
- Short Name:
- J/ApJ/102/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Improved distance moduli for the two globular clusters NGC 5634 and NGC 6229 are derived from a photometric investigation of their cluster-type variables. The resulting values are m-M=16.91+/-0.04 for NGC 5634 and m-M=17.53+/-0.02 for NGC 6229. Both globular clusters are of less than average luminosity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/3131
- Title:
- VMC survey. XXVI. SMC RR Lyrae stars
- Short Name:
- J/MNRAS/473/3131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from the analysis of 2997 fundamental mode RR Lyrae variables located in the Small Magellanic Cloud (SMC). For these objects, near-infrared time series photometry from the VISTA survey of the Magellanic Clouds system (VMC) and visual light curves from the OGLE IV (Optical Gravitational Lensing Experiment IV) survey are available. In this study, the multi-epoch Ks-band VMC photometry was used for the first time to derive intensity-averaged magnitudes of the SMC RR Lyrae stars. We determined individual distances to the RR Lyrae stars from the near-infrared period-absolute magnitude-metallicity (PM_Ks_Z) relation, which has some advantages in comparison with the visual absolute magnitude-metallicity (M_V_-[Fe/H]) relation, such as a smaller dependence of the luminosity on interstellar extinction, evolutionary effects and metallicity. The distances we have obtained were used to study the three-dimensional structure of the SMC. The distribution of the SMC RR Lyrae stars is found to be ellipsoidal. The actual line-of-sight depth of the SMC is in the range 1-10kpc, with an average depth of 4.3+/-1.0kpc. We found that RR Lyrae stars in the eastern part of the SMC are affected by interactions of the Magellanic Clouds. However, we do not see a clear bimodality observed for red clump stars, in the distribution of RR Lyrae stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/494/458
- Title:
- VMC XXXVI. Young stellar variability in LMC
- Short Name:
- J/MNRAS/494/458
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studies of young stellar objects (YSOs) in the Galaxy have found that a significant fraction exhibits photometric variability. However, no systematic investigation has been conducted on the variability of extragalactic YSOs. Here we present the first variability study of massive YSOs in an ~1.5 square degree region of the Large Magellanic Cloud (LMC). The aim is to investigate whether the different environmental conditions in the metal-poor LMC (~0.4-0.5Z_{sun}_) have an impact on the variability characteristics. Multi-epoch near-infrared (NIR) photometry was obtained from the VISTA Survey of the Magellanic Clouds (VMC) and our own monitoring campaign using the VISTA telescope. By applying a reduced {Chi}-square-analysis, stellar variability was identified. We found 3062 candidate variable stars from a population of 362425 stars detected. Based on several Spitzer studies, we compiled a sample of high-reliability massive YSOs: a total of 173 massive YSOs have NIR counterparts (down to Ks~18.5mag) in the VMC catalogue, of which 39 display significant (>3{sigma}) variability. They have been classified as eruptive, fader, dipper, short-term variable, and long-period variable YSOs based mostly on the appearance of their Ks-band light curves. The majority of YSOs are aperiodic; only five YSOs exhibit periodic light curves. The observed amplitudes are comparable or smaller than those for Galactic YSOs (only two Magellanic YSOs exhibit {Delta}Ks>1mag), not what would have been expected from the typically larger mass accretion rates observed in the Magellanic Clouds.