2012CBET.3164....1N

J. P. Ninan, D. K. Ojha, K. K. Mallick, S. K. Ghosh, and J. S. Joshi, Tata Institute of Fundamental Research (TIFR), Mumbai; and B. C. Bhatt, Indian Institute of Astrophysics, Bangalore, report a slow dimming of the young eruptive star V1647 Ori (cf. IAUCs 8284, 8354, 8396, 8600, 8681, 8694, 8968, 8969, 9006, 9079; CBETs 1596, 2104, 2647) from long term optical and near-infrared (NIR) photometric observations made with the 2-m IUCAA Girawali Telescope (+ IFOSC spectrograph and TIFR Near Infrared Camera, TIRCAM2) at Girawali (Pune) and the 2-m Himalayan Chandra telescope (+ HFOSC spectrograph and NIR camera) at Hanle (Ladakh). Representative optical magnitudes of V1647 Ori are: 2008 Sept. 28 UT, V = 18.95 ± 0.03, R = 17.01 ± 0.01, I = 14.96 ± 0.01; 2012 Jan. 17, V = 19.21 ± 0.04, R = 17.26 ± 0.02, I = 15.24 ± 0.02. During the period 2009-2012, the source brightness shows a linear dimming trend of about 0.3 mag in the R and I bands. This linear dimming trend is also present in the brightness of a Herbig-Haro object illuminated by the source. The observations during the period Jan.-Feb. 2012 show an increase in dimming rate, but it can be confirmed only after the source becomes visible once again in 2012. A similar trend is also seen in the following NIR magnitudes: 2009 Oct. 24 UT, J = 10.71 ± 0.05, H = 8.88 ± 0.05, K = 7.44 ± 0.02 (using NIR camera); 2011 Dec. 4, J = 11.24 ± 0.1, H = 9.25 ± 0.1, K = 8.08 ± 0.1 (using TIRCAM2). The source brightness has therefore dimmed by about 0.5 mag in the NIR bands during the period 2009-2011. V1647 Ori has undergone an unexpected second outburst in 2008 after the first outburst in late 2003, which lasted for about 2 years until early 2006 (Ojha et al. 2006, MNRAS 368, 825; Aspin et al. 2009, Ap.J. 692, L67; Aspin et al. 2011, A.J. 142, 135, and references therein).