* Astronomy

Title: Discovery of a nearby twin of SN1987A's nebula around the luminous blue variable HD168625: Was Sk--69 202 an LBV?
Authors: Nathan Smith

Spitzer images of the luminous blue variable (LBV) candidate HD168625 reveal the existence of a bipolar nebula several times larger than its previously-known equatorial dust torus. The outer nebula of HD168625 has a full extent of about 80 arcsec or 0.85 pc, and one of the lobes has a well-defined polar ring. The nebula is a near twin of the triple-ring system around SN1987A. Because of these polar rings, and accounting for stellar/progenitor luminosity, HD168625 is an even closer twin of SN1987A than the B supergiant Sher 25 in NGC3603. HD168625's nebula was probably ejected during a giant LBV eruption and not during a red supergiant phase, so its similarity to the nebula around SN1987A may open new possibilities for the creation of SN1987A's rings. Namely, the hypothesis that Sk-69 202 suffered an LBV-like eruption would avert the complete surrender of single star models for its bipolar nebula by offering an alternative to an unlikely binary merger scenario. It also hints that LBVs are the likely progenitors of some type II supernovae, and that HD168625's nebula is a good example of a pre-explosion environment.

Read more (219kb, PDF)