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Sabina Sagynbayeva @sabinastro.bsky.social · 5h

Polka-dotted Stars II: Starspots and obliquities of Kepler-17 and Kepler-63

Starspots trace stellar magnetic activity and influence both stellar evolution and exoplanet characterization. While occultation-based spot analyses have been applied to individual systems, comparativ...

arxiv.org

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Sabina Sagynbayeva @sabinastro.bsky.social · 2d

This breakfast looks so goodddd🤤

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Sabina Sagynbayeva @sabinastro.bsky.social · 2d

I love this little support group that we virtually created with @astroshashank.bsky.social and @benjaminpope.bsky.social 🫶🏻 haha

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Sabina Sagynbayeva @sabinastro.bsky.social · 2d

Omg that was my attempt 8 months ago 🤣 the actual model code is in Zenodo: doi.org/10.5281/zeno...
But I do need to update my github repo! And I mostly used celerite but I do want to clean up and create a notebook with notes on sampling and stuff. :)

Rotation Periods for Stars in Open Cluster NGC 6819 From Kepler IRIS Light Curves

Samples from the gyrochrone fitting with a Mixture Model from the paper Rotation Periods for Stars in Open Cluster NGC 6819 From Kepler IRIS Light Curves from Sagynbayeva, Colman, & Farr 2025.'gyrochr...

doi.org

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Reposted by Sabina Sagynbayeva

Michael Zingale @michaelzingale.bsky.social · 3d

I like my plot of equipotentials a lot, but I can never shake the fact that @sabinastro.bsky.social calls it the Teenage Mutant Ninja Turtle plot...

zingale.github.io/stars/notebo...

a plot of equipotentials in a binary star system, showing the Roche lobes and Lagrange points. The green color scheme makes it look like a teenage mutant ninja turtle...

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Sabina Sagynbayeva @sabinastro.bsky.social · 3d

Will never unsee it

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

Anyways, like, comment, and hire me PLEASE!!!

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

In the end, we have a beautiful gyrochrone that you should take with a grain of salt just like any other gyrochronal sequence! Also my sample is the largest sample of rotation periods in an open cluster to date! Yay!

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

So if you assume that the uncertainties in period in period and temperature are gaussian, you can imagine that the point is sliding in those error bars until it decided whether to fall on our 5th order Legendre polynomial or not.

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

So the mixture model took the probability weights, and assigned some stars to the background based on their location in the period-temperature space. But we accounted for uncertainties in period and temperature too!

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

Instead, I wrote a Bayesian mixture model. The premise of the model is that some of the stars lie on the gyrochrone, but some of the are what we called “background stars”.

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

For gyrochrone, I wanted to just fit a quick polynomial but Will said he’d remove his name from the paper if I did that. 😂

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

We had to make some quality cuts, remove giants, and we were left with 271 reliable rotations.

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

So to account for that, my GP kernel was a sum of the Rotation term (i.e. the period) and the term that you can think of as a RealTerm in celerite so that it models the red noise.

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

I used gaussian processes to create a Bayesian model to extract periods from pretty low-amplitude light curves. We looked at PSDs and they still had this exponential decline that was the “red noise” in the data.

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

Getting periods from the crowded fields is HARD! So Isabel had to do her own photometry with superstamps, Will came up with a new-ish de-trending method, and I was left with maximizing likelihoods! 😄

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

Wuick thread while I am on the train!

Sabina Sagynbayeva @sabinastro.bsky.social · 6d

Okay people, welcome my new paper into the world!!! With Isabel Colman and @farrwill.bsky.social

arxiv.org/abs/2510.02255

Rotation Periods for Stars in Open Cluster NGC 6819 From Kepler IRIS Light Curves

We present an updated catalog of stellar rotation periods for the 2.5 Gyr open cluster NGC 6819 using the Kepler IRIS light curves from superstamp data. Our analysis uses Gaussian Process modeling to ...

arxiv.org

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

Okay people, welcome my new paper into the world!!! With Isabel Colman and @farrwill.bsky.social

arxiv.org/abs/2510.02255

Rotation Periods for Stars in Open Cluster NGC 6819 From Kepler IRIS Light Curves

We present an updated catalog of stellar rotation periods for the 2.5 Gyr open cluster NGC 6819 using the Kepler IRIS light curves from superstamp data. Our analysis uses Gaussian Process modeling to ...

arxiv.org

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Reposted by Sabina Sagynbayeva

arXiv bot (astro-ph) @krxiv-astro-ph.bsky.social · 6d

Rotation Periods for Stars in Open Cluster NGC 6819 From Kepler IRIS Light Curves
https://arxiv.org/pdf/2510.02255
Sabina Sagynbayeva, Isabel L. Colman, Will M. Farr.

https://arxiv.org/abs/2510.02255

arXiv abstract link

arxiv.org

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Sabina Sagynbayeva @sabinastro.bsky.social · 6d

Some proposals are so short, and my only hope is that all the exoplaneteers in Physics departments have emailed their colleagues a schematic of transits so now everyone is on the same page lmao

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Sabina Sagynbayeva @sabinastro.bsky.social · 7d

I’m addicted to plasma I fear

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Reposted by Sabina Sagynbayeva

Shashank Dholakia @astroshashank.bsky.social · 8d

New paper by me and @benjaminpope.bsky.social! How well can we map a star using optical interferometry?

This is just a submitted preprint at the moment--comments and questions welcome! (1/N)

arxiv.org/abs/2509.25433

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Sabina Sagynbayeva @sabinastro.bsky.social · 8d

Am I having a deja vu?😂

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Reposted by Sabina Sagynbayeva

AAUP @aaup.org · 9d

BREAKING: WE WON!!!
💥 💥 💥

Federal Judge William G. Young ruled today in our lawsuit against the Trump administration that the policy of arresting, detaining, & deporting noncitizen students & faculty members for their pro-Palestinian advocacy violates the 1st Amendment.

Full ruling here:

Findings of Fact & Conclusions of Law – #261 in American Association of University Professors v. Rubio (D. Mass., 1:25-cv-10685) – CourtListener.com

Judge William G. Young: ORDER entered. FINDINGS OF FACT AND RULINGS OF LAW, PURSUANT TO FED. R. CIV. P. 52(A)(Sonnenberg, Elizabeth) (Additional attachment(s) added on 9/30/2025: # 1 Main Document) (J...

www.courtlistener.com

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Sabina Sagynbayeva @sabinastro.bsky.social · 10d

Super excited about my new paper coming soon with Isabel Colman and @farrwill.bsky.social !! This project quickly became another statistics bootcamp for me. 😅

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