Sabina Sagynbayeva
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sabinastro.bsky.social
Sabina Sagynbayeva
@sabinastro.bsky.social
1.1K followers 270 following 250 posts
(astro)Physics PhD candidate @ Stony Brook. Astrobites alum. From Kazakhstan 🇰🇿. She/her.

Musical theater nerd, so pretty much insufferable.

Statistics, planets, and stellar cartography.

https://ssagynbayeva.github.io
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sabinastro.bsky.social
It turns out that you need to be “superthermal” in order to retain a disk! This means the ratio q/qthermal>1(where q is the physical mass of the planet, and qth is a thermal mass).
Figure showing nine contour plots arranged in a 3x3 grid comparing quasi-spherical and classical circumplanetary disk models. Each plot shows density (ρgas) patterns with streamlines indicating flow direction. The plots vary by mass (0.3 M, 1 M, 3 M Jupiter masses, shown in columns) and Hill radius ratio (H/R = 0.05, 0.075, 0.1, shown in rows). The color scale ranges from dark blue (lowest density, -3) to dark red (highest density, 3). All simulations are shown at time = 100 orbits. The quasi-spherical models (left side) show more centrally concentrated, roughly circular density patterns, while the classical circumplanetary disk models (right side, highlighted with a black box) display more elongated, disk-like structures with characteristic flow patterns extending horizontally.
May 23, 2025 at 2:11 AM
sabinastro.bsky.social
It turned out that not all of them have the CPD structure after 100 orbits.
Figure showing nine contour plots arranged in a 3x3 grid comparing quasi-spherical and classical circumplanetary disk models. Each plot shows density (ρgas) patterns with streamlines indicating flow direction. The plots vary by mass (0.3 M, 1 M, 3 M Jupiter masses, shown in columns) and Hill radius ratio (H/R = 0.05, 0.075, 0.1, shown in rows). The color scale ranges from dark blue (lowest density, -3) to dark red (highest density, 3). All simulations are shown at time = 100 orbits. The quasi-spherical models (left side) show more centrally concentrated, roughly circular density patterns, while the classical circumplanetary disk models (right side, highlighted with a black box) display more elongated, disk-like structures with characteristic flow patterns extending horizontally.
May 23, 2025 at 2:11 AM
sabinastro.bsky.social
Okay, that’s a lot! A lot of details in the paper, but the last thing I am excited about is that we were able to recover some 3D information of TOI-3884 with a 1D single-band photometry!!!! Thanks to the friends who got the RV data for that star that we could compare to!
May 1, 2025 at 6:20 PM
sabinastro.bsky.social
We applied approach 1 to a star TOI-3884, which is believed to have a polar spot, and we see the polar spot too considering that our priors are very broad and didn’t assume it! We were also able to see the star-planet pretty high degree of misalignment!
May 1, 2025 at 6:20 PM
sabinastro.bsky.social
We also thought of two approaches if the spots are not static: divide your lightcurve into periodic chunks, draw maps for each chunk and 1) infer posterior distributions for this ensemble of chunks assuming they’re independent, or 2) assume that they are related by a linear interpolation. Both work!
May 1, 2025 at 6:20 PM
sabinastro.bsky.social
But the good news is inclination and obliquity of stars are actually *tractable* in transit light curves, and we can infer them along with the starspots properties!
A corner plot showing posterior distributions and covariances between model parameters from a sampling analysis. The diagonal panels display 1D histograms of individual parameters including mu_phi, sigma_phi, r, c, n, P_star, lambda_star, and i_star, with vertical lines marking median and confidence intervals. The off-diagonal panels show 2D contour plots illustrating correlations between parameter pairs, with color-coded confidence regions (yellow to green to purple). Bold black lines indicate the true or reference values for each parameter. This figure visualizes how well the model constrains each parameter and reveals any degeneracies.
May 1, 2025 at 6:20 PM
sabinastro.bsky.social
If you have a star A with a surface map with an obliquity \lambda and inclination i, then if you create the same star but name it B, flip the map and give the star an obliquity -/lambda and inclination (180-i), the stars A and B will have the same light curves!
