To study disease severity and response to therapy in a large cohort of patients with anti-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR)-associated myositis.
Muscle strength, creatine kinase ...levels and treatments were assessed in anti-HMGCR-positive patients at each clinical visit. Univariate and multivariate analyses were used to analyse the influence of clinical characteristics on strength and the change in strength over time. Whole exome sequencing was performed in a subset of patients.
. Among 50 patients followed for ⩾2 years, only 22 (44%) reached full strength with immunosuppressive therapy; even among those with full strength, 55% continued to have CK levels in excess of 500 IU/l and only three could be tapered off immunosuppressive therapy. Both univariate and multivariate analysis showed that patients who were older at disease onset were stronger at all time points (P < 0.001) and improved faster (P < 0.008) than younger patients; a history of statin exposure was not independently associated with the improvement rate. Younger patients were more likely to have refractory disease (P = 0.02) than older patients. Among eight refractory patients with DNA available for testing, whole exome sequencing did not reveal pathogenic mutations in known dystrophy genes. The risk of cancer was not increased in anti-HMGCR myositis patients compared with the general population.
Anti-HMGCR myositis is usually a chronic disease requiring long-term immunosuppression. Although younger patients had more severe disease and a worse prognosis than older patients, they did not have evidence of a known co-existing muscular dystrophy to explain their persistent, and sometimes progressive, muscle weakness.
Abstract
With a mass in the Neptune regime and a radius of Jupiter, WASP-107b presents a challenge to planet formation theories. Meanwhile, the planet’s low surface gravity and the star’s brightness ...also make it one of the most favorable targets for atmospheric characterization. Here, we present the results of an extensive 4 yr Keck/HIRES radial-velocity (RV) follow-up program of the WASP-107 system and provide a detailed study of the physics governing the accretion of the gas envelope of WASP-107b. We reveal that WASP-107b’s mass is only 1.8 Neptune masses (
M
b
= 30.5 ± 1.7
M
⊕
). The resulting extraordinarily low density suggests that WASP-107b has a H/He envelope mass fraction of >85% unless it is substantially inflated. The corresponding core mass of <4.6
M
⊕
at 3
σ
is significantly lower than what is traditionally assumed to be necessary to trigger massive gas envelope accretion. We demonstrate that this large gas-to-core mass ratio most plausibly results from the onset of accretion at ≳1 au onto a low-opacity, dust-free atmosphere and subsequent migration to the present-day
a
b
= 0.0566 ± 0.0017 au. Beyond WASP-107b, we also detect a second, more massive planet (
) on a wide eccentric orbit (
e
c
= 0.28 ± 0.07) that may have influenced the orbital migration and spin–orbit misalignment of WASP-107b. Overall, our new RV observations and envelope accretion modeling provide crucial insights into the intriguing nature of WASP-107b and the system’s formation history. Looking ahead, WASP-107b will be a keystone planet to understand the physics of gas envelope accretion.
Objective
Patients with immune‐mediated necrotizing myopathy (IMNM) often have autoantibodies recognizing the signal recognition particle (SRP) or HMG‐CoA reductase (HMGCR). Here, we studied a cohort ...of anti‐SRP patients to identify factors associated with disease severity and clinical improvement; we also compared the severity of weakness in those with anti‐SRP versus anti‐HMGCR autoantibodies.
Methods
All anti‐SRP patients in the Johns Hopkins Myositis Cohort from 2002 to 2015 were included. Longitudinal information regarding proximal muscle strength, creatine kinase (CK) levels, and immunosuppressive therapy was recorded at each visit. Univariate and multivariate multilevel regression models were used to assess prognostic factors influencing recovery. Strength in the anti‐SRP patients was compared to strength in 49 previously described anti‐HMGCR subjects.
Results
Data from 37 anti‐SRP patients and 380 total clinic visits were analyzed. Younger age at onset was associated with more severe weakness at the first visit (P = 0.02) and all subsequent visits (P = 0.002). Only 50% of patients reached near‐full or full strength after 4 years of treatment, and most of these continued to have elevated CK levels. Rituximab appeared to be effective in 13 of 17 anti‐SRP patients. Anti‐SRP patients were significantly weaker than those with anti‐HMGCR autoantibodies (−1.3 strength points; P = 0.001).
Conclusion
Younger age at onset is associated with more severe weakness in anti‐SRP myositis. Furthermore, even among anti‐SRP patients whose strength improved with immunosuppression, most had ongoing disease activity as demonstrated by elevated CK levels. Finally, anti‐SRP patients were significantly weaker than anti‐HMGCR patients, providing evidence that these autoantibodies are associated with distinct forms of IMNM.
