[117.10] The Last Heartbeats of a Dying Star: Pulsation of the Post-Asymptotic Giant Branch Star

AAS 201st Meeting, January, 2003
Session 117. Delta Scuti and Pulsating Friends
Poster, Thursday, January 9, 2003, 9:20am-4:00pm, Exhibit Hall AB

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[117.10U] The Last Heartbeats of a Dying Star: Pulsation of the Post-Asymptotic Giant Branch Star - Sakurai's Object (V4334 Sgr)

J.E. Castora, L.M. Winter, E.F. Guinan (Villanova University)

As a ``born-again'' post-asymptotic giant, V4334 Sgr (Sakurai's Object) is undergoing extraordinarily rapid stellar evolution in real time. Yukio Sakurai first discovered the object in 1996 at an apparent magnitude of m_v = +11.4. Prior to its discovery the star was tentatively detected in ESO/SERC plates from 1976 close to the detection magnitude of about m_v = +21.5. The observed rapid brightening observed is best explained as the star, after descending the white dwarf cooling track, underwent a final helium flash and subsequently rapidly brightened.

We present and discuss photoelectric UBVRI observations of V4334 Sgr obtained with the 0.8-m Four College Consortium (FCC) Automated Photoelectric Telescope (APT). This photometry was combined with available photometry and spectroscopy to delineate the star's photometric and spectroscopic behavior. The photometry shows that the star reached a maximum brightness of V = +10.9 mag in 1996/97. During 1998 V4334 Sgr gradually decreased in brightness to m_v \approx +12.5 mag. In Spring 1998 V4335 Sgr showed cepheid-like light oscillations with a period of P \approx 55d. Subsequently the star underwent a rapid decline in brightness reaching m_v \approx +20.5 mag during 1999/2000. As the star dimmed it became very red and continued to be a strong IR source. As in the cases of the related post-AGB stars, FG Sge and V605 Aql, the rapid decrease in light is best explained by extinction from condensing circumstellar dust. In this paper, we discuss the evolution of V4335 Sgr and focus on the analysis and interpretation of the stellar pulsations observed during the declining phases of the recent outburst. The star's luminosity and distance are inferred from its pulsation properties and compared with other estimates.

This research is supported by NSF/RUI Grants AST95-28506 and AST00-71260 which we gratefully acknowledge.

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