scholarly journals Theoretical studies of the infrared emission from circumstellar dust shells - The infrared characteristics of circumstellar silicates and the mass-loss rate of oxygen-rich late-type giants

1989 ◽  
Vol 343 ◽  
pp. 369 ◽  
Author(s):  
W. A. Schutte ◽  
A. G. G. M. Tielens
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Infrared Emission ◽  
Circumstellar Dust ◽  
Theoretical Studies ◽  
Late Type ◽  
Dust Shells

scholarly journals The RCB Stars and their Circumstellar Material

1985 ◽  
Vol 87 ◽  
pp. 151-166
Author(s):  
M.W. Feast
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Circumstellar Dust ◽  
Average Mass ◽  
Circumstellar Material ◽  
Carbon Particles ◽  
Circumstellar Shell

RCB stars are surrounded by circumstellar dust and gas moving radially outwards at ~200 km/sec. The circumstellar shell is made up of discrete puffs of matter, a typical puff occupying an area ~0.03 of a complete shell. On the average puffs are ejected about once every 40 days (comparable with the known pulsation periods of RCB stars). The reddening law of the dust indicates that it is composed of small carbon particles (radii ~100A). The flux from the shell at L typically varies by 1 to 3 mags over periods of 1000-2000 days. The average mass loss rate is ~10−6MO/yr.

scholarly journals OH masers in oxygen-rich late-type stars

2002 ◽  
Vol 206 ◽  
pp. 319-322
Author(s):  
Sandra Etoka ◽  
A.M. Le Squeren
Keyword(s):  
Mass Loss ◽  
Radio Telescope ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Monitoring Programme ◽  
Late Type ◽  
Wide Range ◽  
Ir Stars ◽  
Circumstellar Shell

We present here some noteworthy results of two related studies on oxygen-rich late type stars. The aim of this work was to study the OH circumstellar shell properties in terms of evolution. These studies are based on an OH monitoring programme carried out with the Nançay Radio Telescope. The first study concerns seven Miras distributed along the colour-colour diagram. They were observed at two or three different epochs covering one to seven cycles over a period from 1980 to 1995 at 1612, 1667 and 1665 MHz in both circular polarizations. The second study concerns thirty objects covering a wide range of mass loss rate from Miras to OH/IR stars. They were observed in 1994 at 1665 & 1667 MHz in both circular polarizations.

scholarly journals IRAS Observations of Symbiotic Stars

1989 ◽  
Vol 106 ◽  
pp. 391-400 ◽  
Author(s):  
M. Parthasarathy ◽  
H.C. Bhatt
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Planetary Nebulae ◽  
Evolutionary Stage ◽  
Symbiotic Stars ◽  
Late Type ◽  
Mira Variables ◽  
Show Evidence ◽  
The Masses

AbstractOf the 129 symbiotic stars in Allen's (1984) catalogue, 42 were found to be IRAS sources. Of these 42 IRAS sources, 22 are D-type (symbiotic Miras), 5 are D'-type (yellow symbiotics) and 15 are S-type. The separation of S, D and D’ types into three distinct groups is clearer in the log[fλ(25μm)/fλ(12μm)] versus (H-K) diagram. The IRAS fluxes of S-type symbiotics are consistent with that observed from normal M giants. This result suggests that mass-loss rate from most of the S-type symbiotics is similar to that from normal M giants. The IRAS data of D-type symbiotics shows evidence for the presence of dust envelopes. The masses of the dust envelopes (10-6 to 10-7 Mo) around Miras in D-type symbiotics are similar to that observed in field Mira variables. These results suggest that mass-loss rates in symbiotic Miras are similar to those from field Mira variables and also that the mass loss from symbiotic Miras is pulsationally driven similar to that found in field Mira variables by Whitelock, Pottasch and Feast (1987). Analysis of IRAS data of yellow symbiotics Ml-2, AS201, Cnl-1, Wray 157. and HD149427 suggests that they are young planetary nebulae containing a binary nucleus. Ml-2, AS201 and Cnl-1 show evidence for the presence of evolved hot companions. The evolutionary stage of the late type (F-G) companions is not clear.

Rigid Field Hydrodynamic simulations of the magnetosphere of σ Orionis E

2010 ◽  
Vol 6 (S272) ◽  
pp. 194-195
Author(s):  
Nicholas R. Hill ◽  
Richard H. D. Townsend ◽  
David H. Cohen ◽  
Marc Gagné
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Late Type ◽  
Hydrodynamic Simulations ◽  
X Ray ◽  
Upper Limit ◽  
Magnetically Confined

AbstractWe present Rigid Field Hydrodynamic simulations of the magnetosphere of σ Ori E. We find that the X-ray emission from the star's magnetically confined wind shocks is very sensitive to the assumed mass-loss rate. To compare the simulations against the measured X-ray emission, we first disentangle the star from its recently discovered late-type companion using Chandra HRC-I observations. This then allows us to place an upper limit on the mass-loss rate of the primary, which we find to be significantly smaller than previously imagined.

scholarly journals The Giant Star Ca II Ionization Problem: Mass Loss Revisited

2004 ◽  
Vol 219 ◽  
pp. 651-655 ◽  
Author(s):  
Graham M. Harper ◽  
Alexander Brown ◽  
Thomas Ayres ◽  
Stuart A. Sim
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Stellar Winds ◽  
Late Type ◽  
Giant Star ◽  
Partial Redistribution ◽  
M Stars ◽  
Ionization Balance ◽  
First Time

Pioneering studies of winds from non-coronal evolved late-type stars were plagued by uncertainties in the Ca ionization balance which severely limited the accuracy of derived mass-loss rates. Here we re-examine the Ca II ionization balance in these stellar winds using FUSE spectra which reveal, for the first time, the flux from the photoionizing radiation field shortward of 1045Â. We present a FUSE 912-1185Â spectroscopic survey of evolved late-K and M stars; including the M giants α Cet (M1.5 III), γ Cru (M3.5 III), β Gru (M4.5 III), and R Dor (M8e III). Using FUSE spectra of α Tau (K5 III), supplemented with partial redistribution calculations of H Ly-α and Ly-β, together with UV and radio data, we present a study of α Tau's wind ionization balance and derive new constraints which place the mass-loss rate significantly below that suggested by the Reimers formula.

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