V1647 ORIONIS: ONE YEAR INTO QUIESCENCE

We present new optical, near-IR, and mid-IR observations of the young eruptive variable star V1647 Orionis that went into outburst in late 2004 for approximately two years. Our observations, taken one year after the star had faded to its pre-outburst optical brightness, show that V1647 Ori is still actively accreting circumstellar material. We compare and contrast these data with existing observations of the source from both pre-outburst and outburst phases. From near-IR spectroscopy we identify photospheric absorption features for the first time that allow us to constrain the classification of the young star itself. Our best-fit spectral type is M0 ± 2 sub-classes with a visual extinction of 19 ± 2 magnitudes and a K-band veiling of rK ∼ 1.5 ± 0.2. We estimate that V1647 Ori has a quiescent bolometric luminosity of ∼9.5 L⊙ and a mass accretion rate of ∼1 × 10−6 M⊙ yr−1. Our derived mass and age, from comparison with evolutionary models, are 0.8 ± 0.2 M⊙ and ≲0.5 Myr, respectively. The presence toward the star of shock-excited optical [S ii] and [Fe ii] emission as well as near-IR H2 and [Fe ii] emission perhaps suggests that a new Herbig–Haro flow is becoming visible close to the star.