22 July 2022 at 6:01 pm #611531
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 cross-sections calculated from the Einstein A coefficients and properties of equilibrium.
Attachments:1 August 2022 at 4:03 pm #611715
I 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?
Attachments:25 August 2022 at 7:38 pm #612122Mr Jack MartinParticipant
Interesting papers. I don’t see an email address here or on your website to discuss further.
Jack25 August 2022 at 10:26 pm #612131
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 O215 September 2022 at 5:06 pm #61249329 September 2022 at 3:37 pm #612754
I’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”!
Attachments:1 November 2022 at 2:25 pm #61343116 December 2022 at 2:49 pm #614693
I have added 2 more sections to my, modelling spectral line profiles, Theory document:-
7.1 Multi-Layer Model Extension Applied to the Sun
7.2 Estimating Photosphere Pressure from Surface Gravity
I 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 temperature
I would welcome a “peer review” of this work.
Attachments:25 December 2022 at 8:42 am #614876
Happy 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.
Attachments:27 December 2022 at 12:12 am #614883Grant PrivettParticipant
Have you submitted it to the Journal yet?27 December 2022 at 4:09 pm #614888
Hello 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 cross-sections) 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 re-submit 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.
Ken Whight28 December 2022 at 12:04 pm #614897Andy WilsonKeymaster
I’ve not delved sufficiently deeply into this aspect of spectroscopy to properly comment. However, I can see it is a detailed and interesting model.
Andy3 January 2023 at 3:03 pm #614949
Hi Andy and thanks for your encouraging post.
When I started this project (about 10 years ago) I tried to deduce the photon capture cross-sections 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 cross-sections), 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 cross-section 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?
Ken Whight9 January 2023 at 4:21 pm #615062
I’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
Attachments:14 January 2023 at 2:28 pm #615124
Study 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.
Attachments:20 January 2023 at 1:35 pm #61519221 January 2023 at 11:05 pm #61520723 January 2023 at 9:23 pm #615268
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