Shashank Dholakia
@astroshashank.bsky.social
Astrophysics PhD candidate at University of Queensland | UC Berkeley '21 | Exoplanets and Stars | @astrosoundbites.bsky.social co-host | Astrophotographer shashankdholakia.github.io
A good reminder than when it comes to “space”, astronomers and the actual content of space (eg stars, galaxies, etc) are unfortunately the last consideration
Meredith Rawls@merrdiff.bsky.social · 4w agoThanks, I *do* hate it www.pcmag.com/news/fcc-app...
Advertising international Masters and PhD scholarships in astronomy at Macquarie, one of Australia's leading institutes! Submit an Expression of Interest by 12 July to start your studies in January 2027. We have projects on offer on stars, planets, and galaxies; and instrumentation and data.
PhD and Masters of Research Positions in Astronomy and Astrophysics | American Astronomical Society
Macquarie University is seeking outstanding candidates for PhD and Masters of Research scholarships commencing January 2027.
aas.org
Another subtlety to take into account when modelling exoplanets. They rotate and have tidal interactions, which modifies the vertical forces on the atmosphere besides gravity. Arnav+Hazra arxiv.org/abs/2606.18100 🧪🔭 #exoplanets
Looking forward to having everyone here for Cool Stars in July 2028 - when a total solar eclipse will pass directly over the city centre!
Dr. Caprice Phillips@capricephillips.bsky.social · 2mo agoNext Cool Stars is in Sydney, Australia! Woohoo!
Forgot to mention in this thread! I have posted a barebones script to correct uncal NIRISS data using the sinusoid we infer in our paper. Would be great to try it on any NIRISS data you have lying around and see what the effects are on your data! #astro #exoplanets 🔭 github.com/shashankdhol...
GitHub - shashankdholakia/niriss-cal-inl: Calibrating the JWST NIRISS analog-to-digital converter periodic integral nonlinearity
Calibrating the JWST NIRISS analog-to-digital converter periodic integral nonlinearity - shashankdholakia/niriss-cal-inl
github.com
Shashank Dholakia@astroshashank.bsky.social · 2mo agoAnd finally--the transmission spectra before and after the correction (with the difference on the bottom). The most obvious effect of the sinusoidal systematic is to offset Orders 1 and 2 in NIRISS, which we estimate for WASP-39b at 55ppm. It also seemingly randomly disperses points by ~30ppm. (9/N)
Shout-out to all my collaborators on this paper who made this possible. Especially @benjaminpope.bsky.social for encouraging me to follow these "odd" data quirks
Shashank Dholakia@astroshashank.bsky.social · 2mo agoThread on our new paper on arxiv today! We stumbled across a weird sinusoidal systematic that we think appears in every observation from the NIRISS instrument on JWST. We derive a correction and see how much it impacts exoplanet spectra. (1/N) #astro #exoplanets 🔭🧪 arxiv.org/abs/2606.11983
Thread on our new paper on arxiv today! We stumbled across a weird sinusoidal systematic that we think appears in every observation from the NIRISS instrument on JWST. We derive a correction and see how much it impacts exoplanet spectra. (1/N) #astro #exoplanets 🔭🧪 arxiv.org/abs/2606.11983
Calibration of an Analog-to-Digital Conversion Nonlinearity in JWST/NIRISS
We quantify an unusual flux-dependent systematic which is periodic in raw counts in flight data from the James Webb Space Telescope's Near Infrared Imager and Slitless Spectrograph (JWST/NIRISS), used...
arxiv.org
A starspot on Zeta Andromedae. That’s a surface feature on a star 181 light years away. #astronomy ⚛️🧪 Image: Roettenbacher et al
Thank you Ben!! I obviously couldn't have done it without you! Now to space out for a few days
Benjamin Pope@benjaminpope.bsky.social · 4mo agoJoin me in congratulating soon-to-be Dr @astroshashank.bsky.social on submitting his PhD thesis at UQ: "Mapping the structure and surfaces of stars and exoplanets". It has been a privilege to work with him these years!
really exciting work lead by Catriona Murray! TOI-3884 b is a planet on a polar orbit around an M dwarf. The transit has a persistent starspot crossing event. Using JWST, we measured the properties of the starspot and the Prot of the star 👀 arxiv.org/abs/2603.15414 🔭 #astronomy 🌟 #stellarastro
My first scientific paper is now public on arXiv! TESS struggles with the brightest stars due to saturation from overexposure. This is unfortunate, because these are the stars that are amenable to photon-hungry follow-up methods, such as spectroscopy or interferometry (1/9) arxiv.org/abs/2602.22472
Halo Photometry and Asteroseismology for 98 of the Brightest Stars Observed by TESS
The Transiting Exoplanet Survey Satellite (TESS) mission has facilitated studies of asteroseismology, eclipsing binaries, and transits in many stars. However, the brightest stars saturate TESS, yet th...
arxiv.org
Do you already have a Masters? Do you want to do a PhD in exoplanet radial velocity surveys with me at Macquarie University in Sydney? Then have I got an ad for you!
Discovering exoplanets with machine learning
Develop a machine-learned model of stellar spectra and instrumental quirks, and use it to discover exoplanets in radial velocity data.
mq.edu.au
If you're on the postdoc market for exoplanet/ML applications--strong recommendation to apply for this job at Macquarie, Ben is great!!
Benjamin Pope@benjaminpope.bsky.social · 6mo agoVery happy to advertise a Postdoctoral Research Associate in Exoplanet Science position with me and Christian Schwab at Macquarie University in Sydney. We'll be working on applying machine learning & differentiable physics models to extremely precise radial velocity surveys.
