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A Potential Crisis Ahead for the LMC LBV R71

ATel #6295; Nolan R. Walborn (Space Telescope ScIence Instittute), Roberto C. Gamen (Instituto de Astrofisica La Plata), Rodolfo H. Barba (Universidad de La Serena), Nidia I. Morrell (Las Campanas Observatory)
on 7 Jul 2014; 06:45 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Rodolfo Barba (rbarba@dfuls.cl)

Subjects: Optical, Transient, Variables

The recently digitized Harvard Patrol plates (DASCH, Grindlay et al. 2012, IAUS 285, 29) reveal two broad maxima in the lightcurve of the Luminous Blue Variable R71 (Feast et al. 1960, MNRAS 121, 337) in the Large Magellanic Cloud, centered in 1914 and 1939. At first glance they appear similar, but on closer inspection the second is somewhat narrower and higher. Moreover, comparison with major outbursts in 1973 and currently suggests that the trends of decreasing duration and increasing amplitude continue ( Figure). The intervals between observed outbursts appear to increase, but there are lower level activity and substantial coverage gaps at intermediate epochs. These phenomena suggest a recurrent instability of accelerating amplitude, which is reminiscent of recent discussions on rapid pre-supernova development (Smith & Arnett 2014, ApJ 785, 82; Shiode & Quataert 2014, ApJ 780, 96; Moriya 2014, A&A 564, A83; Moriya et al. 2014, MNRAS 439, 2917). R71 is already known to have an unusually thick dust envelope for an LBV (Bonanos et al. 2009, AJ 138, 1003) and [Ca II] emission lines (Gamen et al. 2012, CBET 3192; Walborn et al. 2012, see pdf; Mehner et al. 2013, A&A 555, A116), both characteristics of red transients; and its current spectrum is the coolest ever observed. We propose that R71 may be approaching either an LBV eruption or a CCSN. This would then be an unprecedented opportunity to observe the prelude to either type of event. Caption for Figure: Harvard Patrol and recent photometry of R71; the former photographic blue magnitudes have been adjusted by 0.5 fainter on the basis of the overlap with ESO photoelectric V photometry during the 1980's.

Figure for "A potential crisis ahead for the LMC LBV R71"