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Binary system with both components variable


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I wish there were a celebrated example of a system where both stars were variable! I can only imagine how spectacular that must be for us to observe from Earth... and how even more spectacular it must be for dwellers of such an exotic two-sun system (if they exist smile.gif )..

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I wish there were a celebrated example of a system where both stars were variable!

What about Mira (the secondary is visible with moderate amateur instruments ... it's a white dwarf which is variable due to accretion from the material being blown away from the red giant primary, and has its own variable star name VZ Ceti).

Celebrated, maybe not, but all the cataclysmic variables (novae, dwarf novae, symbiotic stars like Z And) have intrinsic variability in both components ... some of them are eclipsing binaries too (U Gem, IP Peg).

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I did think about those. They're either too faint or they're non-intrinsic. Even Mira is a really close pair, at less than 3/4 of one arc-second apart in separation..

I calculated there are some 25,000 stars across the sky brighter than magnitude 8.

Now imagine two pulsating, cepheid type variables, each fluctuating by one whole magnitude and both of 6th and 7th magnitudes (primary and secondary) orbiting each other with an angular separation of 10 arc-seconds. That would be a delightful pair of binary variable stars that I'd watch night after night without miss.

Out of 25,000 stars in the sky brighter than magnitude 8, with at least 60% of them in multiple systems, I find it quite astonishing that we don't have even ONE PAIR that could be as celebrated as this example! LOL..

Edited by Starfleet
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imagine two pulsating, cepheid type variables, each fluctuating by one whole magnitude and both of 6th and 7th magnitudes (primary and secondary) orbiting each other with an angular separation of 10 arc-seconds.

Cepheids are rapidly evolving, you would only get a pair of Cepheids if the stars were of identical mass ... this is vanishingly unlikely to happen. If you have a Cepheid in a binary system, the other component is almost certainly going to be a low mass dwarf star which is still on the main sequence, or a white dwarf that has already completed its evolution. Cepheids are intrinsically bright objects (we can see them in distant galaxies, which is why they're useful as "standard candles") so red/orange or white dwarf stars in the system are going to be many magnitudes fainter.

And an angular seperation of 10 arc sec, at the distance of an apparently 6th magnitude Cepheid (into kiloparsecs) would in any case mean that the stars were an optical double rather than a genuine binary system.

There are a few bright double star systems where both stars are A type main sequence stars, pulsating due to instability in their outer layers because the ionization temperature of hydrogen occurs very close to their surfaces. (Delta Scuti type variables) But the amplitudes tend to be very small, not obvious to visual observation.

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