Astrophysics Research Projects: massive star winds, x-ray emission, theoretical models, spectroscopy, laboratory plasma astrophysics David Cohen on leave.

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Presentation transcript:

Astrophysics Research Projects: massive star winds, x-ray emission, theoretical models, spectroscopy, laboratory plasma astrophysics David Cohen on leave …but projects for the next few years

The most massive, luminous stars in the galaxy… …have powerful radiation-driven stellar winds. eta Carina

The Chandra X-ray Observatory (artist’s conception)

Model of wind x-ray emission and absorption (visualization: left; resultant X-ray emission line profile: right; data: inset) Contours of constant optical depth (observer is on the left) wavelength red blue brightness

The basic wind-profile model R o =1.5 R o =3 R o =10   =1,2,8 key parameters: R o &  * j ~  2 for r/R * > R o, = 0 otherwise Adjust the model parameters Adjust the model parameters Fit the data Fit the data Derive the physical properties of the wind from the x-ray line profiles Derive the physical properties of the wind from the x-ray line profiles

 * = 2.0 R o = 1.5  Pup: Fe XVII line at Å - Chandra Major science result: less absorption than expected - stellar wind mass-loss rates have been overestimated (Roban Kramer, ‘03); Kramer, Cohen, & Owocki, Ap.J., 592, 532; Cohen et al., MNRAS, 368, 1905.

Could clumping in the stellar wind play a role? We’ve been making theoretical models of wind clumping and analyzing its effect on x-ray line profiles. Owocki & Cohen, Ap.J., 648, 565

h = (L 3 / ℓ 2 ) = ℓ /f where h, the ‘porosity length’ is the key parameter; ℓ is the clump size and f is the volume fraction filled by clumps

h = (L 3 / ℓ 2 ) = ℓ /f h’ = 0.5 h’ = 1.0 h’ = 2.0 h = h’r Models in the same row have the same effect on x-ray line profiles.

h = (L 3 / ℓ 2 ) = ℓ /f f = 0.1 f = 0.2 f = 0.05 Models on the same diagonal have the same effect on other mass-loss diagnostics.

 Pup  1 Ori C Chandra spectra of massive stars: survey of trends  1 Ori C: hotter plasma, narrower emission lines  Pup (O4 I): cooler plasma, broad emission lines Cohen, IAU Symposium 250, Cambridge Univ. Press, 2008

 Pup  1 Ori C Si XIII Si XIV Mg XI Mg XII H-like/He-like ratio is temperature sensitive

 Pup  1 Ori C Si XIII Si XIV The young O star –  1 Ori C – is hotter Mg XI Mg XII

Laboratory Astrophysics

Creating an X-ray photoionized nebula in the laboratory: Imploding wire array experiments on the Z-machine at Sandia National Laboratory Mike Rosenberg’s (‘08) honors thesis

Swarthmore Spheromak Experiment: magnetic reconnection in solar and space plasmas Using x-ray and UV spectroscopy to diagnose the plasma temperature and kinematics

Vernon Chaplin’s (‘07) honors thesis…and Physics of Plasmas paper.

We calculate model UV/x-ray spectra and compare them to the data collected with various spectrometers in the SSX lab

Theoretical modeling: computers, white board Data (mostly high-energy spectroscopy): from space; from the SSX lab (and the Z-machine at Sandia) By next year… optical spectroscopy with our new 24-inch telescope on the roof of the Science Center

This could be you in summer 2009…but maybe without the flannel shirt.