Abstract
We present a transmission spectrum for the warm (500−600 K) sub-Neptune HD 3167c obtained using the Hubble Space Telescope Wide Field Camera 3 infrared spectrograph. We combine these data, ...which span the 1.125–1.643
μ
m wavelength range, with broadband transit measurements made using Kepler/K2 (0.6–0.9
μ
m) and Spitzer/IRAC (4–5
μ
m). We find evidence for absorption by at least one of H
2
O, HCN, CO
2
, and CH
4
(Bayes factor 7.4; 2.5
σ
significance), although the data precision does not allow us to unambiguously discriminate between these molecules. The transmission spectrum rules out cloud-free hydrogen-dominated atmospheres with metallicities ≤100× solar at >5.8
σ
confidence. In contrast, good agreement with the data is obtained for cloud-free models assuming metallicities >700× solar. However, for retrieval analyses that include the effect of clouds, a much broader range of metallicities (including subsolar) is consistent with the data, due to the degeneracy with cloud-top pressure. Self-consistent chemistry models that account for photochemistry and vertical mixing are presented for the atmosphere of HD 3167c. The predictions of these models are broadly consistent with our abundance constraints, although this is primarily due to the large uncertainties on the latter. Interior structure models suggest that the core mass fraction is >40%, independent of a rock or water core composition, and independent of atmospheric envelope metallicity up to 1000× solar. We also report abundance measurements for 15 elements in the host star, showing that it has a very nearly solar composition.
We present precision 4.5 Spitzer transit photometry of eight planet candidates discovered by the K2 mission: K2-52 b, K2-53 b, EPIC 205084841.01, K2-289 b, K2-174 b, K2-87 b, K2-90 b, and K2-124 b. ...The sample includes four sub-Neptunes and two sub-Saturns, with radii between 2.6 and 18 and equilibrium temperatures between 440 and 2000 K. In this paper we identify several targets of potential interest for future characterization studies, demonstrate the utility of transit follow-up observations for planet validation and ephemeris refinement, and present new imaging and spectroscopy data. Our simultaneous analysis of the K2 and Spitzer light curves yields improved estimates of the planet radii and multiwavelength information that helps validate their planetary nature, including the previously unvalidated candidate EPIC 205686202.01 (K2-289 b). Our Spitzer observations yield an order-of-magnitude increase in ephemeris precision, thus paving the way for efficient future study of these interesting systems by reducing the typical transit timing uncertainty in mid-2021 from several hours to a dozen or so minutes. K2-53 b, K2-289 b, K2-174 b, K2-87 b, and K2-90 b are promising radial velocity (RV) targets given the performance of spectrographs available today or in development, and the M3V star K2-124 hosts a temperate sub-Neptune that is potentially a good target for both RV and atmospheric characterization studies.
Abstract
Non-rocky sub-Jovian exoplanets in high-irradiation environments are rare. LTT 9779b, also known as Transiting Exoplanet Survey Satellite (TESS) object of interest (TOI) 193.01, is one of ...the few such planets discovered to date, and the first example of an ultrahot Neptune. The planet’s bulk density indicates that it has a substantial atmosphere, so to investigate its atmospheric composition and shed further light on its origin, we obtained Spitzer InfraRed Array Camera secondary eclipse observations of LTT 9779b at 3.6 and 4.5
μ
m. We combined the Spitzer observations with a measurement of the secondary eclipse in the TESS bandpass. The resulting secondary eclipse spectrum strongly prefers a model that includes CO absorption over a blackbody spectrum, incidentally making LTT 9779b the first TESS exoplanet (and the first ultrahot Neptune) with evidence of a spectral feature in its atmosphere. We did not find evidence of a thermal inversion, at odds with expectations based on the atmospheres of similarly irradiated hot Jupiters. We also report a nominal dayside brightness temperature of 2305 ± 141 K (based on the 3.6
μ
m secondary eclipse measurement), and we constrained the planet’s orbital eccentricity to
e
< 0.01 at the 99.7% confidence level. Together with our analysis of LTT 9779b’s thermal phase curves reported in a companion paper, our results set the stage for similar investigations of a larger sample of exoplanets discovered in the hot-Neptune desert, investigations that are key to uncovering the origin of this population.
Women in Podcasting: We Should Tune In Werner, Jessie L; Lewiss, Resa E; Pensa, Gita ...
