90 research outputs found
Reanalysis of the FEROS observations of HIP 11952
Aims. We reanalyze FEROS observations of the star HIP 11952 to reassess the
existence of the proposed planetary system. Methods. The radial velocity of the
spectra were measured by cross-correlating the observed spectrum with a
synthetic template. We also analyzed a large dataset of FEROS and HARPS
archival data of the calibrator HD 10700 spanning over more than five years. We
compared the barycentric velocities computed by the FEROS and HARPS pipelines.
Results. The barycentric correction of the FEROS-DRS pipeline was found to be
inaccurate and to introduce an artificial one-year period with a semi-amplitude
of 62 m/s. Thus the reanalysis of the FEROS data does not support the existence
of planets around HIP 11952.Comment: 7 pages, 8 figures, 1 tabl
Radial velocity variations in the young eruptive star EX Lupi
Context. EX Lup-type objects (EXors) are low-mass pre-main sequence objects characterized by optical and near-infrared outbursts attributed to highly enhanced accretion from the circumstellar disk onto the star.
Aims: The trigger mechanism of EXor outbursts is still debated. One type of theory requires a close (sub)stellar companion that perturbs the inner part of the disk and triggers the onset of the enhanced accretion. Here, we study the radial velocity (RV) variations of EX Lup, the prototype of the EXor class, and test whether they can be related to a close companion.
Methods: We conducted a five-year RV survey, collecting 54 observations with HARPS and FEROS. We analyzed the activity of EX Lup by checking the bisector, the equivalent width of the Ca 8662 Å line, the asymmetry of the Ca II K line, the activity indicator SFEROS, the asymmetry of the cross-correlation function, the line depth ratio of the VI/FeI lines, and the TiO, CaH 2, CaH 3, CaOH, and Halpha indices. We complemented the RV measurements with a 14-day optical/infrared photometric monitoring to look for signatures of activity or varying accretion.
Results: We found that the RV of EX Lup is periodic (P = 7.417 d), with stable period, semi-amplitude (2.2 km s-1), and phase over at least four years of observations. This period is not present in any of the above-mentioned activity indicators. However, the RVs of narrow metallic emission lines suggest the same period, but with an anti-correlating phase. The observed absorption line RVs can be fitted with a Keplerian solution around a 0.6 M&sun; central star with msini = (14.7 ± 0.7) MJup and eccentricity of e = 0.24. Alternatively, we attempted to model the observations with a cold or hot stellar spot as well. We found that in our simple model, the spot parameters needed to reproduce the RV semi-amplitude are in contradiction with the photometric variability, making the spot scenario unlikely.
Conclusions: We qualitatively discuss two possibilities to explain the RV data: a geometry with two accretion columns rotating with the star, and a single accretion flow synchronized with the orbital motion of the hypothetical companion; the second scenario is more consistent with the observed properties of EX Lup. In this scenario, the companion's mass would fall into the brown dwarf desert, which, together with the unusually small separation of 0.06 au would make EX Lup a unique binary system. The companion also has interesting implications on the physical mechanisms responsible for triggering the outburst
The Mass-Radius Relationship for Very Low Mass Stars: Four New Discoveries from the HATSouth Survey
We report the discovery of four transiting F-M binary systems with companions
between 0.1-0.2 Msun in mass by the HATSouth survey. These systems have been
characterised via a global analysis of the HATSouth discovery data, combined
with high-resolution radial velocities and accurate transit photometry
observations. We determined the masses and radii of the component stars using a
combination of two methods: isochrone fitting of spectroscopic primary star
parameters, and equating spectroscopic primary star rotation velocity with
