We report an 11-year long series of U BV RI observations and the results of our monitoring of the classical slow nova V723 Cas. We analyze the spectra of this star taken using the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences with a spectral resolution of 3.5–8.5 Å during the nebular stage and at the supersoft X-ray source phase (SSS). This systemhas a large orbital inclination and its orbital period is equal to 0.693265 days. The orbital period increases. We found low-amplitude light variations with the orbital period during the early stages of the outburst and even at the pre-maximum stage. The orbital light curve at the nebular stage is asymmetric and gradually increases its amplitude up to V=2 m in 2006. The asymmetry of the light curve of V723 Cas can be explained by the reflection effect, eclipse of the extended accretion disk, and high rate of mass transfer in the system. The light curve of V723 Cas has developed a plateau due to the SSS phase. In the spectrum of V723 Cas the transition to the SSS phase shows up in an order-of-magnitude increase of the flux of the [Fe X] λ 6374 Å emission, which forms in the expanding envelope. In addition, narrow emission lines λ 6466.4 Å (O V) and λ 6500.5 Å (Fe XVII) also emerged in the spectrum.

Results of simultaneous INTEGRAL and optical observations of the galactic microquasar SS433 in May 2003 and INTEGRAL / RXTE observations in March 2004 are presented. Persistent precessional variability with a maximum to minimum uneclipsed hard X- ray flux ratio of similar to 4 is discovered. The 18 - 60 keV X- ray eclipse is found to be in phase with optical and near infrared eclipses. The orbital eclipse observed by INTEGRAL in May 2003 is at least two times deeper and apparently wider than in the soft X- ray band. The broadband 2 - 100 keV X- ray spectrum simultaneously detected by RXTE/ INTEGRAL in March 2004 can be explained by bremsstrahlung emission from optically thin thermal plasma with kT similar to 30 keV. Optical spectroscopy with the 6- m SAO BTA telescope confirmed the optical companion to be an A5 - A7 supergiant. For the first time, spectorscopic indications of a strong heating effect in the optical star atmosphere are found. The measurements of absorption lines which are presumably formed on the non- illuminated side of the supergiant yield its radial velocity semi- amplitude K-v = 132 9 kms(-1). The analysis of the observed hard X- ray light curve and the eclipse duration, combined with the spectroscopically determined optical star radial velocity corrected for the strong heating effect, allows us to model SS433 as a massive X- ray binary. Assuming that the hard X- ray source in SS433 is eclipsed by the donor star that exactly fills its Roche lobe, the masses of the optical and compact components in SS433 are suggested to be M-v approximate to 30 M-circle dot and M-x approximate to 9 M-circle dot, respectively. This provides further evidence that SS433 is a massive binary system with supercritical accretion onto a black hole.

Results of simultaneous INTEGRAL and optical observations of the galactic microquasar SS433 in May 2003 and INTEGRAL /RXTE observations in March 2004 are presented. Persistent precessional variability with a maximum to minimum uneclipsed hard X-ray flux ratio of ∼4 is discovered. The 18–60 keV X-ray eclipse is found to be in phase with optical and near infrared eclipses. The orbital eclipse observed by INTEGRAL in May 2003 is at least two times deeper and apparently wider than in the soft X-ray band. The broadband 2–100 keV X-ray spectrum simultaneously detected by RXTE/INTEGRAL in March 2004 can be explained by bremsstrahlung emission from optically thin thermal plasma with kT ∼ 30 keV. Optical spectroscopy with the 6-m SAO BTA telescope confirmed the optical companion to be an A5–A7 supergiant. For the first time, spectorscopic indications of a strong heating effect in the optical star atmosphere are found. The measurements of absorption lines which are presumably formed on the non-illuminated side of the supergiant yield its radial velocity semi-amplitude Kv = 132 ± 9 km s−1. The analysis of the observed hard X-ray light curve and the eclipse duration, combined with the spectroscopically determined optical star radial velocity corrected for the strong heating effect, allows us to model SS433 as a massive X-ray binary. Assuming that the hard X-ray source in SS433 is eclipsed by the donor star that exactly fills its Roche lobe, the masses of the optical and compact components in SS433 are suggested to be Mv ≈ 30 M and Mx ≈ 9 M , respectively. This provides further evidence that SS433 is a massive binary system with supercritical accretion onto a black hole.

