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25 April 2024 |
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The onset of photoionization in Sakurai's Object (V4334 Sgr) | | P.A.M. van Hoof
; M. Hajduk
; Albert A. Zijlstra
; F. Herwig
; A. Evans
; G.C Van de Steene
; S. Kimeswenger
; F. Kerber
; S.P.S. Eyres
; | | Date: |
26 Jun 2007 | | Abstract: | We investigate the reheating of the very late thermal pulse (VLTP) object
V4334 Sgr (Sakurai’s Object) using radio observations from the Very Large
Array, and optical spectra obtained with the Very Large Telescope. We find a
sudden rise of the radio flux at 5 and 8 GHz - from <= 90 micro-Jy and 80 +/-
30 micro-Jy in February 2005 to 320 micro-Jy and 280 micro-Jy in June 2006.
Optical line emission is also evolving, but the emission lines are fading. The
optical line emission and early radio flux are attributed to a fast shock (and
not photoionization as was reported earlier) which occurred around 1998. The
fading is due to post-shock cooling and recombination. The recent rapid
increase in radio flux is evidence for the onset of photoionization of carbon
starting around 2005. The current results indicate an increase in the stellar
temperature to 12 kK in 2006. The mass ejected in the VLTP eruption is M_ej >=
1e-4 Msol, but could be as high as 1e-2 Msol, depending mainly on the distance
and the clumping factor of the outflow. We derive a distance between 1.8 and 5
kpc. A high mass loss could expose the helium layer and yield abundances
compatible with those of [WC] and PG1159 stars. | | Source: | arXiv, arxiv.0706.3857 | | Services: | Forum | Review | PDF | Favorites | |
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