255 research outputs found
SPECIES II. Stellar parameters of the EXPRESS program giant star sample
As part of the search for planets around evolved stars, we can understand
planet populations around significantly higher-mass stars than the Sun on the
main sequence. This population is difficult to study any other way,
particularly with radial-velocities since these stars are too hot and rotate
too fast to measure precise velocities. Here we estimate stellar parameters for
all of the giant stars from the EXPRESS project, which aims to detect planets
orbiting evolved stars, and study their occurrence rate as a function of
stellar mass. We analyse high resolution echelle spectra of these stars, and
compute the atmospheric parameters by measuring the equivalent widths for a set
of iron lines, using an updated method implemented during this work. Physical
parameters are computed by interpolating through a grid of stellar evolutionary
models, following a procedure that carefully takes into account the post-MS
evolutionary phases. Probabilities of the star being in the red giant branch
(RBG) or the horizontal branch (HB) are estimated from the derived
distributions. Results: We find that, out of 166 evolved stars, 101 of them are
most likely in the RGB phase, while 65 of them are in the HB phase. The mean
derived mass is 1.41 and 1.87 Msun for RGB and HB stars, respectively. To
validate our method, we compared our results with interferometry and
asteroseismology studies. We find a difference in the radius with
interferometry of 1.7%. With asteroseismology, we find 2.4% difference in logg,
1.5% in radius, 6.2% in mass, and 11.9% in age. Compared with previous
spectroscopic studies, and find a 0.5% difference in Teff, 1% in logg, and 2%
in [Fe/H]. We also find a mean mass difference with respect to the EXPRESS
original catalogue of 16%. We show that the method presented here can greatly
improve the estimates of the stellar parameters for giant stars compared to
what was presented previously.Comment: 24 pages, 17 figures, 15 tables, accepted by A&
Volume-limited sample of low-mass red giant stars, the progenitors of hot subdwarf stars I. Sample selection and binary classification method
The current theory predicts that hot subdwarf binaries are produced from
evolved low-mass binaries that have undergone mass transfer and drastic mass
loss during either a common envelope phase or a stable Roche lobe overflow
while on the red giant branch (RGB). We perform a spectroscopic survey to find
binary systems that include low-mass red giants near the tip of the RGB, which
are predicted to be the direct progenitors of subdwarf B (sdB) stars. We aim to
obtain a homogeneous sample to search for the observational evidence of
correlations between the key parameters governing the formation of sdB stars
and constrain the physics of stable mass transfer. In this work, we
concentrated on the southern hemisphere targets and conducted a spectroscopic
survey of 88 red giant stars to search for the long-period RGB + MS binary
systems within 200\,pc. Combining radial velocity (RV) measurements from
ground-based observations with CORALIE and RV measurements from DR2 and
early data release 3 (eDR3) as well as the astrometric excess noise and RUWE
measurements from DR3, we defined a robust binary classification method.
In addition, we searched for known binary systems in the literature and in the
DR3. We select a total of 211 RGB candidates in the southern hemisphere
within 200\,pc based on the DR2 color-magnitude diagram. Among them, a
total of 33 red giants were reported as binary systems with orbital periods
between 100 and 900 days, some of which are expected to be the direct
progenitors of wide binary sdB stars. In addition, we classified 37 new
MS\,+\,RGB binary candidates, whose orbital parameters will be measured with
future spectroscopic follow-up.Comment: 9 pages, 2 figures, accepted for publication in A&
The Calan-Hertfordshire Extrasolar Planet Search
The detailed study of the exoplanetary systems HD189733 and HD209458 has
given rise to a wealth of exciting information on the physics of exoplanetary
atmospheres. To further our understanding of the make-up and processes within
these atmospheres we require a larger sample of bright transiting planets. We
have began a project to detect more bright transiting planets in the southern
hemisphere by utilising precision radial-velocity measurements. We have
observed a constrained sample of bright, inactive and metal-rich stars using
the HARPS instrument and here we present the current status of this project,
along with our first discoveries which include a brown dwarf/extreme-Jovian
exoplanet found in the brown dwarf desert region around the star HD191760 and
improved orbits for three other exoplanetary systems HD48265, HD143361 and
HD154672. Finally, we briefly discuss the future of this project and the
current prospects we have for discovering more bright transiting planets.Comment: 4 pages, 2 figures, to appear in the conference proceedings "New
Technologies for Probing the Diversity of Brown Dwarfs and Exoplanets"
Shanghai 200
B decays
We review the prospects for B decay studies at the LHC. Contributing authors: J. Baines, S.P. Baranov, P. Bartalini, M. Beneke, E. Bouhova, G. Buchalla, I. Caprini, F. Charles, J. Charles, Y. Coadou, P. Colangelo, P. Colrain, J. Damet, F. De Fazio, A. Dighe, H. Dijkstra, P. Eerola, N. Ellis, B. Epp, S. Gadomski, P. Galumian, I. Gavrilenko, S. George, V.M. Ghete, V. Gibson, L. Guy, Y. Hasegawa, P. Iengo, A. Jacholkowska, R. Jones, A. Khodjamirian, E. Kneringer, P. Koppenburg, H. Korsmo, N. Labanca, L. Lellouch, M. Lehto, Y. Lemoigne, J. Libby, J. Matias, S. Mele, M. Misiak, A.M. Nairz, T. Nakada, A. Nikitenko, N. Nikitin, A. Nisati, F. Palla, E. Polycarpo, J. Rademacker, F. Rizatdinova, S. Robins, D. Rousseau, W. Ruckstuhl, M.A. Sanchis, O. Schneider, M. Shapiro, C. Shepherd-Themistocleous, P. Sherwood, L. Smirnova, M. Smizanska, A. Starodumov, N. Stepanov, Z. Xie, N. Zaitse
