- ID:
- ivo://CDS.VizieR/J/other/PASA/35.7
- Title:
- Long-term BVRI photometry of V2492 Cygni
- Short Name:
- J/other/PASA/35.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results from BVRI photometric observations of the young stellar object V2492 Cyg collected during the period from August 2010 to December 2017 are presented. The star is located in the field of the Pelican Nebula and it was discovered in 2010 due to its remarkable increase in the brightness by more than 5mag in R-band. According to the first hypothesis of the variability, V2492 Cyg is an FUor candidate. During subsequent observations, it was reported that the star shows the characteristics inherent to EXor- and UXor-type variables. The optical data show that during the whole time of observations the star exhibits multiple large amplitude increases and drops in the brightness. In the beginning of 2017, we registered a significant increase in the optical brightness of V2492 Cyg, which seriously exceeds the maximal magnitudes registered after 2010.
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- ID:
- ivo://CDS.VizieR/J/other/Ser/202.31
- Title:
- Long-term BVRI photometry of V900 Mon
- Short Name:
- J/other/Ser/202.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from photometric monitoring of V900 Mon, one of the newly discovered and still under-studied object from the FU Orionis type. The FUor phenomenon is very rarely observed, but it is essential for stellar evolution. Since we only know about twenty stars of this type, the study of each new object is very important for our knowledge. Our data were obtained in optical spectral region with the BVRI Johnson-Cousins set of filters during the period from September 2011 to April 2021. In order to follow the photometric history of the object, we measured its stellar magnitudes on available plates from the Mikulski Archive for Space Telescopes. The collected archival data suggest that the rise in brightness of V900 Mon began after January 1989 and the outburst goes on so far. In November 2009, when the outburst was registered, the star had already reached the level of brightness close to the current one. Our observations indicate that during the period 2011-2017 the stellar magnitude increased gradually in each pass band. The observed amplitude of the ourburst is about 4 magnitudes (R). During the last three years, the increase in brightness has stopped and there has even been a slight decline. The comparison of light curves of the known FUor objects shows that they are very diverse and are rarely repeated. However, the photometric data we have so far show that V900 Mon's light curve is somewhat similar to those of V1515 Cyg and V733 Cep.
- ID:
- ivo://CDS.VizieR/J/A+AS/131/321
- Title:
- Long-term monitoring of active stars. VIII.
- Short Name:
- J/A+AS/131/321
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a part of an extensive program focusing on the global properties and evolution of active stars, high-precision UBV(RI)c photometry of 31 selected stars, collected at the European Southern Observatory over the 14-29 February 1992 interval, is presented. Significant evolution of the light curves, period variations and evidence for long-term variability of the global degree of spottedness are found. Some spectral classifications are revised and the inferred photometric parallaxes are compared, whenever possible, with the values measured by the Hipparcos satellite. Flare events were detected for the star HD 16157=CC Eri, EXO 055609-3804.4=TY Col and HD 119285=V851 Cen. Optical variability was discovered for the Pop II binary HD 89499. These observations contribute to the establishment of a time-extended photometric database which can give important clues on topics such as the stability of spotted areas, differential rotation, solar-like cycles and the correlation between inhomogeneities at different atmospheric levels.
- ID:
- ivo://CDS.VizieR/J/other/PASA/32.21
- Title:
- Long-Term Multicolour Photometry of YSOs
- Short Name:
- J/other/PASA/32.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results from long-term multicolour optical photometric observations of the pre-main sequence stars FHO 26, FHO 27, FHO 28, FHO 29, and V1929 Cyg collected during the period from 1997 June to 2014 December are presented. The objects are located in the dense molecular cloud L935, named 'Gulf of Mexico', in the field between the North America and Pelican nebulae. All stars from our study exhibit strong photometric variability in all optical passbands. Using our BVRI observations and data published by other authors, we tried to define the reasons for the observed brightness variations. The presented paper is a part of our long-term photometric study of the young stellar objects in the region of 'Gulf of Mexico'.
- ID:
- ivo://CDS.VizieR/J/A+A/568/A49
- Title:
- Long-term photometry of pre-MS stars
- Short Name:
- J/A+A/568/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To broaden the search and study stars in the early evolutionary phase, we investigated a sample of 17 pre-main sequence objects previously detected as either H{alpha} emission-line pre-main sequence stars or T Tauri variables located in the field of the North America/Pelican Nebula complex. Johnson-Cousins B, V, Rc, Ic magnitudes and mean color indices for the program stars are determined from more than 12400 measurements from archive photographic plates and from CCD data collected at 7 observatories covering the period of almost 60 years from 1954 up to 2013. We complemented previously rare insights on the photometry of the program stars and presented their photometric history, which for almost all program stars is the first long term photometric monitoring on a timescale of 6 decades. Eight program stars are found to be classical T Tauri stars of variability type II, while 6 program stars are weak-line T Tauri stars of variability type I. For the first time, periodicity is found for three stars: V1716 Cyg indicates a 4.15 day period, V2051 Cyg indicates a 384 day period, and V521 Cyg a period of 503 days.
