Search Publications
Estimating the Injection Duration of 20 MeV Protons in Large Western Solar Energetic Particle Events
Lugaz, Noé; Li, Gen
An ad hoc analytical calculation is presented to infer the duration of injection of 20 MeV protons in 21 selected western solar energetic particle (SEP) events. We convolve the solution of diffusion equation with a "triangle" source to model the time-intensity profiles over the onset and the peaking phase. The effects of "corotating" flux tubes an…
X-ray irradiation of three planets around Hyades star K2 -136
Fernández Fernández, Jorge; Wheatley, Peter J.
We study the X-ray irradiation and likely photoevaporation of the three planets around the star K2-136. These are the Earth-sized K2-136 b, the mini-Neptune K2-136 c, and the super-Earth K2-136 d. XMM-Newton observations of the star indicate an X-ray luminosity of $(1.18\pm0.1)\times10^{28}$ erg s$^{-1}$ in the range 0.15 to 2.4 keV, resulting in …
Modeling the Photometric Variability of Alpha2 CVn with a Dynamical Magnetosphere
Pfeffer, Cameron M.; McSwain, M. Virginia
Alpha2 Canum Venaticorum (α 2 CVn) is a strongly magnetic star with peculiar chemical signatures and periodic variability that have been long attributed to the diffusion of magnetic elements through the photosphere, leading to chemical spots across the stellar surface. However, recent studies of other magnetic hot stars are c…
Efficient labelling of solar flux evolution videos by a deep learning model
Chatterjee, Subhamoy; Muñoz-Jaramillo, Andrés; Lamb, Derek A.
Machine learning is becoming a critical tool for the interrogation of large, complex data. Labelling, defined as the process of adding meaningful annotations, is a crucial step of supervised machine learning. However, labelling datasets is time consuming. Here we show that convolutional neural networks (CNNs) trained on crudely labelled astronomic…
A detailed study of the barium central star of the planetary nebula Abell 70
Munday, James; Jones, David; Miszalski, Brent +4 more
We present a detailed study of the barium star at the heart of the planetary nebula Abell 70. Time-series photometry obtained over a period of more than 10 yr demonstrates that the barium-contaminated companion is a rapid rotator with temporal variability due to spots. The amplitude and phasing of the photometric variability change abruptly; howev…
Periodic Oscillations in LASCO Coronal Mass Ejection Speeds: Space Seismology
Gopalswamy, Nat; Yashiro, Seiji; Michalek, Grzegorz
Coronal mass ejections (CMEs) are energetic eruptions of organized magnetic structures from the Sun. Therefore, the reconnection of the magnetic field during ejection can excite periodic speed oscillations of CMEs. A previous study showed that speed oscillations are frequently associated with CME propagation. The Solar and Heliospheric Observatory…
Morphological and hydrological analysis of volcanic flank valleys - Evidence for a volcanic origin
Bahia, Rickbir S.
Valley networks incising the flanks of Martian volcanoes are potential evidence of geologically recent fluvial activity, either via geothermal heating of snowmelt and groundwater upwelling [Gulick and Baker, 1989, 1990; Gulick et al., 1997; Gulick, 2001; Hynek et al., 2010], or summit snowpack melt [Fassett and Head, 2006, 2007]; however, their or…
The Gaia AVU-GSR parallel solver: Preliminary studies of a LSQR-based application in perspective of exascale systems
Lattanzi, M. G.; Becciani, U.; Bucciarelli, B. +6 more
The Gaia Astrometric Verification Unit-Global Sphere Reconstruction (AVU-GSR) Parallel Solver aims to find the astrometric parameters for ∼ 108 stars in the Milky Way, the attitude and the instrumental specifications of the Gaia satellite, and the global parameter γ of the post Newtonian formalism. The code iteratively solves a system o…
The double-lined spectroscopic binary orbit of the massive supergiant HD 152147: A new target for interferometry
Gamen, R.; Barbá, R. H.; Morrell, N. I. +4 more
We present a new spectroscopic orbit of the O-type binary system HD 152147. We identify absorption lines in both components and use their radial velocities to determine the orbit, which results in a period of P = 50.2199 ± 0.0007 d, an eccentricity e = 0.738 ± 0.007, and a mean separation between the components of asin i = 151 ± 1 R⊙. C…
Disentangling the neighbouring pulsars SXP 15.3 and SXP 305
Udalski, A.; Coe, M. J.; Roy, A. +8 more
SXP 15.3 and SXP 305 are two Be X-ray binaries in the Small Magellanic Cloud that are spatially separated by ~7 arcsec. The small separation between these sources has, in the past, resulted in confusion about the origin of the emission from the combined region. We present long-term optical and X-ray monitoring results of both sources, where we stu…