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 This topic has 17 replies, 4 voices, and was last updated 1 year, 4 months ago by Ken Whight.

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22 July 2022 at 6:01 pm #611531Ken WhightParticipant
I attach a paper on modelling the Sun’s photosphere that I would like reviewed. It presents a “simple” model of stellar photospheres that nontheless seems to make a good attempt at predicting spectral properties of a number of stars and in particular delivers good estimates of the pressure and thickness of the Sun’s photosphere.
I think the approach is novel as it makes no use of “oscillator strengths” instead it uses photon capture crosssections calculated from the Einstein A coefficients and properties of equilibrium.Attachments:
1 August 2022 at 4:03 pm #611715Ken WhightParticipantI have also used my software to model the blue component of Albireo in an attempt to separate the absorption and emission components. In the process I can calculate possible thicknesses and corresponding pressures of the star’s photosphere as a function of an “impact Parameter” does this relation look reasonable?
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25 August 2022 at 7:38 pm #612122Mr Jack MartinParticipantKen,
Interesting papers. I don’t see an email address here or on your website to discuss further.
Jack
25 August 2022 at 10:26 pm #612131Ken WhightParticipantHi Jack,
Thanks for your interest, I started this project shortly after I retired and after many frustrating dead ends, as I struggled to understand the physics, I think I finally have the answer to the question “what would a black body photosphere look like spectroscopicly.I’m in the process of writing a followup paper on modelling Albireo B’s disk as a Kepler orbit disk and also have promising initial results for Deneb and Vega in the pipeline.
I would be very interested in discussing this work with you and others particularly if it resulted in some way of estimating the collision parameter to fix the thickness and pressure of a star’s photosphere.
Sent from Samsung Mobile on O2
15 September 2022 at 5:06 pm #612493Ken WhightParticipantI have completed a spectral analysis of Deneb
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29 September 2022 at 3:37 pm #612754Ken WhightParticipantI’m uploading a document that sets out in detail all the theory I’ve used/developed to model thermal equilibrium spectral line profiles. I would like to know if equation 6.32, for photon capture cross section, is correct and if it is correct is it known? If it’s not correct where is the mistake in the derivation and if it is correct and unknown can I claim it as the “Whight relation”!
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1 November 2022 at 2:25 pm #613431Ken WhightParticipantI have also applied my model to Vega
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16 December 2022 at 2:49 pm #614693Ken WhightParticipantI have added 2 more sections to my, modelling spectral line profiles, Theory document:
7.1 MultiLayer Model Extension Applied to the Sun
7.2 Estimating Photosphere Pressure from Surface GravityI hope now to be able to:
1 determine the pressure and thickness of a star’s photosphere
2 obtain a relation between the pressure impact parameter and photosphere temperatureI would welcome a “peer review” of this work.
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25 December 2022 at 8:42 am #614876Ken WhightParticipantHappy Christmas everyone! The theoretical side of my modelling project is complete. I can now make credible estimates of stellar photosphere pressures and thicknesses from Hydrogen Balmer series spectral line profiles. I attach the (hopefully) final version of my paper studying the Sun’s photosphere using my model via reflection spectra off Europa.
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27 December 2022 at 12:12 am #614883Grant PrivettParticipantHave you submitted it to the Journal yet?
27 December 2022 at 4:09 pm #614888Ken WhightParticipantHello Grant. I submitted an early form of my work about 10 years ago (I was trying to separate stellar absorption from decreation ring emission in spectra from the fast rotator Albireo B). It was thoroughly reviewed and was rightly rejected as I had not fully understood all the physics. However since then I believe I have addressed the reviewers concerns and may have new results in the area of opacity (photon capture crosssections) which I believe is still a problematic area (Atomic Astrophysics and Spectroscopy, Anil Pradhan and Sultana N. Nahar). I am also getting good results when applying my methods to a number of stars.
I did try to resubmit a paper on this work about six months ago but it was not forwarded onto review hence these posts. I am hoping that someone with relevant knowledge will review the work and discuss it with me.
Regards
Ken Whight28 December 2022 at 12:04 pm #614897Andy WilsonKeymasterI’ve not delved sufficiently deeply into this aspect of spectroscopy to properly comment. However, I can see it is a detailed and interesting model.
Best wishes,
Andy3 January 2023 at 3:03 pm #614949Ken WhightParticipantHi Andy and thanks for your encouraging post.
When I started this project (about 10 years ago) I tried to deduce the photon capture crosssections purely from the idea that they were proportional to capture rates. The BAA review of my original paper highlighted the fact that the Einstein coefficients needed to be included. This sent me on a bit of a lengthy “wild goose chase” as, although I eventually realised the B coefficients could be expressed in units of area (the same units as crosssections), the variation of the B’s with wavelength was far to strong to reproduce my experimental results for absorption line depths. I only had the Planck and Boltzmann functions plus the B coefficients and various physical constants to play with and I just could not reproduce the Balmer series relative absorption line depths across the various stars I had modelled.
In desperation I returned to my original approach as represented by equation A.4.10 (in my previously attached Europa paper) and deduced equation A.4.15 using my, now fairly detailed, knowledge of Einstein Coefficients. Equation A.4.15 contains Einstein A coefficients which vary much more slowly with wavelength than the B’s and they appear in a summation so are really only converting the expression to the correct units, the variation of relative line depths in the spectral series is being determined by the Boltzmann and Planck functions. This form of crosssection performed well across the stars I had measured.
I would like to know how my analysis compares to the conventional approach using “oscillator strengths and B coefficients but have not managed to find such n analysis in the literature can anyone point me in the right direction?
Regards
Ken Whight9 January 2023 at 4:21 pm #615062Ken WhightParticipantI’ve finished my analysis of the star Albireo B and obtained estimates of the stars photosphere thickness and pressure. I’ll analyse it’s disk in a future paper
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14 January 2023 at 2:28 pm #615124Ken WhightParticipantStudy of Vega/Sirius updated. If anyone wants to play with my software it can be downloaded from my website (www.thewhightstuff.co.uk) and I am happy to guide people throght it.
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20 January 2023 at 1:35 pm #615192Ken WhightParticipantI’ve also looked at Deneb, are my results realistic?
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21 January 2023 at 11:05 pm #615207Ken WhightParticipantHere’s my resulys for Altair
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23 January 2023 at 9:23 pm #615268Ken WhightParticipantStudy of Sulaphat attached. This is the last star I have data for.
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