Search Publications
Single-spacecraft Identification of Flux Tubes and Current Sheets in the Solar Wind
Servidio, Sergio; Pecora, Francesco; Greco, Antonella +3 more
A novel technique is presented for describing and visualizing the local topology of the magnetic field using single-spacecraft data in the solar wind. The approach merges two established techniques: the Grad-Shafranov (GS) reconstruction method, which provides a plausible regional two-dimensional magnetic field surrounding the spacecraft trajector…
Asteroseismology of Massive Stars with the TESS Mission: The Runaway β Cep Pulsator PHL 346 = HN Aqr
Gazeas, Kosmas; Bowman, Dominic M.; Ricker, George R. +21 more
We report an analysis of the first known β Cep pulsator observed by the Transiting Exoplanet Survey Satellite (TESS) mission, the runaway star PHL 346 = HN Aqr. The star, previously known as a singly periodic pulsator, has at least 34 oscillation modes excited, 12 of those in the g-mode domain and 22 p modes. Analysis of archival data implies that…
Deep ATCA and VLA Radio Observations of Short-GRB Host Galaxies. Constraints on Star Formation Rates, Afterglow Flux, and Kilonova Radio Flares
Palazzi, E.; Greiner, J.; Hunt, L. K. +6 more
We report the results of an extensive radio-continuum observing campaign of host galaxies of short gamma-ray bursts (GRBs). The goal of this survey was to search for optically obscured star formation, possibly indicative of a population of young short-GRB progenitors. Our sample comprises the hosts and host-galaxy candidates of 16 short-GRBs from …
GD358: Three Decades of Observations for the In-depth Asteroseismology of a DBV Star
Kim, S. -L.; Hoyer, D.; Montgomery, M. H. +39 more
We report on the analysis of 34 years of photometric observations of the pulsating helium atmosphere white dwarf GD358. The complete data set includes archival data from 1982 to 2006, and 1195.2 hr of new observations from 2007 to 2016. From this data set, we extract 15 frequencies representing g-mode pulsation modes, adding 4 modes to the 11 mode…
Dynamo Wave Patterns inside of the Sun Revealed by Torsional Oscillations
Kosovichev, Alexander G.; Pipin, Valery V.
Torsional oscillations represent bands of fast and slow zonal flows around the Sun, which extend deep into the convection zone and migrate during solar cycles toward the equator following the sunspot “butterfly” diagram. Analysis of helioseismology data obtained in 1996-2018 for almost two solar cycles reveals zones of deceleration of the torsiona…
Damping of Propagating Kink Waves in the Solar Corona
Morton, Richard J.; Tiwari, Ajay K.; Régnier, Stéphane +1 more
Alfvénic waves have gained renewed interest since the existence of ubiquitous propagating kink waves were discovered in the corona. It has long been suggested that Alfvénic waves play an important role in coronal heating and the acceleration of the solar wind. To this effect, it is imperative to understand the mechanisms that enable their energy t…
Short-term Variability of Evolved Massive Stars with TESS
Davenport, James R. A.; Dorn-Wallenstein, Trevor Z.; Levesque, Emily M.
We present the first results from a study of Transiting Exoplanet Survey Satellite (TESS) Sector 1 and 2 light curves for eight evolved massive stars in the LMC: six yellow supergiants (YSGs) and two luminous blue variables (LBVs), including S Doradus. We use an iterative prewhitening procedure to characterize the short-timescale variability in al…
Evidence for a Massive Warm-Hot Circumgalactic Medium around NGC 3221
Nicastro, Fabrizio; Mathur, Smita; Gupta, Anjali +3 more
We report a 3.4σ detection of the warm-hot, massive, extended circumgalactic medium (CGM) around an L ⋆ star-forming spiral galaxy NGC 3221, using deep Suzaku observations. The temperature of the gas is 106.1 K, comparable to that of the Milky Way CGM. The spatial extent of the gas is at least 150 kpc. For a β-model of densit…
Possible Evidence for Cosmic-Ray Acceleration in the Type Ia SNR RCW 86: Spatial Correlation between TeV Gamma-Rays and Interstellar Atomic Protons
Rowell, G.; Fukui, Y.; Mitsuishi, I. +13 more
We present a detailed morphological study of TeV gamma-rays, synchrotron radiation, and interstellar gas in the young Type Ia supernova remnant (SNR) RCW 86. We find that the interstellar atomic gas shows good spatial correlation with the gamma-rays, indicating that the TeV gamma-rays from RCW 86 are likely predominantly of hadronic origin. In con…
Dust-to-gas Ratio Resurgence in Circumstellar Disks Due to the Formation of Giant Planets: The Case of HD 163296
Marzari, F.; Testi, L.; Polychroni, D. +1 more
The amount of dust present in circumstellar disks is expected to steadily decrease with age due to the growth from µm-sized particles to planetesimals and planets. Mature circumstellar disks, however, can be observed to contain significant amounts of dust and possess high dust-to-gas ratios. Using HD 163296 as our case study, we explore how …