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NSVS 7984734

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MUY's picture
NSVS 7984734

Hi all,

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?




FRF's picture
NSVS light curve

Hi Eddy,

Here you can find the NSVS light curve of this star:

Clear skies,


FRF's picture
According to the NSVS light

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:,asas3,0,0...

Sebastian Otero
Sebastian Otero's picture
Not a real outburst

Hi guys,
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.



FRF's picture
This is strange... :O Thanx

This is strange... :O

Thanx Sebastian for the research!


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