- ID:
- ivo://CDS.VizieR/J/AJ/147/3
- Title:
- BV(RI)c light curves of V2421 Cyg
- Short Name:
- J/AJ/147/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first precision BVRI light curves, synthetic light curve solutions, and a period study for the high amplitude solar type binary, V2421 Cygni. The light curves have the appearance of an Algol (EA) type; however, it is made up of dwarf solar type components in a detached mode with a period of only 0.6331 days with an amplitude of about a full magnitude, i.e., it is a precontact W UMa binary. Flare-like disruptions occur in the light curves following the primary and secondary eclipses possibly due to the line-of-sight track of a gas stream. An associated stream spot and splash spot cause bright equatorial spots on the stellar surface of the primary star. The more massive star is the gainer, making this system a classic, albeit dwarf, Algol.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/392/1181
- Title:
- BV(RI)c photometry of 3C 273
- Short Name:
- J/MNRAS/392/1181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The long baseline simultaneous multiband (BVRI) observations of blazar 3C 273 are presented. We have made 758 optical multiband observations with the Yunnan Astronomical Observatory (YAO) 103cm and Shanghai Astronomical Observatory (SHAO) 156cm from 2003 January to 2005 April. In our observational campaign, the average colour indices are B-V=0.21, V-R= 0.26 and R-I=0.31 . The mean magnitudes in B, V, R and I are 12.895, 12.698, 12.441 and 12.139, respectively. The source is in a steady state over observational campaign. The correlations between colour index and brightness are discussed. We find that the correlations of B-V versus B, V-R versus V and R-I versus R have significant negative correlation, while B-V versus V, V-R versus R and R-I versus I have positive correlation. These strong correlations imply that the spectrum becomes bluer (flatter) when the source becomes brighter, and redden (softer) when the source fades both in intraday and long-term variability. The spectral evolution trends of 3C 273 are consistent with those of BL Lac objects.
- ID:
- ivo://CDS.VizieR/J/AJ/132/111
- Title:
- BV(RI)_C_photometry of 77 Hyades stars
- Short Name:
- J/AJ/132/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New BV(RI)C observations of 77 stars in the Hyades are reported and discussed. The new observations are used to test published magnitudes and color indices for that cluster. For values of (V-R)C and (R-I)C published previously by Taylor & Joner (1985AJ.....90..479T and 2005, Cat. <J/ApJS/159/100>), the tests reveal no detectable scale-factor problems. In addition, the tests show that possible zero-point corrections to the published data can be no larger than a few millimagnitudes. These test results indicate that future studies requiring precision photometry for Hyades stars would be well served by selecting data samples from sources as close as possible to the native Cousins system. Tests of B-V photometry published by Johnson & Knuckles (1955ApJ...122..209J) reveal a zero-point ambiguity of approximately 8mmag in the new data that will require further measurements to resolve.
- ID:
- ivo://CDS.VizieR/J/A+AS/130/109
- Title:
- BV(RI)c photometry of ON 231
- Short Name:
- J/A+AS/130/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the most continuous data base of optical multiband data ever published on the BL Lacertae object ON 231 (W Com). The data have been collected during an intensive and coordinated BV(RI)c monitoring campaign carried out in the period from March 1994 to March 1997. During our campaign, the source brightness was at the highest level ever observed. The light curve shows a complex structure, characterized by the presence of three major outbursts having the observed maxima in March 1995, February 1996, and January 1997, when ON 231 reached its historical maximum (B~=14.2). Variability on time scales from a few hours up to a month have frequently been observed and the light curve seems to be the superposition of many flares with different amplitudes and time scales. The broad-band optical spectral energy distribution is characterized by a spectral slope which correlates with the flux level. In particular, the higher is the flux the flatter is the spectrum.
- ID:
- ivo://CDS.VizieR/J/A+A/395/11
- Title:
- BV(RI)c photometry of ON 231 during outburst
- Short Name:
- J/A+A/395/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the optical monitoring of the BL Lac object ON 231 from 1997 to the spring 2001, including the large outburst of spring 1998. After this event the mean source luminosity declined slowly and continued to show changes greater than one magnitude. A simple analysis of the variability time scales in the best-sampled segments of the light curve reveals that the luminosity changes were faster during the burst and slowed down in the subsequent years.
