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ASASSN-15ks (CrA), astrometry and identification needed

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Sebastian Otero
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ASASSN-15ks (CrA), astrometry and identification needed

Another CV candidate that comes with a puzzle.

ASASSN-15ks is a new ASAS-SN CV discovery at 18 35 43.91 -40 43 30.1 (in Corona Australis).
Usually the positions in the original ASAS-SN discovery page are within a radius of 3-4" from the true variable's position. In this case, we are talking about a 6" offset: the ASAS-SN team identifies the CV as USNO-B1.0 0492-0700672 (V= 16.2) at 18 35 43.43 -40 43 28.5, 6" to the WNW of the reported position. Also, the amplitude is only 1.6 mag. (16.2 to 14.6 in V).
This is suspicious.

At the same time, the 16th mag. star has a close 18 mag. companion 2" to its West (18 35 43.21 -40 43 28.7) which might also be the actual CV. The 16.2 mag. value given above is for the blend of the two stars.

So astrometry is required to properly identify the new CV.

*Is it the 16th mag. star?
*Is it the 18th mag. companion?
*Is it a "new" star with no counterpart 6" to the ESE of the 16th mag. star?

You are the ones to solve this puzzle :)


Sebastian Otero
VSX Team
American Association of Variable Star Observers

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484