We aim to derive the physical properties of the recurrent nova T Pyx and the structure of the ejecta during the early stages of expansion of the 2011 outburst .
The nova was observed with high resolution spectroscopy ( R \approx 65000 spectroscopy , beginning 1 day after discovery of the outburst and continuing through the last visibility of the star at the end of May 2011 .
The interstellar absorption lines of Na I , Ca II , CH , CH ^ { + } , and archival H I 21 cm emission line observations have been used to determine a kinematic distance .
Interstellar diffuse absorption features have been used to determine the extinction independent of previous assumptions .
Sample Fe-peak line profiles show the optical depth and radial velocity evolution of the discrete components .
We propose a distance to T Pyx \geq 4.5kpc , with a strict lower limit of 3.5 kpc ( the previously accepted distance ) .
We derive an extinction , E ( B-V ) \approx 0.5 \pm 0.1 , that is higher than previous estimates .
The first observation , Apr .
15 , displayed He I , He II , C III , and N III emission lines and a maximum velocity on P Cyg profiles of the Balmer and He I lines of \approx 2500 km s ^ { -1 } characteristic of the fireball stage .
These ions were undetectable in the second spectrum , Apr .
23 , and we use the recombination time to estimate the mass of the ejecta , 10 ^ { -5 } f M _ { \odot } for a filling factor f .
Numerous absorption line systems were detected on the Balmer , Fe-peak , Ca II , and Na I lines , mirrored in broader emission line components , that showed an “ accelerated ” displacement in velocity .
We also show that the time sequence of these absorptions , which are common to all lines and arise only in the ejecta , can be described by recombination front moving outward in the expanding gas without either a stellar wind or circumstellar collisions .
By the end of May , the ejecta were showing signs of turning optically thin in the ultraviolet .