Looking for the counterpart of the naked-eye optical transient OT120926

Just as we resubmitted our paper on "OT120926", a transient astronomical object briefly visible to the naked eye, DASCH released more data.  DASCH is the Digital Access to a Sky Century at Harvard: over 100 years of photographic plate images of the sky digitized and put online.  The location of OT120926 is in the new data release, but even DASCH does not solve the mystery of what object on the sky was responsible for this bright, transient flare.

Neither of the two bright stars near the position of OT 120926 show any sign of flares in over 1000 images.  The fainter nearby star SDSS J1436+1553 shows no sign of flaring in 15 images.

The presumed M dwarf star LP 440-48 has a possible detection in 1905.252749 (plate ac06251), shown in the first thumbnail below.  [All thumbnails show star BD+16 2671 at center and star TYC 1477-341-1 at top, just left of center.]

First thumbnail

Second thumbnail

Third thumbnail

The first thumbnail shows an object in the left half of the image which could be LP 440-48 in a flare to magnitude ~11.6.  However, the second thumbnail is the very next image of the field in the DASCH database (1905.263690, plate ac06267), and it shows a possible object between BD +16 2671 and TYC 1477-341-1.  And the third thumbnail is the next image after that in DASCH (1905.280362, plate am03455), showing a possible object to the right of BD +16 2671.

The presence of three one-off "objects" in a rough arc on three images taken in sequence four and then six days apart makes the identification of LP 440-48 in a flare on the first image uncertain.  On the other hand, DASCH images taken shortly before and after the sequence above show no further evidence for a single moving object (like an asteroid) which might explain the observations.

Detailed inspection of the images and scanned plates might help determine whether the "objects" in question are likely to be real astronomical sources or just plate flaws or other artifacts, but such a task is beyond the scope of this investigation.  A more straightforward way forward would be to obtain a spectrum of LP 440-48 and to look for any signs of stellar activity in it; such a spectrum has been obtained by Mansi Kasliwal (Carnegie).

Still, it's cool to be using photographs of the sky taken over 100 years ago for science!