The 2004-2006 Outburst and Environment of V1647 Ori

Abstract

We studied the brightness and spectral evolution of the young eruptive star V1647 Ori during its recent outburst in the period 2004 FebruaryY2006 September. We performed a photometric follow-up in the bands V, R C , I C , J, H, and K s , as well as visible and near-IR spectroscopy. The main results derived from combining our data with those published by other authors are as follows: the brightness of V1647 Ori stayed more than 4 mag above the preoutburst level until 2005 October, when it started a rapid fading. In the high state we found a periodic component in the optical light curves with a period of 56 days. The delay between variations of the star and variations in the brightness of clumps of nearby nebulosity corresponds to an angle of 61 AE 14 between the axis of the nebula and the line of sight. The overall appearance of the infrared and optical spectra did not change in the period 2004 MarchY2005 March, although a steady decrease of H i emission-line fluxes could be observed. In 2006 May, in the quiescent phase, the He i 1.083 m line was observed in emission, contrary to its deep blueshifted absorption observed during the outburst. The J À H and H À K s color maps of the infrared nebula reveal an envelope around the star whose largest extension is about 18 00 (0.03 pc). The color distribution of the infrared nebula suggests reddening of the scattered light inside a thick circumstellar disk. Comparison of the K s and H images of McNeil's Nebula, the conical nebulosity illuminated by V1647 Ori, shows that HH 22A, the Spitzer infrared source, and the bright clump C of the nebula may be unrelated objects. We show that the observed properties of V1647 Ori could be interpreted in the framework of the thermal instability models of Bell and coworkers. V1647 Ori might belong to a new class of young eruptive stars, defined by relatively short timescales, recurrent outbursts, a modest increase in bolometric luminosity and accretion rate, and an evolutionary state earlier than that of typical EXors.

Exploring the circumstellar environment of the young eruptive star V2492 Cygni

“…3, right) shows that not only the colors, but also the magnitude changes follow the reddening path, suggesting the same ΔA V ≈ 20 mag. This is different from what was observed for V1647 Ori, where the color changes were consistent with reddening, but the magnitudes required additional color-independent flux changes as well (Acosta-Pulido et al 2007). …”

“…We observed V2492 Cyg with the LIRIS instrument installed on the 4.2 m William Herschel Telescope (WHT) at the Observatorio del Roque de Los Muchachos (Spain). The description of the instrument can be found in Acosta-Pulido et al (2007). On 2011 July 21/22 JHK S images were taken, while on 2011 August 1/2 long-slit intermediate resolution spectra in the ZJ and HK bands were obtained.…”

“…We observed HIP 103694, a G2-type star, as telluric calibrator. The data reduction of both the images and the spectra were done in the same way as in Acosta-Pulido et al (2007). The spectra were flux calibrated using JHK S photometry taken with TCS on 2011 August 3/4.…”

“…Recent studies of some young eruptive stars suggest that the flux changes of these systems are due to the combination of two effects of comparable amplitude. One effect is an intrinsic brightening related to the appearance of a new, accretion-fueled hot component in the system, while the other is a dust-clearing event that reduces the extinction along the line of sight (see, e.g., V1647 Ori in Aspin 2004 andAcosta-Pulido et al 2007; or PV Cep in Kun et al 2011). The simultaneity of the accretion and extinction changes suggests that they might be physically linked, and it is the changing accretion luminosity that causes changes in the inner disk structure.…”

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

“…Thus, 2003 outburst lasted for a total of ∼ 2 years and V1647 Ori returned to its pre-outburst phase in early 2006. 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.…”