Variable Stars - V2492 Cyg
Type FUOR Click for lightcurve Variables of the FU Orionis type, which are collectively known in the literature as FUors. Characterized by a unique major gradual increase in brightness by about 4-6 mag. following which they show a complex absorption spectrum much like that of a F or G-type supergiant star, a powerful shortward-shifted P Cyg-like absorption component at Hα and a strong Li I λ6707 absorption line. They may stay constant at maximum brightness or decline slowly by 1-2 mag. several months after the initial rise. These variables probably mark one of the evolutionary stages of T Tauri-type stars as evidenced by an outburst of one member, V1057 Cyg, but its decline (2.5 mag. in 11 years) commenced immediately after maximum brightness was attained. All presently known FUors are coupled with reflecting cometary nebulae. AAVSO Alert Notice #573  April 6, 2017 Dr. Nicolas Grosso (CNRS, Observatoire Astronomique de Strasbourg) has requested AAVSO assistance in monitoring the young eruptive star (FUOR type) V2492 Cyg from the optical to the infrared in support of X-ray observations with XMM-Newton scheduled for 2017 April 18 UT. The XMM observations will take place: 2017-04-18 03:27:07 UT - 2017-04-18 14:17:07 UT. AAVSO observations indicate that V2492 Cyg, which has been declining from outburst, appears to be rebrightening, so nightly observations beginning immediately are critical. Dr. Grosso writes: "V2492 Cyg is a young eruptive star located in the Pelican Nebula which displayed a first optical/IR outburst in 2010 (Itagaki and Yamaoka 2010, CBET #2426; Munari et al. 2010, CBET #2428; Covey et al. 2011, AJ, 141, 40; Kospal et al. 2011, A&A, 527, A133 (2011A&A...527A.133K); Aspin 2011, AJ, 141, 196 (2011AJ....141..196A); Hillenbrand et al. 2013, AJ, 145, 59 (2013AJ....145...59H); Kospal et al. 2013, A&A, 551, A62 (2013A&A...551A..62K)). According to Hillenbrand et al. (2013) the source high-amplitude variability is driven both by accretion (perhaps analogous to V1647 Ori; see, e.g., Kastner et al. 2004, Nature, 430, 429 (2004Natur.430..429K)), and extinction. A second complex optical/infrared outburst occurred in 2012-2013 (Kospal et al. 2013). "Recently, Ibryamov & Semkov (2017, ATel #10170) reported a new record brightness in the optical of V2492 Cyg, peaking at V=13.52 mag on 2017 March 5 and exceeding significantly the registered maximal magnitudes after 2010. Subsequently, Munari et al. (2017, ATel #10183) reported V=13.93 on 2017 March 17, suggesting a slight decay; Steve O'Connor (AAVSO member) observed V=14.27 on 2017 March 26 confirming it. But, we cannot exclude intrinsic variability (dipping) during a plateau phase as observed in the 2012-2013 outburst. Munari et al. (2017) also obtained a deep optical echelle spectrum of V2492 Cyg, showing a lot of emission lines as observed in 2010 Sept 5 (Aspin 2011), but with now far stronger absorptions." To support the XMM observations, beginning now and continuing through April 30, observers are requested to obtain "simultaneous optical to infrared photometry (BVRIJHK and/or the equivalent Sloan filter) in order to monitor the behaviour of the extinction and accretion, and to compare it with the level of X-ray emission that will be observed with XMM-Newton." Specifically, nightly snapshots in as many filters as possible are requested, with priority on BVRcIc filters, 5% photometry (transformed). It is extremely important that photometry be transformed; please make every effort to transform your data before submitting them. Dr. Grosso notes that the source may be bright enough (J~10, H~9, and K~8 mag) for JHK/Ks photometry. Visual observations are also welcome. V2492 Cyg has a range of V magnitude 13.5 - 20. As of 2017 April 5.46178 UT (JD 2457848.96178) it was 14.192 V +/-0.024 (MGW, G. Myers, Hillsborough, CA). In addition to the observations in support of the XMM observations, weekly multicolor snapshots from May through December 2017 are requested, since it is not known whether the maximum of the outburst has already occurred.
Hills Observatory: 1 January 2013 to 14 August 2018
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