Embed Size (px)
DESCRIPTION
Hot DQ White Dwarf Stars : A New Challenge to Stellar Evolution. Patrick Dufour,University of Arizona James Liebert, University of Arizona Gilles Fontaine, Université de Montréal Natalie Behara, Observatoire Paris-Meudon. Outline. -A Brief Introduction to White Dwarfs -Spectral Evolution - PowerPoint PPT Presentation
Citation preview
Hot DQ White Dwarf Stars : A New Challenge to Stellar Evolution
Patrick Dufour,University of Arizona
James Liebert, University of Arizona
Gilles Fontaine, Université de Montréal
Natalie Behara, Observatoire Paris-Meudon
Outline
-A Brief Introduction to White Dwarfs
-Spectral Evolution
-DQ White Dwarfs
-Hot DQ
-H1504+65 and Evolutionary Scenario
Jordan & Rauch 1994
Werner & Herwig 2006
“Born-Again scenario”
DODZ
DC
DQ
DADB
PG1159
Evolution
DC
Teff~150,000 K
Helium-richHydrogen-rich
~4000 K
??
DB gap
RCrB?
EHe?
CE?
???
Outline
-A Brief Introduction to White Dwarfs
-Spectral Evolution
-DQ White Dwarfs
-Hot DQ
-H1504+65 and Evolutionary Scenario
Dufour et al. 2005
Dufour et al. 2005
Log q(He) = MHe/M*
log q(He)=-4.0
log q(He)=-3.0
log q(He)=-2.0
FRD
Brassard et al. 2006
G 35-26
11,000 K < Teff < 14,000 K
8.8 < log g < 9.0
C/He ~ 3x10-2
G 227-5
12,000 K < Teff < 13,000 K
log g fixed at 8.0
C/He ~ 3x10-3
Thejll et al. 1990Wegner & Koester 1985
G 227-5
Outline
-A Brief Introduction to White Dwarfs
-Spectral Evolution
-DQ White Dwarfs
-Hot DQ
-H1504+65 and Evolutionary Scenario
G 227-5
Dufour et al 2005
Naive expectation
1- Calculate hotter DQ models
2- Make fits
3- Write paper
4- Move on to the next project
Pure Helium
Log C/He = 0
Log C/He= 1
Pure Carbon
24,000 K, log g = 8.0, 8.5 and 9.0
∫HdTeff4 /4
Outline
-A Brief Introduction to White Dwarfs
-Spectral Evolution
-DQ White Dwarfs
-Hot DQ
-H1504+65 and Evolutionary Scenario
Werner & Herwig 2006
Typical PG 1159 abundances:
33% He
50% C
15% O
2% Ne
H1504+65
• Teff ~ 175,000 K – 200,000 K• Log g = 8• C ~ 48 %• O ~ 48 %• He < 1 %• Extreme PG1159 ?• Burned carbon ?• O/Ne/Mg core ?
Pure carbon, Teff = 30,000 K
DO
DCDZDQ
DA
DB
PG1159
Evolution
DC
150,000 K
Helium-richHydrogen-rich
~4000 K DQ (2nd sequence ?)
H1504+65
Hot DQ
H and He poor
?
Conclusions
-Discovery of a new type of star : white dwarfs with pure carbon atmospheres
-cool down version of H1504+65?
-High mass stars on MS around 8-10 Msun?
-O/Ne/Mg core ?
-Higher S/N observations (MMT) coming soon
-more theoretical calculations/other evolutionary scenario?
Thank you
