Detection of C_2_, CN, and NaI D absorption in the AGB remnant of HD 56126.
Abstract
We present the detection of molecular absorption lines in the optical spectrum of the post-AGB star HD 56126. The C_2_ Phillips A^1PI_u_-X^1SIGMA^+^_g_(1,0), (2,0), and (3,0); Swan d^3PI_g_-a^3PI_u_(0,0) and (1,0); and CN Red system A^2PI-X^2SIGMA^+^(1,0), (2,0), (3,0), and (4,0) bands have been identified. From the identification of the molecular bands we find an expansion velocity of 8.5+/-0.6km/s independent of excitation condition or molecular specie. On the basis of the expansion velocity, rotational temperatures, and molecular column densities we argue that the line-forming region is the AGB remnant. This is in agreement with the expansion velocity derived from the CO lines. We find column densities of logN_C_2__=15.3+/-0.3cm^-2^ and logN_CN_=15.5+/-0.3cm^-2^, and rotational temperatures of T_rot_=242+/-20K and T_rot_=24+/-5K respectively for C_2_ and CN. By studying molecular line absorption in optical spectra of post-AGB stars we have found a new tracer of the AGB remnant. From comparison with the results of CO and IR observations it is possible to obtain information on non-spherical behavior of the AGB remnant. Using different molecules with different excitation conditions it should be possible to study the AGB remnant as a function of the distance to the star, and thus as a function of the evolutionary status of the star on the AGB.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 1996
- DOI:
- 10.48550/arXiv.astro-ph/9510122
- arXiv:
- arXiv:astro-ph/9510122
- Bibcode:
- 1996A&A...310..893B
- Keywords:
-
- MOLECULAR PROCESSES;
- CIRCUMSTELLAR MATTER;
- STARS: INDIVIDUAL: HD 56126;
- STARS: AGB AND POST-AGB;
- Astrophysics
- E-Print:
- Accepted by A&