58 research outputs found
Coordinated interplay between palmitoylation, phosphorylation and SUMOylation regulates kainate receptor surface expression
Kainate receptors (KARs) are key regulators of neuronal excitability and synaptic transmission. KAR surface expression is tightly controlled in part by post-translational modifications (PTMs) of the GluK2 subunit. We have shown previously that agonist activation of GluK2-containing KARs leads to phosphorylation of GluK2 at S868, which promotes subsequent SUMOylation at K886 and receptor endocytosis. Furthermore, GluK2 has been shown to be palmitoylated. However, how the interplay between palmitoylation, phosphorylation and SUMOylation orchestrate KAR trafficking remains unclear. Here, we used a library of site-specific GluK2 mutants to investigate the interrelationship between GluK2 PTMs, and their impact on KAR surface expression. We show that GluK2 is basally palmitoylated and that this is decreased by kainate (KA) stimulation. Moreover, a non-palmitoylatable GluK2 mutant (C858/C871A) shows enhanced S868 phosphorylation and K886 SUMOylation under basal conditions and is insensitive to KA-induced internalisation. These results indicate that GluK2 palmitoylation contributes to stabilising KAR surface expression and that dynamic depalmitoylation promotes downstream phosphorylation and SUMOylation to mediate activity-dependent KAR endocytosis
Tree-Ring-Reconstructed Summer Temperatures from Northwestern North America during the Last Nine Centuries*
Northwestern North America has one of the highest rates of recent temperature increase in the world, but the putative âdivergence problemâ in dendroclimatology potentially limits the ability of tree-ring proxy data at high latitudes to provide long-term context for current anthropogenic change. Here, summer temperatures are reconstructed from a Picea glauca maximum latewood density (MXD) chronology that shows a stable relationship to regional temperatures and spans most of the last millennium at the Firth River in northeastern Alaska. The warmest epoch in the last nine centuries is estimated to have occurred during the late twentieth century, with average temperatures over the last 30 yr of the reconstruction developed for this study [1973â2002 in the Common Era (CE)] approximately 1.3° ± 0.4°C warmer than the long-term preindustrial mean (1100â1850 CE), a change associated with rapid increases in greenhouse gases. Prior to the late twentieth century, multidecadal temperature fluctuations covary broadly with changes in natural radiative forcing. The findings presented here emphasize that tree-ring proxies can provide reliable indicators of temperature variability even in a rapidly warming climate
The TESS-Keck Survey. III. A Stellar Obliquity Measurement of TOI-1726 c
We report the measurement of a spectroscopic transit of TOI-1726c, one of two planets transiting a G-type star with V = 6.9 in the Ursa Major Moving Group (~400 Myr). With a precise age constraint from cluster membership, TOI-1726 provides a great opportunity to test various obliquity excitation scenarios that operate on different timescales. By modeling the RossiterâMcLaughlin (RM) effect, we derived a sky-projected obliquity of â1^(+35)_(â32)â. This result rules out a polar/retrograde orbit and is consistent with an aligned orbit for planet c. Considering the previously reported, similarly prograde RM measurement of planet b and the transiting nature of both planets, TOI-1726 tentatively conforms to the overall picture that compact multitransiting planetary systems tend to have coplanar, likely aligned orbits. TOI-1726 is also a great atmospheric target for understanding differential atmospheric loss of sub-Neptune planets (planet b 2.2 Râ and c 2.7 Râ both likely underwent photoevaporation). The coplanar geometry points to a dynamically cold history of the system that simplifies any future modeling of atmospheric escape
TKS X: Confirmation of TOI-1444b and a Comparative Analysis of the Ultra-short-period Planets with Hot Neptunes
We report the discovery of TOI-1444b, a 1.4- super-Earth on a
0.47-day orbit around a Sun-like star discovered by {\it TESS}. Precise radial
velocities from Keck/HIRES confirmed the planet and constrained the mass to be
. The RV dataset also indicates a possible
non-transiting, 16-day planet (). We report a tentative
detection of phase curve variation and secondary eclipse of TOI-1444b in the
{\it TESS} bandpass. TOI-1444b joins the growing sample of 17
ultra-short-period planets with well-measured masses and sizes, most of which
