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[vsnet-campaign-be 2] Delta Sco information
Delta Sco information
Repeated here for new readers:
Delta Sco: a new extremely bright Gamma Cas-type star in outburst
The following messages are from Sebastian Otero. Delta Sco has now
become one of the brightest gamma Cas stars (active Be stars) among
historically recorded outbursts of this class. The phenomenon is apparently
ongoing, and the object may attain the 1-st magnitude brightness.
Please watch closely and report your observations!
Subject: [vsnet-be 2] (fwd) Delta Sco - GCAS???
The bright B0.5IV star DELTA SCORPII is probably brighter than normal.
It looks like 2.2 instead of 2.3.
I searched for photometric data in the past and there are several
measurements in the range 2.31 - 2.33. But there is one isolate 2.21
(Hogg A.R., 1958, "Photometric observations of 244 bright stars") that
makes me suspicious. It's been some weeks since I noticed this probable
little brightening but I hadn't paid much attention. In addition, the
Hipparcos Catalogue gives a brighter value of 2.29.
Several suitable comparison stars may be used in estimating:
GAMMA CEN: 2.16
ALPHA LUP and EPSILON CEN: ~2.30*
KAPPA SCO: 2.40*
ETA OPH: 2.43
(These 3 stars are BCEP variables but the amplitude is very small)
Of course, the variability is too small for being followed visually, but
it would be interesting to do some photometry in order to confirm this
probable brightening. Could it be a possible GCAS variable? The
behaviour is similar to that of ALPHA ARAE and ETA CENTAURI. Could a new
spectrum taken right now show emission lines?
I hope someone can measure it. I just have my eyes...
Sebastian Otero.
Subject: [vsnet-be 3] SPECTROSCOPIC CONFIRMATION of Delta Scorpii variability
WE HAVE A NEW VARIABLE STAR CONFIRMED.
And it's one of the brightest.
Spectroscopic observations show that the H Alpha line is in emission.
DELTA SCORPII IS A NEW GCAS star.
This confirmation came from Spain and it will be reported to the IAU.
Sebastian Otero.
Recent observations:
YYYYMMDD(UT) mag observer
20000626.901 22 (S. Otero)
20000630.028 22 (S. Otero)
20000704.078 22 (S. Otero)
20000716.928 21 (S. Otero)
20000717.123 21 (S. Otero)
20000718.949 21 (S. Otero)
20000720.018 20 (S. Otero)
Subject: [vsnet-be 6] DELTA SCORPII CONFIRMATION
The discovery of the Be nature of Delta Scorpii has already been
reported to the IAU.
After the discovery by Sebasti=E1n Otero, Liga Ibero-Americana de
Astronomia, of a gradual brightening at optical wavelenghts which starts
at least one month ago, spectroscopic observations were undertaken by
Juan Fabregat, University of Valencia, Spain, and P. Reig, Foundation for
Research and Technology-Hellas and University of Crete, Greece.
Spectra taken with the 1.3m telescope at Skinakas Observatory (Crete,
Greece), with spectral resolution of 0.3 nm. in the range 580-760 nm.,
reveal the H-alpha line in emission. Measured equivalent widths are
-0.34+-0.02 nm. on July 19.89, and -0.33+-0.02 nm. (FWHM 0.69+-0.01
nm.) on July 20.90.
The bright star delta Scorpii (HD 143275, HR 5953, V =3D 2.32, MK
B0.3IV) is currently undergoing a major optical and H-alpha outburst.
In 1990 Cote and van Kerkwijk (A&A 274, 870, 1993) observed weak emission
on the flanks of the H-alpha line core in absorption, and proposed the
classification of delta Sco as a Be star. All other observations in the
literature present a normal absorption-line spectrum. The observations
reported here constitute the first detection of emission lines in delta
Sco, and confirm its Be star nature.
The A&A paper is at:
http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=3D1993A%26A...274..870C
I thank John Fabregat and P. Reig for its work.
It seems Delta Sco is well worthy of a GCAS star classification since its
brightening is already detectable with the naked eye, with almost 0.3
magnitudes and counting.
I'll let you know when more information and estimates were made.
New sequence for estimates now that the star is brighter is:
1.84 = EPS SGR; 1.86 = THE SCO; 2.08 = ALP OPH; 2.09 = SIG SGR;
2.16 = GAM CEN; 2.30 = ALP LUP; 2.40 = KAP SCO; 2.43 = ETA OPH and
2.51 = BET SCO.
Best regards,
Sebastian Otero.
vsnet-adm@kusastro.kyoto-u.ac.jp
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