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Properties of Radial Velocities Measurement Based on LAMOST-II Medium-resolution Spectroscopic Observations
Wu, H.; Chen, L.; Wang, R. +28 more
The radial velocity (RV) is a basic physical quantity that can be determined through the Doppler shift of the spectrum of a star. The precision of the RV measurement depends on the resolution of the spectrum we used and the accuracy of wavelength calibration. In this work, radial velocities of the Large Sky Area Multi-Object Fibre Spectroscopic Te…
Quiescent Discrete Auroral Arcs: A Review of Magnetospheric Generator Mechanisms
Echim, Marius M.; Borovsky, Joseph E.; Otto, Antonius +7 more
One of the longstanding questions of space science is: How does the Earth's magnetosphere generate auroral arcs? A related question is: What form of energy is extracted from the magnetosphere to drive auroral arcs? Not knowing the answers to these questions hinders our ability to determine the impact of auroral arcs on the magnetospheric system. M…
Homogeneously derived transit timings for 17 exoplanets and reassessed TTV trends for WASP-12 and WASP-4
Molina, D.; Bretton, M.; Jones, H. R. A. +34 more
We homogeneously analyse ∼3.2 × 105 photometric measurements for ∼1100 transit light curves belonging to 17 exoplanet hosts. The photometric data cover 16 years (2004-2019) and include amateur and professional observations. Old archival light curves were reprocessed using up-to-date exoplanetary parameters and empirically debiased limb-…
Multifractal and Chaotic Properties of Solar Wind at MHD and Kinetic Domains: An Empirical Mode Decomposition Approach
Marcucci, Maria Federica; Consolini, Giuseppe; Alberti, Tommaso +3 more
Turbulence, intermittency, and self-organized structures in space plasmas can be investigated by using a multifractal formalism mostly based on the canonical structure function analysis with fixed constraints about stationarity, linearity, and scales. Here, the Empirical Mode Decomposition (EMD) method is firstly used to investigate timescale fluc…
Constraining the evolution of stellar rotation using solar twins
Bedell, Megan; Meléndez, Jorge; Bean, Jacob L. +7 more
The stellar rotation versus age relation is commonly considered a useful tool to derive reliable ages for Sun-like stars. However, in the light of Kepler data, the presence of apparently old and fast rotators that do not obey the usual gyrochronology relations led to the hypothesis of weakened magnetic breaking in some stars. In this letter, we co…
Three Z Camelopardalis-type dwarf novae exhibiting IW Andromedae-type phenomenon
Kato, Taichi
I found that V507 Cyg, IM Eri, and FY Vul are Z Cam-type dwarf novae and they showed sequences of standstill terminated by brightening, in contrast to fading as ordinary Z Cam stars do, followed by damping oscillation. These sequences are characteristic to IW And-type objects (also known as anomalous Z Cam stars). New additions to the IW And-type …
Merging Cluster Collaboration: Optical and Spectroscopic Survey of a Radio-selected Sample of 29 Merging Galaxy Clusters
Bradač, M.; Jee, M. J.; van Weeren, R. J. +11 more
Multi-band photometric and multi-object spectroscopic surveys of merging galaxy clusters allow for the characterization of the distributions of constituent DM and galaxy populations, constraints on the dynamics of the merging subclusters, and an understanding of galaxy evolution of member galaxies. We present deep photometric observations from Sub…
Searching for the GD-1 stream progenitor in Gaia DR2 with direct N-body simulations
Bovy, Jo; Webb, Jeremy J.
We perform a large suite of direct N-body simulations aimed at revealing the location of the progenitor, or its remnant, of the GD-1 stream. Data from Gaia DR2 reveal that the GD-1 stream extends over ≈100°, allowing us to determine the stream's leading and trailing ends. Our models suggest that the length of the stream is consistent with a dynami…
The Transiting Multi-planet System HD15337: Two Nearly Equal-mass Planets Straddling the Radius Gap
Torres, Guillermo; Cochran, William D.; Endl, Michael +53 more
We report the discovery of a super-Earth and a sub-Neptune transiting the star HD 15337 (TOI-402, TIC 120896927), a bright (V = 9) K1 dwarf observed by the Transiting Exoplanet Survey Satellite (TESS) in Sectors 3 and 4. We combine the TESS photometry with archival High Accuracy Radial velocity Planet Searcher spectra to confirm the planetary natu…
The magnetic early B-type Stars II: stellar atmospheric parameters in the era of Gaia
Wade, G. A.; Neiner, C.; Shultz, M. E. +6 more
Atmospheric parameters determined via spectral modelling are unavailable for many of the known magnetic early B-type stars. We utilized high-resolution spectra together with non-local thermodynamic equilibrium models to measure effective temperatures Teff and surface gravities log g of stars for which these measurements are not yet avai…