753 research outputs found
The California Planet Survey IV: A Planet Orbiting the Giant Star HD 145934 and Updates to Seven Systems with Long-Period Planets
We present an update to seven stars with long-period planets or planetary
candidates using new and archival radial velocities from Keck-HIRES and
literature velocities from other telescopes. Our updated analysis better
constrains orbital parameters for these planets, four of which are known
multi-planet systems. HD 24040 b and HD 183263 c are super-Jupiters with
circular orbits and periods longer than 8 yr. We present a previously unseen
linear trend in the residuals of HD 66428 indicative on an additional planetary
companion. We confirm that GJ 849 is a multi-planet system and find a good
orbital solution for the c component: it is a planet in a 15 yr
orbit (the longest known for a planet orbiting an M dwarf). We update the HD
74156 double-planet system. We also announce the detection of HD 145934 b, a planet in a 7.5 yr orbit around a giant star. Two of our stars, HD
187123 and HD 217107, at present host the only known examples of systems
comprising a hot Jupiter and a planet with a well constrained period yr,
and with no evidence of giant planets in between. Our enlargement and
improvement of long-period planet parameters will aid future analysis of
origins, diversity, and evolution of planetary systems.Comment: 16 pages, 13 figures. Accepted for publication in Ap
Forming Giant Planets Around Late-M Dwarfs: Pebble Accretion and Planet-Planet Collision
We propose a pebble-driven core accretion scenario to explain the formation
of giant planets around the late-M dwarfs of $M_{\star}{=}0.1{-}0.2 \
M_{\odot}0.01 \ M_{\oplus}{\lesssim}100{>}50 \ M_{\oplus}\alpha_{\rm t}
{\sim} 10^{-3}{-}10^{-2}$.Comment: 22 pages, 13 figures, 3 tables, Accepted for publication in A&
Detection and Preliminary Characterisation of Polluted White Dwarfs from Gaia EDR3 and LAMOST
We present a catalogue of 62 polluted white dwarfs observed by the 9th
Low-Resolution Data Release of the Large Sky Area Multi-Object Fiber
Spectroscopic Telescope (LAMOST LRS DR9v1; R1,800) and the Early Data
Release 3 (EDR3) of the Gaia Mission. Among these stellar remnants, 30 are new
discoveries with previously unknown traces of calcium pollution. To generate
our catalogue, we used a database of 4,324 unique Gaia EDR3 white dwarf
candidates with LAMOST LRS DR9v1 observations, many of which have been
spectroscopically confirmed by other telescopes. For these stars, we developed
a quantitative method to detect calcium absorption in their spectra between
3,900-4,000, which we then validated through visual
inspection and multiple literature cross-checks. Our catalogue provides the
astrometric and photometric properties of the white dwarf candidates,
incorporates supplementary data (e.g. Montreal White Dwarf Database, MWDD;
PanSTARRS; the Hubble Space Telescope), and indicates the possibility of
calcium pollution in their atmospheres. For our final sample of polluted white
dwarfs, we also determine the main atmospheric properties of 23 sources with
effective temperatures 25,000K and no existing calcium
abundances in the MWDD. Our analysis represents a first step towards measuring
the full atmospheric composition of these stars and learning about the bulk
properties of their accreted material. As we venture into the era of wide-field
spectroscopic surveys, our work highlights the importance of combining
large-scale databases for identifying and characterising new polluted white
dwarfs.Comment: 29 pages, 14 figures (+3 in the Appendix), 5 tables (+5 in the
Appendix). Accepted for publication in MNRA
Fibroblast Growth Factor 23 Does Not Directly Influence Skeletal Muscle Cell Proliferation and Differentiation or Ex Vivo Muscle Contractility
Skeletal muscle dysfunction accompanies the clinical disorders of chronic kidney disease (CKD) and hereditary hypophosphatemic rickets. In both disorders, fibroblast growth factor 23 (FGF23), a bone-derived hormone regulating phosphate and vitamin D metabolism, becomes chronically elevated. FGF23 has been shown to play a direct role in cardiac muscle dysfunction; however, it is unknown whether FGF23 signaling can also directly induce skeletal muscle dysfunction. We found expression of potential FGF23 receptors ( Fgfr1-4) and α-Klotho in muscles of two animal models (CD-1 and Cy/+ rat, a naturally occurring rat model of chronic kidney disease-mineral bone disorder) as well as C2C12 myoblasts and myotubes. C2C12 proliferation, myogenic gene expression, oxidative stress marker 8-OHdG, intracellular Ca2+ ([Ca2+]i), and ex vivo contractility of extensor digitorum longus (EDL) or soleus muscles were assessed after treatment with various amounts of FGF23. FGF23 (2-100 ng/ml) did not alter C2C12 proliferation, expression of myogenic genes, or oxidative stress after 24- to 72-h treatment. Acute or prolonged FGF23 treatment up to 6 days did not alter C2C12 [Ca2+]i handling, nor did acute treatment with FGF23 (9-100 ng/ml) affect EDL and soleus muscle contractility. In conclusion, although skeletal muscles express the receptors involved in FGF23-mediated signaling, in vitro FGF23 treatments failed to directly alter skeletal muscle development or function under the conditions tested. We hypothesize that other endogenous substances may be required to act in concert with FGF23 or apart from FGF23 to promote muscle dysfunction in hereditary hypophosphatemic rickets and CKD
TOI-150: A transiting hot Jupiter in the TESS southern CVZ
We report the detection of a hot Jupiter ($M_{p}=1.75_{-0.17}^{+0.14}\
M_{J}R_{p}=1.38\pm0.04\ R_{J}\log
g=4.152^{+0.030}_{-0.043}\beta=-79.59^{\circ}$). We confirm the
planetary nature of the candidate TOI-150.01 using radial velocity observations
from the APOGEE-2 South spectrograph and the Carnegie Planet Finder
Spectrograph, ground-based photometric observations from the robotic
Three-hundred MilliMeter Telescope at Las Campanas Observatory, and Gaia
distance estimates. Large-scale spectroscopic surveys, such as APOGEE/APOGEE-2,
now have sufficient radial velocity precision to directly confirm the signature
of giant exoplanets, making such data sets valuable tools in the TESS era.
Continual monitoring of TOI-150 by TESS can reveal additional planets and
subsequent observations can provide insights into planetary system
architectures involving a hot Jupiter around a star about halfway through its
main-sequence life.Comment: 13 pages, 3 figures, 2 tables, accepted to ApJ
The HD 192263 system: planetary orbital period and stellar variability disentangled
As part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS), we
present new radial velocities and photometry of the HD 192263 system. Our
analysis of the already available Keck-HIRES and CORALIE radial velocity
measurements together with the five new Keck measurements we report in this
paper results in improved orbital parameters for the system. We derive
constraints on the size and phase location of the transit window for HD
192263b, a Jupiter-mass planet with a period of 24.3587 \pm 0.0022 days. We use
10 years of Automated Photoelectric Telescope (APT) photometry to analyze the
stellar variability and search for planetary transits. We find continuing
evidence of spot activity with periods near 23.4 days. The shape of the
corresponding photometric variations changes over time, giving rise to not one
but several Fourier peaks near this value. However, none of these frequencies
coincides with the planet's orbital period and thus we find no evidence of
star-planet interactions in the system. We attribute the ~23-day variability to
stellar rotation. There are also indications of spot variations on longer (8
years) timescales. Finally, we use the photometric data to exclude transits for
a planet with the predicted radius of 1.09 RJ, and as small as 0.79 RJ.Comment: 9 pages, 6 tables, 6 figures; accepted to Ap
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