spin-orbit synchronisation. These new very low mass companions are HATS550-016B
(0.110 -0.006/+0.005 Msun, 0.147 -0.004/+0.003 Rsun), HATS551-019B (0.17
-0.01/+0.01 Msun, 0.18 -0.01/+0.01 Rsun), HATS551-021B (0.132 -0.005/+0.014
Msun, 0.154 -0.008/+0.006 Rsun), HATS553-001B (0.20 -0.02/+0.01 Msun, 0.22
-0.01/+0.01 Rsun). We examine our sample in the context of the radius anomaly
for fully-convective low mass stars. Combining our sample with the 13 other
well-studied very low mass stars, we find a tentative 5% systematic deviation
between the measured radii and theoretical isochrone models.Comment: 17 pages, 8 figures, accepted for publication in MNRA
HATS-1b: The first transiting planet discovered by the hatsouth survey
We report the discovery of HATS-1b, a transiting extrasolar planet orbiting the moderately bright V = 12.05 G dwarf star GSC 6652-00186, and the first planet discovered by HATSouth, a global network of autonomous wide-field telescopes. HATS-1b has a period of P ≈ 3.4465 days, mass of Mp ≈ 1.86 MJ, and radius of Rp ≈ 1.30 RJ. The host star has a mass of 0.99 M⊙ and radius of 1.04 R⊙. The discovery light curve of HATS-1b has near-continuous coverage over several multi-day timespans, demonstrating the power of using a global network of telescopes to discover transiting planets.Development of the HATSouth project was funded by NSF
MRI grant NSF/AST-0723074, operations are supported by
NASA grant NNX09AB29G, and follow-up observations received
partial support from grant NSF/AST-1108686. Followup
observations with the ESO 2.2 m/FEROS instrument were performed under MPI guaranteed time (P087.A-9014(A),
P088.A-9008(A), P089.A-9008(A)) and Chilean time (P087.C-
0508(A)). A.J. acknowledges support from Fondecyt project
1095213, Ministry of Economy ICM Nuclei P07-021-F and
P10-022-F, Anillo ACT-086 and BASAL CATA PFB-06. V.S.
acknowledges support form BASAL CATA PFB-06. M.R. acknowledges
support from a Fondencyt postdoctoral fellowship
N 3120097 and contributions from the ALMA-CONICYT
FUND Project N 31090015. R.B. and N.E. acknowledge support
from Fondecyt project 1095213. Work at the
Australian National University is supported by ARC Laureate
Fellowship Grant FL0992131. We acknowledge the use of
the AAVSO Photometric All-Sky Survey (APASS), funded by
the Robert Martin Ayers Sciences Fund, and the SIMBAD
database, operated at CDS, Strasbourg, France
Hats-3b: An inflated hot jupiter transiting an F-type star
We report the discovery by the HATSouth survey of HATS-3b, a transiting extrasolar planet orbiting a V = 12.4 F dwarf star. HATS-3b has a period of P = 3.5479 days, mass of Mp = 1.07 M J, and radius of R p = 1.38 R J. Given the radius of the planet, the
HATS-4b: A dense hot Jupiter transiting a super metal-rich G star
We report the discovery by the HATSouth survey of HATS-4b, an extrasolar planet transiting a V = 13.46 mag
G star. HATS-4b has a period of P ≈ 2.5167 days, mass of Mp ≈ 1.32 MJup, radius of Rp ≈ 1.02 RJup, and
density of ρp = 1.55 ± 0.16 g cm−3 ≈ 1.24 ρJup. The host star has a mass of 1.00 M , a radius of 0.92 R , and a
very high metallicity [Fe/H]= 0.43 ± 0.08. HATS-4b is among the densest known planets with masses between
1 and 2 MJ and is thus likely to have a significant content of heavy elements of the order of 75 M⊕. In this paper
we present the data reduction, radial velocity measurements, and stellar classification techniques adopted by the
HATSouth survey for the CORALIE spectrograph. We also detail a technique for simultaneously estimating v sin i
and macroturbulence using high resolution spectra.Development of the HATSouth project was funded by NSFMRI
grant NSF/AST-0723074, operations have been supported by
NASA grants NNX09AB29G and NNX12AH91H, and followup
observations receive partial support from grant NSF/AST-
1108686. A.J. acknowledges support from FONDECYT project
1130857, BASAL CATA PFB-06, and projects IC120009 “Millennium
Institute of Astrophysics (MAS)” and P10-022-F of the
Millennium Science Initiative, Chilean Ministry of Economy.
