Detection of an optical outburst from Swift J1943.4+0228
ATel #15600; Yuankun Wang (UW) and Eric C. Bellm (UW) on behalf of the Zwicky Transient Facility Collaboration
on 8 Sep 2022; 20:34 UT
Credential Certification: Eric Bellm (ecbellm@uw.edu)
Subjects: Optical, Transient
We report an optical brightening of the Galactic X-ray transient Swift J1942.4+0228 (Krimm et al. 2012, ATel #4049) with the Zwicky Transient Facility (ZTF; Bellm et al. 2019, Graham et. al 2019). ZTF detected the source (internally designated as ZTF22abcvwog) with image differencing at m_g ~ 19.3 +/- 0.05 on 2022-08-26.18. Forced photometry on the previous ZTF observation on 2022-08-24.2 showed the source at m_g ~21.1 +/- 0.2 and m_r ~20.3 +/- 0.09 either near quiescence or at early outburst. No source was detected in g-band images taken on 2022-08-22. No excess is apparent in the Swift-BAT daily lightcurves.
The source reached peak brightness during an apparent fast flare on 2022-08-30.2 at m_g ~ 18.67 +/- 0.03 and m_r ~ 18.60 +/- 0.02. The main profile of the outburst peaked earlier, on 2022-08-28.2 at m_r ~18.86 +/- 0.03. The source has begun to fade; the latest observations by ZTF on 2022-09-05.3 show the source at m_r ~ 19.67 +/- 0.12 and m_g ~ 19.73 +/- 0.13. Realtime public photometry may be obtained from alert brokers such as ANTARES,
Lasair, or
ALeRCE.
Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW. The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham).
We acknowledge further support from the NSF under grant AST-1812779 and the Heising-Simons Foundation under grant 2018-0908.
