Swift observation of the dwarf nova candidate ASASSN-19jp

ATel #12674; K. Sokolovsky, E. Aydi, L. Chomiuk, A. Kawash, J. Strader (MSU), K. Mukai (NASA/GSFC), K. Z. Stanek, C. S. Kochanek, J. Shields (OSU), B. J. Shappee (Univ. of Hawaii)
on 19 Apr 2019; 19:31 UT
Credential Certification: Kirill Sokolovsky (kirx@scan.sai.msu.ru)

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The g=14.6 optical transient ASASSN-19jp = AT2019dey was discovered on 2019-04-10.41 by the ASAS-SN survey 5 degrees from the Galactic center. Swift observed ASASSN-19jp for 1ks on 2019-04-14.686 UT. No X-ray source associated with the transient was detected by the XRT with an upper limit of 0.004 +/-0.003 cts/s. Following Rosen et al. (2016 A&A, 590, 1) we convert the count rate to the 0.2-12 keV energy flux limit of 1.8*10^(-13) ergs/cm^2/s by assuming the absorbed power law spectrum with the photon index of 1.7 and N_HI=3*10^(20) cm^-2. The known X-ray source 3XMM J173413.8-332456 lies 1.7" from the transient, but its flux of (1.7+/-0.8) 10^(-14) ergs/cm^2/s is well below the Swift upper limit. An unrelated bright X-ray source known as the Rapid Burster (MXB 1730-335; van den Eijnden et al. 2017 MNRAS, 466, L98) is visible at the XRT image.

ASASSN-19jp is detected by the UVOT with an ultraviolet (Vega) magnitude of UVW1=14.73 +/-0.02. The source position 17:34:13.75 -33:24:54.6 +/-0.2" J2000 is measured relative to UCAC3 (Zacharias et al. 2010 AJ, 139, 2184) stars in the UVOT field of view. The estimated uncertainty of the UVOT position excludes the proposed association with a Gaia DR2 source (the nearest one is 1" away). The ASAS-SN photometry bracketing the Swift/UVOT observation

 
2019-04-14.3597 g=15.49 +/-0.06  
2019-04-15.2460 g=15.82 +/-0.10  

suggests that the object is very blue which favors the explanation that ASASSN-19jp is a relatively nearby dwarf nova rather than a distant highly-extinct classical nova.

We thank the Neil Gehrels Swift Observatory team and PI, Brad Cenko, for rapid scheduling of this ToO observation.

ASAS-SN lightcurve of ASASSN-19jp