arXiv:0809.4756v1 [astro-ph] 27 Sep 2008
COMMISSIONS 27 AND 42 OF THE IAU
INFORMATION BULLETIN ON VARIABLE STARS
00 Month 200x
HU ISSN 0374 – 0676
EARLY SPECTROSCOPY AND PHOTOMETRY OF THE
NEW OUTBURST OF V1647 ORI
1Konkoly Observatory, H-1525 Budapest, P.O.Box 67, Hungary, e-mail: firstname.lastname@example.org
V1647 Ori is a young eruptive variable star, illuminating a variable reflection nebula
(McNeil’s Nebula). The previous outburst of the star between 2004 January and 2005
October has been extensively documented in the literature (e.g. Brice˜ no et al. 2004,
Ojha et al. 2006, Acosta-Pulido et al. 2007, Fedele et al. 2007). Optical, near-, and mid-
infrared observations of the star during the quiescent period following the outburst (Aspin
et al. 2008) suggested a spectral type of M0±0.2, mass 0.8±0.2M⊙, and age <0.5Myr for
V1647 Ori. The observed properties of the outburst of V1647 Ori are different in several
respects from both the EXor and FUor type outbursts, and suggest that this star probably
represents a new type of of eruptive young stars, younger and more deeply embedded than
EXors, and exhibiting variations on shorter time scales than FUors.
A new outburst of the star was announced on 27th August 2008.
detected the apparent brightening of V1647 Ori 26 August. The flux-calibrated optical
spectrum of the star, obtained by Aspin (2008) on Aug 30, showed strong Hα emission
line with P Cygni profile, the CaII triplet lines in emission, and suggested a Johnson R
magnitude of 17.3, corresponding to a brightening of some 6 mag in the R-band with
respect to the quiescent phase.
In order to compare the present brightness and emission line strengths of the star with
those observed at the beginning of the outburst in 2004 I observed V1647 Ori between 28
August and 1 September 2008, using the CAFOS instrument on the 2.2-m telescope of
Calar Alto Observatory (Spain). Spectra covering the wavelength region of 4800–7800˚ A
were obtained on Aug 29 and 31, using the grism G–100 whose dispersion is 2.12˚ A/pix.
Grism R–100, having a dispersion of 2.04˚ A/pix was used for observing the spectral region
5800–9000˚ A on Aug 28, 30, and Sep 1. The exposure time was 1800 s for each spectrum.
The spectrum of a He–Hg–Rb lamp was observed for wavelength calibration. Direct
images, each with an exposure time of 60 s, were taken immediately after the spectroscopic
observations, utilizing the central 1024×1024 pixel region of the SITe 2048×2048 chip.
The image scale was 0.53′′/pix. The 9-arcmin field of view included seven secondary
standard stars published by Semkov (2004). Two IC-band images were obtained on both
August 28 and 29, and two images both in the IC and RC bands were taken on the
remaining three nights. Data reduction and analysis were performed in IRAF. One-
dimensional spectra were extracted from the spectroscopic images using the ‘apextract’
package of IRAF. The spectrum of the nebula was also extracted from the images obtained
through grism G–100. The resulting spectra were wavelength-calibrated and analysed in