- ID:
- ivo://CDS.VizieR/J/A+AS/142/347
- Title:
- BVRI photometry of NGC 6789
- Short Name:
- J/A+AS/142/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present the results of a detailed B, V, R, I, and H{alpha} study of the isolated nearby blue compact dwarf (BCD) galaxy NGC 6789. The observed galaxy has not yet been resolved into stars up to now. On CCD frames obtained with 6m BTA telescope and 2.5m Nordic telescope the galaxy is well resolved. Its colour-magnitude diagram confirms the two component (core-halo) galaxy morphology, which consists of two stellar populations distinct in structure and colour: an inner high surface-brightness young population within 150pc from the center of the galaxy, and a relatively low surface-brightness intermediate-age population extending out to at least 600pc. The distance to the galaxy, estimated from the tip of the red giant branch (TRGB) is 2.1Mpc which places NGC 6789 close to the Local Group. From the mean colour of the RGB, the mean metal abundance of the halo population is estimated as [Fe/H]=~-1dex.
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- ID:
- ivo://CDS.VizieR/J/A+AS/129/569
- Title:
- BVRI photometry of OJ 287
- Short Name:
- J/A+AS/129/569
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of BVRI CCD photometric monitoring and fast photometry in the I band for the blazar OJ 287 in 1994-1995 are presented. The predicted outburst of the blazar had been observed, the maximum appeared in 1994 November, after that, the luminosity decreased by 1.6mag for about three months and dropped to near the level in 1994 April. Rapid variations with timescales of minutes, hours and one day were observed in our observations, with small amplitude. The amplitude of the most rapid variations (minutes) is in the range of 0.043-0.12mag . The results of the statistical analysis of the fast photometry data are as follows. In five nights out of six rapid variability appeared in the sampling interval, which ranged from 3.4 minutes to 6.5 minutes, with a rms amplitude of flux variations of 1.70%-2.3%. The rapid variability can be explained by the model of shocks within turbulent jet or of vortices and magnetic flux tubes on accretion disk.
- ID:
- ivo://CDS.VizieR/J/PASP/106/828
- Title:
- BVRI photometry of Omega Cen
- Short Name:
- J/PASP/106/828
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BVRI photometry is given for stars in the omega Centauri (= NGC 5139 = C 1323-472) calibration field for the Wide Field/Planetary Camera of the Hubble Space Telescope.
- ID:
- ivo://CDS.VizieR/J/AN/326/3
- Title:
- BVRI photometry of 4 open clusters
- Short Name:
- J/AN/326/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry of the galactic open clusters NGC 2627, NGC 5617, Pismis 7, and Ruprecht 75 is presented. For the first cluster, BV data are given, for the others the data are BV(RI)_c. The star coordinates are relative to the corresponding cluster center. The observations were carried out from the Complejo Astronomico El Leoncito (Argentina), and from Las Campanas (Chile). Each cluster was observed on two different nights; when possible, measurements for a given star were averaged. NGC 2627 observations were carried out from CASLEO on the nights of 7-8 January 1997 and 23-24 April 2001, in the BV filters. NGC 5617 data in the BVRI filters were obtained at Las Campanas on the nights 10-11 and 11-12 April 1996, and at CASLEO on the 1-2 April 2001 night. Pismis 7 was observed from Campanas on the 13-14 and 15-16 April 1996 nights (BVRI). Ruprecht 75 data in the BVRI filters were obtained at Las Campanas on the 12-13 April 1996 night, and at CASLEO on the 20-21 April 2001 night.