We describe the results of a long-slit spectroscopic study of an unusual star complex in the nearby spiral galaxy NGC 6946 using the SAO 6-m telescope and the Keck 10-m telescope. The complex resembles a circular bubble 600 pc in diameter with a young super star cluster (SSC) near the center. The kinematics of ionized gas is studied through Ha emission with several slit positions. Position-velocity diagrams show two distinct features with high speed motions. One is an irregularly shaped region to the east of the SSC, 270 pc in size, in which most of the Ha emission is blue shifted by 120 km/s, and another is a 350 pc shell centered on the SSC with positive and negative velocity shifts of 60 km/s. Balmer and HeI absorption lines in the SSC give an age of 12-13 Myr, which is consistent with the photometric age but significantly older than the kinematic ages of the high speed regions. The energetics of the SSC and its interaction with the environment are considered. The expansion energies exceed 10^52 ergs, but the power outputs from winds and supernova in the SSC are large enough to account for this. The intensities of Balmer, [NII], and [SII] emission lines within and around the complex indicate that shock excitation makes a significant contribution to the emission from the most energetic region.

We present CCD B,V and R surface photometry for a subsample of 67 blue compact galaxies (BCGs) drawn from the First and Second Byurakan surveys. We outline the range of typical photometric parameters for the investigated subsample. The surface brightness profiles were built for all BCGs. The profile decomposition was done using two-component model: an exponential disk and/or a gaussian component at small effective radii. The (B-V) and for the part of galaxies (V-R) color profiles were derived. The analysis shows the variety of morphologies, and large range of galaxy sizes and exponential disk structural parameters. We use these data to check possible correlations between various physical parameters and gain insight into star-forming processes in BCGs. We compare structural parameters for our BCGs to those of other types of dwarf galaxies – dIrr, dE and LSBD galaxies to look for possible connections between them and BCGs.

We describe the goals of the Hamburg/SAO survey (HSS) for emission-line galaxies and present preliminary results on the new sample of blue compact (BCG)/Hii-galaxies created in the frame of the HSS. In particular, data on the BCG space distribution in the currently best-studied sky area RA = 7(h)30(m) 17(h)30(m), Dec = +35degrees - +40.5degrees are briefly discussed. A similar to 10% fraction of BCGs populates very low galaxy density regions, probably indicating filaments of faint galaxies penetrating into voids. Some results on the search for the most metal-deficient BCGs are also summarized. Four new HSS BCGs with O/H < 1/20 (O/H),D add 30% to the sample of such galaxies discovered during the past decade.

The study of group properties of the extremely metal-deficient gas-rich local dwarfs is very promising for the understanding the galaxy formation process at high redshifts. About 20 such objects have been picked up from the literature in the recent review by Kunth & Ostlin(2000). However part of these galaxies got low metallicity as a result of earlier observations, and can have rather large uncertainties in their cited element abundances. Before to perform the detailed studies of such galaxies as of some extreme group, it is useful to revise their metallicities. We present the results of the SAO 6m telescope spectrophotometry of two Blue Compact Galaxies (BCG) reported from earlier studies as very metal-poor objects. Well measured [O III] line 4363 A allows to deduce the temperature in HII regions and get reliable abundances of chemical elements. For UM 133 we derive 12+log(O/H) = 7.63+/-0.02, coincident with the published value. UM 382, according to our data, is significantly more metal-rich: its 12+log(O/H) = 7.82+/-0.03 in comparison to the published value 7.45. The third galaxy, UM 283 seems have got its very low 12+log(O/H) = 7.59 due to a misprint. We used its published emission line intensities and derived instead the value of 7.95. Thus the latter two galaxies should NOT be considered as the extremely metal-poor BCGs.

We present first results of spectrophotometry with the6-m Russia telescope of a new sample of BCGs. The candidates were found on the digitized objective-prism photo plates of the Hamburg Quasar Survey by selecting objects with a high probability to be strong [OIII] λ5007 Å emitters. The intensity of the [OIII] λ4363 Åline was measured in all observed galaxies, allowing to determine directly the temperature in the HII regions and to derive their oxygen abundances. In the sample log(O/H)+12 varies in the range of 7.6 to 8.4. A complete sample of 46 BCGs with an EW([OIII]) λ5007 ≥100 Å was constructed and used for statistical analysis. This sample and related volume limited subsamples were used to derive the observed distribution of O/H. Using evolutionary synthesis models of star-formation bursts, we corrected the observed distribution for observational selection effects due to different values of EW(Hβ). This is a first attempt to reconstruct the real metallicity distribution among BCGs at modern epoch. An interesting additional result is a very high fraction of certain and probable WR galaxies in our sample.

