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Probing the mass-loss history of the unusual Mira variable R Hya through its infrared CO wind

Decin, L; Blomme, L; Reyniers, M; Ryde, Nils LU and Hinkle, K H (2008) In Astronomy & Astrophysics 484(2). p.55-401
Abstract
Context. The unusual Mira variable R Hya is well known for its declining period between AD 1770 and 1950, which is possibly attributed to a recent thermal pulse.

Aims. The goal of this study is to probe the circumstellar envelope (CSE) around R Hya and to check for a correlation between the derived density structure and the declining period.

Methods. We investigate the CSE around R Hya by performing an in-depth analysis of (1.) the photospheric light scattered by three vibration-rotation transitions in the fundamental band of CO at 4.6 $mu$m; and (2.) the pure rotational CO J = 1-0 through 6-5 emission lines excited in the CSE. The vibrational-rotational lines trace the inner CSE within 3.5´´, whereas the pure rotational... (More)
Context. The unusual Mira variable R Hya is well known for its declining period between AD 1770 and 1950, which is possibly attributed to a recent thermal pulse.

Aims. The goal of this study is to probe the circumstellar envelope (CSE) around R Hya and to check for a correlation between the derived density structure and the declining period.

Methods. We investigate the CSE around R Hya by performing an in-depth analysis of (1.) the photospheric light scattered by three vibration-rotation transitions in the fundamental band of CO at 4.6 $mu$m; and (2.) the pure rotational CO J = 1-0 through 6-5 emission lines excited in the CSE. The vibrational-rotational lines trace the inner CSE within 3.5´´, whereas the pure rotational CO lines are sensitive probes of the cooler gas further out in the CSE.

Results. The combined analysis bear evidence of a change in mass-loss rate some 220 yr ago (at ~150 $R_{star}$ or ~1.9 arcsec from the star). While the mass-loss rate before AD 1770 is estimated to be ~ $2 imes 10^$ $M_{odot}$/yr, the present day mass-loss rate is a factor of ~20 lower. The derived mass-loss history nicely agrees with the mass-loss rate estimates by Zijlstra et al. (2002) on the basis of the period decline. Moreover, the recent detection of an AGB-ISM bow shock around R Hya at 100 arcsec to the west by Wareing et al. (2006) shows that the detached shell seen in the 60 $mu$m IRAS images can be explained by a slowing-down of the stellar wind by surrounding matter and that no extra mass-loss modulation around 1-2 arcmin needs to be invoked.

Conclusions. Our results give empirical evidence to the thermal-pulse model, which is capable of explaining both the period evolution and the mass-loss history of R Hya . (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
stars: mass-loss, stars: circumstellar matter, stars: AGB and post-AGB, line: profiles, radiative transfer, stars: individual: R Hya
in
Astronomy & Astrophysics
volume
484
issue
2
pages
55 - 401
publisher
EDP Sciences
external identifiers
  • wos:000256309700014
  • scopus:44449141960
ISSN
0004-6361
DOI
10.1051/0004-6361:20079312
language
English
LU publication?
yes
id
ec6585c2-fcda-446f-9e1c-4ee5c7e19840 (old id 945387)
date added to LUP
2008-01-23 11:23:07
date last changed
2017-01-01 05:30:52
@article{ec6585c2-fcda-446f-9e1c-4ee5c7e19840,
  abstract     = {Context. The unusual Mira variable R Hya is well known for its declining period between AD 1770 and 1950, which is possibly attributed to a recent thermal pulse.<br/><br>
Aims. The goal of this study is to probe the circumstellar envelope (CSE) around R Hya and to check for a correlation between the derived density structure and the declining period.<br/><br>
Methods. We investigate the CSE around R Hya by performing an in-depth analysis of (1.) the photospheric light scattered by three vibration-rotation transitions in the fundamental band of CO at 4.6 $mu$m; and (2.) the pure rotational CO J = 1-0 through 6-5 emission lines excited in the CSE. The vibrational-rotational lines trace the inner CSE within 3.5´´, whereas the pure rotational CO lines are sensitive probes of the cooler gas further out in the CSE.<br/><br>
Results. The combined analysis bear evidence of a change in mass-loss rate some 220 yr ago (at ~150 $R_{star}$ or ~1.9 arcsec from the star). While the mass-loss rate before AD 1770 is estimated to be ~ $2 	imes 10^$ $M_{odot}$/yr, the present day mass-loss rate is a factor of ~20 lower. The derived mass-loss history nicely agrees with the mass-loss rate estimates by Zijlstra et al. (2002) on the basis of the period decline. Moreover, the recent detection of an AGB-ISM bow shock around R Hya at 100 arcsec to the west by Wareing et al. (2006) shows that the detached shell seen in the 60 $mu$m IRAS images can be explained by a slowing-down of the stellar wind by surrounding matter and that no extra mass-loss modulation around 1-2 arcmin needs to be invoked.<br/><br>
Conclusions. Our results give empirical evidence to the thermal-pulse model, which is capable of explaining both the period evolution and the mass-loss history of R Hya .},
  author       = {Decin, L and Blomme, L and Reyniers, M and Ryde, Nils and Hinkle, K H},
  issn         = {0004-6361},
  keyword      = {stars: mass-loss,stars: circumstellar matter,stars: AGB and post-AGB,line: profiles,radiative transfer,stars: individual: R Hya},
  language     = {eng},
  number       = {2},
  pages        = {55--401},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {Probing the mass-loss history of the unusual Mira variable R Hya through its infrared CO wind},
  url          = {http://dx.doi.org/10.1051/0004-6361:20079312},
  volume       = {484},
  year         = {2008},
}