- ID:
- ivo://CDS.VizieR/J/A+A/327/61
- Title:
- BV(RI)c photometry of S5 0716+714
- Short Name:
- J/A+A/327/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 2 reports the journal of observations. For each date the measured magnitudes and their uncertainties in the four filters together with the used telescope are given. In some occasions several images were made in the course of the same night to search for intraday variability; these nights are indicated by an asterisk. The magnitude uncertainties have been evaluated by taking into account the mean dispersion of the internal error, but not the errors on the absolute calibration.
- ID:
- ivo://CDS.VizieR/J/A+A/451/435
- Title:
- BV(RI)c photometry of S5 0716+714
- Short Name:
- J/A+A/451/435
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We address the topic of the intra-night optical variability of the BL Lac object S5 0716+714. To this purpose a long-term observational campaign was carried out, from 1996 to 2003, which allowed the collection of a very large data set, containing 10675 photometric measurements obtained in 102 nights. The source brightness varied in a range of about 2mag, although the majority of the observations were performed when it was in the range 13.0<R<13.75. Variability time scales were estimated from the rates of magnitude variation, which were found to have a distribution function well fitted by an exponential law with a mean value of 0.027mag/h, corresponding to an e-folding time scale of the flux {tau}_F_=37.6h. The highest rates of magnitude variation were around 0.10-0.12mag/h and lasted less than 2h. These rates were observed only when the source had an R magnitude <13.4, but this finding cannot be considered significant because of the low statistical occurrence. The distribution of {tau}_F_ has a well-defined modal value at 19h. Assuming the recent estimate of the beaming factor {delta} about 20, we derived a typical size of the emitting region of about (5x10^16^)/(1+z)cm. The possibility of searching for a possible correlation between the mean magnitude variation rate and the long-term changes in the velocity of the superluminal components in the jet is discussed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/384/1675
- Title:
- BVRIc photometry of Stock 8
- Short Name:
- J/MNRAS/384/1675
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVIc CCD photometry of the young open cluster Stock 8 with the aim of studying its basic properties such as the amount of interstellar extinction, distance, age, stellar contents and initial mass function (IMF). We also studied the star formation scenario in this region. From optical data, the radius of the cluster is found to be ~6arcmin (~3.6pc) and the reddening within the cluster region varies from E(B-V)=0.40 to 0.60mag. The cluster is located at a distance of 2.05+/-0.10kpc. Using H{alpha} slitless spectroscopy and Two Micron All Sky Survey (2MASS) near-infrared (NIR) data we identified H{alpha} emission and NIR-excess young stellar objects (YSOs), respectively.
- ID:
- ivo://CDS.VizieR/J/BaltA/14/41
- Title:
- BV(RI)C photometry of 4 S-type AGB
- Short Name:
- J/BaltA/14/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present FCAPT differential Johnson BV and Cousins RI photometry and radial velocities of the S-type AGB stars RS Cnc, ST Her, OP Her and HR Peg. We performed multiperiodic analyses of this photometry to learn about the frequencies of variability. The B, V, R, and I light curves are generally in phase. RS Cnc has periods of order 122 and 248 days. Repeating the analyses using our data with the extensive V and R photometry of Percy et al. (2001PASP..113..983P) shows several periods near 248 days and a period near 135 days. The primary period of ST Her appears to be about 144 days although it is manifested most readily by its 103 day alias. OP Her and HR Peg exhibit periods, respectively, of about 416 and 116 days and of 54 and 74 days. The differences between our data set and the larger one of Percy et al. (2001PASP..113..983P) for RS Cnc raises important questions about multiperiodic analyses for AGB stars.
- ID:
- ivo://CDS.VizieR/J/A+A/370/503
- Title:
- BV(RI)c photometry of 7 symbiotic stars
- Short Name:
- J/A+A/370/503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table1.dat contains the UBV(RI)c magnitudes of the symbiotic stars AS 323, Ap 3-1, CM Aql, V1413 Aql, V443 Her, V627 Cas, V919 Sgr estimated on the Asiago archive plates. The date is given in the year/month/day format, and the magnitude is estimated in steps of 0.05mag
