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GCN Circular 15575

Subject
GRB 131127B: archival confirmation of iPTF13ecv as a CV
Date
2013-12-04T15:06:54Z (10 years ago)
From
Denis Denisenko at SAI MSU <d.v.denisenko@gmail.com>
D. Denisenko (Sternberg Astronomical Institute at Moscow State
University) reports:

The position of the optical transient iPTF13ecv (Singer et al., GCN
15524) in the Fermi field of GRB 131127B (von Kienlin, GCN 15528) was
observed in the past with the NEAT project (Teegarden et al., ApJ Vol.
589, pp. L51-L53, 2003). A total of 87 images were obtained on 33
different nights from 1998 July 19 to 2005 Sep. 08. Images can be
downloaded from the SkyMorph website at
http://skyview.gsfc.nasa.gov/skymorph/obs.html The object at the
position of iPTF13ecv was detected in outburst on four last nights,
namely on 2005 Aug. 21, Sep. 01, 07 and 08. It was below the detection
limit (typically 19.5-20.0m) on the other nights.

The following photometry was obtained from the unfiltered NEAT images
using SDSS J203153.05+005858.4 as a reference star with r=16.40:

20050821.372  17.0
20050901.371  18.1
20050908.271  19.3

The coordinates of the object measured from the combination of three
2005-08-21 images are (J2000.0): 20 31 47.76 +00 59 23.8, consistent
to 0.4" with the position reported by Singer et al. and to 1" with
those by Quadri et al. (GCN 15543).

Comparison of NEAT images of the variable object in outburst (2005
Aug. 21, Sep. 01 and 08) and at quiescence is uploaded to
http://master.sai.msu.ru/static/OT/iPTF13ecv-NEAT-2005.jpg (5'x5' FOV
centered at the variable). Reference star is marked on the bottom left
(2005-09-01) panel as 16.4r.

No object is detected at this position on the combination of 26 good
quality NEAT images to the limit ~22.5m. No previous outbursts were
found on 15 DSS plates. Combination of DSS plates and SDSS color image
suggests that the object is fainter than 23m at quiescence. 2005
outburst amplitude about 6 mag and duration of at least about 20 days
are typical for superoutbursts of SU UMa-type dwarf novae.

Thus, the cataclysmic variable nature of iPTF13ecv already determined
spectroscopically by Keck telescopes (Singer et al., GCN 15574) is
independently confirmed by the archival light curve, once again
showing the powerful capabilities of data mining methods.

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