The 2011 outburst of the recurrent novaT Pyx. Evidence for a face-on bipolar ejection.

Olivier Chesneau (1) , A. Meilland (1) , D. P. K. Banerjee (2) , Jean-Baptiste Le Bouquin (3) , H. Mcalister (4, 5) , F. Millour (1) , S.T. Ridgway (6) , A. Spang (1) , T.A. ten Brummelaar (4) , M. Wittkowski (7) , N. M. Ashok (2) , M. Benisty (8) , J.-P. Berger (7) , T. S. Boyajian (5) , C. Farrington (4) , P.J. Goldfinger (4) , A. Mérand (7) , N. Nardetto (1) , R. Petrov (1) , T. Rivinius (7) , G. Schaefer (5) , G. Zins (3)

1 FIZEAU - Laboratoire Hippolyte Fizeau
2 PRL - Physical Research Laboratory [Ahmedabad]
3 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
4 CHARA - Center for High Angular Resolution Astronomy
5 Georgia State University
6 NOAO - National Optical Astronomy Observatory
7 ESO - European Southern Observatory
8 MPIA - Max-Planck-Institut für Astronomie

We report on near-IR interferometric observations of the outburst of the recurrent nova T Pyx. We obtained near-IR observations of T Pyx at dates ranging from t=2.37d to t=48.2d after the outburst, with the CLASSIC recombiner, located at the CHARA array, and with the PIONIER and AMBER recombiners, located at the VLTI array. These data are supplemented with near-IR photometry and spectra obtained at Mount Abu, India. Slow expansion velocities were measured (<300km/s) before t=20d (assuming D=3.5kpc). From t=28d on, the AMBER and PIONIER continuum visibilities (K and H band, respectively) are best simulated with a two component model consisting of an unresolved source plus an extended source whose expansion velocity onto the sky plane is lower than 700km/s. The expansion of the Brgamma line forming region, as inferred at t=28d and t=35d is slightly larger, implying velocities in the range 500-800km/s, still strikingly lower than the velocities of 1300-1600km/s inferred from the Doppler width of the line. Moreover, a remarkable pattern was observed in the Brgamma differential phases. A semi-quantitative model using a bipolar flow with a contrast of 2 between the pole and equator velocities, an inclination of i=15° and a position angle P.A.=110° provides a good match to the AMBER observables (spectra, differential visibilities and phases). At t=48d, a PIONIER dataset confirms the two component nature of the H band emission, consisting of an unresolved stellar source and an extended region whose appearance is circular and symmetric within error bars.These observations are most simply interpreted within the frame of a bipolar model, oriented nearly face-on. This finding has profound implications for the interpretation of past, current and future observations of the expanding nebula.

Domaines: Astrophysique stellaire et solaire [astro-ph.SR]; Astrophysique stellaire et solaire [astro-ph.SR]

Olivier Chesneau, A. Meilland, D. P. K. Banerjee, Jean-Baptiste Le Bouquin, H. Mcalister, et al.. The 2011 outburst of the recurrent novaT Pyx. Evidence for a face-on bipolar ejection.. Astronomy and Astrophysics - A&A, 2011, pp._. ⟨hal-00625395v3⟩