59 research outputs found
The L 98-59 System: Three Transiting, Terrestrial-Size Planets Orbiting A Nearby M Dwarf
We report the Transiting Exoplanet Survey Satellite (TESS) discovery of three terrestrial-size planets transiting L 98-59 (TOI-175, TIC 307210830)âa bright M dwarf at a distance of 10.6 pc. Using the Gaia-measured distance and broadband photometry, we find that the host star is an M3 dwarf. Combined with the TESS transits from three sectors, the corresponding stellar parameters yield planet radii ranging from 0.8 Râ to 1.6 Râ. All three planets have short orbital periods, ranging from 2.25 to 7.45 days with the outer pair just wide of a 2:1 period resonance. Diagnostic tests produced by the TESS Data Validation Report and the vetting package DAVE rule out common false-positive sources. These analyses, along with dedicated follow-up and the multiplicity of the system, lend confidence that the observed signals are caused by planets transiting L 98-59 and are not associated with other sources in the field. The L 98-59 system is interesting for a number of reasons: the host star is bright (V = 11.7 mag, K = 7.1 mag) and the planets are prime targets for further follow-up observations including precision radial-velocity mass measurements and future transit spectroscopy with the James Webb Space Telescope; the near-resonant configuration makes the system a laboratory to study planetary system dynamical evolution; and three planets of relatively similar size in the same system present an opportunity to study terrestrial planets where other variables (age, metallicity, etc.) can be held constant. L 98-59 will be observed in four more TESS sectors, which will provide a wealth of information on the three currently known planets and have the potential to reveal additional planets in the system
Curvature-bias corrections using a pseudomass method
Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy â(s)=13 TeV during 2016, 2017 and 2018. The biases are determined using ZâÎŒ + ÎŒ - decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10-4 GeV-1 level, improves the ZâÎŒ + ÎŒ - mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass
Natural and anthropogenic controls on sediment rating curves in northern California coastal watersheds
A spectroscopic survey of EC4, an extended cluster in Andromeda's halo
We present a spectroscopic survey of candidate red giant branch stars in the
extended star cluster, EC4, discovered in the halo of M31 from our CFHT/MegaCam
survey, overlapping the tidal streams, Stream Cp and Stream Cr. These
observations used the DEep Imaging Multi-Object Spectrograph (DEIMOS) mounted
on the Keck II telescope to obtain spectra around the CaII triplet region with
~1.3 Angstroms resolution. Six stars lying on the red giant branch within 2
core-radii of the centre of EC4 are found to have an average
vr=-287.9^{+1.9}_{-2.4}km/s and velocity dispersion of 2.7^{+4.2}_{-2.7}km/s,
taking instrumental errors into account. The resulting mass-to-light ratio for
EC4 is M/L=6.7^{+15}_{-6.7}Msun/Lsun, a value that is consistent with a
globular cluster within the 1 sigma errors we derive. From the summed spectra
of our member stars, we find EC4 to be metal-poor, with [Fe/H]=-1.6+/-0.15. We
discuss several formation and evolution scenarios which could account for our
kinematic and metallicity constraints on EC4, and conclude that EC4 is most
comparable with an extended globular cluster. We also compare the kinematics
and metallicity of EC4 with Stream Cp and Stream Cr, and find that EC4 bears a
striking resemblance to Stream Cp in terms of velocity, and that the two
structures are identical in terms of both their spectroscopic and photometric
metallicities. From this we conclude that EC4 is likely related to Stream Cp.Comment: 13 pages, 7 figures, MNRAS accepte
Sensory Considerations in the Replacement in Dark Chocolate of Sucrose by Other Carbohydrate Sweeteners
The Pristine Dwarf-Galaxy survey â II. In-depth observational study of the faint Milky Way satellite Sagittarius II
International audienceWe present an extensive study of the Sagittarius II (Sgr II) stellar system using MegaCam g and i photometry, narrow-band, metallicity-sensitive calcium H&K doublet photometry and Keck II/DEIMOS multiobject spectroscopy. We derive and refine the Sgr II structural and stellar properties inferred at the time of its discovery. The colourâmagnitude diagram implies Sgr II is old (12.0 ± 0.5 Gyr) and metal poor. The CaHK photometry confirms the metal-poor nature of the satellite ([Fe/H] _CaHK = â2.32 ± 0.04 dex) and suggests that Sgr II hosts more than one single stellar population (â || dex). Using the Ca infrared triplet measured from our highest signal-to-noise spectra, we confirm the metallicity and dispersion inferred from the Pristine photometric metallicities ([Fe/H]_spectro = â2.23 ± 0.05 dex, || dex). The velocity dispersion of the system is found to be || after excluding two potential binary stars. Sgr IIâs metallicity and absolute magnitude ( = â5.7 ± 0.1 mag) place the system on the luminosityâmetallicity relation of the Milky Way dwarf galaxies despite its small size. The low but resolved metallicity and velocity dispersions paint the picture of a slightly dark-matter-dominated satellite (â || M_â L||â ). Furthermore, using the Gaia Data Release 2, we constrain the orbit of the satellite and find an apocentre of || and a pericentre of ||â . The orbit of Sgr II is consistent with the trailing arm of the Sgr stream and indicates that it is possibly a satellite of the Sgr dSph that was tidally stripped from the dwarfâs influence
Accretion in action:Phase space coherence of stellar debris and globular clusters in andromeda's south-west cloud
Immune response is an important aspect of the antitumor effect produced by a CD40L-encoding oncolytic adenovirus
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