Kevin Hardegree-Ullman
@kevinkhu
Research Scientist at Caltech/IPAC-NExScI studying all things related to exoplanets! Opinions are my own.
Netflix has always been terrible at suggesting things to watch. Now we know why. Time to drop Netflix.
Michelle Kunimoto pointing out the importance of *automated* vetting of #exoplanet candidates. Manual inspection introduces uncharacherizable biases! #Sagan2026
All Roman transiting #exoplanet demographics will require a uniform stellar catalog. Check out Ashley Elliott's #Sagan2026 poster about the Roman GBTDS All-Star Catalog!
#Sagan2026, we have more responses to the *interactive* poster, don't forget to add your own thoughts!
If you're at #Sagan2026, come check out my *interactive* #exoplanet poster! The Near-Infrared Transit Explorer (NITE) is a survey mission concept designed to find Earth-sized planets in the habitable zones of M dwarfs!
This is funny to come home to for a split second before you realize what they got into. #DogShaming
We had three very nice (partial) nights on IRTF earlier this week, so of course our last night of this semester is not very good. It also kinda looks like a big twirly storm is brewing south of Hawaii. 🔭😶🌫️🌀
The next steps will be to monitor variability (WEATHER!) on these Y dwarfs with JWST. This opens up opportunities for far more spectral detail and help bridge the gaps between brown dwarfs and gas giant planets! So, if you're on a JWST TAC, please give the Y dwarf folks some time!
Y dwarfs are also consistent with the notion from S. A. Metchev et al. (2015) that the maximum observed variability amplitude increases with decreasing spectral type for brown dwarfs.
The variability fraction of Y dwarfs supports the hypothesis that clouds are the cause of this variability. Interestingly, the variability fraction appears to drop for T dwarfs then rise for Y dwarfs (go read the paper for more info!).
Y dwarfs generally have stable light curves over timescales of months, but in some cases show clear changes in amplitude.
We found that ~60% of Y dwarfs were variable in the first epoch (at both 3.6 and 4.5 microns), and 35% (at 3.5 microns) and 75% (at 4.5 microns) were variable in the second epoch.
We observed 16 Y dwarfs with Spitzer at 3.6 and 4.5 microns. Each target was monitored continuously for 24 hours (12 h at 3.6 and 12 h at 4.5) in two different epochs separated by several months.
Typical brown dwarfs have clouds with a range of molecules from carbon monoxide and methane to more interesting minerals like magnesium silicates and liquid iron. The colder the brown dwarf, the more cloud layers and the more diverse the cloud species. Y dwarfs sit between T dwarfs and Jupiter.
Brown dwarfs are not massive enough to fuse hydrogen like stars, but are generally massive enough to fuse deuterium. Continuing the alphabet soup of stellar classification (OBAFGKM - stars), we have L, T, and Y as brown dwarf classes in decreasing temperature order.
I got new glasses a month ago and they have been bothering me with extra reflections and glare. Today I realized the edge of the lenses are polished rather than frosted. I've never had that issue before with my glasses. Would not recommend. #Optics
We tested and validated COUNTESS on existing TESS planet candidates. After running COUNTESS on ~26,000 targets with TESS-SPOC light curves. We found 10 brand new exoplanet candidates that passed all vetting tests! Our pipeline is sensitive to a wide range of periods and planet sizes.
In this first paper, we focused on the Northern CVZ. We took TESS-SPOC light curves, detrended them using Wōtan, searched for planets using GERBLS, fit for planet signals using EXOTIC, vetted for false alarms and false positives using LEOVetter, and statistically validated with TRICERATOPS.
The TESS CVZs are two 450 square degree regions at the ecliptic poles, covering areas ~4 times the Kepler field of view. The CVZs contain ~800,000 main-sequence stars brighter than a TESS magnitude of 16.
It is "squirrel spread out flat in the shade on a concrete wall" hot today in Pasadena.
Today was the annual @caltechipac.bsky.social picnic. There's a dessert bake-off every year, and this year's theme was "Forty & Festive" because IPAC has been around for 40 years. My "Cosmic Brownies" took the prize this year!
I was just about to come here to say this. I pass by this sign frequently!
My #1 non-science comment when reviewing papers I'm on is about verb tense. This great article from a few years ago has many great tips about writing and developing astronomy research papers, but especially the succinct examples about using verb tenses correctly! scixplorer.org/abs/2022NatA...
Addendum: A very poor illustration of what I think happened on that day.
Hmm. I was looking forward to remotely observing tonight, but I don't think that's going to happen. 🔭😶🌫️
While searching for whatever the dog rolled in, I saw this Monarch butterfly just chilling in the grass.