Search

Start Over Subject variable stars
191. BVRI light curves of KIC 6382916
ID:
ivo://CDS.VizieR/J/MNRAS/433/394
Title:
BVRI light curves of KIC 6382916
Short Name:
J/MNRAS/433/394
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of a multisite photometric campaign on the high-amplitude {delta} Scuti star KIC 6382916 in the Kepler field. The star was observed over a 85-d interval at five different sites in North America and Europe during 2011. Kepler photometry and ground-based multicolour light curves of KIC 6382916 are used to investigate the pulsational content and to identify the principal modes. High-dispersion spectroscopy was also obtained in order to derive the stellar parameters and projected rotational velocity. From an analysis of the Kepler time series, three independent frequencies and a few hundred combination frequencies are found. The light curve is dominated by two modes with frequencies f1=4.9107d^-1^ and f2=6.4314d^-1^. The third mode with f3=8.0350d^-1^ has a much lower amplitude. We attempt mode identification by examining the amplitude ratios and phase differences in different wavebands from multicolour photometry and comparing them to calculations for different spherical harmonic degree, l. We find that the theoretical models for f1 and f2 are in a best agreement with the observations and lead to value of l=1 modes, but the mode identification of f3 is uncertain due to its low amplitude. Non-adiabatic pulsation models show that frequencies below 6d^-1^ are stable, which means that the low frequency of f1 cannot be reproduced. This is a further confirmation that current models predict a narrower pulsation frequency range than actually observed.
192. BVRI light curves of KIC Cepheids
ID:
ivo://CDS.VizieR/J/MNRAS/413/2709
Title:
BVRI light curves of KIC Cepheids
Short Name:
J/MNRAS/413/2709
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report results of initial work done on selected candidate Cepheids to be observed with the Kepler space telescope. Prior to the launch, 40 candidates were selected from previous surveys and data bases. The analysis of the first 322d of Kepler photometry, and recent ground-based follow-up multicolour photometry and spectroscopy allowed us to confirm that one of these stars, V1154 Cyg (KIC 7548061), is indeed a 4.9d Cepheid. Using the phase lag method, we show that this star pulsates in the fundamental mode. New radial velocity data are consistent with previous measurements, suggesting that a long-period binary component is unlikely. No evidence is seen in the ultraprecise, nearly uninterrupted Kepler photometry for non-radial or stochastically excited modes at the micromagnitude level. The other candidates are not Cepheids, but an interesting mix of possible spotted stars, eclipsing systems and flare stars.
193. BVRI light curves of NGC 247 Cepheids
ID:
ivo://CDS.VizieR/J/ApJ/694/1237
Title:
BVRI light curves of NGC 247 Cepheids
Short Name:
J/ApJ/694/1237
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report VRI CCD observations of nine Cepheids in the South Polar (Sculptor) Group spiral galaxy NGC 0247. Periods of these Cepheids range from 20 to 70 days. Over the past 20 years, the brightest Cepheid in our sample, NGC 0247:[MF09] C1, has decreased its period by 6%, faded by 0.8mag in the V band, and become bluer by 0.23mag in (V-I).
194. BVRI observations of LMC Cepheids
ID:
ivo://CDS.VizieR/J/ApJS/142/71
Title:
BVRI observations of LMC Cepheids
Short Name:
J/ApJS/142/71
Date:
21 Oct 2021
Publisher:
CDS
Description:
A homogeneous set of ground-based BVRI observations of ~600 Cepheids is presented to check the Cepheid period-luminosity (PL) zero point for the Large Magellanic Cloud (LMC). The sample of Cepheids is completely self-contained and has been reduced consistently to eliminate photometric differences caused by combining multiple sources of photometry. The Cepheid distances to nearby galaxies obtained by the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale were computed assuming a "standard" PL relation based on a compilation of photoelectric observations of 34 Cepheids and a standard distance modulus to the LMC of 18.50. The final Key Project results substituted a statistically stronger PL relation obtained by the OGLE collaboration. In this paper we compare our data with the OGLE PL relation; the subsample of LMC Cepheids with similar periods to those discovered in the nearby galaxies is fainter at the relevant periods by 0.04+/-0.02mag than the OGLE sample. Substituting in turn this PL relation for that of the OGLE collaboration would raise the Hubble constant by 2%+/-1%, a correction which is not significant. The multicolor data set will also be useful in considering the effects of reddening and chemical composition and deriving an improved Cepheid period-luminosity relation for the LMC.