While the importance of large-scale motions in dwarf galaxies, generated during the periods of enhanced SF is widely recognized, little is known on the parameters of expanding shells in the extremely metal-deficient BCGs. We show the first results from the 6-m Russian and 4-m KPNO telescopes demonstrating the presence of expanding ionized shells around the regions with current SF burst in 6 new BCG/HII galaxies with the oxygen abundance in the range of log(O/H)+12 = 7.35 to ∼7.6, and MB in the range –11.m5 to –15.m7.Their Hα velocity curves, sampled with the accuracy of 3–5km s-1 show invariably significant deviations correlated with the positions of bright HII regions. The shape of these deviations in the plane `V vs R' imply radial expansions with the amplitudes of ten to a hundred km s-1. The diameters of corresponding shells are in the range0.1–1 kpc. Since the efficiency of stellar winds for very low metallicities is significantly reduced, the main energetics of the shells discovered in extremely metal-poor galaxies should be powered by the cumulative effect of SN explosions. These shells represent the wide range of ages and thus can be in principle used to confront the results of model simulations on shell dynamics.

Among the galaxies which were included in the Atlas and Catalogue of Interacting galaxies by Vorontsov-Vel'yaminov thereafter VV) as multiple systems ("nests", "chains" and similarly looking systems), there are many objects, where the interaction is not evident. Some of them are single objects, including low-mass galaxies with active star formation (SF). In this work we present the description of observations and results of the long-slit spectrophotometry with the Russian 6 m telescope of three VV-galaxies looking like double or multiple systems, and HI observations of one of them in order to elucidate their nature, determine their metallicity, kinematic properties and the evolution status. Galaxies VV 432 and VV 747 are found to be dwarf systems with low oxygen abundance (O/H approximate to 1/22 and 1/12 of the solar value, respectively). Their velocity curves indicate quite slow rotation with respective maximum velocities of about 60 and 80 km s(-1), in agreement with their low luminosities. The distance to VV 432 is rather uncertain. If it is a member of Virgo Cluster, this is the most metal-deficient known galaxy of this aggregate. For galaxy VV 543 the measured emission-line redshift 0.047 appeared ten times larger than it was given in the original paper and is cited in databases. This "system" evidently represents an optical pair of two galaxies with large velocity difference. The fainter western component is an HII-galaxy, while the brighter one is an absorption-line early-type galaxy with the radial velocity being 1600 km s(-1) lower.

We present the second part of the Hamburg/SAO Survey for Emission-Line Galaxies (HSS therein, SAO – Special Astrophysical Observatory, Russia) which is based on the digitized objective-prism photoplates database of the Hamburg Quasar Survey (HQS). The main goal of the project is the search for emission-line galaxies (ELG) in order to create a new deep sample of blue compact/Hii galaxies (BCG) in a large sky area. Another important goal of this work is to search for new extremely low-metallicity galaxies. In this paper we present new results of spectroscopy obtained with the 6 m Russian telescope. The main ELG candidate selection criteria applied are blue or flat enough continuum (near λ4000 A) and the presence of strong or moderate [Oiii]λλ4959, 5007 A emission lines recognized on digitized prism spectra of galaxies with the survey estimated B-magnitudes in the range 16 − 19. 5. No other criteria were applied. The spectroscopy resulted in detection and quantitative spectral classification of 134 emission-line objects. For 121 of them the redshifts are determined for the first time. For 13 ELGs known before emission line ratios are presented at first time. 108 of 134 emission-line objects are classified as BCG/Hii galaxies and probable BCGs, 6 – as QSOs, 1 – as Seyfert galaxy, 1 – as super-association in a dwarf spiral galaxy, 2 – as probable LINERs, 14 are low excitation objects – either of starburst nuclei (SBN), or dwarf amorphous nuclei Send offprint requests to: sap@sao.ru ? Deceased September 22, 1996. 1 Tables 2 to 6 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html. Figures A1 to A13 will be made available only in the electronic version of the journal. Appendix A is only available at http://www.edpsciences.com starburst galaxy (DANS) type, and 2 – nonclassified. 23 galaxies did not show significant emission lines. The five most metal-deficient BCGs discovered have oxygen abundances log(O/H)+12 in the range 7.4 to 7.7, similar to the most metal-deficient BCGs known before.