Questions tagged [variable-star]

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51 views

Is Betelgeuse is continually expelling material on the scale of the 2019/2020 event?

The AUGUST 13, 2020 Phys.org article Results from Hubble suggest that Betelgeuse's recent dimming was due to material ejected from the star says: ...the star's unexpected and significant dimming ...
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0answers
35 views

Why are the W UMa variable subtypes labelled “A” and “W”?

The W Ursae Majoris variables (eclipsing contact binary stars) are divided into the A- and W-types. As described in Wilson (1978) "On the A-type W UMa systems": There are two recognized ...
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2answers
90 views

Why does the Gaia color-magnitude diagram have this shape?

I was looking at the visualization tools of Gaia, and tried plotting a color-magnitude diagram. On the right hand side of the image, photGMeanMag (mag) (the amount ...
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2answers
58 views

How variable does a star have to be, to be a variable star?

Variable stars are stars whose apparent magnitude varies. But there are so many phenomena that can cause a star to be variable, that I would expect all stars to be variable. A rotating star has a ...
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Color index B-V of the dimming Betelgeuse

Using AAVSO light curve generator I have plotted V and B magnitudes of Betelgeuse in the past 150 days to see trend of B-V color index. If dust would be the cause of the recent drop in the star ...
2
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1answer
66 views

What are these data in light curve generator

I'm generating light curves for some variable stars on the AAVSO website (see https://www.aavso.org/lcg ) . I can choose what type of data must be plotted. Can you explain what they are? Thank you in ...
22
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1answer
2k views

Are stars expected to become dimmer before a supernova?

With the recent news about the "fainting" of Betelgeuse and the speculation that this might be a precursor to a supernova, I'm wondering if there is any theoretical/observational basis for this ...
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74 views

When we say a variable star is “fainting” does it mean something more or different than “dimming” or “fading”?

A comment below the question Does the current “fainting” of Betelgeuse show any spectral trends that differ from it's normal variability? suggests that "dimming" would be a better term, but I have a ...
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159 views

Does the current “fainting” of Betelgeuse show any spectral trends that differ from it's normal variability?

update: With all the newest news about including what the Dr. Becky video discusses as linked in How do magnetic fields mess with astronomers' observations? I'll bet this question can now be ...
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0answers
76 views

Why do these photometric observations of Betelgeuse look “quantized” in 0.1 magnitude steps?

The most interesting question related to this Will Kinney tweet would be what's going on with Betelgeuse? but I can't help but wonder why much but not all of the photometric data is clustered in ...
2
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1answer
63 views

Astrophysics of Supernovae - Energy over Distance?

I need this for worldbuilding, but it is a physics question. I want to be able calculate the energy over distance from a hypernova of a variable star like Eta Carinae. Understanding what energy levels ...
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1answer
98 views

Brown dwarf magnetic activity

I have not been able to find an answer to my question through google, and therefore ask it on this medium. Do brown dwarfs have spots and faculae similar to other heavier stars?
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0answers
25 views

Large amplitude dipole pulsator

Consider a semiregular variable with amplitude of 1.5 mag. Is it possible to explain brightness variations by purely dipole pulsations?
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1answer
92 views

What is period doubling in a variable star?

I'm coming across the concept of "period doubling" in RR Lyrae stars. When I look up what period doubling is on the Internet, I find general-level explanations of bifurcations of dynamical systems ...
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1answer
110 views

Are stars beyond the asteroid belt less constant?

If we graph the variability of a small bright star which is lined up with the asteroid belt, is it less constant than stars that are far away from the asteroid belt? To what degree does variability ...
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1answer
106 views

Stopping down a telescope to reduce brightness by 5 magnitudes

Suppose we have a variable star with a change in magnitude between maximum and minimum of 5 mag. How much would you need to stop down a telescope (block some of the area) so that the star at maximum ...
2
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1answer
187 views

What leads to increase in opacity in kappa mechanism?

I understand that the kappa mechanism (that leads to star variability) causes an increase of opacity with increasing temperature in partial ionization zones. However, I'm not sure I understand what ...
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2answers
776 views

Do stars vary their own brightness?

All I could find on the internet was about how stars vary in brightness depending on their distance to Earth, temperature, type of star... But my question is, can a star can change its brightness.
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1answer
920 views

How to find a Cepheid's pulsation period using its graph?

Basically, I've been seeing these graphs that say: Cepheid Period-Luminosity Relation and the Period axis is supposed to be "logarithmic"; How does this graph work? Since the luminosity of a star ...
1
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1answer
101 views

Variable Types of Stars

I'm trying to decode the Variable Types of stars in the Hipparcos Library. I see there are a number of stars for example :- EA/AR - Does that mean the star is both a EA(Eclipsing Binary Star) and AR ...