195. BVRI observations of the FUor star V582 Aur
ID:
ivo://CDS.VizieR/J/A+A/556/A60
Title:
BVRI observations of the FUor star V582 Aur
Short Name:
J/A+A/556/A60
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from optical photometric and spectroscopic observations of the eruptive pre-main sequence star V582 Aur. Variability of the star was reported a few years ago when it was suspected as a possible FU Orionis object. Due to the small number of currently known FUors, a new object of this type is ideal target for follow-up photometric and spectroscopic observations. We carried out BVRI CCD photometric observations in the field of V582 Aur from 2009 August to 2013 April. We acquired high-, medium-, and low-resolution spectroscopy of V582 Aur during this period. To study the pre-outburst variability of the target and construct its historical light curve, we searched for archival observations in photographic plate collections. The pre-outburst photographic observations of V582 Aur show low-amplitude light variations typical of T Tauri stars. Archival photographic observations indicate that the increase in brightness began in late 1984 or early 1985 and the star reached the maximum level of brightness at 1986 January. Our BVRI photometric observations show large amplitude variations ({Delta}V~2.8mag.) during the 3.5 year period of observations. Most of the time, however, the star remains in a state close to the maximum brightness. The deepest drop in brightness was observed in the spring of 2012, when the brightness of the star fell to a level close to the pre-outburst. The multicolor photometric data show a color reversal during the minimum in brightness, which is typical of UX Ori variables.
196. BVRI photometry in NGC4147
ID:
ivo://CDS.VizieR/J/PASP/117/1325
Title:
BVRI photometry in NGC4147
Short Name:
J/PASP/117/1325
Date:
21 Oct 2021
Publisher:
CDS
Description:
New BVRI broadband photometry and astrometry are presented for the globular cluster NGC 4147, based upon measurements derived from 524 ground-based CCD images mostly either donated by colleagues or retrieved from public archives. We have also reanalyzed five exposures of the cluster obtained with WFPC2 on the Hubble Space Telescope in the F439W and F555W (B and V) filters.
197. BVRI photometry of HR 1105
ID:
ivo://CDS.VizieR/J/A+A/333/952
Title:
BVRI photometry of HR 1105
Short Name:
J/A+A/333/952
Date:
21 Oct 2021
Publisher:
CDS
Description:
BVRI photometry of the extrinsic S star HR 1105 shows a stable periodic light variability with a period of 24.76 days superimposed upon long term changes presumably related to the orbital period. The variations are in phase for all four magnitudes with the amplitude of this variability being about the same for B and V, but smaller for R and even smaller for I. As the primary is a M3 III star, these brightness changes are mostly likely due to the pulsation of the primary star.
198. BVRI photometry of luminous stars in M31 and M33
ID:
ivo://CDS.VizieR/J/AJ/154/81
Title:
BVRI photometry of luminous stars in M31 and M33
Short Name:
J/AJ/154/81
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first four years of BVRI photometry from an on-going survey to annually monitor the photometric behavior of evolved luminous stars in M31 and M33. Photometry was measured for 199 stars at multiple epochs, including 9 classic Luminous Blue Variables (LBVs), 22 LBV candidates, 10 post-RGB A/F type hypergiants, and 18 B[e] supergiants. At all epochs, the brightness is measured in the V-band and at least one other band to a precision of 0.04-0.10 mag down to a limiting magnitude of 19.0-19.5. Thirty three stars in our survey exhibit significant variability, including at least two classic LBVs caught in S Doradus-type outbursts. A hyperlinked version of the photometry catalog is at http://go.uis.edu/m31m33photcat
199. BVRI Photometry of 14 PMS stars
ID:
ivo://CDS.VizieR/J/other/BAJ/24.62
Title:
BVRI Photometry of 14 PMS stars
Short Name:
J/other/BAJ/24.6
Date:
21 Oct 2021
Publisher:
CDS
Description:
New photometric data from CCD multicolour BVRI observations of 14 pre-main sequence stars during the period from 2013 April to 2015 September are presented. The studied objects are located in the field of 'Gulf of Mexico' in the NGC 7000/IC 5070 star-forming complex. The stars from our study exhibit different types of photometric variability in all optical passbands. Using our long-term observations and data published by other authors, we tried to define the reasons for the observed brightness variations. On the basis of our new data previously unknown periodicity in the light curve of the star LkHa 189 (2.45-days) was registered.
200. BVRI photometry of 5 PMS stars
ID:
ivo://CDS.VizieR/J/other/BAJ/22.3
Title:
BVRI photometry of 5 PMS stars
Short Name:
J/other/BAJ/22.3
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new data from BVRI photometric observations of five PMS stars during the period from April 2013 to July 2014. The stars are located in the field of NGC 7000/IC 5070 ("Gulf of Mexico") - a region with active star formation. The presented paper is a continuation of our long-term photometric investigations of the young stellar objects in this region. The long-term multicolor photometric observations of PMS stars are very important for their exact classification. Our results show that the studied stars exhibit different types of photometric variability in all bands. We tried to classify them using our data from the long-term photometry and data published by other authors.