TITLE: GCN CIRCULAR NUMBER: 25923 SUBJECT: LIGO/Virgo S190930t: ATLAS Forced photometry of ZTF19acbpqlh (AT2019rpn) DATE: 19/10/02 13:02:40 GMT FROM: Stephen Smartt at Queen's U/Belfast S. J. Smartt, K. W. Smith (QUB), S. Srivastav, T.-W. Chen (MPE), D. R. Young, M. Fulton, (QUB) L. Denneau, H. Flewelling, A. Heinze, J. Tonry, H. Weiland (IfA, Univ. Hawaii), A. Rest (STScI), B. Stalder (LSST), C. Stubbs (Harvard), O. McBrien, M. Dobson, J. Gillanders, D. O'Neil, P. Clark, S. Sim (QUB) The transient ZTF19acbpqlh (AT2019rpn) was reported by Stein et al. (GCN 25899) at r = 20.02 within the 95% localisation bayestar map (LVC et al. GCN 25876). ATLAS covered this region on 6 recent epochs, and forced PSF photometry on the difference images at the position of this transient gives the following 3-sigma limiting magnitudes and two 4-sigma detections. 58752.21516 c < 18.24 58754.21109 o < 18.71 58755.35411 c < 21.00 58756.60703339205 == s190930t discovery 58756.2132 c < 19.47 58757.23448 o 19.84 +/- 0.26 58758.21185 o 19.68 +/- 0.27 All mags are AB. c = cyan filter (a g+r composite) o = orange filter (a i+r composite) Tan et al. (GCN 25916) reported r = 20.7 +/- 0.3 which could imply a significant fade, although the uncertainty is significant. Our measurements imply the transient is flat or slowly rising. Karambelkar et al (GCN 25921) give a tentative identification of broad H-alpha in their blue spectrum. Our ATLAS photometry would support their conclusion of a young, relatively faint, type II SN. But further data are required to confirm.