Mon. Not. R. Astron. Soc., 478, 2541-2556 (2018/August-1)
An unusual transient in the extremely metal-poor Galaxy SDSS J094332.35+332657.6 (Leoncino Dwarf).
FILHO M.E. and SANCHEZ ALMEIDA J.
Abstract (from CDS):
We have serendipitously discovered that Leoncino Dwarf, an ultrafaint, low-metallicity record-holder dwarf galaxy, may have hosted a transient source, and possibly exhibited a change in morphology, a shift in the centre of brightness, and peak variability of the main (host) source in images taken approximately 40 yr apart; it is highly likely that these phenomena are related. Scenarios involving a Solar System object, a stellar cluster, dust enshrouding, and accretion variability have been considered, and discarded, as the origin of the transient. Although a combination of time-varying strong and weak lensing effects, induced by an intermediate-mass black hole (104-5 x 105 M☉) moving within the Milky Way halo ( 0.1-4 kpc), can conceivably explain all of the observed variable galaxy properties, it is statistically highly unlikely according to current theoretical predictions, and, therefore, also discarded. A cataclysmic event such as a supernova/hypernova could have occurred, as long as the event was observed towards the later/late-stage descent of the light curve, but this scenario fails to explain the absence of a post-explosion source and/or host H II region in recent optical images. An episode related to the giant eruption of a luminous blue variable star, a stellar merger or a nova, observed at, or near, peak magnitude may explain the transient source and possibly the change in morphology/centre of brightness, but cannot justify the main source peak variability, unless stellar variability is evoked.
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
galaxies: dwarf - galaxies: individual: (SDSS J094332.35+332657.6) - galaxies: irregular - galaxies: peculiar - galaxies: photometry
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