2012A&A...544L..18L


C.D.S. - SIMBAD4 rel 1.7 - 2020.05.27CEST04:49:03

2012A&A...544L..18L - Astronomy and Astrophysics, volume 544, L18-18 (2012/8-1)

Observational evidence for composite grains in an AGB outflow. MgS in the extreme carbon star LL Pegasi.

LOMBAERT R., DE VRIES B.L., DE KOTER A., DECIN L., MIN M., SMOLDERS K., MUTSCHKE H. and WATERS L.B.F.M.

Abstract (from CDS):

The broad 30 µm feature in carbon stars is commonly attributed to MgS dust particles. However, reproducing the 30µm feature with homogeneous MgS grains would require much more sulfur relative to the solar abundance. Direct gas-phase condensation of MgS occurs at a low efficiency. Precipitation of MgS on SiC precursor grains provides a more efficient formation mechanism, such that the assumption of homogeneous MgS grains may not be correct. Using a Monte Carlo-based radiative transfer code, we aim to model the 30µm feature of the extreme carbon star LL Peg with MgS dust particles. We find that for LL Peg this modeling is insensitive to the unknown MgS optical properties at λ<10µm. When MgS is allowed to be in thermal contact with amorphous carbon and SiC, the amount of MgS required to reproduce the strength of 30µm feature agrees with the solar abundance of sulfur, thereby resolving the reported MgS mass problem. We conclude that MgS is a valid candidate to be the carrier of the 30µm feature when it is part of a composite grain population that has optical properties representative of an ensemble of particle shapes.

Abstract Copyright:

Journal keyword(s): stars: AGB and post-AGB - stars: abundances - stars: evolution - stars: mass-loss - stars: winds, outflows - stars: carbon

Status at CDS:  

Simbad objects: 4

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Number of rows : 4

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14744 1
2 HD 56126 pA* 07 16 10.2589670319 +09 59 47.953674864   9.20 8.32     F0/5Ia 303 0
3 IRC +10216 C* 09 47 57.40632 +13 16 43.5648     10.96     C9,5e 2127 0
4 RAFGL 3068 C* 23 19 12.60744 +17 11 33.1332           C 248 0

    Equat.    Gal    SGal    Ecl

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2020.05.27-04:49:03

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