are compatible with an Earth-like composition. We take this opportunity to
examine the expanding sample of ultra-short-period planets () and
contrast them with the newly discovered sub-day ultra-hot Neptunes
(, TOI-849 b, LTT9779 b and K2-100). We find that
1) USPs have predominately Earth-like compositions with inferred iron core mass
fractions of 0.320.04; and have masses below the threshold of runaway
accretion (), while ultra-hot Neptunes are above the threshold
and have H/He or other volatile envelope. 2) USPs are almost always found in
multi-planet system consistent with a secular interaction formation scenario;
ultra-hot Neptunes (1 day) tend to be ``lonely' similar
to longer-period hot Neptunes(1-10 days) and hot Jupiters. 3) USPs
occur around solar-metallicity stars while hot Neptunes prefer higher
metallicity hosts. 4) In all these respects, the ultra-hot Neptunes show more
resemblance to hot Jupiters than the smaller USP planets, although ultra-hot
Neptunes are rarer than both USP and hot Jupiters by 1-2 orders of magnitude.Comment: Accepted too AJ. 12 Figures, 4 table
The TESS-Keck Survey II: An Ultra-Short Period Rocky Planet and its Siblings Transiting the Galactic Thick-Disk Star TOI-561
We report the discovery of TOI-561, a multi-planet system in the galactic
thick disk that contains a rocky, ultra-short period planet (USP). This bright
() star hosts three small transiting planets identified in photometry
from the NASA TESS mission: TOI-561 b (TOI-561.02, P=0.44 days, ), c (TOI-561.01, P=10.8 days,
), and d (TOI-561.03, P=16.3 days,
). The star is chemically ([Fe/H],
[/H]) and kinematically consistent with the galactic
thick disk population, making TOI-561 one of the oldest (Gyr) and
most metal-poor planetary systems discovered yet. We dynamically confirm
planets b and c with radial velocities from the W. M. Keck Observatory High
Resolution Echelle Spectrometer. Planet b has a mass and density of
and gcm, consistent with
a rocky composition. Its lower-than-average density is consistent with an
iron-poor composition, although an Earth-like iron-to-silicates ratio is not
ruled out. Planet c is and gcm,
consistent with an interior rocky core overlaid with a low-mass volatile
envelope. Several attributes of the photometry for planet d (which we did not
detect dynamically) complicate the analysis, but we vet the planet with
high-contrast imaging, ground-based photometric follow-up and radial
velocities. TOI-561 b is the first rocky world around a galactic thick-disk
star confirmed with radial velocities and one of the best rocky planets for
thermal emission studies.Comment: Accepted at The Astronomical Journal; 25 pages, 10 figure
The TESS-Keck Survey. XI. Mass Measurements for Four Transiting sub-Neptunes orbiting K dwarf TOI-1246
Multi-planet systems are valuable arenas for investigating exoplanet architectures and comparing planetary siblings. TOI-1246 is one such system, with a moderately bright K dwarf (V=11.6, K=9.9) and four transiting sub-Neptunes identified by TESS with orbital periods of 4.31 d, 5.90 d, 18.66 d, and 37.92 d. We collected 130 radial velocity observations with Keck/HIRES and TNG/HARPS-N to measure planet masses. We refit the 14 sectors of TESS photometry to refine planet radii (2.97±0.06 Râ,2.47±0.08 Râ,3.46±0.09 Râ, 3.72±0.16 Râ), and confirm the four planets. We find that TOI-1246 e is substantially more massive than the three inner planets (8.1±1.1Mâ, 8.8±1.2Mâ, 5.3±1.7Mâ, 14.8±2.3Mâ). The two outer planets, TOI-1246 d and TOI-1246 e, lie near to the 2:1 resonance (Pe/Pd=2.03) and exhibit transit timing variations. TOI-1246 is one of the brightest four-planet systems, making it amenable for continued observations. It is one of only six systems with measured masses and radii for all four transiting planets. The planet densities range from 0.70±0.24 to 3.21±0.44g/cm3, implying a range of bulk and atmospheric compositions. We also report a fifth planet candidate found in the RV data with a minimum mass of 25.6 ± 3.6 Mâ. This planet candidate is exterior to TOI-1246 e with a candidate period of 93.8 d, and we discuss the implications if it is confirmed to be planetary in nature
The TESS-Keck Survey. XI. Mass Measurements for Four Transiting Sub-Neptunes Orbiting K Dwarf TOI-1246
