BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//jEvents 2.0 for Joomla//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VTIMEZONE
TZID:America/Chicago
BEGIN:STANDARD
DTSTART:20220110T120000
RDATE:20220313T030000
TZOFFSETFROM:-0500
TZOFFSETTO:-0600
TZNAME:America/Chicago CST
END:STANDARD
BEGIN:STANDARD
DTSTART:20221106T010000
RDATE:20230312T030000
TZOFFSETFROM:-0500
TZOFFSETTO:-0600
TZNAME:America/Chicago CST
END:STANDARD
BEGIN:STANDARD
DTSTART:20231105T010000
RDATE:20240310T030000
TZOFFSETFROM:-0500
TZOFFSETTO:-0600
TZNAME:America/Chicago CST
END:STANDARD
BEGIN:STANDARD
DTSTART:20241103T010000
RDATE:20250309T030000
TZOFFSETFROM:-0500
TZOFFSETTO:-0600
TZNAME:America/Chicago CST
END:STANDARD
BEGIN:STANDARD
DTSTART:20251102T010000
RDATE:20260308T030000
TZOFFSETFROM:-0500
TZOFFSETTO:-0600
TZNAME:America/Chicago CST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:20220313T030000
RDATE:20221106T010000
TZOFFSETFROM:-0600
TZOFFSETTO:-0500
TZNAME:America/Chicago CDT
END:DAYLIGHT
BEGIN:DAYLIGHT
DTSTART:20230312T030000
RDATE:20231105T010000
TZOFFSETFROM:-0600
TZOFFSETTO:-0500
TZNAME:America/Chicago CDT
END:DAYLIGHT
BEGIN:DAYLIGHT
DTSTART:20240310T030000
RDATE:20241103T010000
TZOFFSETFROM:-0600
TZOFFSETTO:-0500
TZNAME:America/Chicago CDT
END:DAYLIGHT
BEGIN:DAYLIGHT
DTSTART:20250309T030000
RDATE:20251102T010000
TZOFFSETFROM:-0600
TZOFFSETTO:-0500
TZNAME:America/Chicago CDT
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Stars, Planets, and ISM seminar
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Stars, Planets, and ISM seminar
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230111T120000
DTEND;TZID=America/Chicago:20230111T130000
SEQUENCE:0
RRULE:FREQ=WEEKLY;UNTIL=20230427T000000Z;INTERVAL=1;BYDAY=WE
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:No talk scheduled
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:No talk scheduled
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230111T120000
DTEND;TZID=America/Chicago:20230111T130000
RECURRENCE-ID;TZID=America/Chicago:20230111T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Organizational Meeting and Talk
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Organizational Meeting and talk:
Jaime Pineda,
Max Planck Institute for Extraterrestrial Physics
A Spatially Resolved Map of Cosmic-Ray Ionization Rate<
/p>
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230118T120000
DTEND;TZID=America/Chicago:20230118T130000
RECURRENCE-ID;TZID=America/Chicago:20230118T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:No talk scheduled
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
No talk scheduled
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230125T120000
DTEND;TZID=America/Chicago:20230125T130000
RECURRENCE-ID;TZID=America/Chicago:20230125T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Adam Muzzin, York University
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:How to Build a Big Galaxy
Abstract
The most massive galaxies in the
universe are rare, but because of this, their formation history imposes som
e of the strongest constraints on our models of galaxy formation. In
the local universe, massive galaxies like M87 appear relatively dull, with
elliptical morphologies, old stars, and little ongoing star formation. 
; For decades, archeological studies predicted that most of the action duri
ng these galaxies’ formation must have occurred at much higher redshift (z
> 2 or more). Deep and wide field surveys of the near infrared sky
are now allowing us to directly observe the progenitors of local massive g
alaxies as they are forming. I will show state-of-the-art observation
s of this process up to z ~ 6, where we are finding that the early stages o
f massive galaxy formation are in fact extremely dynamic, with huge bursts
of dust-obscured star formation, ubiquitous AGN activity, and significant m
orphological evolution. I will also discuss what we are just starting
to learn in the JWST era, where we are observing the process of massive ga
laxy formation out to its initial stages at z ~ 10-15.