- ID:
- ivo://CDS.VizieR/J/A+A/423/935
- Title:
- BVRI photometry of OQ 530
- Short Name:
- J/A+A/423/935
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of VLBI and optical observations are presented for the BL Lac object OQ 530 (B1418+546), whose long-term optical variability is characterised by a decreasing mean luminosity trend. EVN images at 1.6GHz and 5GHz of OQ 530 show a very bright core with a much weaker jet extending to about 35-40mas. The radio flux density from the core in June 2001 was much higher than that measured in February 1999. A similar increase was also found from nearly simultaneous optical photometry, while the total flux density of the jet remained unchanged. The structure of the jet shows several knots which move outward with an apparent superluminal motion with a beta_app_>=3.5h^-1^. The region within about 3mas from the core contains a component not well resolved in our images and emerging from it in the jet direction. That component was also detected in images taken from 1990 to 1997 and it seems to be a rather stable structural feature. Using nearly simultaneous optical and radio data, we can describe the SED of the synchrotron peak with a simple formula, approximating a power law at low frequencies and a log-parabola at the high ones, whose maximum lies in the range 3.5-5x10^13^Hz, and the extrapolation in the X-ray range give a flux comparable to that observed with BeppoSAX.
- ID:
- ivo://CDS.VizieR/J/AJ/119/777
- Title:
- BVRI photometry of Sagittarius dwarf irregular galaxy
- Short Name:
- J/AJ/119/777
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep BVRI CCD photometry of the stars in the dwarf irregular galaxy SagDIG, obtained on the photometric night of 1994 October 8 (UT) using the University of Hawaii 2.2 m telescope at Mauna Kea.
- ID:
- ivo://CDS.VizieR/J/PASP/114/1382
- Title:
- BVRI photometry of Stock 1 stars
- Short Name:
- J/PASP/114/1382
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BVRI photometry and J2000.0 positions have been obtained for stars in the field of the open cluster Stock 1. The photometry has been combined with available spectral types and proper motions to investigate cluster membership. We conclude that Stock 1 is a young cluster with a reddening of E(B-V)=0.16+/-0.04, a distance modulus of V_0_-M_V_=7.5+/-0.1, and an age of 300+/-50Myr.
- ID:
- ivo://CDS.VizieR/J/AJ/144/37
- Title:
- BVRI photometry of the eclipsing binary BS Vul
- Short Name:
- J/AJ/144/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed study of the close eclipsing binary BS Vulpeculae. Although it is relatively bright (V: 10.9-11.6mag) and belongs to short-periodic variable stars (P=0.48days), it is rather neglected. To perform a thorough period analysis, we collected all available photometric observations that span the time interval of 1898-2010. Observations include archive photographic plate measurements and visually determined eclipse minima timings done in 1979-2003, which were later shown to be biased to accommodate the existing linear ephemeris. Applying our own direct period analysis we found a well-defined shortening of the orbital period of dP/dt=-6.70(17)x10^-11^=-2.11(6)ms/yr, which implies a continual mass flow from the primary to the secondary component. Using the 2003 version of the Wilson-Van Hamme code, our new complete BV(IR)_C_ light curves were analyzed and the physical parameters of the system were derived. We found that BS Vul is a near contact binary system with the primary component filling its critical Roche lobe. The luminosity enhancement on the left shoulder of the secondary minimum shown in the light curves can be explained as a result of a persistent hot spot on the secondary due to the mass transfer from the primary component to the secondary one and heating the facing hemisphere of the secondary component, which is consistent with our result of period analysis. With the period decrease, BS Vul will evolve toward the contact phase. It is another good observational example as predicted by the theory of thermal relaxation oscillations.
- ID:
- ivo://CDS.VizieR/J/PASP/121/1366
- Title:
- BVR light curves of BX Peg
- Short Name:
- J/PASP/121/1366
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of new CCD photometry for the contact binary BX Peg, made during three successive months beginning on 2008 September. As do historical light curves, our observations display an O'Connell effect and the November data by themselves indicate clear evidence for very short-term brightness disturbance.
- ID:
- ivo://CDS.VizieR/J/A+A/519/A78
- Title:
- BVR light curves of KR Com
- Short Name:
- J/A+A/519/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the detailed analysis of triple system KR Com with different observational techniques - photometry, interferometry, and period variation. The use of BVR photometry of the close-contact binary KR Com, which is the primary component of a triple system, helps us to better describe the properties of the components. The interferometric data obtained during the last 30 years sufficiently determine the visual orbit, but the use of minima timings of KR Com for the study of period variation together with the visual orbit is a novel approach in this system.
