The 1966-1967 Outburst of V1647 Orionis and the Appearance of McNeil's Nebula

Abstract

We present the results of an investigation aimed at characterizing previous eruptions of V1647 Orionis, the illuminating star of McNeil's Nebula. Photographic plates and films from the Asiago Observatory (1960Y1998) and Harvard Observatory (1898Y1974) collections were inspected for the nebula. We have determined that, to the plate limits, the known eruption of 1966Y1967 is the only one detected during the 38 yr period covered by the Asiago archive. In the Harvard collection, we did not find any additional occurrences in approximately 400 plates of the region taken over the last 100 yr. Based on the Asiago material, we here present a study of the 1966Y1967 event.McNeil's Nebula and V1647 Ori are clearly visible on 19 plates obtained with the Asiago 67/92 cm Schmidt telescope from 1966 October 22 to 1967 March 4. The object is not seen on plates taken in 1966 March nor in 1967 November, thus setting a minimum duration time for the eruptive event of 5 months and a maximum of 20 months. The 19 plates showing McNeil's Nebula were digitized, and a morphological and photometric analysis of the object was undertaken. These data show temporal photometric variability, as well as structural differences between different color bands. We finally compare the 1966Y1967 event to the recent 2003Y2006 eruption and consider the nature of V1647 Ori within the framework of EX LupiY and FU OrionisYtype eruptions.

REAPPEARANCE OF McNEIL'S NEBULA (V1647 ORIONIS) AND ITS OUTBURST ENVIRONMENT

“…Our lightcurve of V1647 Ori does not show any 56 day periodicity which was reported by Acosta-Pulido et al Aspin et al (2006), also had similar magnitude to the present one, however, all these three outbursts have different timescales. Implications of this fact on outburst model will be discussed in Section 4.…”

“…These illumination changes in nebula imply a structural change in the circumstellar matter above the disc and cavity. A similar pattern and conclusion were also reported between 1966, 2003 and 2008 outbursts by Aspin et al (2006. Similar analysis of image pairs taken between 2008 and 2012 did not show any significant morphological changes.…”

“…Acosta-Pulido et al (2007) estimated the inclination angle of disc to be 61 • and also estimated the accretion rate to be 5 × 10 −6 M yr −1 during outburst and 5 × 10 −7 M yr −1 in 2006 quiescent state. Aspin et al (2006) reported that ∼ 37 years prior to 2003 outburst, i.e. in 1966, V1647 Ori had undergone a similar magnitude of outburst, lasting for a duration somewhere between 5 to 20 months.…”

V1647 Orionis: Reinvigorated Accretion and the Re-Appearance of McNeil's Nebula

“…a P Cygni profile), and vi) an associated, generally curving, reflection nebula. What has been gleamed with regard to V1647 Ori, however, is somewhat contradictory to these definitive characteristics in that it had a relatively short outburst period (approximately 26 months), its optical and NIR outburst spectra possessed strong atomic and molecular emission features, and the eruption was shown to be repetitive - Aspin et al (2006) described an earlier event commencing in 1966. Such properties have more in common with those observed in the "EXor" class of eruptive variables, named after their class progenitor, EX Lupi (Herbig 1989).…”

The ALMA early science view of FUor/EXor objects – IV. Misaligned outflows in the complex star-forming environment of V1647 Ori and McNeil's Nebula

“…After its identification in 2003, two more outbursts were identified: a 1966 outburst identified using archival photometric plates (Aspin et al 2006) Ninan et al (2013) carried out a 4.5 year photometric study of V1647 Ori and report that at the end of their campaign in 2012, V1647 Ori was still in outburst after almost half a decade. The frequency and length of these outbursts, combined with several spectral features characteristic of both FUors and EXors emphasize the ambiguity between the FUor or EXor classification of V1647 Ori (Audard et al 2014, and ref.…”