Multiplanet systems are valuable arenas for investigating exoplanet architectures and comparing planetary siblings. TOI-1246 is one such system, with a moderately bright K dwarf (V = 11.6, K = 9.9) and four transiting sub-Neptunes identified by TESS with orbital periods of 4.31, 5.90, 18.66, and 37.92 days. We collected 130 radial velocity observations with Keck/HIRES and TNG/HARPS-N to measure planet masses. We refit the 14 sectors of TESS photometry to refine planet radii (2.97 +/- 0.06 R (circle plus), 2.47 +/- 0.08 R (circle plus), 3.46 +/- 0.09 R (circle plus), and 3.72 +/- 0.16 R (circle plus)) and confirm the four planets. We find that TOI-1246 e is substantially more massive than the three inner planets (8.1 +/- 1.1 M (circle plus), 8.8 +/- 1.2 M (circle plus), 5.3 +/- 1.7 M (circle plus), and 14.8 +/- 2.3 M (circle plus)). The two outer planets, TOI-1246 d and TOI-1246 e, lie near to the 2:1 resonance (P (e)/P ( d ) = 2.03) and exhibit transit-timing variations. TOI-1246 is one of the brightest four-planet systems, making it amenable for continued observations. It is one of only five systems with measured masses and radii for all four transiting planets. The planet densities range from 0.70 +/- 0.24 to 3.21 +/- 0.44 g cm(-3), implying a range of bulk and atmospheric compositions. We also report a fifth planet candidate found in the RV data with a minimum mass of 25.6 +/- 3.6 M (circle plus). This planet candidate is exterior to TOI-1246 e, with a candidate period of 93.8 days, and we discuss the implications if it is confirmed to be planetary in nature
The TESS Grand Unified Hot Jupiter Survey. II. Twenty New Giant Planets
NASA's Transiting Exoplanet Survey Satellite (TESS) mission promises to
improve our understanding of hot Jupiters by providing an all-sky,
magnitude-limited sample of transiting hot Jupiters suitable for population
studies. Assembling such a sample requires confirming hundreds of planet
candidates with additional follow-up observations. Here, we present twenty hot
Jupiters that were detected using TESS data and confirmed to be planets through
photometric, spectroscopic, and imaging observations coordinated by the TESS
Follow-up Observing Program (TFOP). These twenty planets have orbital periods
shorter than 7 days and orbit relatively bright FGK stars ().
Most of the planets are comparable in mass to Jupiter, although there are four
planets with masses less than that of Saturn. TOI-3976 b, the longest period
planet in our sample ( days), may be on a moderately eccentric orbit
(), while observations of the other targets are consistent
with them being on circular orbits. We measured the projected stellar obliquity
of TOI-1937A b, a hot Jupiter on a 22.4 hour orbit with the Rossiter-McLaughlin
effect, finding the planet's orbit to be well-aligned with the stellar spin
axis (). We also investigated the possibility that
TOI-1937 is a member of the NGC 2516 open cluster, but ultimately found the
evidence for cluster membership to be ambiguous. These objects are part of a
larger effort to build a complete sample of hot Jupiters to be used for future
demographic and detailed characterization work.Comment: 67 pages, 11 tables, 13 figures, 2 figure sets. Resubmitted to ApJS
after revision
TESS Giants Transiting Giants. I.: A Noninflated Hot Jupiter Orbiting a Massive Subgiant
While the population of confirmed exoplanets continues to grow, the sample of confirmed transiting planets around evolved stars is still limited. We present the discovery and confirmation of a hot Jupiter orbiting TOI-2184 (TIC 176956893), a massive evolved subgiant (M â = 1.53 ± 0.12 M oË, R â = 2.90 ± 0.14 R oË) in the Transiting Exoplanet Survey Satellite (TESS) Southern Continuous Viewing Zone. The planet was flagged as a false positive by the TESS Quick-Look Pipeline due to periodic systematics introducing a spurious depth difference between even and odd transits. Using a new pipeline to remove background scattered light in TESS Full Frame Image data, we combine space-based TESS photometry, ground-based photometry, and ground-based radial velocity measurements to report a planet radius of R p = 1.017 ± 0.051 R J and mass of M p = 0.65 ± 0.16 M J . For a planet so close to its star, the mass and radius of TOI-2184b are unusually well matched to those of Jupiter. We find that the radius of TOI-2184b is smaller than theoretically predicted based on its mass and incident flux, providing a valuable new constraint on the timescale of post-main-sequence planet inflation. The discovery of TOI-2184b demonstrates the feasibility of detecting planets around faint (TESS magnitude > 12) post-main-sequence stars and suggests that many more similar systems are waiting to be detected in the TESS FFIs, whose confirmation may elucidate the final stages of planetary system evolution
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