From Ryan White @astroryan.bsky.social : There are a few locations in the solar system where the push and pull of gravity mellows out and you can orbit in (relative) peace. Read all about these islands of tranquility we call Lagrange points! ⚛️ 🔭 ☄️ 🧪 astrobites.org/2026/01/29/w...
What’s the (Lagrange) point?
There are a few locations in the solar system where the push and pull of gravity mellows out and you can orbit in (relative) peace. Read all about these islands of tranquility we call Lagrange points!
astrobites.org
Stories from #SpaceAustralia in 2025: Checking out the God of Chaos — Apep — using JWST and the VLT. This unique triple stellar system is wild! Some nice work on one of the papers here led by fellow Macquarie University student Ryan White! 🔭
SpaceAustralia.com@spaceaustralia.com · 9mo agoTwo new papers have used data from JWST and ESO's VLT to help uncover new details of the chaos amongst the stars: Apep @rami.spaceaustralia.com spoke with one of the paper's lead authors @astroryan.bsky.social about this incredible system. www.spaceaustralia.com/news/order-a... #SpaceAustralia 🔭
6 days of sunspots evolution. AR4296 and AR4294 OK, this is getting really tricky to arrange. :-} #astronomy #astrophotography
One thing I will miss about UQ is the incredible biodiversity on campus. Thread of all the animals I photographed yesterday along one stretch of railing about 10m long. (warning to the squeamish about bugs) Starting with this bronze hopper (Helpis minitabunda): (1/N) #bugsky #nature #spidersky 🌿
I love this way of explaining papers!! Check this out by @astroryan.bsky.social !
Ryan White@astroryan.bsky.social · 9mo agoTo finish it off, I've also done an annotated version of the paper complete with silly drawings and accessible language! These are inspired by @clairelamman.bsky.social , and you can read this and more here: ryanwhite1.github.io/wolf-rayet.h... 4/4 ⚛️🔭🧪
Very excited to share the NASA/ESA/STScI press release of our team's work on Apep! It's a terrific writeup, complete with a brand new beautiful visualisation of the nebula geometry. 1/? ⚛️🔭🧪 science.nasa.gov/missions/web...
Webb First to Show 4 Dust Shells 'Spiraling' Apep, Limits Long Orbit - NASA Science
NASA’s James Webb Space Telescope has delivered a first of its kind: a crisp mid-infrared image of a system of four serpentine spirals of dust, one expanding
science.nasa.gov
More h-alpha solar timelapses. Here's a loop of plasma twisting off AR4247 from yesterday around 21:30UTC. This might have been part of a small C-class flare. I think it looks like a tornado on the Sun! 🔭 #astronomy #astrophotography
This is exactly the reason every mission and scientist should have a wide-open data policy! PUNCH has specific science objectives (looking at the solar wind) – but in the right hands the data can reveal amazing things NOT part of our original science. Giving those hands access is best for all. ☀️🔭🧪
@kwalsh4a.bsky.social · 9mo agoInterstellar comet 3I Atlas from all clear filter data from PUNCH's WFI3 satellite on October 29th. This is the combination of 134 separate images. It's again visible in single frames (moving coming next). Probably visual magnitude ~9.5ish.
Absolutely delighted to read this news after an anxious wait - Christian Schwab and I will be looking for a postdoc on extremely precise radial velocities at Macquarie soon! Congratulations to everyone on what looks like an unusually large haul of projects for astronomy.
ARC Tracker@arc-tracker.bsky.social · 9mo ago🚨 #DiscoveryProjects #DP26 announcement: ❗️Outcomes announced publicly for Discovery Projects 2026❗️ See ARC's RMS for list ➡️ rms.arc.gov.au/RMS/Report/D... /bot
Really cool astrobite about a really cool paper!
Astrobites@astrobites.bsky.social · 10mo agoFrom Ryan White @astroryan.bsky.social : What does the surface of a red supergiant star look like? It’s no polarising statement to say that it has more in common with a pot of bubbling soup than you might think! 🔭✨☄️ astrobites.org/2025/10/21/a...
My attempt at Comet A6 Lemmon from subpar conditions last night. Wispy clouds still visible in the final image. Was surprisingly bright, p sure I could see it with the unaided eye! Easy through binocs. Canon R5, RF100mm f2.8 19 images, ISO 800, 30s f3.2 🔭 #astronomy #comet
1.5 hour timelapse of the Sun in hydrogen-alpha. I set this up quite late in the day and the Sun was pretty quiet so I was surprised how much evolution is visible in the prominences, granulation and the active region. I'll have to try more of this. Video is set to loop forwards, then in reverse 🔭
In a companion paper, PhD student @maxecharles.bsky.social applies this to reconstructing complex images, not just fields of dots. We apply a regularised maximum likelihood method to restore clean, diffraction limited imaging by fitting directly to pixel level data.
Image reconstruction with the JWST Interferometer
Flying on board the James Webb Space Telescope (JWST) above Earth's turbulent atmosphere, the Aperture Masking Interferometer (AMI) on the NIRISS instrument is the highest-resolution infrared interfer...
arxiv.org
In the first paper Louis Desdoigts (ex PhD in my group, now Leiden postdoc) learns a model for the entire AMI system's optical physics together with a neural network 'effective detector model' the sensor, which suffers from a serious 'brighter-fatter effect' that blurs images at the pixel level.
AMIGO: a Data-Driven Calibration of the JWST Interferometer
The James Webb Space Telescope (JWST) hosts a non-redundant Aperture Masking Interferometer (AMI) in its Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument, providing the only dedicate...
arxiv.org
