[IAUC] CBET 3192: 20120725 : BRIGHTENING OF R71 = HDE 269006

[quai en eps.harvard.edu]

                                                  Electronic Telegram No. 3192
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 en eps.harvard.edu (alternate cbat en iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


BRIGHTENING OF R71 = HDE 269006
     R. Gamen, Instituto de Astrofisica de La Plata, CONICET, Universidad
Nacional de la Plata; N. Walborn, Space Telescope Science Institute; N.
Morrell, Las Campanas Observatory, Carnegie Observatories; R. Barba, Instituto
de Ciencias Astronomicas y de la Tierra, CONICET, San Juan; and E. Fernandez
Lajus, Instituto de Astrofisica de La Plata, CONICET, Universidad Nacional de
la Plata, write that the luminous blue variable HDE 269006 (= R71) in the
Large Magellanic Cloud continues to brighten in the visual since their last
report in 2009 (IAUC 9082), when it was at magnitude V = 9.  Differential
photometry from images obtained in Apr. 2012 shows that R71 has brightened by
0.6 mag in V since Apr. 2010 and is currently at V approximately 8.3.  This
unprecedented rise in its light curve is accompanied by spectacular variations
in its optical spectrum.  In Aug. 2009, it resembled a (peculiar) early-F
supergiant, while currently R71 displays early-G supergiant characteristics,
on the basis of ionization ratios of absorption lines such as Fe I/Fe II as
well as the strength and width of the Ca II H and K absorption lines.
Concurrently, H-alpha has transformed from a P-Cyg profile into a centrally
reversed, symmetrical broad emission (alternatively, an absorption line with
symmetrical emission wings), while the Ca II infrared triplet (849.8-, 854.2-,
and 866.2-nm) emission has declined and strong forbidden [Ca II] 729.1- and
732.4-nm emission lines have appeared -- along with weaker ones of [O I-II],
[N II], and [S II].  This is the first report of [Ca II] emission in an
apparent S Dor event to their knowledge and suggests comparison with the red
transients (Humphreys et al. 2011, Ap.J. 743, 118).  R71 is previously known
to have an unusually strong dust signature in the infrared (Bonanos et al.
2009, A.J. 138, 1003, and references therein).  Further monitoring is
indicated to determine the nature and  outcome of the current event.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2012 CBAT
2012 July 25                     (CBET 3192)              Daniel W. E. Green