Issue |
A&A
Volume 387, Number 3, June I 2002
|
|
---|---|---|
Page(s) | 1013 - 1021 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20020468 | |
Published online | 17 May 2002 |
The spectrum of the recurrent nova U Scorpii during the 1999 outburst
Astronomical Observatory of Padova, Asiago Section, Osservatorio Astrofisico, 36012 Asiago (Vi), Italy
Corresponding author: iijima@astras.pd.astro.it
Received:
10
May
2001
Accepted:
25
February
2002
An optical spectrum covering the range λ
λ4300–6900 Å of the recurrent
nova U Sco in outburst was taken on February 26th 1999, only 16 hours after
maximum. Broad emission lines of H I, He I, N II, N III were seen on the
spectrum, while the emission line of He II λ4686 was not yet seen.
The FWHM of the emission component of Hα was 8000 km s-1 and
the FWZI was roughly 12000 km s-1. The emission line of Hα had blue
(-3250 km s-1), central (+30 km s-1), and red (+2770 km s-1) peaks, among which
the red one was the most prominent. A narrow absorption component of
Hα blue-shifted by -4850 km s-1 was seen. The other prominent
lines had a main emission peak red-shifted by km s-1 and a
weak secondary peak blue-shifted by
km s-1. Most of He I
and N II lines were flanked by a narrow absorption component blue-shifted by
about -4300 km s-1 which was a good clue for the detailed identification
of these lines. These absorption components and some emission lines of
N II faded very rapidly and nearly disappeared one day after our
observation. The widths of the emission lines decreased with time. The
radial velocities of three emission peaks of Hα were -1560 km s-1, +60
km s-1 and +1800 km s-1on March 14th, 17 days after maximum,
when the blue one became stronger than the others.
The helium abundance by the number of atom of the ejecta is estimated as
N(He)/N(H)
which is much lower than those found in previous
works, and is not different from those of normal classical novae. Adopting
the distance 6 kpc, the mass of the ejecta is estimated as
.
Key words: stars: individual: U Sco / novae, cataclysmic variables
© ESO, 2002
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