YY Her Outburst

Information about outbursts of eruptive stars, Be activity, ...
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Francois Teyssier
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YY Her Outburst

Post by Francois Teyssier »

YY Her is a symbiotic star, whose luminosity is ~ 13.
It undergoes an outburst. Current magnitude is about 12.

Here's a spectum in low state and aavso luminosity curve

Image

Image

Image

François Teyssier
Francois Teyssier
Posts: 1520
Joined: Fri Sep 23, 2011 1:01 pm
Location: Rouen
Contact:

Re: YY Her Outburst

Post by Francois Teyssier »

YY Her in outbust (mag ~12)
it should be noted, compared to the spectrum in the quiescent state, the rise of high excitation lines ([OIII], He II and the blend "4640" CIII/NIII)

Image

François Teyssier
Francois Teyssier
Posts: 1520
Joined: Fri Sep 23, 2011 1:01 pm
Location: Rouen
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Re: YY Her Outburst

Post by Francois Teyssier »

First published results about the outburst :


Electronic Telegram No. 2861
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University;
20 Oxford St.; Cambridge, MA 02138; U.S.A.
e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network

YY HERCULIS
U. Munari, Istituto Nazionale di Astrofisica, Padova Astronomical
Observatory; A. Siviero Department of Astronomy, University of Padova; G. L.
Righetti, F. Castellani, S. Dallaporta, M. Graziani, G. Cherini, S. Moretti, S.
Tomaselli, and A. Frigo, ANS Collaboration, write that the symbiotic star YY
Her is entering a new active phase. The last such phase ended six years ago,
and was characterized by three brightness maxima occurring in early 2003,
mid-2004 and late 2005 when, according to ANS Collaboration data, it peaked at
B = 12.69, B-V = +0.78, V-I_c = +1.75 on 2005 Nov. 20. In the following years,
the star has remained in quiescence, with its light curve being modulated by
reflection effect and ellipsoidal distortion for a total of 0.4-mag amplitude
around a mean value B = 14.17. Around 2011 Sept. 12, YY Her began to brighten
above the normal quiescence level, peaking at B = 13.01, B-V = +0.76, U-B =
-0.19, V-R_c = +0.83, V-I_c = +1.89 on Oct. 4. Its rise has since then halted,
the last measurement for Oct. 9 giving B = 13.12, B-V = +0.82, U-B = -0.19,
V-R_c = +0.88, V-I_c = +1.99. The authors obtained a low-resolution,
absolutely calibrated spectrum of YY Her on Oct. 7 with the Asiago 1.22-m
telescope (range 328-790 nm; 0.23 nm/pixel dispersion). The last spectrum
that the authors obtained of YY Her with the same instrumentation and with the
star in quiescence was on Aug. 24. The spectrum obtained on Oct. 4 shows a
general increase in the absolute intensities of emission lines [H_beta, He I
587.6-nm and He II 468.6-nm changed from an integrated flux of 13.2, 2.2, and
4.4, to 19.7, 5.1, and 11.9 in units of 10**(-13) erg cm**(-2) s**(-1),
respectively] and increase in excitation conditions (the He II 468.6-nm/H_beta
ratio increased from 0.32 to 0.60; He I 587.6-nm/H_beta from 0.17 to 0.26;
and [Ne III] 386.9-nm/H I 389.0-nm from 0.34 to 0.80). The largest changes in
the emission lines were those of [O III] 500.7-nm, which rose from 0.003 to
0.170 compared to H_beta, and the N III-C III 464- to 465-nm complex that
was not visible in the Aug. 24 and Oct. 7 spectra is instead prominent. Only
[Ne V] 334.5-, 342.6-nm behaved the opposite way. The [Ne V] 342.6-nm/O III
344.5-nm ratio declined from 3.62 to 0.41. A high-resolution echelle spectrum
(range 365-735 nm; resolving power 22000) of YY Her was obtained on Oct. 4
with the Asiago 1.82-m telescope. All emission lines are sharp, with a FWHM
of 100 km/s for hydrogen Balmer and He I lines, 135 km/s for He II, and 150
km/s for [O III]. No line shows an obvious P-Cyg profile.

NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.

(C) Copyright 2011 CBAT
2011 October 12 (CBET 2861) Daniel W. E. Green
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