Transcript DUPREE_SPLINTER

SLEUTHING MASS OUTFLOW
FROM EVOLVED STARS
Optical/IR Spectroscopy from
the MMT, KECK II, and Magellan
Andrea Dupree (SAO/CfA)
Sz. Meszaros (SAO), Jay Strader (CfA), and
Graeme H. Smith (UCSC)
Cool Stars 15/Splinter: St. Andrews 21-25 July 2008
STELLAR EVOLUTION PROBLEMS ….
CMD depends on metallicity, but what is the ‘second parameter’????
Poster children for second parameter: NGC 362 & NGC 288
(Bellazzini et al. 2001; Catelan et al. 2001)
Candidates for second parameter:
age, environment (including free-floating planets); primordial He
abundance; surface pollution (helium); CNO abundances;
rotation; mass loss…..
FOCUS ON MASS LOSS …
 Mass loss is required
theoretically on red giant
branch to match CMD of
clusters , but the mass
presumably lost has
‘VANISHED’!
 Where and when does
mass loss occur?
 What are the
spectroscopic signatures
of mass loss or mass
flow?
Omega Centauri
Diagnostics of
atmospheric motions
Need to know where the
diagnostic forms….
Contribution functions for
a metal deficient giant star
MMT/Hectochelle observations
of globular clusters: M13, M15, & M92
240 fibres available to capture spectra
in selected orders: H-α and Ca II (H&K)
Ca K in M13
H-α in M92
Bisectors marked
Sz. Meszaros et al. 2008, 2009
H–α Bisector Velocities
Outflow velocities (H–α)
increase with luminosity,
and are higher for AGB stars
No dependence
on [Fe/H]
Stars with IR excess in M15 (Spitzer)
show same outflow velocity as other
red giants
Meszaros et al 2008
Ca K3 shows higher (accelerating) outflow than H-α
Ca K3
H–α
Helium 10830Ǻ observed with NIRSPEC/KECK II
in M13 and metal-poor field giants
 Maps wind to higher levels of chromosphere
Visible in warmer stars
Reveals high velocities ~100 km s-1
Comparable to stellar escape velocity at 2Rstar
AGB and RGB
RHB stars
with Graeme Smith (UCSC) and Jay Strader (CfA) [2008]
Winds detected in metal-poor stars
He I 10830Ǻ ubiquitous in
warm stars
Frequent extension
to ~90 km s-1
MV
M ~2x10-9 Msun yr-1
with Graeme Smith (UCSC) and Jay Strader (CfA)
CONCLUSIONS
H-α
reveals increasing outflow velocity
with luminosity.
 Ca K3 suggests accelerating expansion
 Outflows similar for metallicity
[Fe/H] = –1.5 to –2.3
IR-excess giants not distinguishable from
other giants in M15
No ‘superwind’ detected
Mass loss (V ~ Vescape) discovered in rgb, rhb, agb
objects with He I 10830Ǻ