Abstract
We show that metal line blanketing has an important effect on the atmospheres of hot stars, and we argue that the omission of metal line blanketing in previous non-LTE model atmospheres of O-type stars has led to underestimates of surface gravity and stellar mass. In addition to wind emission, metal line blanketing contributes to the solution of the long-standing discrepancy between spectroscopic and evolutionary masses for O-type stars. To support our argument, we calculated a series of non-LTE stellar atmospheres for O and Of-type stars. We compared the predicted profiles of hydrogen and helium lines produced by (1) a static plane-parallel H-He model, (2) a metal line-blanketed static model, and (3) an extended expanding model atmosphere. We find that simple H-He models produce stronger lines than do our metal line-blanketed models. Consequently, they lead to underestimated gravities. Wind emission is more effective in filling in the wings of H or He lines in the case of large mass-loss rates typical of extreme Of stars. These findings apply equally to young, massive O-type stars and to highly evolved stars, i.e., central stars of planetary nebulae. The lower gravities derived from H-He models yield underestimated masses for young O-type stars, and overestimated masses for highly evolved stars.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 359-362 |
| Number of pages | 4 |
| Journal | Astrophysical Journal |
| Volume | 465 |
| Issue number | 1 PART I |
| State | Published - 1996 |
| Externally published | Yes |
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Keywords
- Stars: Atmospheres
- Stars: Early-type
- Stars: Evolution
- Stars: Fundamental parameters
ASJC Scopus subject areas
- Space and Planetary Science
Cite this
Toward resolving the "mass discrepancy" in o-type stars. / Lanz, Thierry; De Koter, Alex; Hubeny, Ivan -; Heap, Sara R.
In: Astrophysical Journal, Vol. 465, No. 1 PART I, 1996, p. 359-362.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Toward resolving the "mass discrepancy" in o-type stars
AU - Lanz, Thierry
AU - De Koter, Alex
AU - Hubeny, Ivan -
AU - Heap, Sara R.
PY - 1996
Y1 - 1996
N2 - We show that metal line blanketing has an important effect on the atmospheres of hot stars, and we argue that the omission of metal line blanketing in previous non-LTE model atmospheres of O-type stars has led to underestimates of surface gravity and stellar mass. In addition to wind emission, metal line blanketing contributes to the solution of the long-standing discrepancy between spectroscopic and evolutionary masses for O-type stars. To support our argument, we calculated a series of non-LTE stellar atmospheres for O and Of-type stars. We compared the predicted profiles of hydrogen and helium lines produced by (1) a static plane-parallel H-He model, (2) a metal line-blanketed static model, and (3) an extended expanding model atmosphere. We find that simple H-He models produce stronger lines than do our metal line-blanketed models. Consequently, they lead to underestimated gravities. Wind emission is more effective in filling in the wings of H or He lines in the case of large mass-loss rates typical of extreme Of stars. These findings apply equally to young, massive O-type stars and to highly evolved stars, i.e., central stars of planetary nebulae. The lower gravities derived from H-He models yield underestimated masses for young O-type stars, and overestimated masses for highly evolved stars.
AB - We show that metal line blanketing has an important effect on the atmospheres of hot stars, and we argue that the omission of metal line blanketing in previous non-LTE model atmospheres of O-type stars has led to underestimates of surface gravity and stellar mass. In addition to wind emission, metal line blanketing contributes to the solution of the long-standing discrepancy between spectroscopic and evolutionary masses for O-type stars. To support our argument, we calculated a series of non-LTE stellar atmospheres for O and Of-type stars. We compared the predicted profiles of hydrogen and helium lines produced by (1) a static plane-parallel H-He model, (2) a metal line-blanketed static model, and (3) an extended expanding model atmosphere. We find that simple H-He models produce stronger lines than do our metal line-blanketed models. Consequently, they lead to underestimated gravities. Wind emission is more effective in filling in the wings of H or He lines in the case of large mass-loss rates typical of extreme Of stars. These findings apply equally to young, massive O-type stars and to highly evolved stars, i.e., central stars of planetary nebulae. The lower gravities derived from H-He models yield underestimated masses for young O-type stars, and overestimated masses for highly evolved stars.
KW - Stars: Atmospheres
KW - Stars: Early-type
KW - Stars: Evolution
KW - Stars: Fundamental parameters
UR - http://www.scopus.com/inward/record.url?scp=21344472066&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=21344472066&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:21344472066
VL - 465
SP - 359
EP - 362
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1 PART I
ER -