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230201T120000
DTEND;TZID=America/Chicago:20230201T130000
RECURRENCE-ID;TZID=America/Chicago:20230201T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Two Talks
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Kyle Kaplan, SOFIA Science Center
How To Absolu
te Flux Calibrate Your IGRINS Observations: Method and Scientific Applicati
on
Abstract
I will present a metho
d for absolute flux calibrating data from the Immersion GRating INfrared Sp
ectrometer (IGRINS) to within 20% or better accuracy using the spectrum of
the accompanying standard star. &n
bsp;Most IGRINS observations have a hot (typically A0V) standard sta
r observed at a similar airmass for empirical relative flux calibration and
telluric correction. This method can be updated to absolute flux calibrate and better telluric
correct IGRINS data by estimating the standard star’s PSF and slit-losses d
uring observation and fitting the standard star spectrum with synthetic spe
ctra generated by stellar atmosphere models which are normalized to the sta
r’s photometric magnitudes.
I will discuss each step in the process and the unforeseen caveats I
encountered such as wavelength dependent slit-losses and spectrally peculi
ar standard stars. Fi
nally, I will present preliminary results for absolute flux calibrated mole
cular hydrogen emission lines from the Photodissociation Regions presented
in Kaplan et al. (2021) and show how the absolute flux calibrated emission
line fluxes can be directly compared to results from different instruments
and to radiative transfer models.
This method can be used to absolute flux calibrate any IGRINS
data with an accompanying standard star observation, enabling new science w
ith existing archival data.
Abstract
In this talk I will briefly summarize the impo
rtance of magnetic fields in the Universe, particularly in the field of ste
llar astrophysics. I will present some of the challenges of the field,
and the impact of stellar magnetic fields on other areas of astrophysics,
such as exoplanet characterization and the habitability zone.
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230208T120000
DTEND;TZID=America/Chicago:20230208T130000
RECURRENCE-ID;TZID=America/Chicago:20230208T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Keith Hawkins, The University of Texas at Austin
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Chemical Cartography Reveals Spiral Structure in the Milky
Way
Abstract
I will update the Seminar community on recent progress on using che
mical cartographic studies to explore the structure of the Milky Way’s disk
.
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230215T120000
DTEND;TZID=America/Chicago:20230215T130000
RECURRENCE-ID;TZID=America/Chicago:20230215T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Zoe Hackshaw, The University of Texas at Austin
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:The R-Process Alliance: On the origin of the highly r-process enhanc
ed metal-poor star J0010-1735
Abstract
h2>
We present a detailed chemical abundance and kinematic analysis of a
chemically peculiar Milky Way (MW) halo field, metal-poor ([Fe/H] = -2.4),
highly enhanced r-process star ([Eu/Fe] = 1.22), 2MASS J00101758-1735387 (h
ereafter J0010-1735, also known as HE0007-1752 discovered as part of the R-
Process Alliance. Analysis of its chemical abundances shows that its light
(C, Na, Al, K), alpha (Mg, Si, Ti), as well as Fe-peak (Sc, Cr, Mn, C
o, Ni and Zn) elements, except for Ca, are sub-solar, and are systematicall
y deficient as compared to field MW halo stars. We then investigate possibl
e origins and chemical enrichment scenarios that could explain J0010-1
735's observed chemical abundance pattern. Its kinematic analysis based on
Gaia EDR3, supplemented by its unusual abundance pattern indicates a likely
accretion origin from an old stellar system, such as the MW or Large Magel
lanic Cloud (LMC) dwarf satellite galaxies, which have previously undergone
an r-process enrichment event. Moreover, we detect Th in J0010-1
735 from which we determine a cosmochronometric age of 12.5 pm 4.2 Gyr
s. This allows us to place an observational age constraint on the UFD syste
ms from which stars such as J0010-1735 were born and accreted, as well
as the r-process enrichment event itself.
