We present multi-epoch mid-infrared ( IR ) photometry and the optical discovery observations of the “ impostor ” supernova ( SN ) 2010da in NGC 300 using new and archival Spitzer Space Telescope images and ground-based observatories .
The mid-infrared counterpart of SN 2010da was detected as SPIRITS 14bme in the SPitzer InfraRed Intensive Transient Survey ( SPIRITS ) , an ongoing systematic search for IR transients .
Before erupting on May 24 , 2010 , the SN 2010da progenitor exhibited a constant mid-IR flux at 3.6 and only a slight \sim 10 \% decrease at 4.5 \mu m between Nov 2003 and Dec 2007 .
A sharp increase in the 3.6 \mu m flux followed by a rapid decrease measured \sim 150 d before and \sim 80 d after the initial outburst , respectively , reveal a mid-IR counterpart to the coincident optical and high luminosity X-ray outbursts .
At late times after the outburst ( \sim 2000 d ) , the 3.6 and 4.5 \mu m emission increased to over a factor of 2 times the progenitor flux and is currently observed ( as of Feb 2016 ) to be fading , but still above the progenitor flux .
We attribute the re-brightening mid-IR emission to continued dust production and increasing luminosity of the surviving system associated with SN 2010da .
We analyze the evolution of the dust temperature ( T _ { \mathrm { d } } \sim 700 - 1000 K ) , mass ( M _ { \mathrm { d } } \sim 0.5 - 3.8 \times 10 ^ { -7 } \mathrm { M } _ { \odot } ) , luminosity ( L _ { \mathrm { IR } } \sim 1.3 - 3.5 \times 10 ^ { 4 } \mathrm { L } _ { \odot } ) and the equilibrium temperature radius ( R _ { \mathrm { eq } } \sim 6.4 - 12.2 AU ) in order to resolve the nature of SN 2010da .
We address the leading interpretation of SN 2010da as an eruption from a luminous blue variable ( LBV ) high-mass X-ray binary ( HMXB ) system .
We propose that SN 2010da is instead a supergiant ( sg ) B [ e ] -HMXB based on similar luminosities and dust masses exhibited by two other known sgB [ e ] -HMXB systems .
Additionally , the SN 2010da progenitor occupies a similar region on a mid-IR color-magnitude diagram ( CMD ) with known sgB [ e ] stars in the Large Magellanic Cloud .
The lower limit estimated for the orbital eccentricity of the sgB [ e ] -HMXB ( e > 0.82 ) from X-ray luminosity measurements is high compared to known sgHMXBs and supports the claim that SN 2010da may be associated with a newly formed HMXB system .