Infrared photometry of five long-period binaries

We present and discuss JHKLM photometry for five long-period binaries (VV Cep, ZZ CMi, WY Gem, ε Aur, and ζ Aur). The IR radiation from WY Gem may contain a component with a period of ～430 days, attributable to temperature pulsations of an M supergiant. The 3.5-and 5-μm radiation from the eclipsing binary ε Aur outside the eclipse exhibits excess (relative to the light from an F supergiant) fluxes which correspond to the emission from a cool source with a temperature of ～1000 K. For the eclipsing binary Aur, we present the hitherto unpublished results of our optical and IR photometry during 1982–1985, when a primary eclipse was observed in the system.     

Results of Optical Monitoring of Cataclysmic Variable GK Per in 2004

The preliminary results of ground-based UBV photometric and CCD observations of cataclysmic variable GK Per during the outburst in autumn of 2004 are presented.     

Combined color indices and photometric structures of the galaxies NGC 834 and NGC 1134

Surface BVRI photometry is presented for two spiral galaxies with a complex photometric structure: NGC 834 and NGC 1134. We propose to introduce the combined color indices Q _BVI and Q _VRI to investigate the photometric structure of the galaxies. These color indices depend only slightly on selective absorption, which allows them to be used to study the photometric structure of “dusty” galaxies. Evolutionary stellar-population models show that Q _BVI is most sensitive to the presence of blue stars, while Q _VRI depends on local Hα equivalent width. A ring with active star formation manifests itself on the Q _BVI map for NGC 834 at a distance of ～15 from its center, and a spiral structure shows up on the Q _VRI map for NGC 1134 in its inner region. The Q _BVI –Q _VRI diagram can provide information about the current stage of a star's formation in various galactic regions. A comparison of the color indices for the galaxies with their model values allows us to estimate the color excesses and extinction in various galactic regions.     

Hα emission line morphologies in Markarian starburst galaxies

We present broad bandR and narrow band Hα emission line images of a sample of optically selected starburst galaxies from the Markarian lists. The emission line morphology is studied and global properties like luminosities, equivalent widths and star formation rates are derived. The radial distribution of Ha flux and the EW are determined using concentric aperture photometry on the emission line and the continuum images. Ha flux is generally found to peak in the nuclear region and fall off outwards. The EW is found to peak off-center in most of the cases implying that though the intensity of emission is maximum at the nucleus, the star formation activity relative to the underlying continuum often peaks away from the center in Markarian starburst galaxies.     

The Visual Light Curve Of C/1995 O1 (Hale-Bopp) From Discovery To Late 1997

We present a light curve of C/1995 O1 (Hale-Bopp) compiledfrom more than 3000 visual observations of the comet made by members of the The Astronomer Group world-wide. These observations cover the period from discovery through to the end of 1997. The light curve shows that the rate of brightening of the comet varied widely at different times, with rapid rates of brightening at high heliocentric distance pre-perhelion and a comparably rapid post-perihelion fade. There is no evidence that the comet was suffering a large photometric outburst when first discovered, although a small outburst can be identified at perihelion. At least five difficult brightening regimes can be identified in the light curve between discovery and perihelion. From 2.5 AU to perihelion the rate of brightening with decreasing heliocentric distance was typical for “fairly” new comets(n ∼ 3.5, where “n” is the power law exponent of the heliocentric distance), although this was preceded by a period of very slow brightening with n ∼ 1 from r ∼ 4.0 AU to r ∼ 2.8 AU and followed by an initially more rapid brightening which appears to be related to the on-set of rapid water sublimation activity. We derive the light curve parameters at different stages of the comet's apparition. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gain calibration of CCD systems at VBO

The system gain of two CCD systems in regular use at the Vainu Bappu Observatory, Kavalur, is determined at a few gain settings. The procedure used for the determination of system gain and base-level noise is described in detail. The Photometrics CCD system at the 1-m reflector uses a Thomson-CSF TH 7882 CDA chip coated for increased ultraviolet sensitivity. The gain is programme-selected through the parameter ‘cgain’ varying between 0 and 4095 in steps of 1. The inverse system gain for this system varies almost linearly from 27.7 electrons DN^-1 at cgain = 0 to 1.5 electrons DN^-1 at cgain = 500. The readout noise is ≲ 11 electrons at cgain = 66. The Astromed CCD system at 2.3-m Vainu Bappu Telescope uses a GEC P8603 chip which is also coated for enhanced ultraviolet sensitivity. The amplifier gain is selected in discrete steps using switches in the controller. The inverse system gain is 4.15 electrons DN^-1 at the gain setting of 9.2, and the readout noise ∼ 8 electrons.     

The Herbig Ae/Be Star V586 Ori

Studies of the Herbig Ae/Be star V586 Ori based on photoelectric observations in the Strömgren system are reported. It is found that as the brightness decreases, the Balmer discontinuity index initially increases and then begins to drop. As the star fades, the index decreases. We have previously found similar variations in the indices and C for UX Ori, RR Tau, and V351 Ori. It is shown that V586 Ori has the characteristics of a shell-star.     

On the shape of elliptical galaxies

We propose a test for the existence of prolate elliptical galaxies based on the properties of the photometric parameters introduced in the Córdoba surface photometry.