Permanente journal,
09/2020, Volume:
24, Issue:
3
Journal Article
Abstract
HD 106315 and GJ 9827 are two bright, nearby stars that host multiple super-Earths and sub-Neptunes discovered by K2 that are well suited for atmospheric characterization. We refined the ...planets’ ephemerides through Spitzer transits, enabling accurate transit prediction required for future atmospheric characterization through transmission spectroscopy. Through a multiyear high-cadence observing campaign with Keck/High Resolution Echelle Spectrometer and Magellan/Planet Finder Spectrograph, we improved the planets’ mass measurements in anticipation of Hubble Space Telescope transmission spectroscopy. For GJ 9827, we modeled activity-induced radial velocity signals with a Gaussian process informed by the Calcium II H&K lines in order to more accurately model the effect of stellar noise on our data. We measured planet masses of
M
b
= 4.87 ± 0.37
M
⊕
,
M
c
= 1.92 ± 0.49
M
⊕
, and
M
d
= 3.42 ± 0.62
M
⊕
. For HD 106315, we found that such activity radial velocity decorrelation was not effective due to the reduced presence of spots and speculate that this may extend to other hot stars as well (
T
eff
> 6200 K). We measured planet masses of
M
b
= 10.5 ± 3.1
M
⊕
and
M
c
= 12.0 ± 3.8
M
⊕
. We investigated all of the planets’ compositions through comparison of their masses and radii to a range of interior models. GJ 9827 b and GJ 9827 c are both consistent with a 50/50 rock-iron composition, GJ 9827 d and HD 106315 b both require additional volatiles and are consistent with moderate amounts of water or hydrogen/helium, and HD 106315 c is consistent with a ∼10% hydrogen/helium envelope surrounding an Earth-like rock and iron core.
We present a new Spitzer transit observation of K2-28b, a sub-Neptune (Rp = 2.45 0.28 R⊕) orbiting a relatively bright (Vmag = 16.06, Kmag = 10.75) metal-rich M4 dwarf (EPIC 206318379). This star is ...one of only seven with masses less than 0.2 known to host transiting planets, and the planet appears to be a slightly smaller analogue of GJ 1214b ( ). Our new Spitzer observations were taken two years after the original K2 discovery data and have a significantly higher cadence, allowing us to derive improved estimates for this planet's radius, semimajor axis, and orbital period, which greatly reduce the uncertainty in the prediction of near future transit times for the James Webb Space Telescope (JWST) observations. We also evaluate the system's suitability for atmospheric characterization with JWST and find that it is currently the only small ( ) and cool (<600 K) planet aside from GJ 1214b with a potentially detectable secondary eclipse. We also note that this system is a favorable target for near-infrared radial velocity instruments on larger telescopes (e.g., the Habitable Planet Finder on the Hobby-Eberly Telescope), making it one of only a handful of small, cool planets accessible with this technique. Finally, we compare our results with the simulated catalog of the Transiting Exoplanet Survey Satellite (TESS) and find K2-28b to be representative of the kind of mid-M systems that should be detectable in the TESS sample.
Abstract
K2-55b is a Neptune-sized planet orbiting a K7 dwarf with a radius of
, a mass of 0.688 ± 0.069
, and an effective temperature of
K. Having characterized the host star using near-infrared ...spectra obtained at IRTF/SpeX, we observed a transit of K2-55b with
Spitzer/
Infrared Array Camera (IRAC) and confirmed the accuracy of the original
K2
ephemeris for future follow-up transit observations. Performing a joint fit to the
Spitzer/IRAC
and
K2
photometry, we found a planet radius of
, an orbital period of
days, and an equilibrium temperature of roughly 900 K. We then measured the planet mass by acquiring 12 radial velocity (RV) measurements of the system using the High Resolution Echelle Spectrometer on the 10 m Keck I Telescope. Our RV data set precisely constrains the mass of K2-55b to
, indicating that K2-55b has a bulk density of
g cm
−3
and can be modeled as a rocky planet capped by a modest H/He envelope (
M
envelope
= 12 ± 3%
M
p
). K2-55b is denser than most similarly sized planets, raising the question of whether the high planetary bulk density of K2-55b could be attributed to the high metallicity of K2-55. The absence of a substantial volatile envelope despite the high mass of K2-55b poses a challenge to current theories of gas giant formation. We posit that K2-55b may have escaped runaway accretion by migration, late formation, or inefficient core accretion, or that K2-55b was stripped of its envelope by a late giant impact.
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