First far–UV observations of KQ Puppis with FUSE *
XMM Science Operations Centre, VILSPA, PO Box 50727, 28080 Madrid, Spain
2 Dipartimento di Fisica, Università La Sapienza, Piazzale Aldo Moro 3, 00185 Roma, Italy
3 Istituto di Astrofisica Spaziale e Fisica Cosmica, CNR, Area di Ricerca Tor Vergata, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
Corresponding author: R. González-Riestra, firstname.lastname@example.org
Accepted: 20 November 2002
We report the first far–ultraviolet spectrum of the emission line spectroscopic binary KQ Pup (M2Iab+B0Ve), obtained with FUSE shortly after conjunction at orbital phase . The spectrum presents a sharp flux cutoff at 1040 Å; longwards, it is dominated by a large amount of resonant and low excitation transitions of neutral and singly ionized species, probably mostly of circumsystem origin, and by the Lyman absorption bands of H2, whose strength corresponds to an interstellar H2 column density of ~ cm-2, indicating a fraction of molecular hydrogen 2N(H2)/[ N(Hi)+2N(H2)] of ~0.4. An N(Hi)/EB-V ratio of is derived from the IUE spectra. The long–term UV monitoring of KQ Pup with IUE, HST and FUSE reveals a large decrease of the far–UV flux since orbital phase 0.82 and occupying more than 0.3 of the orbital period. This “shell” episode is attributed to line absorption and to Lyα Rayleigh scattering due to an extended dense cool envelope in the line of sight of the B star.
Key words: stars: binaries: spectroscopic / stars: individual: KQ Pup / stars: mass-loss / ultraviolet: stars
Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985. The HST spectrum used in this paper was obtained from the Multimission Archive at the Space Telescope Science Institute (MAST).
© ESO, 2003