Questions tagged [variable-star]

Questions regarding stars that undergo changes in their spectra, temperature, or luminosity.

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What element drives pulsations in T Tauri Stars?

What element drives pulsations on T Tauri stars? I understand that T Tauri stars are variable and pulsate, and I also know that other stars pulsate as well. My thinking is that a T Tauri star would ...
Astrovis's user avatar
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2 votes
1 answer
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Tracking variable stars?

Is there a website or application I can use do track the brightness of variable stars and notify of any unusual or particularly spectacular changes. I am particularly interested in tracking the blaze ...
Harrychink's user avatar
7 votes
2 answers
498 views

Does the expansion and contraction of a variable star affect the measured radial velocity?

I've measured the heliocentric radial velocity of Beta Cephei using the doppler shift of the helium lines, I corrected for earth's motion using the doppler shift of the oxygen in the atmosphere. I ...
Jackson's user avatar
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3 votes
1 answer
152 views

Period-Luminosity Relation of Cepheids via Gaia Data

I was trying to verify Leavitt's Law of Period Luminosity Relationships of Cepheid Variables using Gaia data. To do this I calculated the period using the Lomb Scargle Periodogram for 1450 stars and ...
Ambica Govind's user avatar
6 votes
1 answer
584 views

Intuitive connection between the periods of oscillation of Betelgeuse and the elemental concentrations at its core? (Betelgeuse; Saio et al. (2023))

Preamble (yes it's long, but it's part of this question's premise, so need to spell it out) Dr. Becky's recent video New study claims Betelgeuse supernova IMMINENT (decades not centuries!) | Night Sky ...
uhoh's user avatar
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Computing Algol's apparent magnitude from TESS observation data

A helpful developer downloaded a light curve of Algol from STScI's MAST service of the TESS archive for me. Its content looks like this: ...
velkyvont's user avatar
1 vote
0 answers
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Minima of variable stars

There's a handy website showing the minima of Algol. Is there such a website for other variable stars? Or could you give me a code for computing the minimum of a variable star?
velkyvont's user avatar
1 vote
3 answers
134 views

Getting (variable) apparent magnitude of Algol

I've heard that in ancient Egypt they had a calendar to determine the lucky and less lucky days, which alternated approximately every 2.8 days. According to researchers, this may have been related to ...
velkyvont's user avatar
2 votes
0 answers
60 views

Finding the uncertainty in period for String-Length Minimization calculation

I wrote a Python script that calculates the period of an unevenly sampled data set using the String-Length Minimization method. You can read about that method here: A period-finding method for sparse ...
Zachary Kennedy's user avatar
8 votes
2 answers
224 views

What are the twinkling stars in the New Horizons Arrokoth approach?

I've circled them in this edit: Source: https://commons.m.wikimedia.org/wiki/File:New_Horizons_Approach_to_Arrokoth.ogv Note, this has generated frames, see the source....
Rabbi Kaii's user avatar
2 votes
1 answer
325 views

How does one actually fold a light curve?

I'm studying the variable stars (periodic variables with brightness changes repeating over time), and to examine the shape of the light curve it is useful to fold the data points at this period and ...
Saturn.'s user avatar
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What determines how accurate a particular method is at finding the period between Lomb-Scargle and String Length Minimization?

I've been using the Lomb-Scargle and String Length Minimization methods to find the periods of various astronomical objects with unevenly spaced data. I wanted to see if I could find any patterns ...
Zachary Kennedy's user avatar
6 votes
1 answer
83 views

Other than Lomb-Scargle Periodograms and String Length Minimization, what other methods can be used to find the period of unevenly spaced data?

I'm doing some research into how different methods of finding the period with unevenly spaced data compare with each other. So far, I've looked at the Lomb-Scargle and String-Length Minimization. I ...
Zachary Kennedy's user avatar
1 vote
0 answers
44 views

(Wikipedia) UY Scuti: variable apparent magnitude, non-variable absolute magnitude?

According to https://en.wikipedia.org/wiki/UY_Scuti Apparent magnitude (V) 8.29 - 10.56 Absolute magnitude (MV) −6.2 UY Scuti, being a variable star, obviously has variable apparent magnitude; ...
Cheng's user avatar
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1 answer
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What does a fitted curve for the period of a variable star, tell me about the star?

If I have enough data of a variable star to make a light curve for it's whole period, and If I fit a function to that light curve, can that fitted function tell me anything about the properties of ...
Zachary Kennedy's user avatar
2 votes
0 answers
32 views

Database of distant stars

I'm writing a report on using machine learning techniques in astrophysics. I'd like to perform 3 tasks: Generating a Hertzsprung-Russel diagram and clustering the results into the main types of stars ...
John Miller's user avatar
10 votes
1 answer
112 views

How do astronomers distinguish between Cepheids and other types of variable stars?

So my understanding of how Cepheid is used as standard candle to determine distance of galaxies is like this: Astronomers observe a galaxy, notice an object within that galaxy whose brightness ...
mudiwii's user avatar
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5 votes
1 answer
135 views

How do you tell if a variable star is periodic or not by its light curve?