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230222T120000
DTEND;TZID=America/Chicago:20230222T130000
RECURRENCE-ID;TZID=America/Chicago:20230222T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Lillian Jiang, The University of Texas at Austin
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:A Deep H-alpha Imaging Survey to Probe the Demographics of Accreting
Planets at Wide Separations
Abstract
Direct imaging surveys have largely been limited by their reliance on
detecting giant planets in thermal emission, resulting in a biased understa
nding of planet demographics at wide separations. Hot-start planets have hi
gher luminosities at young ages and are therefore preferentially favored to
be found in high-contrast imaging observations. In contrast, cold-start pl
anets---those that experience a loss of initial energy through accretion lu
minosity---are difficult to detect, and sub-Jovian low-mass planets at wide
separation remain largely unexplored. The H-alpha emission from accretion
signatures of planets can be used to overcome these limitations. This appro
ach provides an alternative assessment of planet occurrence rates regardles
s of their formation history and enables the search for accreting sub-Jovia
n-mass planets for the first time. I will present results from a deep H-alp
ha imaging survey of over 200 members of the ~2 Myr old star-forming region
IC 348 obtained using HST/WFC3-UVIS. This study will provide important ins
ight into the demographics of accreting long-period giant planets and their
formation processes, and may uncover a hidden population of planets that a
re currently difficult to detect using traditional direct imaging methods.<
/p>
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230308T120000
DTEND;TZID=America/Chicago:20230308T130000
RECURRENCE-ID;TZID=America/Chicago:20230308T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:No talk scheduled
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:No talk scheduled
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230315T120000
DTEND;TZID=America/Chicago:20230315T130000
RECURRENCE-ID;TZID=America/Chicago:20230315T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Margot Fitz Axen, The University of Texas at Austin
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:The Impact of Cosmic Rays on Star Formation
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230322T120000
DTEND;TZID=America/Chicago:20230322T130000
RECURRENCE-ID;TZID=America/Chicago:20230322T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Erica Sawczynec, The University of Texas at Austin
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Second Year Research Talk
Manufacturing Immer
sion Gratings, Evolving Circumstellar Disks, and the Archive In-Between
Abstract
The Immersion GRating INfrared Spectrometer (IGRINS) is a high resolutio
n (R~45,000) NIR spectrograph that simultaneously covers the H & K band
s (1.45-2.45 um) in a single pointing. After being commissioned at McDonald
Observatory in 2014, IGRINS has had continued success at both the Lowell D
iscovery Channel Telescope (from 2016-2018) and Gemini South (2018-Present)
, producing over 26,000 H- & K-band spectra over 9 years on sky. I intr
oduce The Raw and Reduced IGRINS Spectral Archive (RRISA) which provides st
reamlined public access to IGRINS raw and reduced data products featuring o
ver 3,600 unique observations of both science targets and A0V standards. Us
ing the archive, I have selected a sample of 106 Taurus objects to study mo
lecular hydrogen (H_2) emission in the inner disks of young stellar objects
(YSOs). Armed with the ability to detect over a hundred H_2 emission lines
with IGRINS and physical models describing H_2 emissivity in the circumste
llar disk, I discuss progress towards understanding the dominate circumstel
lar H_2 excitation mechanism for YSOs. Turning towards new science, I brief
ly touch on the legacy of IGRINS science through RRISA and a new era of inc
reased science capabilities with the Giant Magellan Telescope Near I
nfrared Spectrograph (GMTNIRS). I motivate the need for an improved UV expo
sure system to manufacture higher quality J-band gratings for future instru
ments. Finally, I discuss progress with the lab experiments leading to the
redesign of the UV exposure system that will enable J-band grating manufact
uring success.
