M. Parthasarathy

Spectroscopy of the post-AGB star HD 101584 (IRAS 11385-5517)

From an analysis of the spectrum (4000 Angstrom to 8800 Angstrom) of HD 101584 it is found that most of the neutral and single ionized metallic lines are in emission. The forbidden emission lines of [OI] 6300 Angstrom and 6363 Angstrom and [CI] 8727 Angstrom are detected, which indicate the presence of a very low excitation nebula. The H alpha, FeII 6383 Angstrom, Nd D-1, D-2 lines and the CaII IR triplet lines show P-Cygni profiles indicating a mass outflow. The H alpha line shows many velocity components in the profile. The FeII 6383 Angstrom also has almost the same line profile as the H alpha line indicating that they are formed in the same region. From the spectrum synthesis analysis we find the atmospheric parameters to be T-eff = 8500 K, log g = 1.5, V-turb = 13 km s(-1) and [Fe/H] = 0.0. From an analysis of the absorption lines the photospheric abundances of some of the elements are derived. Carbon and nitrogen are found to be overabundant. From the analysis of Fe emission lines we derived T-exi = 6100 K +/- 200 for the emission line region.

Light curve analysis of Hipparcos data for the massive O-type eclipsing binary UW CMa

Abstract Hipparcos photometric data for the massive O-type binary UW CMa were analysed within the framework of the Roche model. Photometric solutions were obtained for five mass ratios in the qxa0=xa0M2/M1xa0=xa00.5–1.5 range. The system is found to be in a contact configuration. Independently of q, the best-fitting model solutions correspond to the orbital inclination ixa0∼xa071° and the temperature of the secondary component T2xa0∼xa033500xa0K, at the fixed temperature of the primary T1xa0=xa033750xa0K. Considering that the spectrum of the secondary is very weak, photometric solutions corresponding to the contact configuration favor the mass ratio q smaller than unity (in which case the luminosity of the secondary is smaller than that of the primary). The absolute parameters of the system are estimated for different values of the mass ratio.

Line identification and photometric history of the hot post-AGB star Hen 3−1013 (IRAS 14331−6435)

We present a study of the high-resolution optical spectrum for the hot post-asymptotic giant branch (post-AGB) star, Hen 3-1013, identified as the optical counterpart of the infrared sourceIRAS 14331-6435. For the first time the detailed identifications of the observed absorption and emission features in the wavelength range 3700-9000 AA is carried out. Absorption lines of HI, HeI, CI, NI, OI, NeI, CII, NII, OII, SiII, SII, ArII, FeII, MnII, CrII, TiII, CoII, NiII, SIII, FeIII and SIV were detected. From the absorption lines, we derived heliocentric radial velocities of

The nature of the Stingray nebula from radio observations

V_r=-29.6pm0.4

Evolved A-type stars

km/s. We have identified emission permitted lines of OI, NI, FeII, MgII, SiII and AlII. The forbidden lines of [NI], [FeII], [CrII] and [NiII] have been identified also. Analysis of [NiII] lines in the gaseous shell gives an estimate for the electron density

The chemical composition of algol systems – III. Beta Lyrae–nucleosynthesis revealed

N_esim10^7

Low resolution spectroscopy of hot post-AGB candidates

cm

Emission band and continuum photometry of Comet West (1975n) – I. Heliocentric dependence of the flux in the emission bands and the continuum

^{-3}

Tidal disruption and tidal coalescence in binary stellar systems

and the expansion velocity of the nebula

BVRI photometry of a few `unidentified' IRAS sources

V_{exp}=12