SLEUTHING MASS OUTFLOW FROM EVOLVED STARS Optical/IR Spectroscopy from the MMT, KECK II, and...
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Transcript of SLEUTHING MASS OUTFLOW FROM EVOLVED STARS Optical/IR Spectroscopy from the MMT, KECK II, and...
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), andGraeme 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
Contribution functions for a metal deficient giant star
Diagnostics of atmospheric motions
Need to know where the diagnostic forms….
MMT/Hectochelle observations of globular clusters: M13, M15, & M92
240 fibres available to capture spectrain selected orders: H-α and Ca II (H&K)
Ca K in M13
H-α in M92Bisectors marked
Sz. Meszaros et al. 2008, 2009
Outflow velocities (H–α)increase with luminosity,and are higher for AGB stars
No dependence on [Fe/H]
H–α Bisector Velocities
Stars with IR excess in M15 (Spitzer) show same outflow velocity as other red giants
Meszaros et al 2008
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
M ~2x10-9 Msun yr-1
MV
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