Article

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

09/2011;
Source: arXiv

ABSTRACT 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^{\circ} and a position angle P.A.=110^{\circ} 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.

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    ABSTRACT: We present the first high spatial resolution monitoring of the dust forming nova V1280 Sco performed with the Very Large Telescope Interferometer (VLTI). Spectra and visibilities were obtained from the onset of the dust formation 23 days after discovery till day 145, using the instruments AMBER and MIDI. These interferometric observations are complemented by near-infrared data from the 1.2m Mt. Abu Infrared Observatory, India. The observations are first interpreted with simple models but more complex models, involving a second shell, are necessary to explain the data obtained from t=110d after outburst. This behavior is in accordance with the light curve of V1280 Sco which exhibits a secondary peak around t=106d, followed by a new steep decline, suggesting a new dust forming event. Spherical dust shell models generated with the DUSTY code are also used to investigate the parameters of the main dust shell. Using uniform disk and Gaussian models, these observations allow us to determine an apparent linear expansion rate for the dust shell of 0.35 +/- 0.03 mas/day and the approximate time of ejection of the matter in which dust formed as t_ejec=10.5+/-7d, i.e. close to the maximum brightness. This information, combined with the expansion velocity of 500+/-100km/s, implies a distance estimate of 1.6+/-0.4kpc. The dust mass generated was typically 2-8 10^-9 solar mass per day. Considering that the dust forming event lasted at least 200-250d, the mass of the ejected material is likely to have exceeded 10^-4 solar mass.
    Astronomy and Astrophysics 04/2008; · 5.08 Impact Factor

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