Thu, 09/13/2018 - 20:00
While the state of this project is generally quite good, there remain some gaps of coverage, so certain stars which I follow still do not have any comp stars in their vicinity. V394 Cra is one example. It has been several years without coverage at the region around 18:00 -39:00, and I am wondering why the gaps cannot be finally closed out, and this problem be solved 100% ?
Mike
Hi Mike,
There is some photometry (rather incomplete) here with CMC15. I shall let you know when (if!) I have produced a sequence.
The amplitude of 6m is too small for a nova though - do I guess you think this might be an NR or DN?
How does the CMC15 photometry compare to APASS in accuracy? Have you compared them on overlapping fields? Hopefully its better than the GSC or USNO-A2.0 !
Yes, the star is a suspected NR...
Hi Mike,
CMC uses different passbands and would probably come out a bit below APASS in 'first-choice' decisions but the sequence team (which I've just joined) use it - though obviously preferring APASS. But this field is not covered by APASS so we are forced to use other surveys. Quoting from the sequence team advice sheet: "the resultant B filter conversions may have a larger uncertainty when compared with Henden... less used now since APASS... but a decent option if needed". Incidentally, what mag range would you require?
Just a little fun note - since my planetarium software was open at the time I looked up data for V394 CrA and it gave a min of 13.5 (hence my comment on the type) but it seems the min is actually 19.5 - in which case this could be a classical nova. Looks like that software could do with an update!
Until formal field photometry becomes available, I have put together a provisional sequence (albeit a partial one) that is photometrically based on the 94 (BCB-030) and 86 (BCB-044) comps located about 25-30 arc-min ESE of V394. The selected comps have B-V values of 1.0 or less except comps #6 and #14 which are very close to 1.1. None of sequence stars have close companions that might interfere with visual observation. Very interesting observing target !
V394 CrA provisional sequence:
Comp #, rounded 2000.0 coordinates (as per VPHOT) , Vmag, visualmag.
2 *** 18 00 15 -38 57 29 *** 9.21 *** 92
6 *** 18 00 30 -38 50 31 *** 10.27 *** 103
13 *** 18 00 35 -39 02 22 *** 11.81 *** 118
11 *** 18 00 12 -39 01 18 *** 12.68 *** 127
12 *** 18 00 09 -39 00 00 *** 12.67 *** 127
14 *** 18 00 32 -39 01 00 *** 13.31 *** 133
15 *** 18 00 25 -39 00 00 *** 14.06 *** 141
16 *** 18 00 26 -39 00 54 *** 14.29 *** 143
17 *** 18 00 22 -39 00 24 *** 15.18 *** 152
Kind regards,
Steve
VSX describes the two observed outbursts, in 1949 (Erro) and 1987 (Liller). Eclipses are noted as well so NR+E.
Steve
I note the brightest close companion in V is about 15.7 , approx 15 arc-sec WNW. Quite crowded. Careful with ID. Var is currently fainter than 16.5V.
Steve