How would one estimate the rotation period of a star from its spectrum

AI Thread Summary
The discussion centers on estimating a star's rotation period using its spectral data, specifically observing shifts in flux due to starspots. The "bumps" in the flux profile indicate the movement of a starspot across the star's surface as it rotates. The challenge lies in correlating the observed wavelength shifts to a time scale for accurate rotational period estimation. Reference material, including a figure from Gray's work, is suggested for further understanding. The conversation emphasizes the need for a time-based analysis to derive the rotation period effectively.
SJay16
Messages
19
Reaction score
1
Homework Statement
Using the profiles in Figure 18.29, make an estimate for the rotation period of σ Gem.
Relevant Equations
N/A
Screenshot (156).png

The figure is shown; the measurements were taken on two consecutive observing nights. The Ordinate is the flux normalized to continuum and the abscissa is the wavelength scale. You can see the "bumps" indicated by the arrows referring to some Starspot as the spot moves on the profile; assuming a single time-stable position-stable spot.

The "bumps" slightly shifts, as indicated by the arrows in the top line profile compared to the bottom profile, as the spot "moves across" the surface as the star as it rotates; I'm just not sure how to get an estimate of the rotational period from this given just the wavelength for the abscissa, it would make sense if the abscissa was on a timescale.

Figure reference : Gray, D. (2005). The Observation and Analysis of Stellar Photospheres (3rd ed.), page 498. Cambridge: Cambridge University Press. doi:10.1017/CBO9781316036570
 
Physics news on Phys.org

Thread 'Rolling without slipping on a curved surface'

Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
View full post »

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'A bead-mass oscillatory system problem'

Thread 'A bead-mass oscillatory system problem'

I can't figure out how to find the velocity of the particle at 37 degrees. Basically the bead moves with velocity towards right let's call it v1. The particle moves with some velocity v2. In frame of the bead, the particle is performing circular motion. So v of particle wrt bead would be perpendicular to the string. But how would I find the velocity of particle in ground frame? I tried using vectors to figure it out and the angle is coming out to be extremely long. One equation is by work...
View full post »

Similar threads

What is GJ 1214 b: A Super-Earth Water World Orbiting a Red Dwarf Star?
Replies
1
Views
7K
I Some questions about Cosmic Microwave Background radiation
Replies
13
Views
6K
Estimating the impact of CO2 on global mean temperature
2
Replies
89
Views
37K

Hot Threads

Recent Insights

Back
Top