The top part of the image shows two stars with surface features (dark and bright regions) and labeled 3D coordinate axes (x, y, z). The star on the left has a stellar inclination of 80 degrees and a projected obliquity of -30 degrees. The star on the right has a stellar inclination of 100 degrees and a projected obliquity of 30 degrees. Though the viewing angles are different, the surface patterns look similar from the observer’s point of view. The bottom part of the image is a light curve plot showing relative flux over time. Two light curves—one in black for the left star and one in pink for the right star—overlap almost perfectly, illustrating that different stellar orientations can produce nearly indistinguishable spot-crossing signals.
May 1, 2025 at 6:20 PM
sabinastro.bsky.social
Characterizing staspots (where they are? How big they are?) is *hard* because there are soooo manyyyyy degeneracies at play! But, if the star has a planet, and that planet is transitting then that gives us so much valuable info due to spot-crossing events!
A four-panel diagram illustrates how different stellar surface features affect transit light curves. Each row shows a star and a transiting planet on the left, and the corresponding light curve on the right. a) A uniformly colored star with no planet or features; the light curve is flat, indicating constant brightness. b) A limb-darkened star with a transiting planet; the light curve shows a smooth, symmetric dip. c) A star with a large dark spot; as the planet crosses the spot, the light curve dip becomes asymmetric with a small bump during the transit. d) A star with complex surface features (spots and bright regions); the light curve displays an irregular dip with noticeable variations and wiggles, reflecting the stellar surface complexity.
May 1, 2025 at 6:20 PM
sabinastro.bsky.social
Just wanted to share that Pluto was a SUPERHERO on the plane from NYC to Santa Barbara!! The most patient good boy💗
An orange-white dog sleeping on a lap. There’s a person reading a book on the neighboring seat. Orange-white beagle smiling while seating on the floor of an airport.
January 22, 2025 at 6:49 PM
sabinastro.bsky.social
I met my hero yesterday! He had to wait until I stop crying to take a pic with me!
A picture of a girl with a wide smile wearing a pink coat. She’s wearing glasses. She is next to a man who has a beard, and is wearing a black crewneck and is sitting on a chair. He is holding the vinyl record of his album WARRIORS with a big “W” on the cover. There’s a poster with the big “W” behind the girl. This is me with Lin-Manuel Miranda.
December 13, 2024 at 2:03 AM
sabinastro.bsky.social
Laughing at @farrwill.bsky.social’s notes on my Jupyter notebooks
A computer screen with a white background with a text that says “If it is too small (<0.1) you can add walkers (and prayer).
December 10, 2024 at 7:40 PM
sabinastro.bsky.social
Well, THIS seemed quite passive aggressive
A spotify wrapped screenshot that says “Your biggest listening day was July 20 with 490 minutes. Where do you find the time?” The letters are white the background is black and pink.
December 6, 2024 at 3:11 AM
sabinastro.bsky.social
If you’re at Cool Stars right now, make sure to check out my poster! She’s beautiful and full of fun stats!!🌟
June 27, 2024 at 4:13 AM
sabinastro.bsky.social
Today @farrwill.bsky.social said “fold it in phase” multiple times, and I couldn’t stop laughing because this reminded of the “fold in the cheese” moment in Schitt’s Creek. 😭🤣
The image shows a blonde woman with glasses and a black-haired guy next to her. It is a moment from the TV show called “Schit’s Creek.” The woman says “you fold it in”, and the guy says “I understand that. But how? How do i fold it?”
September 9, 2023 at 12:10 AM
sabinastro.bsky.social
Poor Rex! Hope everything will be fine soon! Here’s Pluto saying hi:
A white-orange-colored dog sitting on the ground smiling. He has a pink leash and his tongue is out.
August 24, 2023 at 10:33 AM
sabinastro.bsky.social
Whatever twitter alternative you’re using (or whether it’s twitter itself), just remember that you can make your “tweets” more accessible by adding Alt texts to your pictures! Here’s an example:
it is a photo of a dog’s head sleeping on a pink blanket. His head has white-orange color patterns, and he has freckles on his nose.
July 9, 2023 at 10:15 PM