We report optical extinction properties of dust for a sample of 26 early-type galaxies based on the analysis of their multicolour CCD observations. The wavelength dependence of dust extinction for these galaxies is determined and the extinction curves are found to run parallel to the Galactic extinction curve, which implies that the properties of dust in the extragalactic environment are quite similar to those of the Milky Way. For the sample galaxies, value of the parameter R V , the ratio of total extinction in V band to selective extinction in B and V bands, lies in the range 2.03−3.46 with an average of 3.02, compared to its canonical value of 3.1 for the Milky Way. A dependence of R V on dust morphology of the host galaxy is also noticed in the sense that galaxies with a well defined dust lane show tendency to have smaller R V values compared to the galaxies with disturbed dust morphology. The dust content of these galaxies estimated using total optical extinction is found to lie in the range 10 4 to 10 6 M , an order of magnitude smaller than those derived from IRAS flux densities, indicating that a significant fraction of dust intermixed with stars remains undetected by the optical method. We examine the relationship between dust mass derived from IRAS flux and the X-ray luminosity of the host galaxies.The issue of the origin of dust in early-type galaxies is also discussed.

We present multicolor surface and aperture photometry in the B, V, R, and K 0 bands for a sample of 34 lenticular galaxies from the Uppsala General Catalogue. From surface photometric analysis, we obtain radial profiles of surface brightness, colors, ellipticity, position angle, and the Fourier coefficients that describe the departure of isophotal shapes from a purely elliptical form; we find the presence of dust lanes, patches, and ringlike structure in several galaxies in the sample. We obtain total integrated magnitudes and colors and find that these are in good agreement with the values from the Third Reference Catalogue. Isophotal colors are correlated with each other, following the sequence expected for early-type galaxies. The color gradients in lenticular galaxies are more negative than the corresponding gradients in elliptical galaxies. There is a good correlation between BÀV and BÀR color gradients, and the mean gradients in the BÀV, BÀR, and VÀK 0 colors are À0:13 AE 0:06, À0:18 AE 0:06, and À0:25 AE 0:11 mag dex À1 in radius, respectively.

We present results of optical broad-band and narrow-band Hα observations of a sample of forty nearby early-type galaxies. The majority of sample galaxies are known to have dust in various forms viz. dust lanes, nuclear dust and patchy/filamentary dust. A detailed study of dust was performed for 12 galaxies with prominent dust features. The extinction curves for these galaxies run parallel to the Galactic extinction curve, implying that the properties of dust in these galaxies are similar to those of the Milky-Way. The ratio of total to selective extinction (R V ) varies between 2.1 to 3.8, with an average of 2.9±0.2, fairly close to its canonical value of 3.1 for our Galaxy. The average relative grain size a Gal of dust particles in these galaxies turns out to be 1.01±0.2, while dust mass estimated using optical extinction lies in the range ∼ 10 2 to 10 4 M ⊙ . The Hα emission was detected in 23 out of 29 galaxies imaged through narrow-band filters with the Hα luminosities in the range 10 38 -10 41 erg sec −1 . The mass of the ionized gas is in the range ∼ 10 3 -10 5 M ⊙ . The morphology and extent of ionized gas is found similar to those of dust, indicating possible coexistence of dust and ionized gas in these galaxies. The absence of any apparent correlation between blue luminosity and normalized IRAS dust mass is suggestive of merger related origin of dust and gas in these galaxies.

Abstract.A new BV R photometry of six prominent RS CVn stars: V711 Tau, UX Ari, IM Peg, II Peg, σ Gem and λ And, carried out during 1995-97, is presented. The new results reveal significant evolution in the shape as well as in the amplitude of light curves of these binaries. The traditional two-starspot model has been used to obtain the spot parameters from the observed light curves of the stars. Changes in spot area and their location on stellar surface can be noticed from extracted spot parameters. Some of these stars are found to have significant variation in (B − V ) and (V −R) colour indices. The (V − R) colour index variation found in IM Peg, II Peg and λ And have been used for determining starspot effective temperatures.