R.B. and N.E. are supported by CONICYT-PCHA/Doctorado
Nacional. R.B. acknowledges additional support from Nucleus
P10-022-F of the Millennium Science Initiative, Chilean Ministry
of Economy. V.S. acknowledges support form BASAL
CATA PFB-06. M.R. acknowledges support from FONDECYT
postdoctoral fellowship 3120097. Australian access to the Magellan Telescopeswas supported
through the National Collaborative Research Infrastructure
Strategy of the Australian Federal Government. Work at the Australian National University is supported by
ARC Laureate Fellowship Grant FL0992131. We acknowledge
the use of the AAVSO Photometric All-Sky Survey (APASS),
funded by the RobertMartin Ayers Sciences Fund, NASA’s Astrophysics
Data System Bibliographic Services, and the SIMBADdatabase,
operated at CDS, Strasbourg, France. Operations
at the MPG/ESO 2.2 m Telescope are jointly performed by the
Max Planck Gesellschaft and the European Southern Observatory
Synthesis and preliminary DNA-binding studies of diimineplatinum(II) complexes containing 3-or 4-pyridineboronic acid
HATS-2b: A transiting extrasolar planet orbiting a K-type star showing starspot activity
We report the discovery of HATS-2b, the second transiting extrasolar planet
detected by the HATSouth survey. HATS-2b is moving on a circular orbit around a
V=13.6 mag, K-type dwarf star (GSC 6665-00236), at a separation of 0.0230 \pm
0.0003 AU and with a period of 1.3541 days. The planetary parameters have been
robustly determined using a simultaneous fit of the HATSouth,
MPG/ESO~2.2\,m/GROND, Faulkes Telescope South/Spectral transit photometry and
MPG/ESO~2.2\,m/FEROS, Euler~1.2\,m/CORALIE, AAT~3.9\,m/CYCLOPS radial-velocity
measurements. HATS-2b has a mass of 1.37 \pm 0.16 M_J, a radius of 1.14 \pm
0.03 R_J and an equilibrium temperature of 1567 \pm 30 K. The host star has a
mass of 0.88 \pm 0.04 M_Sun, radius of 0.89 \pm 0.02 R_Sun and shows starspot
activity. We characterized the stellar activity by analysing two photometric
follow-up transit light curves taken with the GROND instrument, both obtained
simultaneously in four optical bands (covering the wavelength range of
3860-9520 \AA). The two light curves contain anomalies compatible with
starspots on the photosphere of the parent star along the same transit chord.Comment: 13 pages, 8 figures, accepted by A&
Genetic and Chemical Modifiers of a CUG Toxicity Model in Drosophila
Non-coding CUG repeat expansions interfere with the activity of human Muscleblind-like (MBNL) proteins contributing to myotonic dystrophy 1 (DM1). To understand this toxic RNA gain-of-function mechanism we developed a Drosophila model expressing 60 pure and 480 interrupted CUG repeats in the context of a non-translatable RNA. These flies reproduced aspects of the DM1 pathology, most notably nuclear accumulation of CUG transcripts, muscle degeneration, splicing misregulation, and diminished Muscleblind function in vivo. Reduced Muscleblind activity was evident from the sensitivity of CUG-induced phenotypes to a decrease in muscleblind genetic dosage and rescue by MBNL1 expression, and further supported by the co-localization of Muscleblind and CUG repeat RNA in ribonuclear foci. Targeted expression of CUG repeats to the developing eye and brain mushroom bodies was toxic leading to rough eyes and semilethality, respectively. These phenotypes were utilized to identify genetic and chemical modifiers of the CUG-induced toxicity. 15 genetic modifiers of the rough eye phenotype were isolated. These genes identify putative cellular processes unknown to be altered by CUG repeat RNA, and they include mRNA export factor Aly, apoptosis inhibitor Thread, chromatin remodelling factor Nurf-38, and extracellular matrix structural component Viking. Ten chemical compounds suppressed the semilethal phenotype. These compounds significantly improved viability of CUG expressing flies and included non-steroidal anti-inflammatory agents (ketoprofen), muscarinic, cholinergic and histamine receptor inhibitors (orphenadrine), and drugs that can affect sodium and calcium metabolism such as clenbuterol and spironolactone. These findings provide new insights into the DM1 phenotype, and suggest novel candidates for DM1 treatments
Cytoplasmic γ-actin and tropomodulin isoforms link to the sarcoplasmic reticulum in skeletal muscle fibers
Tropomodulins, cytoplasmic γ-actin, and small ankyrin 1.5 mechanically stabilize the sarcoplasmic reticulum and maintain myofibril alignment in skeletal muscle fibers
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