CS22 Splinter Session

Learning from the Coldest Worlds in the era of JWST

Co-Chairs: Jackie Faherty, AMNH & Aaron Meisner NOIR Lab

Read below for a description of our session and the slate of speakers.

2:00 – 2:15pm Program Introduction by Jackie Faherty and Aaron Meisner

2:15 – 2:45pm Big Sample results that use JWST data

• Sam Beiler – Probing Fundamental Properties of the Coldest Brown Dwarfs in the Era of JWST
• Ben Burningham – Detailed retrieval analysis of 13 T and Y dwarfs using JWST/NIRSpec G395H data

2:45 – 3:30pm Individual objects that have been modeled using JWST data

• Melanie Rowland – Protosolar D/H Abundance in the Coldest Brown Dwarf
• Ben Lew – High-precision atmospheric characterization of a peculiar Y dwarf with JWST
• Jessica Copeland – Probing the atmospheric structure and composition of the cool T9 dwarf WISE 0751

3:30 – 4:00pm BREAK

4:00 – 4:30pm Model predictions that cover JWST data

• David Coria – Exoplanetary Origins: Unraveling Planetary Formation and Accretion Histories with CNO Isotopologues
• James Mang – Atmospheric Models for Substellar Objects in Chemical Disequilibrium with Water and Ammonia Clouds

4:30 – 5:00pm Cold brown dwarf variables and what we will see with JWST

• Natalia Oliveros-Gomez – An Informed and Systematic Method to Identify Variable T and Y dwarfs
• Allison McCarthy – Pressure Dependent Light Curve Features in the Planetary Mass Object SIMP0136+0933

5:00 – 5:30pm Poster Pop and Round Table discussion on JWST large proposals for the future of the brown dwarf community

SESSION GOALS AND DESCRIPTION: Brown dwarfs have long been described as a missing link population that connects stellar astrophysics with planetary science.  Brown dwarfs do not have stable hydrogen burning but rather cool through their lives morphing through the spectral classes as they age.  They have temperatures between ~3000 — 250K which define the spectral classifications of L,T, and Y. The Y dwarfs are a recent addition to our assortment of known compact objects and they comprise the coldest sources likely formed through the star formation process.  These cold objects are directly comparable to Jupiter, with the coldest known Y dwarf — WISE J085510.83-071442.5 — at a temperature of ~250 K — just 100 K warmer than Jupiter.  

The coldest brown dwarfs are a powerful collection of astronomical objects.  In their own right, they represent the end of the stellar mass function and (possibly) the height of the planetary mass function. They are primarily found isolated with no host star therefore they can be studied directly using ground and spaced based telescopes. From a planetary perspective, they represent state of the art tests of Jupiter-like atmospheres.  Unlike any known imaged world or transiting planet, cold brown dwarfs can be overplotted on top of data from Jupiter and results can be meaningfully compared/contrasted to understand the diversity of atmospheric phenomena in worlds beyond our own.  

A primary issue in using Y dwarfs as a laboratory for studying atmospheric diversity, is that they present an extraordinary observational challenge for ground-based telescopes given their intrinsic faintness and need for infrared instrumentation. The coldest substellar mass objects emit very little flux at near-infrared wavelengths (< 2.5 μm) and therefore require mid-infrared (~3–25 μm) studies to fully understand their spectral energy distributions and atmosphere properties.  The Spitzer space telescope enabled parallax measurements for the majority of the coldest substellar objects, and this critical parameter allowed us to group and differentiate sources via a color-magnitude diagram (CMD).  However before the launch of JWST, we had just hints at the strong spectral diversity we would uncover in the population.   Now, with JWST GTO, GO cycle 1 and 2 data coming in or published, we have extraordinary insights into the spread in properties of cold worlds outside the solar system.  This session will invite Y dwarf observers and modelers from across the brown dwarf community to present the insights gleaned since JWST began providing data in 2022 as well as the hope for the future of observing in upcoming cycles.  Our aim is to provide a session that gives the complete picture of cold brown dwarf spectral diversity and open a door for the synergy between what we see amongst brown dwarfs, how that might aid in future direct imaging campaigns of cold exoplanets, and also link to what we see amongst solar system planets like Jupiter.  Given the sources that have JWST data published or upcoming, our session will focus on revealing the spectral complement to CMD diversity already spotted.  This means our session will be able to showcase the Y dwarf  (a) temperature sequence  (b) low metallicity sequence (c) low gravity sequence (d) binary sequence  and (e) cloud or overall chemical spread simultaneous with model advancements. 

TIMELINESS OF THE SESSION AND IMPORTANCE FOR CS22: With the launch of JWST, cold brown dwarfs have taken the mainstage in observations and we are now in an era of accelerated observational knowledge.  There are numerous GTO and GO programs obtaining spectra of sources that we previously could only characterize by their position on a CMD. Given that Cool Stars is a gathering conference for brown dwarf scientists, we want to use this splinter session as a means to let the community synergistically reveal results from the first two years of JWST observing.  While the final day of the conference is marked as a “brown dwarfs and giant exoplanets” half day, this splinter is sharply focused on advancements made by JWST on the Y dwarf front and the implications for cold exoplanet and solar system science. 

SPLINTER FORMAT: For our splinter, the 180 minute allotted time slot will allow us to cover observation and theory.  We will have two 80 minute sessions with a 20 minute break in the middle.  We will also reserve at least 10 minutes for a poster pop/lightning talk for anyone with a relevant poster on the topic.  With the remaining 150 minutes of content,  we will host 9 speakers giving 15 minute talks (12+3).  We will reserve 15 minutes for a general discussion with the audience about targets of interest and look to engage in a community effort to plan for the upcoming cycles of JWST.  Amongst our selected speakers, we will be inclusive of all gender and racial groups and will arrange live streaming and teleconference connections to encourage remote participation for those researchers seeking to reduce their travel and carbon footprint.