KWS pre-discovery observations of CSS160603:162117+441254 = 2MASS J16211735+4412541

ATel #9113; Hiroyuki Maehara (Okayama Astrophysical Observatory, NAOJ)
on 4 Jun 2016; 08:05 UT
Credential Certification: Hiroyuki Maehara (h.maehara@oao.nao.ac.jp)

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I report pre-discovery observations of an outburst of CSS160603:162117+441254 = 2MASS J16211735+4412541 (Drake et al., ATel #9112) with the Kamogata-Kiso-Kyoto Wide-field Survey (KWS) imager (f.l. = 105-mm lens + SBIG ST-8XME CCD Camera). According to the KWS photometric database, the object was already in outburst at V=13.3 on 2016-06-01.616 (UT) and was also detected on 2016-06-02 and 2016-06-03 at V=13.1-13.2. The V-Ic color index of the object during the outburst is V-Ic ~ 1. The following table presents the preliminary photometry (and upper limit) of the object from the KWS database.

 
Date (UT)          Magnitude Error   Filter Remarks 
2016-05-28.64472   13.978    0.904   V      # single detection 
2016-05-30.63299   13.636    0.885   V      # single detection 
2016-06-01.61598   13.126    0.279   V 
2016-06-01.61601   12.191    0.335   Ic 
2016-06-01.61638   13.443    0.368   V 
2016-06-01.61640   12.987    0.697   Ic 
2016-06-02.61935   12.953    0.238   V 
2016-06-02.61937   12.317    0.373   Ic 
2016-06-02.61941   <13.2     --      B 
2016-06-02.61973   13.279    0.321   V 
2016-06-02.61976   11.982    0.275   Ic 
2016-06-02.61980   <13.1     --      B 
2016-06-03.63627   13.217    0.321   V 
2016-06-03.63667   13.043    0.273   V