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Cian O'Toole

@astrotoole.bsky.social

59 followers 50 following 8 posts

PhD researcher in Brown Dwarf Variability in Trinity College Dublin. cianotoole11.github.io/cianotoole.g…

Posts Replies Media

Reposted by Cian O'Toole

Astronomy Picture of the Day 🪐 @apod.shinyakato.dev · 06/10/2026

🔭 A Complete Auroral Oval from SMILE Credit: ESA, CAS, SMILE, UVI ap261006

A round Earth takes up most of the video. The dayside and nightside are visible. A swirling, moving aurora is visible surrounding Earth's North Pole. There are some bright objects that speckle the background.

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Cian O'Toole @astrotoole.bsky.social · 21/05/2026

Congrats Tom!!

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Cian O'Toole @astrotoole.bsky.social · 28/03/2026

We also find evidence for long term variability in each of these object's light curves when comparing to archival observations! I would like to sincerely thank my supervisor @johannavos.bsky.social for their guidance throughout this project and to all the co-authors who made this paper what it is!

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Cian O'Toole @astrotoole.bsky.social · 28/03/2026

We constructed models to reproduce the effects of auroral, cloud and magnetic spot driven variability on the spectral variability amplitude of each object. We find that clouds and magnetic spots can reproduce the observed variability in each of our objects.

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Cian O'Toole @astrotoole.bsky.social · 28/03/2026

We plot the colour modulation of each object, similar to Lew et al 2020, expanding their sample of 12 brown dwarfs into a hotter parameter space. We find that 2 of our 3 objects exhibit 'flatter' slopes than any of the 2020 sample, indicating that as they rotate, they become brighter and bluer.

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Cian O'Toole @astrotoole.bsky.social · 28/03/2026

We find that all three of our objects, the L3 dwarf 2M1721+33, the L3.5 dwarf 2M0036+18 and the L1 dwarf 2M1906+40 are all variable! Using a combination of Gaussian process fitting and periodograms, we deduce a new rotational period for 2M1721+33 of 4.93^{+0.4}{-0.2} hours!

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Cian O'Toole @astrotoole.bsky.social · 28/03/2026

I am delighted to share that my first paper has now been accepted for publication in Astronomy and Astrophysics and is now on the arXiv!! arxiv.org/abs/2603.24663 In this paper I disentangle the drivers of variability in three early L-dwarfs using HST/WFC3. More info below 🧵!!

arxiv.org

Disentangling auroral, cloud and magnetic spot driven variability in three early L-dwarfs with HST/WFC3

Variability monitoring provides an unparalleled insight into the atmospheric processes of brown dwarfs and directly imaged exo-planets. Inhomogeneous clouds, aurorae and magnetic spots have all been p...

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Reposted by Cian O'Toole

Johanna Vos @johannavos.bsky.social · 27/03/2026

TWO recently accepted papers on arxiv today from our group, led by PhD students @maddielam.bsky.social and @astrotoole.bsky.social. If you like brown dwarfs, variability, clouds, aurorae and/or magnetic spots there is something here for you! 👀 arxiv.org/abs/2603.24662 arxiv.org/abs/2603.24663

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Reposted by Cian O'Toole

Evert Nasedkin @evertnasedkin.bsky.social · 26/09/2025

🔭 It's paper day! Today I'm sharing the latest in a series of papers looking at the weather on other worlds, in this case bringing you the weather report from a nearby T-dwarf, SIMP-0136. 🪐 🧵 to follow...

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Reposted by Cian O'Toole

Dr. Jessie Christiansen @aussiastronomer.bsky.social · 06/08/2025

Images from Palomar at 2 different infrared wavelengths last night - one that Saturn's methane atmosphere absorbs, and one the it reflects! (The faint point source is the moon, Tethys!) Taken by David Ciardi, Catherine Clark, @lowbacca.bsky.social and Miranda Felsmann; animated by me (and ezgif!)

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Cian O'Toole @astrotoole.bsky.social · 24/07/2025

We chose this object as it is an extremely well characterised aurorally emitting T dwarf. There are two ongoing JWST programs characterising it's aurora and atmosphere in the infrared. It has an exceptionally strong magnetic field and we believe that it is the ideal object to search for UV aurorae!

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Cian O'Toole @astrotoole.bsky.social · 22/07/2025

I'm absolutely delighted to share that my Hubble Space Telescope proposal has been accepted! We will search for the first UV detection of an aurora outside the solar system on the brown dwarf 2M1047, using simultaneous observations from HST and the VLA. Stay tuned for some very exciting science! 🔭📡

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Reposted by Cian O'Toole

Johanna Vos @johannavos.bsky.social · 30/06/2025

Very proud of Cian O'Toole who gave his very first conference talk at #EAS2025 last week. 🔭 He is investigating the drivers of variability in three brown dwarfs using observations from HST, VLA and a new framework for modelling variable atmospheres. Paper is incoming so watch this space! 📄📄📄

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