- ID:
- ivo://CDS.VizieR/J/other/JAD/18.5
- Title:
- Long-term photometry of 11 RS CVn stars
- Short Name:
- J/other/JAD/18.5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present BVRI photometry of short-period (P<1d) eclipsing RS CVn binary star systems collected between 1988 and 2009 at Mount Laguna Observatory. Most of the data are for ER Vul and WY Cnc, with light curves nearly every year during that time period. I also present light curves for at least several years for XY UMa, BH Vir, CG Cyg, RT And, and UV Psc. I have fewer light curves for SV Cam, UV Leo, 1E1919+0427, and GSC 2038-0293. In addition to the eclipsing short-period systems, I also include UBVRI data for two longer period non-eclipsing RS CVn binary systems: UZ Lib and DM UMa, as well as two active chromosphere single stars: FK Com and HD 199178.
- ID:
- ivo://CDS.VizieR/J/other/PASA/32.11
- Title:
- Long-term UBVRI photometry of GM Cep
- Short Name:
- J/other/PASA/32.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results from UBVRI photometric observations of the pre-main sequence star GM Cephei obtained in the period April 2011 - August 2014 are reported in the paper. Presented data are a continuation of our photometric monitoring of the star started in 2008. GM Cep is located in the field of the young open cluster Trumpler 37 and over the past years it has been an object of intense photometric and spectral studies. The star shows a strong photometric variability interpreted as a possible outburst from EXor type in previous studies. Our photometric data for a period of over six years show a large amplitude variability ({Delta}V~2.3mag) and several deep minimums in brightness are observed. The analysis of the collected multicolor photometric data show the typical of UX Ori variables a colour reversal during the minimums in brightness. The observed decreases in brightness have a different shape, and evidences of periodicity are not detected. At the same time, high amplitude rapid variations in brightness typical for the classical T Tauri stars also present on the light curve of GM Cep. The spectrum of GM Cep shows the typical of classical T Tauri stars wide H alpha emission line and absorption lines of some metals. We calculate the outer radius of the H{alpha} emitting region as 10.4+/-0.5R_{sun}_ and the accretion rate as 1.8x10^-7^M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/AJ/157/22
- Title:
- Luminous and variable stars in NGC 2403 and M81
- Short Name:
- J/AJ/157/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of spectroscopy and multi-wavelength photometry of luminous and variable star candidates in the nearby spiral galaxies NGC 2403 and M81. We discuss specific classes of stars, the Luminous Blue Variables (LBVs), B[e] supergiants (sgB[e]), and the high-luminosity yellow hypergiants. We identify two new LBV candidates, and three sgB[e] stars in M81. We also find that some stars that were previously considered LBV candidates are actually field stars. The confirmed and candidate LBVs and sgB[e] stars together with the other confirmed members are shown on the HR Diagrams for their respective galaxies. We also present the HR Diagrams for the two "SN impostors", V37 (SN2002kg) and V12 (SN1954J) in NGC 2403 and the stars in their immediate environments.
- ID:
- ivo://CDS.VizieR/J/ApJ/836/64
- Title:
- Luminous variable stars in M31 & M33. IV.
- Short Name:
- J/ApJ/836/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this series of papers we have presented the results of a spectroscopic survey of luminous stars in the nearby spirals M31 and M33. Here, we present spectroscopy of 132 additional stars. Most have emission-line spectra, including luminous blue variables (LBVs) and candidate LBVs, Fe II emission line stars, the B[e] supergiants, and the warm hypergiants. Many of these objects are spectroscopically similar and are often confused with each other. We examine their similarities and differences and propose the following guidelines that can be used to help distinguish these stars in future work. (1) The B[e] supergiants have emission lines of [OI] and [FeII] in their spectra. Most of the spectroscopically confirmed sgB[e] stars also have warm circumstellar dust in their spectral energy distributions (SEDs). (2) Confirmed LBVs do not have the [OI] emission lines in their spectra. Some LBVs have [FeII] emission lines, but not all. Their SEDs show free-free emission in the near-infrared but no evidence for warm dust. Their most important and defining characteristic is the S Dor-type variability. (3) The warm hypergiants spectroscopically resemble the LBVs in their dense wind state and the B[e] supergiants. However, they are very dusty. Some have [FeII] and [OI] emission in their spectra like the sgB[e] stars, but are distinguished by their A- and F-type absorption-line spectra. In contrast, the B[e] supergiant spectra have strong continua and few if any apparent absorption lines. Candidate LBVs should share the spectral characteristics of the confirmed LBVs with low outflow velocities and the lack of warm circumstellar dust.
- ID:
- ivo://CDS.VizieR/J/AJ/115/1894
- Title:
- M31A eclipsing binaries and Cepheids
- Short Name:
- J/AJ/115/1894
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have undertaken a long-term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder, M31 and M33, using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, DEBs provide us with the potential to determine these distances with an accuracy better than 5%. The extensive photometry obtained in order to detect DEBs provides us with good light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries, the distance estimates will be free of any intermediate steps. As a first step in the DIRECT project, between 1996 September and 1997 January we obtained 36 full nights on the Michigan-Dartmouth-MIT Observatory 1.3m telescope and 45 full/partial nights on the F. L. Whipple Observatory 1.2m telescope to search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper, second in a series, we present the catalog of variable stars, most of them newly detected, found in the field M31A [({alpha},{delta})=(11.34{deg}, 41.73{deg}), J2000.0]. We have found 75 variable stars: 15 eclipsing binaries, 43 Cepheids, and 17 other periodic, possible long-period or nonperiodic variables. The catalog of variables, as well as their photometry and finding charts, is available via anonymous ftp and the World Wide Web. The CCD frames are available upon request.