Questions tagged [stellar-astrophysics]

Questions about inducing chemistry, physics, and many more branches of science into astronomy.

16 questions with no upvoted or accepted answers
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What was the absolute limit to the possible sizes of the first stars formed from “primordial material with no metals”?

This answer to Why don't or (can't) stars be more than 325 or so times the mass of the sun? What limits their size? includes the following: ...The upper limit you refer to is for compositions similar ...
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41 views

How does SOHO know what's going on in the sun's magnetic feild?

SOHO can image the sun's magnetosphere. I don't have the foggiest idea how they manage it, because at most a satellite can have a single compass, and measure one point in the magnetic field. I thought ...
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49 views

Strength of core-envelope coupling in stars

For a star with a given Zero-Age Main Sequence (ZAMS) mass, as a function of metallicity how strongly is the star's core coupled to its envelope? I understand that the core-envelope boundary is only (...
2
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28 views

Is the magnetic field strength of a star predictable from mass, composition, age and angular momentum alone?

This answer to Which stellar properties can we describe as “first principles” in which we can derive the rest? contains an intriguing bit: That states that composition and mass are the two key ...
2
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33 views

Paper recommendations for career guidance

I'm an undergraduate student in astronomy and I'm one year from graduating, but I feel I still can't choose what career path I want to pursue. To date I've only had two courses of proper astrophysics ...
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52 views

To which extent is optically thick photon transport related to conduction?

When speaking about energy transport, the textbook, physics-101 always lists three possibilities: radiation convection conduction Now when studying radiation transport in (stellar) atmospheres and ...
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82 views

Where can I find raw text, ascii, or binary data from the GALEX satellite?

I am looking for stars in the GALEX data through the GALEX data using GALEXview and plugging in their Henry Draper Numbers http://galex.stsci.edu/galexview/ But the task is tedious by hand. Is there ...
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46 views

What does the Sun “look like” below 100 MHz?

Radio2space.com's The Radio Sun says: At very low frequencies (below 0.1 GHz) and therefore at very long wavelengths (> 3m) the solar disk appears much bigger and brighter in the center, and its ...
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24 views

Period of pulsation of a star and its relation to free fall and acoustic waves

In this paper, the period $\Pi$ of pulsation for a star can be obtained by means of the virial theorem: $$\Pi = 2\pi\sqrt{\frac{sR^3}{(3\gamma - 4)qGM}}$$ where $s$ and $q$ are constants relating to ...
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34 views

Relation between oscillator strengths $\log{gf}$ and the Einstein $A$-coefficient, rotational quantum number,

I'm analyzing the spectra of M dwarfs. Some authors characterize the lines with the oscillator strengths $\log{gf}$ while others follow different paths with the Einstein $A$-coefficient. I would like ...
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62 views

Compute the total stellar mass of galaxy with major influence of Red Giants luminosity

Suppose that all stars in this galaxy were born in a single major-merger burst event about 10 Gyr ago If the luminosity in the B band (absolute magnitude in B-band is equal to -21.22) is dominated by ...
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16 views

How to determine arrival time delay given dispersion measure?

In an online textbook, the following formula is given to calculate the arrival time delay between two frequencies, $v_1, v_2$ in a dispersed radio pulse: $$t_1 - t_2 = 4.15 \cdot DM [(v_1/\text{GHz})^{...
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26 views

What is the highest redshift a galaxy with a known stellar mass can be observed?

As part of my research, I would need the following information which it seems I cannot find it in literature. I would like to know what are the highest redshifts at which $10^{7}$, $10^{8}$, and $10^{...
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30 views

Binary star system effects at the barycenter

I haven't been able to find anything on this so far. Using Alpha Centauri as the study, what events/effects ( if any ) would happen between the two stars? More specifically, between the gravitational ...
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22 views

Calculate rest flux density from emitted flux density derived from fits data of SDSS data tool

Say I have a spectrum of a galaxy at a redshift z, with flux density units of erg/s/cm^2/Angstrom. I'd like to convert flux density(in the same units) at z=0, i.e. at its rest it's rest emisison. How ...
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46 views

Theoretical values of radius and mass of O9.5 II star

Where to find please theoretical values of radius and mass of O9.5 II star? I mean something like in this article. However, there are only O I, O III and O V stars in this article.