OUTBURST OF R71 IN THE LARGE MAGELLANIC CLOUD

GAMEN, R.C.; BARBÁ, R.H.; WALBORN, N.; BONANOS, A.; MORRELL, N.; LENNON, D.; FERRERO, G.; PRESTON, G.; SCHKOLNIK, E.; JONES, A.; WILLIAMS, P.; KATO, T.

International Astronomical Union. Central Bureau for Astronomical Telegrams

Harvard University

Lugar: Boston; Año: 2009 p. 1 - 1

0081-0304

HDE 269006 (R71) is a known LBV star located in the LMC. After a large maximum in 1975 (V approx. 9.9), the star faded to V of about 10.8 - 11.0. The progress of a new outburst was first reported by Peter Williams vsnet-alert-9969 and 9970, March 2008) and Taichi Kato (vsnet-alert-10013, April 2008) based on visual observations and the ASAS-3 (Pojmanski 2002, AcA, 52, 397) photometric database. Also, Munari et al. (2009, A&A 503, 511) reported that R71 had changed from quiescent to outburst stage, based on its brightening to V = 9.97 and RAVE spectroscopy (observation date February 2008) which showed it to be similar to an early-A supergiant. In early August 2009, Mr. Albert Jones (New Zealand; private communication to A.B.) also reported an unusual visual brightening of R71 to about 9th magnitude. Inspection of  the ASAS-3 photometric database (ASAS 050207-7120.2) shows that the unusually gradual rise in the light curve of R71 started approximately 5 years ago, albeit with some oscillations during that time, becoming steeper over the last 1300 days. Actually, at this moment R71 is the visually brightest star in LMC. Follow-up spectroscopic observations obtained from CASLEO (Argentina) on Aug. 9 by G.F.; and from LCO (Chile) on Aug. 20 and 24 by E.S., and on Aug. 26 by G.P., showed that the spectrum of R71 resembles that of an extreme early-F type hypergiant. This spectrum is significantly cooler than that previously seen at the maximum state in 1970-1977, when the system reached an A1 Ieq spectral type (Thackeray 1974, MNRAS, 168, 221; Wolf, Appenzeller & Stahl 1981, A&A, 103, 94). Currently the spectrum of R71 displays a populous set of sharp and deep absorption lines of singly ionized and  neutral metals characteristic of an F0 Ia spectrum. Narrow and distinctive P Cyg profiles in H-alpha, H-beta, Fe II (multiplet 42) and Ca II infrared triplet emission lines are also present. This high-state spectrum is unprecedented in R71 and, together with the unprecedented visual magnitude, indicates an extreme outburst in this LBV star, with the characteristic conservation of the bolometric magnitude.