I am following NSVS 7984734 (or SDSS J171513.35+230533.1) with the BRT. In the VSX it is catalogued as a possible UG with a range of 11.7 - 15.3R. Can someone give more info about this possible outburst?
Here you can find the NSVS light curve of this star:
According to the NSVS light curve it seems this star was in outburst in September 2009.
CRTS light curve show this star in quiescent in the last 3000 days:
Negative in ASAS-3:
I don't think that outburst was real.
If we keep all the observations, including those with suspected flags we get:
1442.129246 14.452 0.256 0
1442.183986 11.859 0.029 0
1442.184306 11.755 0.026 0
1443.228286 11.615 0.033 0
1448.179756 12.134 0.046 0
1452.126306 11.721 0.03 14336
1452.184216 14.36 0.253 2048
1454.163493 13.779 0.088 2050
1454.164513 13.477 0.067 2048
1455.197583 13.145 0.078 2048
1457.162543 11.937 0.123 14338
1460.159633 13.667 0.075 0
Some pairs of observations are highly suspicious. At JD 2451442, a 14.452 and a 11.859 mag. datapoint spaced by just an hour and a half. The same at JD 2451452. Also a bright datapoint at 11.937 on 2451457 when the rest of the data points to an intermediate brightness state.
The datapoints with flag 14336 or 14338 are usually too bright and might be wrong but the mag. of those datapoints is similar to the "outburst magnitudes" which is also suspicious.
Then we have a synonym:
which shows a gap in the data at the "outburst dates", excepting these three observations:
1450.184596 8.557 0.03 1540
1452.132346 14.582 0.333 15872
1456.171633 15.278 0.374 1536
The first one is simply unbelievable. And the other two are not consistent at all with the data at the same dates for the other synonym.
If we add that there is no other outburst recorded in CRTS or ASAS and that the star has V= 15.0 in APASS too (with B-V= 1.0; J-K= 0.47), I think that something affected the NSVS photometry at those dates.
One thing to do when we have these doubts is to look for similar features in nearby stars something that John Greaves suggested to do in his original post to cvnet-discussion (but he came to the opposite conclusion).
And indeed, we have this light curve:
which shows the same outburst at the same dates (with smaller amplitude)
That is a star 1.8' SE from the suspected UG so there is no blending issues.
And this is a star 2.0' to the NW:
Also showing the brigthening.
There seems to be a SE-NW line at least 4' long showing problems in that area. Couldn't find a minor planet there on those dates but something must have affected those images.
This star is not variable.
This is strange... :O
Thanx Sebastian for the research!
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