Dramatic increase of the near-IR flux of the young source V2492 Cyg

ATel #7436; A. A.Arkharov (St. Petersburg Observatory, Russia), D. Lorenzetti (INAF – Osservatorio Astronomico di Roma, Monte Porzio, Italy), T. Giannini (INAF – Osservatorio Astronomico di Roma, Monte Porzio, Italy), S. Antoniucci (INAF – Osservatorio Astronomico di Roma, Monte Porzio, Italy), A. Di Paola (INAF – Osservatorio Astronomico di Roma, Monte Porzio, Italy), F. Vitali (INAF – Osservatorio Astronomico di Roma, Monte Porzio, Italy), V. M.Larionov (Astronomical Institute of St. Petersburg University, Russia)
on 23 Apr 2015; 14:08 UT
Credential Certification: Dario Lorenzetti (dloren@mporzio.astro.it)

Tweet

In the framework of our EXor monitoring program dubbed EXORCISM (EXOR OptiCal and Infrared Systematic Monitoring - Antoniucci et al. 2013 PPVI, Lorenzetti et al. 2007 ApJ 665, 1182; Lorenzetti et al. 2009 ApJ 693, 1056), we are now observing a new increase of the near-IR brightness of the protostar V2492 Cyg, based on data taken at the AZT24 1m IR telescope (Campo Imperatore, Italy). V2492 Cyg is located in the North American Nebula and its first outburst was discovered and investigated by Covey et al. 2011 AJ 141, 40, who associated the brightening to an enhanced accretion and outflow. Our observations of V2492 Cyg cover a period of 2 years (since Apr. 2013 to Apr. 2015) and are summarized in the Table below:

JD-2400000.5	J(mag)	H(mag)	K(mag)
56390.6	11.48	9.63	7.95
56506.5	11.92	10.12	8.41
56510.5	11.78	10.06	8.38
56515.4	11.83	10.12	8.44
56517.4	11.66	9.95	8.30
56539.5	11.66	10.12	8.56
56559.4	11.42	9.88	8.29
56562.4	11.76	10.07	8.43
56575.4	11.69	10.03	8.46
56579.3	11.50	9.91	8.42
56594.3	12.13	10.17	8.43
56645.2	12.49	10.17	8.33
56820.5	13.73	11.02	9.03
56877.5	14.12	11.33	9.14
56879.5	13.93	11.10	8.97
56899.5	13.16	10.71	8.74
56930.5	12.95	10.55	8.63
56938.3	12.75	10.54	8.68
56939.3	12.93	10.76	8.90
56950.3	13.45	10.88	8.87
56956.5	13.78	11.04	8.90
56958.4	14.06	11.23	9.05
56960.2	14.28	11.38	9.05
56961.2	14.31	11.35	9.09
56962.2	14.64	11.62	9.33
56963.2	14.72	11.64	9.33
56964.2	14.84	11.73	9.39
56970.2	15.56	12.26	9.68
56975.3	15.78	12.33	9.76
57134.6	12.00	10.47	8.38

Typical errors of the near-IR magnitudes are less than 0.03 mag. The corresponding J band light-curve is shown in this figure. After a slow fading (until MJD 56878.5) the source underwent a sudden brightness increase followed by a very fast declining of 3.0 Jmag in one month. Our latest observation indicates a new brightness increase of about 4 Jmag, which is also associated with a significant color variation: the source became bluer while brightening (ΔJ = 3.78, ΔH = 1.86, ΔK = 1.38). The two colors plot [J-H] vs. [H-K] (depicted in this figure) indicates that the source fluctuations are compatible with an extinction variation ΔA_V of about 20 mag. Such an occurrence confirms the results of Hillenbrand et al. 2013 AJ 145,59, who presented a previous (2009-2012) near-IR monitoring, and concluded that both accretion- and extinction-driven mechanisms are responsible for the source variability.