Astrophysics Research Projects: massive star winds, x-ray emission, theoretical models,...
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![Page 1: Astrophysics Research Projects: massive star winds, x-ray emission, theoretical models, spectroscopy, laboratory plasma astrophysics David Cohen on leave.](https://reader030.fdocuments.in/reader030/viewer/2022032522/56649d625503460f94a4483a/html5/thumbnails/1.jpg)
Astrophysics Research Projects: Astrophysics Research Projects: massive star winds, x-ray emission, theoretical models, massive star winds, x-ray emission, theoretical models,
spectroscopy, laboratory plasma astrophysicsspectroscopy, laboratory plasma astrophysics
David CohenDavid Cohen
on leave 2007-08…but projects for on leave 2007-08…but projects for the next few yearsthe next few years
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The most massive, luminous stars in the galaxy…The most massive, luminous stars in the galaxy…
……have powerful radiation-driven have powerful radiation-driven stellar windsstellar winds..
eta Carinaeta Carina
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The The ChandraChandra X-ray Observatory (artist’s conception) X-ray Observatory (artist’s conception)
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Model of wind x-ray emission and absorption (visualization: left; Model of wind x-ray emission and absorption (visualization: left; resultant X-ray emission line profile: right; data: inset)resultant X-ray emission line profile: right; data: inset)
Contours of constant optical depth Contours of constant optical depth (observer is on the left)(observer is on the left)
wavelengthwavelength
redblue
brig
htne
ss
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The basic wind-profile modelThe basic wind-profile model
Ro=1.5
Ro=3
Ro=10
=1,2,8
key parameters: key parameters: RRoo & & **
€
∗≡κM
⋅
4πR∗v∞
j ~ 2 for r/R* > Ro,
= 0 otherwise
€
=∗R∗dz'
r'2 (1− R∗r ')β
z
∞
∫
• Adjust the model parametersAdjust the model parameters
• Fit the dataFit the data
• Derive the physical properties of Derive the physical properties of the wind from the x-ray line profilesthe wind from the x-ray line profiles
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* = 2.0
Ro = 1.5
Pup: Fe XVII line at 15.014 Å - Chandra
Major science result: less absorption than expected - stellar wind mass-loss Major science result: less absorption than expected - stellar wind mass-loss rates have been overestimated (Roban Kramer, ‘03); Kramer, Cohen, & rates have been overestimated (Roban Kramer, ‘03); Kramer, Cohen, &
Owocki, Owocki, Ap.JAp.J., 592, 532; Cohen et al., ., 592, 532; Cohen et al., MNRASMNRAS, 368, 1905., 368, 1905.
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Could Could clumpingclumping in the stellar wind play a role? in the stellar wind play a role?
We’ve been making theoretical models We’ve been making theoretical models of wind clumping and analyzing its effect of wind clumping and analyzing its effect
on x-ray line profiles.on x-ray line profiles.
Owocki & Cohen, Owocki & Cohen, Ap.JAp.J., 648, 565., 648, 565
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hh = ( = (LL33//ℓℓ22) = ) = ℓℓ//ffwhere where hh, the ‘porosity , the ‘porosity
length’ is the key length’ is the key parameter; parameter; ℓ ℓ is the is the
clump size andclump size and f f is the is the volume fraction filled volume fraction filled
by clumpsby clumps
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hh = ( = (LL33//ℓℓ22) = ) = ℓℓ//ff
h’ = 0.5
h’ = 1.0h’ = 1.0
h’ = 2.0h’ = 2.0
h h = h’r= h’r
Models in the same Models in the same row have the same row have the same effect on x-ray line effect on x-ray line profiles.profiles.
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hh = ( = (LL33//ℓℓ22) = ) = ℓℓ//ff
f = 0.1f = 0.1
f = 0.2f = 0.2
f = 0.05
Models on the same Models on the same diagonal have the diagonal have the same effect on other same effect on other mass-loss mass-loss diagnostics.diagnostics.
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Pup
1 Ori C
ChandraChandra spectra of massive stars: survey of trends spectra of massive stars: survey of trends
11 Ori C: hotter plasma, narrower emission lines Ori C: hotter plasma, narrower emission lines
Pup (O4 I): cooler plasma, broad emission linesPup (O4 I): cooler plasma, broad emission lines
Cohen, Cohen, IAU Symposium 250IAU Symposium 250, Cambridge Univ. Press, 2008, Cambridge Univ. Press, 2008
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Pup
1 Ori C
Si XIII
Si XIVSi XIVMg XIMg XIMg XIIMg XII
H-likeH-like//He-likeHe-like ratio is temperature sensitive ratio is temperature sensitive
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Pup
1 Ori C
Si XIII
Si XIVSi XIV
The young O star – The young O star – 11 Ori C – is hotter Ori C – is hotter
Mg XIMg XIMg XIIMg XII
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Laboratory AstrophysicsLaboratory Astrophysics
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Creating an X-ray photoionized nebula in the laboratory: Creating an X-ray photoionized nebula in the laboratory:
Imploding wire array experiments on the Z-machine at Imploding wire array experiments on the Z-machine at Sandia National LaboratorySandia National Laboratory
Mike Rosenberg’s (‘08) honors thesisMike Rosenberg’s (‘08) honors thesis
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Swarthmore Spheromak Experiment: Swarthmore Spheromak Experiment: magnetic reconnection in solar and space magnetic reconnection in solar and space
plasmasplasmas
Using x-ray and UV spectroscopy to diagnose Using x-ray and UV spectroscopy to diagnose the plasma temperature and kinematicsthe plasma temperature and kinematics
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Vernon Chaplin’s Vernon Chaplin’s (‘07) honors (‘07) honors thesis…and thesis…and Physics of PlasmasPhysics of Plasmas paper.paper.
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We calculate We calculate model UV/x-ray model UV/x-ray spectra and spectra and compare them to compare them to the data collected the data collected with various with various spectrometers in spectrometers in the SSX labthe SSX lab
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Theoretical modeling: computers, white boardTheoretical modeling: computers, white board
Data (mostly high-energy spectroscopy): from space; Data (mostly high-energy spectroscopy): from space; from the SSX lab (and the Z-machine at Sandia)from the SSX lab (and the Z-machine at Sandia)
By next year… optical spectroscopy with By next year… optical spectroscopy with our new 24-inch telescope on the roof of our new 24-inch telescope on the roof of the Science Centerthe Science Center
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This could This could be you in be you in summer summer 2009…but 2009…but maybe maybe without the without the flannel shirt.flannel shirt.