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230329T120000
DTEND;TZID=America/Chicago:20230329T130000
RECURRENCE-ID;TZID=America/Chicago:20230329T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:James Mang, The University of Texas at Austin
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Second Year Research Talk
Modeling Water Clou
ds in Substellar Atmospheres in the Era of JWST
Abstract
Water clouds are expected to form on Y dwarfs and g
iant planets with Teff < 450 K, drastically altering their at
mospheric compositions and thermal emission spectra. With JWST revolutioniz
ing our observations of these ultra-cool worlds, we need to be prepared wit
h a new generation of cloudy atmospheric models if we want to accurately ch
aracterize these objects. Here, I will present our investigation into the c
urrent prescription of water cloud formation and the improvements we have m
ade based on a comparison with microphysical models. Our focus is to reduce
the computational expense of microphysical water cloud models without comp
romising the accuracy of the cloud's optical properties and observational f
eatures on these cold substellar objects. Most importantly, I will discuss
the differences we see in the simulated spectra between the current water c
loud prescription and those with our new microphysically informed water clo
uds as we prepare for our upcoming JWST observations of WISE 0855, the cold
est known brown dwarf. This new framework for modeling cloudy substellar at
mospheres will enable us to explore this new frontier of characterizing tem
perate giant exoplanets with JWST.
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230405T120000
DTEND;TZID=America/Chicago:20230405T130000
RECURRENCE-ID;TZID=America/Chicago:20230405T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Malia Kao, The University of Texas at Austin
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Second Year Research Talk
Photometric Survey
of High-Mass Pulsating White Dwarfs
Abstract
<
/div>
Abstract
White dwarfs (WDs) are the endpoint of stellar evolut
ion for 97% of the stars in our universe. WDs are no longer undergoing nucl
ear fusion so their cooling rate is assumed to be well-known and their cool
ing ages are often used for dating stellar populations. A majority of WDs a
re hydrogen-atmosphere (DA) and eventually enter a temperature range where
they begin to pulsate, allowing us to use asteroseismology to probe their i
nteriors. Another phenomenon that occurs for all WDs is core crystallizatio
n which releases latent heat and causes a delay in the WD cooling process.
This could change our determination of stellar population ages by 1 Gyr or
more. High-mass WDs (≳1 M⊙) begin to crystallize at a higher temperature th
an WDs of lower masses. A majority of WDs are around 0.6 M⊙ and b
egin crystallization at temperatures below the range where DA WDs pulsate,
so probing the crystalline interiors through asteroseismology is not possib
le. Using data from Gaia and the Zwicky Transient Facility, we have identif
ied 38 candidate pulsators with masses high enough to be undergoing core cr
ystallization within the pulsational instability strip. Fourteen of these h
ave been confirmed as pulsators, increasing the number of known ultramassiv
e pulsators from 3 to 17. Pulsators with suitable properties could all
ow us to constrain the cooling rate and the crystallized mass fraction of t
he interior.
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230412T120000
DTEND;TZID=America/Chicago:20230412T130000
RECURRENCE-ID;TZID=America/Chicago:20230412T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Jackson White, The University of Texas at Austin
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Second Year Research Talk
Quasi-Molecular Lin
eshapes in White Dwarf Star Atmospheres
<
div class="rl_sliders nn_sliders accordion panel-group" id="set-rl_sliders-
11" role="presentation">
Abstract
My abstract is "Quasi-molecular resonances
are spectral features that form due to transient close collisions between n
eighboring plasma particles in hot dense plasmas. The UV spectra of white d
warf stars is particularly sensitive to Lyman-series H2+ quasi-molecular re
sonances, and the modeling of these features can substantially impact white
dwarf stellar parameter fits. In this talk we present a novel method for c
alculating atomic spectral line shape profiles with H2+ resonances included
, using a new change-of-basis approach. With this treatment we have removed
a number of physical approximations that have previously been relied upon,
including the binary collision approximation. We show new hydrogen Lyman-α
profiles calculated with this method and discuss some of the differences c
ompared to past theory. Finally we highlight this method’s rather unique tr
eatment of radiator unitarity and possible applications to future opacity c
alculations.
