# Questions tagged [cepheids]

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### Lorentz transformation for stars

If a star that has regular pulses(standard candle) is flying away from us at relativistic velocity(very distant), would that pulses look like very sluggish compared to a non-relativistic velocity(...
110 views

### How does the Hubble Space Telescope “Drift and Shift”?

The Phys.org article Mystery of the universe's expansion rate widens with new Hubble data says: Astronomers have been using Cepheid variables as cosmic yardsticks to gauge nearby intergalactic ...
87 views

### Classification and discovery of stars

How do astronomers find the difference between a 'Cephid Variable Star' and distinct normal stars with opaque objects blocking it's light, like stars with planets revolving around them while both ...
135 views

### Type I delta-Cepheid star, calculation of apparent maginute and luminosity

I am curious to see if I have calculated this correctly: A Type I delta-Cepheid star with a one month (30day) period is put at the distance of the star Vega. a) Determine the apparent magnitude ...
178 views

### Deriving phase of a pulsating star from list of Julian date values of observing brightness

I want to convert the list of Julian date values of observing brightness of a Cepheid variable into its phase. The equation I found in the Internet is the following: \mathrm{Phase}= \frac{\mathrm{...
829 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 ...
400 views

### How do we know that the intrinsic brightness of Cepheid variables corresponds to their period?

As I understand it, beyond parallax the next way of estimating the distance to astronomical objects is by using a relationship between the period and intrinsic luminosity of Cepheid variables. How do ...
68 views

### Interstellar reddening for Cepheids

How were interstellar reddening values for cepheid first calculated? I mean, other than using the derived equation to get extinction-corrected magnitude of Cepheids, I want to know how to drive them ...
63 views

### Calculating angular diameter amplitude from angular diameter variations of Cepheid variable

I'm a high school student but have as much interests in Cepheid variable as the professionalists. I'm trying to derive independent distances to Cepheid with the Baade-Wesselink method. I got the ...
55 views

### Using the surface-brightness relation for Cepheids

I'm a high school student who is doing research about Cepheid variables. I'm in the process of deriving distance to Cepheid using the Baade-Wesselink method, which utilises the surface brightness ...
588 views

### Did Gaia actually generate complete light curves for 212 Cepheids in other galaxies?

The recent BBC news item Gaia clocks speedy cosmic expansion says that a recent Gaia measurement of 212 Cepheid variables in other galaxies within the local group yields a Hubble constant of ~73 km/s/...
128 views

### Which software is appropriate to integrate radial velocity with respect to time [closed]

I'm a high school student and currently I'm trying to use Baade-Wesselink method to independently derive period-luminosity relation of Cepheid variables. I noticed that to get the linear radius ...
113 views

### Integrating radial velocity with respect to time

I'm a highschool student who is writing a research paper about plotting Period-Luminosity graph of the Cepheid variables by deriving distance through independent method such as trigonometric parallax ...
443 views

### Pulsation Modes of Cepheids

There are various modes of Cepheids like single modes: fundamental (F), first overtone (1O), and likewise. And then we have double modes: F/1O, 1O/2O etc. triple modes: 1O/2O/3O etc. What ...
66 views

### How to calculate a phase shift in the process of deriving Baade-Wesselinke distance?

The above is the equation used in the Baade-Wesselink method to independently get distances to Cepheid variables (in the process of deriving Period-Luminosity relation). According to the paper New ...
157 views

### Distance of extra-galactic Classical Cepheids

There have been many questions and answers about finding the distance of a star from the earth. But as I did some research on the net, I found that we have specific approaches for finding the ...
52 views

### Change in angular diameter of Cepheid variables

I'm a highschool student and in the process of writing a research paper of deriving period-lumniosity relation of Cepheid variable independently of the pre-existing PL relation. Thus, I need to derive ...