I have light curves for a particular star. I'm able to construct a periodogram of the stars' light curve, a plot of the power of the light curve vs. the signal's period. For a nonperiodic but ...
tgs123's user avatar
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1 vote
1 answer
82 views

What is an actual value for the Eddington pulsation constant?

What numerical value does the pulsation constant $Q$ take in the formula that Eddington derived for variable stars: $$P\sqrt{\rho} = Q,$$ where $\rho$ — average star density, $P$ — period?
Александр Иванов's user avatar
1 vote
1 answer
53 views

What is the period of Gamma Cassiopeiae?

Gamma Cassiopeiae is a variable star whose magnitude changes between 1.6 and 3. On what timescale does it vary? The Wikipedia page says that it is irregular, but what is the timescale of its ...
usernumber's user avatar
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1 vote
1 answer
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What is the unit for durations on the AAVSO website?

The AAVSO website has a page for observers with binoculars. On this page, there is a table with stars of interest, and the period of each variable is indicated. However, the unit for the period is not....
usernumber's user avatar
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2 votes
1 answer
48 views

Be stars - short variations

The origin of short-times variations in the brightness of Be stars is not clear. Some researchers consider them a consequence of non-radial pulsations. Some researchers consider them a consequence of ...
Elena Greg's user avatar
2 votes
0 answers
55 views

Spurious periods of stars

What exactly is meant by spurious periods of stars? E. Tanner writes in Spurious Periods in Spectroscopic Binaries in 1948 Furthermore: Can spurious periods be produced by aliasing, and how can they ...
Junaid Ihsan's user avatar
3 votes
0 answers
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What is the theoretical maximum variability a pulsating red giant can have such that a habitable planet can stay habitable for long periods of time?

I was reading about red giants and came across this statement: Some research suggests that, during the evolution of a 1 M☉ star along the red-giant branch, it could harbor a habitable zone for ...
WarpPrime's user avatar
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0 votes
2 answers
98 views

Frequency analysis on Semiperiodic object(s) using Lomb-Scargle

So I already did a frequency analysis of the SRv-type's light curve using Period04. I already have the 'periodicities' of the object/star of choice which is quite hard since the latter/other periods ...
CGHA's user avatar
  • 105
2 votes
0 answers
172 views

Why do the pulsations of a Cepheid variable occur?

I understand the theory of the mechanism by which Cepheid variables pulsate, where helium is ionised and deionised, leading to changes in diameter. However, I am unsure if the brightness changes due ...
Matthew H's user avatar
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3 votes
2 answers
95 views

Calibrating raw photometric measurements

So I have a photometry data sourced from Solar Mass Ejection Imager's (SMEI) server as an ‘add-on data’ for my point source of interest (a variable star) with a 104 minute cadence. However, it’s not ...
CGHA's user avatar
  • 105
3 votes
2 answers
75 views

Delta Velorum - non-observed variable star

I am a beginner variable star observer from the Southern Hemisphere (but with experience in astronomy) and, when I was looking for VS to observe, I saw that Del Vel has almost no observations. Thus, ...
Vitor Z.'s user avatar
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How do you correct the Period-Luminosity relationship for metallicity?

Refer to the link: https://www.astro.utoronto.ca/DDO/research/cepheids/cepheids.html Tha author has used the relationship $M_V=-2.902log(P)-1.203$. It is mentioned that this is not corrected for ...
Kushagra's user avatar
-1 votes
1 answer
163 views

How is V1057 Cygni supposed to go from K type dwarf to F type giant?

FU Orionis variables are protostars that go through massive outbursts that drastically change the star's spectral type and magnitude. With the star V1057 Cygni, this star was known to go from a K type ...
WarpPrime's user avatar
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2 votes
0 answers
56 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 ...
Dave Gremlin's user avatar
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1 vote
2 answers
522 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 ...
usernumber's user avatar
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2 votes
2 answers
104 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 ...
usernumber's user avatar
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10 votes
1 answer
190 views

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 ...
Leos Ondra's user avatar
  • 1,074
2 votes
1 answer
99 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 ...
Francesco Sollazzi's user avatar
22 votes
1 answer
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 ...
user avatar
3 votes
1 answer
165 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 ...
uhoh's user avatar
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7 votes
1 answer
322 views

Did the late 2019 "fainting" of Betelgeuse show any spectral trends that differ from it's normal variability?

update: (August 2020) 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 ...
uhoh's user avatar
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1 vote
0 answers
130 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 ...
uhoh's user avatar
  • 30.7k
2 votes
1 answer
107 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 ...
dboggs95's user avatar
  • 121
3 votes
1 answer
184 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?
user4437416's user avatar
3 votes
0 answers
27 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?
Boris Safonov's user avatar
3 votes
1 answer
165 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 ...
NeutronStar's user avatar
  • 2,663
2 votes
1 answer
128 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 ...
bandybabboon's user avatar
  • 4,250
0 votes
1 answer
152 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 ...
Dimension Obscura's user avatar
2 votes
1 answer
493 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 ...
NeutronStar's user avatar
  • 2,663
2 votes
2 answers
1k 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.
Dan Wears Prada's user avatar
1 vote
1 answer
2k 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 ...
Potato Comet's user avatar
2 votes
1 answer
183 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 ...
MiscellaneousUser's user avatar