A long-period transiting substellar companion in the super-Jupiters to brown dwarfs mass regime and a prototypical warm-Jupiter detected by TESS
We report on the confirmation and follow-up characterization of two long-period transiting substellar companions on low-eccentricity orbits around TIC 4672985 and TOI-2529, whose transit events were detected by the TESS space mission. Ground-based photometric and spectroscopic follow up from different facilities, confirmed the substellar nature of TIC 4672985 b, a massive gas giant, in the transition between the super-Jupiters and brown-dwarfs mass regime. From the joint analysis we derived the following orbital parameters: P = 69.0480+0.0004−0.0005 d, Mp = 12.74+1.01−1.01 MJ, Rp =1.026+0.065−0.067 RJ and e = 0.018+0.004−0.004 . In addition, the RV time series revealed a significant trend at the ∼ 350 m s−1 yr−1level, which is indicative of the presence of a massive outer companion in the system. TIC 4672985 b is a unique example of a transiting substellar companion with a mass above the deuterium-burning limit, located beyond 0.1 AU and in a nearly circular orbit. These planetary properties are difficult to reproduce from canonical planet formation and evolution models. For TOI-2529 b, we obtained the following orbital parameters: P = 64.5949+0.0003−0.0003 d, Mp =2.340+0.197−0.195 MJ, Rp = 1.030+0.050−0.050 RJ and e = 0.021+0.024−0.015 , making this object a new example of a growing population of transiting warm giant planets
A long-period transiting substellar companion in the super-Jupiters to brown dwarfs mass regime and a prototypical warm-Jupiter detected by TESS
We report on the confirmation and follow-up characterization of two
long-period transiting substellar companions on low-eccentricity orbits around
TIC 4672985 and TOI-2529, whose transit events were detected by the TESS space
mission. Ground-based photometric and spectroscopic follow-up from different
facilities, confirmed the substellar nature of TIC 4672985 b, a massive gas
giant, in the transition between the super Jupiters and brown dwarfs mass
regime. From the joint analysis we derived the following orbital parameters: P
= 69.0480 d, Mp = 12.74 Mjup, Rp = 1.026 Rjup and e = 0.018. In addition, the
RV time series revealed a significant trend at the 350 m/s/yr level, which is
indicative of the presence of a massive outer companion in the system. TIC
4672985 b is a unique example of a transiting substellar companion with a mass
above the deuterium-burning limit, located beyond 0.1 AU and in a nearly
circular orbit. These planetary properties are difficult to reproduce from
canonical planet formation and evolution models. For TOI-2529 b, we obtained
the following orbital parameters: P = 64.5949 d, Mp = 2.340 Mjup, Rp = 1.030
Rjup and e = 0.021, making this object a new example of a growing population of
transiting warm giant planets.Comment: Accepted in A&
Interplay between n-3 and n-6 long-chain polyunsaturated fatty acids and the endocannabinoid system in brain protection and repair.
The brain is enriched in arachidonic acid (ARA) and docosahexaenoic acid (DHA), long-chain polyunsaturated fatty acids (LCPUFA) of the n-6 and n-3 series, respectively. Both are essential for optimal brain development and function. Dietary enrichment with DHA and other long-chain n-3 PUFA, such as eicosapentaenoic acid (EPA) have shown beneficial effects on learning and memory, neuroinflammatory processes and synaptic plasticity and neurogenesis. ARA, DHA and EPA are precursors to a diverse repertoire of bioactive lipid mediators, including endocannabinoids. The endocannabinoid system comprises cannabinoid receptors, their endogenous ligands, the endocannabinoids, and their biosynthetic and degradation enzymes. Anandamide (AEA) and 2-archidonoylglycerol (2-AG) are the most widely studied endocannabinoids, and are both derived from phospholipid-bound ARA. The endocannabinoid system also has well established roles in neuroinflammation, synaptic plasticity and neurogenesis, suggesting an overlap in the neuroprotective effects observed with these different classes of lipids. Indeed, growing evidence suggests a complex interplay between n-3 and n-6 LCPUFA and the endocannabinoid system. For example, long-term DHA and EPA supplementation reduces AEA and 2-AG levels, with reciprocal increases in levels of the analogous endocannabinoid-like DHA and EPA-derived molecules. This review summarises current evidence of this interplay and discusses the therapeutic potential for brain protection and repair
Using State Space Exploration to Determine How Gene Regulatory Networks Constrain Mutation Order in Cancer Evolution
Cancer develops via the progressive accumulation of somatic mutations, which subvert the normal operation of the gene regulatory network of the cell. However, little is known about the order in which mutations are acquired in successful clones. A particular sequence of mutations may confer an early selective advantage to a clone by increasing survival or proliferation, or lead to negative selection by triggering cell death. The space of allowed sequences of mutations is therefore constrained by the gene regulatory network. Here, we introduce a methodology for the systematic exploration of the effect of every possible sequence of oncogenic mutations in a cancer cell modelled as a qualitative network. Our method uses attractor identification using binary decision diagrams and can be applied to both synchronous and asynchronous systems. We demonstrate our method using a recently developed model of ER-negative breast cancer. We show that there are differing levels of constraint in the order of mutations for different combinations of oncogenes, and that the effects of ErbB2/HER2 over-expression depend on the preceding mutations
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