1,598 research outputs found
UBVRI photometric comparison sequences for symbiotic stars
We present accurate UBVRI photometric comparison sequences around 20
symbiotic stars. The sequences extend over wide brightness and color ranges,
and are suited to cover quiescence as well as outburst phases. The sequences
are intended to assist both present time photometry as well as measurement of
photographic plates from historical archives. The types of variability
presented by symbiotic stars are reviewed. Individual notes on the known
photometric behaviour of the program stars are provided.Comment: in press in Astron.Astrophys.Supp
Recent photometry of symbiotic stars - XII
We present new photometric observations of 15 symbiotic stars (EG And, Z And,
AE Ara, BF Cyg, CH Cyg, CI Cyg, V1329 Cyg, TX CVn, AG Dra, Draco C-1, RW Hya,
SY Mus, AR Pav, AG Peg, AX Per) covering their last orbital cycle(s) from
2003.9 to 2007.2. We obtained our data by both classical photoelectric and CCD
photometry. Main results are: EG And brightened by about 0.3 mag in U from
2003. A 0.5 mag deep primary minimum developed in the U light curve (LC) at the
end of 2006. Z And continues its recent activity that began during the 2000
autumn. A new small outburst started in summer of 2004 with the peak
U-magnitude of about 9.2. During the spring of 2006 the star entered a massive
outburst. It reached its historical maximum at U = 8.0 in 2006 July. AE Ara
erupted in 2006 February with Dm(vis) approx. 1.2 mag. BF Cyg entered a new
active stage in 2006 August. A brightness maximum (U approx. 9.4) was measured
during 2006 September. CH Cyg persists in a quiescent phase. During 2006 June -
December about 2 mag decline in all colours was measured. CI Cyg started a new
active phase during 2006 May - June. After 31 years it erupted by about 2 mag
in U. TX CVn maintains a bright stage with U approx. 10.5 from 2003. AG Dra
entered a new major outburst in 2006 June. It reached its maximum at U = 8.0 in
2006 September. AR Pav persists at a low level of the activity. AG Peg's LC
profile varies markedly during different orbital cycles. AX Per continues its
quiescent phase.Comment: 4 pages text, 12 figures, 18 tables, accepted for publication in
Astron. Nachrichte
SALT observations of southern post-novae
We report on recent optical observations of the stellar and the nebular
remnants of 22 southern post-novae. In this study, for each of our targets, we
obtained and analysed long-slit spectra in the spectral range 3500-6600 A and
in H+NII narrow-band images. The changes in the emission lines'
equivalent widths with the time since the outburst agree with earlier published
results of other authors. We estimated an average value =2.37 for the
exponent of the power law fitted to the post-novae continua. Our observations
clearly show the two-component structure of the V842 Cen expanding nebulae,
owing to the different velocities of the ejected matter. We discovered an
expanding shell around V382 Vel with an outer diameter of about 12 arcsec.Comment: 24 pages, 19 figures, A&A accepte
- …