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230419T120000
DTEND;TZID=America/Chicago:20230419T130000
RECURRENCE-ID;TZID=America/Chicago:20230419T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Katie Teixeira, The University of Texas at Austin
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Second Year Research Talk
Evolution of the At
mosphere of TRAPPIST-1c Through Outgassing and Escape
Abstract
With the successful deployment of J
WST, and its aim to potentially search for biosignatures on exoplanets, an
important endeavor, at present, is to determine whether the rocky planets w
e observe are likely to have atmospheres at all. M dwarfs, the main host st
ars of JWST’s rocky planet targets, are thought to pose a major threat to p
lanetary atmospheres due to their high magnetic activity over several billi
on-year timescales, and might completely strip atmospheres. Several Cycle 1
GO programs are testing this hypothesis, observing some of the most intere
sting rocky planets that we know, e.g., those in the TRAPPIST-1 system. An
interesting case-study is TRAPPIST-1c, which receives almost the same bolom
etric flux as Venus. We might, therefore, expect TRAPPIST-1c to possess a t
hick, CO2-dominated atmosphere. In this talk, I will present results from r
ecent observations that constrain the size of TRAPPIST-1c's atmosphere. To
interpret these results, I have developed and run coupled time-depende
nt simulations of planetary outgassing and atmospheric escape, processes th
at most influence atmospheres, to model the evolution of TRAPPIST-1c’s atmo
sphere. I will review the results of these simulations, specifically the co
nstraints that they place on the history of TRAPPIST-1c’s atmospheric and g
eological properties. Finally, I will discuss the implications of these res
ults for the other TRAPPIST-1 planets, and future developments that will he
lp further characterize the evolution of their atmospheres.
DTSTAMP:20240328T093810Z
DTSTART;TZID=America/Chicago:20230426T120000
DTEND;TZID=America/Chicago:20230426T130000
RECURRENCE-ID;TZID=America/Chicago:20230426T120000
SEQUENCE:0
TRANSP:OPAQUE
END:VEVENT
BEGIN:VEVENT
UID:e7a4b8be2599729db619937e91d0e942
CATEGORIES:Stars, Planets, and ISM Seminar
SUMMARY:Michael Gully-Santiago, The University of Texas at Austin
LOCATION:PMA 15.216B and online
DESCRIPTION;ENCODING=QUOTED-PRINTABLE:A Profoundly Evaporating Planet in the HP
F Helium Exospheres Program
<
div class="rl_sliders nn_sliders accordion panel-group" id="set-rl_sliders-
13" role="presentation">
Abstract
The statistical dearth of small planets revealed
by Kepler and Keck suggests that transformational photoevaporation may be a
compulsory stage in the evolution of planets between 1.5 and 2 Earth radii
. A search for actively evaporating planets has ensued. The Habitable Zone
Planet Finder (HPF) Spectrograph Exospheres program aims to expand the sear
ch across a diverse range of planet and host star properties via the 10830
Ångstrom Helium triplet, a sensitive probe of active atmospheric escape. He
re we present a detection of >10% absorption depth during transit spectr
oscopy of a highly irradiated, low-gravity, hot Saturn. The 13.8 hours of o
n-sky integration time over 41 HET tracks provides enough out-of-transit ph
ase coverage as to reveal comparably deep absorption preceding the transit,
evincing a large leading tail. This configuration can be understood as the
escaping material overflowing its small Roche lobe, and advecting most of
the gas into the stellar—and not planetary---rest frame, consistent with th
e Doppler velocity structure seen in the Helium line profiles. We, therefor
e, attribute the leading tail to Keplerian shear, with some mix of preferen
tial mass loss from dayside heating and/or a dayside pile-up into a headwin
d of weak stellar wind. The observation of a profoundly evaporating h
ighly irradiated hot Saturn confirms the prediction of a "sweet spot" for r
unaway evaporation from the Ohmic Dissipation theory put forth by Batygin,
Stevenson, and Bodenheimer in 2011, before the dearth of such objects was w
idely known. This connection naturally explains the lack of inflated sub-Sa
turns later seen by Thorngren and Fortney as a consequence of the ephemeral
lifetimes of this category.