AMBER/VLTI interferometric observations of the recurrent Nova RS Ophiuchii 5.5 days after outburst

Abstract

Aims. We report on spectrally dispersed interferometric AMBER/VLTI observations of the recurrent nova RS Oph five days after the discovery of its outburst on 2006 Feb. 12. Methods. Using three baselines ranging from 44 to 86 m, and a spectral resolution of λ/δλ = 1500, we measured the extension of the milliarcsecond-scale emission in the K band continuum and in the Brγ and He I 2.06 µm lines, allowing us to get an insight into the kinematics of the line forming regions. The continuum visibilities were interpreted by fitting simple geometric models consisting of uniform and Gaussian ellipses, ring and binary models. The visibilities and differential phases in the Brγ line were interpreted using skewed ring models aiming to perform a limited parametric reconstruction of the extension and kinematics of the line forming region. Results. The limited uv coverage does not allow discrimination between filled models (uniform or Gaussian ellipses) and rings. Binary models are discarded because the measured closure phase in the continuum is close to zero. The visibilities in the lines are at a low level compared to their nearby continuum, consistent with a more extended line forming region for He I 2.06 µm than Brγ. The ellipse models for the continuum and for the lines are highly flattened (b/a ∼ 0.6) and share the same position angle (PA ∼ 140• ). Their typical Gaussian extensions are 3.1 × 1.9 mas, 4.9 × 2.9 mas and 6.3 × 3.6 mas for the continuum, Brγ and He I 2.06 µm lines, respectively. Two radial velocity fields are apparent in the Brγ line: a slow expanding ring-like structure (v rad ≤ 1800 km s −1 ), and a fast structure extended in the E-W direction (v rad ∼ 2500−3000 km s −1 ), a direction that coincides with the jet-like structure seen in the radio. These results confirm the basic fireball model, contrary to the conclusions of other interferometric observations conducted by Monnier et al. (2006a, ApJ, 647, L127).

The 2011 outburst of the recurrent nova T Pyxidis. Evidence for a face-on bipolar ejection

“…Some recent examples suggest that bipolarity in the ejecta of classical/recurrent novae may be relatively frequent: RS Oph (Ribeiro et al 2009;Bode et al 2007;Chesneau et al 2007), V445 Pup (Woudt et al 2009), V1280 Sco (Chesneau et al 2008;Chesneau et al, in prep. ) or HR Del (Harman & O'Brien 2003).…”

Spectral evolution of the recurrent nova RS Ophiuchi during the 2006 outburst and some mysterious phenomena

“…Numerous works studied the new outburst in multiple spectral regions, e.g., in X-rays Ness et al 2007;Vaytet et al 2007), in optical ), in infrared (Das et al 2006;Chesneau et al 2007;Evans et al 2007a,b;Lane et al 2007), and in radio wavelength . Some theoretical work on the explosion was carried out (e.g., Hachisu et al 2006).…”

Nova Eruptions with Infrared Interferometric Observations

“…These results were also contrary to Monnier et al (2006). Furthermore, Chesneau et al (2007) found two velocity fields in the Brγ line; a slowly expanding ring-like structure (v rad ≤ 1800 km s −1 ), and a fast structure extended in the E-W direction (v rad ∼ 2500-3000 km s −1 ). A two velocity component was also required to replicate the Hubble Space Telescope narrow band imaging observations of the resolved remnant, at day 155 after eruption, and the ground-based optical spectroscopy (Ribeiro et al 2009).…”

“…The AMBER instrument on the Very Large Telescope Interferometer (VLTI) was also used, on day 5.5 after eruption, to measure the K-band continuum and the Brγ and HeI 2.06 µm lines (Chesneau et al 2007). The K-band emission is dominated by free-free emission and had a smaller size than the Brγ and HeI lines (3x2 mas, 5x3 mas, and 6x4 mas, respectively).…”