Search Publications
Chemical abundances of planetary nebulae from optical recombination lines - III. The Galactic bulge PN M 1-42 and M 2-36
Barlow, M. J.; Liu, X. -W.; Storey, P. J. +2 more
We present deep, high-resolution optical spectra of two Galactic bulge planetary nebulae (PN), M 1-42 and M 2-36. The spectra show very prominent and rich optical recombination lines (ORLs) from C, N, O and Ne ions. Infrared spectra from [formmu10]2.4-197µm were also obtained using the Short and Long Wavelength Spectrometer (SWS and LWS) on …
Multiwavelength analyses of the extraordinary nova LMC 1991*
Della Valle, M.; Baron, E.; Shore, S. N. +3 more
LMC 91 was a very fast, classical nova and the brightest nova ever observed in the Large Magellanic Cloud. It was extensively observed during both its early optically thick and its nebular evolution in the optical and UV wavelength regions. We successfully fit all the optically thick spectra using a grid of spherically symmetric, non-LTE, line-bla…
Chemical abundances and winds of massive stars in M31: a B-type supergiant and a WC star in OB 10
Smartt, S. J.; Crowther, P. A.; Dufton, P. L. +5 more
We present high quality spectroscopic data for two massive stars in the OB 10 association of M31, OB 10-64 (B0 Ia) and OB 10-WR1 (WC6). Medium resolution spectra of both stars were obtained using the ISIS spectrograph on the William Herschel Telescope. This is supplemented with Hubble Space Telescope STIS UV spectroscopy and Keck I HIRES data for …
Optical spectroscopy of X-Mega targets - II. The massive double-lined O-type binary HD 93205
Morel, T.; Rauw, G.; Barbá, R. H. +8 more
A new high-quality set of orbital parameters for the O-type spectroscopic binary HD 93205 has been obtained combining échelle and coudé CCD observations. The radial velocity orbits derived from the Heii λ4686Å (primary component) and Hei λ4471Å (secondary component) absorption lines yield semi-amplitudes of 133+/-2 and 314+/-2kms-1 for …
SwSt 1: an O-rich planetary nebula around a C-rich central star
Crowther, P. A.; Barlow, M. J.; de Koter, A. +2 more
The hydrogen-deficient [WCL] type central star HD 167362 and its planetary nebula (PN) SwSt 1 are investigated. The central star has a carbon-rich emission-line spectrum, and yet the nebula exhibits a 10-µm emission feature from warm silicate dust, perhaps indicating a recent origin for the carbon-rich stellar spectrum. Its stellar and nebul…
Cyclic and secular variation in the temperatures and radii of extreme helium stars
Pollacco, Don; Jeffery, C. Simon; Starling, Rhaana L. C. +1 more
The ultraviolet properties of 17 extreme helium stars have been examined using 150 IUE spectra. Combining short-wave and long-wave image pairs and using a grid of hydrogen-deficient model atmospheres and a χ2 minimization procedure, 70 measurements of effective temperature (Teff), angular diameters (θ) and interstellar extinc…
The stellar composition of the star formation region CMa R1 - II. Spectroscopic and photometric observations of nine young stars
de Winter, D.; van den Ancker, M. E.; Tjin A Djie, H. R. E. +4 more
We present new high- and low-resolution spectroscopic and photometric data of nine members of the young association CMa R1. All the stars have circumstellar dust at some distance, as could be expected from their association with reflection nebulosity. Four stars (HD52721, HD53367, LkHα220 and LkHα218) show Hα emission and we argue that they are He…
A peculiar metal-rich star, HD 135485
Dufton, P. L.; Lennon, D. J.; Ryans, R. S. I. +3 more
Local thermodynamic equilibrium (LTE) absolute and differential abundances are presented for a peculiar metal-rich B-type star, HD 135485. These suggest that HD 135485 has a general enrichment of ~0.5dex in all the metals observed (C, N, O, Ne, Mg, Al, Si, P, S, Cl, Ar, Sc, Ti, Cr, Mn, Fe and Sr), except for nickel. The helium enhancement and henc…
Understanding the atmospheric structure of T Tauri stars - II. UV spectroscopy of RY Tau, BP Tau, RU Lupi, GW Ori and CV Cha
Lanzafame, A. C.; Brooks, D. H.; Costa, V. M. +1 more
We report results from our study of International Ultraviolet Explorer (IUE) data of a group of T Tauri stars (TTS). Comparisons between UV-line fluxes in these stars and in the Sun indicate very high levels of activity in their atmospheres and comparatively higher electron densities. Spectroscopic diagnostic line ratios indicate densities over an…
Far-ultraviolet extinction and diffuse interstellar bands
Krełowski, J.; Megier, A.; Aiello, S. +2 more
We relate the equivalent widths of the major diffuse interstellar bands (DIBs) near 5797 and 5780Å with different colour excesses, normalized by E(B-V), which characterize the growth of interstellar extinction in different wavelength ranges. It is demonstrated that the two DIBs correlate best with different parts of the extinction curve, and the r…