Section: PZ: main journal
We present the results of our long-term homogeneous spectroscopy of T~Tau, the prototype T~Tauri star. We demonstrate that the star's absorption spectrum varies in time and is weakly correlated with variations of brightness and emission spectrum. With increasing intensities of emission lines, the veiling of the photospheric absorption decreases. It is suggested that the absorption-spectrum variations are due to variable additional emission superimposed on the photospheric spectrum and that the amount of veiling is inversely correlated with the emission-line strength in the spectrum of the star.
Period Changes in the Algol-type Eclipsing Binary System TYC 1744 2329 1
We present the discovery and the times of primary minima for the eclipsing binary TYC 1744 2329 1 = ASAS 003933+2730.5. Our CCD observations compared to times of minima derived from the archival photographic plates and from the NSVS and ASAS-3 data clearly show that the orbital period of the system is variable.
GSC 7672:2238: a binary system near the Delta Scuti star AI Vel
We report the results of a photometric and spectroscopic study of an eclipsing binary star in the field of the Delta Scuti variable AI~Vel. Time-series CCD photometry was performed allowing almost complete phase coverage. Our period search gave an orbital period of 0.9719d. The light curve is typical of short-period Algol stars and suggests the presence of phase-related increase of brightness (φ=0.1-0.2) which can be due to mass transfer phenomena. Another possibility is the presence of a spotted region. Spectroscopic observation shows the Balmer Hα absorption line, typical of Algol systems with a transient or absent disc.
We present the results of our long-time homogeneous low-resolution spectroscopy of T Tau, the prototype T Tauri star. We show that the star's spectral activity was different at different times of the observations and possibly was cyclic, with a many-year cycle. Variable emission activity in spectral lines at different brightness ranges was revealed. During the star's brightest state, equivalent widths of hydrogen emission lines show variations up to the factor of 5. The observed properties of the emission spectrum can be explained by the disk-accretion theory.
CCD UBVRI photometry is presented for the type Ia supernova 2004fu in NGC 6949. The light and colour curves are typical for this class of objects, the absolute magnitude at maximum and decline rate are in agreement with the relationship between these parameters established for SNe Ia.
Photometric observations of Supernovae 2000E, 2001B, 2001V, and 2001X
CCD BVRI photometry is presented for two type Ia supernovae 2000E and 2001V, for SN Ib 2001B and SN II-P 2001X. The parameters of light curves and absolute magnitudes at maximum light are estimated. It is shown that all four supernovae are typical for their classes considering the shape of their light curves and maximum luminosity.
Photometric elements and stellar parameters for the contact binary RZ UMi
The contact binary RZ UMi was discovered by Goranskij (1982), who also attributed it to the W UMa class with a period of 0.33735283 days. No other observations of this star have been published since. We therefore re-observed RZ UMi at Beersel Hills Observatory on nine nights between May 2001 and March 2003. The instrument used was a 0.4 m Newtonian telescope, equipped first with a SBIG ST7E CCD camera (2001-2002) and later with a ST10 XME camera (2003). The 2001 observations are unfiltered. From 2002 onwards, a V filter according to the specifications of Bessell (1995) was used. The exposure times varied between 120 and 180 seconds. All images were reduced with the aperture photometry procedure of the Mira AP software package and darkframed and flatfielded according to standard procedures.
Our BVR CCD photometric study of the globular cluster NGC 7006 permitted us to find two new suspected RR Lyrae variables. A cluster chart is presented with the position of known and suspected variables marked.
Classifications and light elements, based on data mining in the ASAS-3 and ROTSE-I/NSVS data, are presented for 100 variable stars, 78 of them from the NSV catalog. Availability of online observations makes it possible to suggest all these stars for GCVS Name-Lists.
We report discovery and investigation of missed supernova 1985 on Moscow archive plates.