Search Publications
Understanding the Duration of Solar and Stellar Flares at Various Wavelengths
Reep, Jeffrey W.; Airapetian, Vladimir S.
Recent irradiance measurements from numerous heliophysics and astrophysics missions including Solar Dynamics Observatory (SDO), GOES, Kepler, TESS, Chandra, the X-ray Multi-Mirror Mission, and NICER have provided critical input into understanding the physics of the most powerful transient events on the Sun and magnetically active stars:solar and s…
A Young White Dwarf Orbiting PSR J1835-3259B in the Bulge Globular Cluster NGC 6652
Cadelano, Mario; Pallanca, Cristina; Ferraro, Francesco R. +8 more
We report on the discovery of the companion star to the millisecond pulsar PSR J1835-3259B in the Galactic globular cluster NGC 6652. Taking advantage of deep photometric archival observations acquired through the Hubble Space Telescope in near-UV and optical bands, we identified a bright and blue object at a position compatible with that of the r…
Modeling the Formation and Evolution of Solar Wind Microstreams: From Coronal Plumes to Propagating Alfvénic Velocity Spikes
Rouillard, Alexis P.; Réville, Victor; Gannouni, Bahaeddine
We investigate the origin of mesoscale structures in the solar wind called microstreams, defined as enhancements in the solar wind speed and temperature that last several hours. They were first clearly detected in Helios and Ulysses solar wind data and are now omnipresent in the "young" solar wind measured by the Parker Solar Probe and Solar Orbit…
Composite Bulges. III. A Study of Nuclear Star Clusters in Nearby Spiral Galaxies
Beckman, John E.; Bender, Ralf; Drory, Niv +17 more
We present photometric and morphological analyses of nuclear star clusters (NSCs)-very dense, massive star clusters present in the central regions of most galaxies-in a sample of 33 massive disk galaxies within 20 Mpc, part of the "Composite Bulges Survey." We use data from the Hubble Space Telescope including optical (F475W and F814W) and near-IR…
Searching for Gravitational-wave Counterparts Using the Transiting Exoplanet Survey Satellite
Jayaraman, Rahul; Ricker, George R.; Vanderspek, Roland +3 more
In 2017, the LIGO and Virgo gravitational-wave (GW) detectors, in conjunction with electromagnetic (EM) astronomers, observed the first GW multimessenger astrophysical event, the binary neutron star (BNS) merger GW170817. This marked the beginning of a new era in multimessenger astrophysics. To discover further GW multimessenger events, we explore…
ALMA Reveals Hidden Morphologies in the Molecular Envelope of VY Canis Majoris
Humphreys, R. M.; Decin, L.; Richards, A. M. S. +2 more
The J = 2 → 1 transition of CO near 230 GHz and the J = 3 → 2 line of HCN at 265 GHz have been imaged in the envelope of the red hypergiant star, VY Canis Majoris (VY CMa), using the Atacama Large Millimeter Array (ALMA) with angular resolutions 0.″2-1.″5; single-dish data were added to provide sensitivity up to 30″. These images reveal a far more…
The Hα Luminosity Function of Galaxies at z 4.5
Illingworth, Garth D.; Labbé, Ivo; Bouwens, Rychard J. +5 more
We present the Hα luminosity function (LF) derived from a large sample of Lyman break galaxies at z ~ 4.5 over the GOODS-South and North fields. This study makes use of the new, full-depth Spitzer/IRAC [3.6] and [4.5] imaging from the GOODS Re-ionization Era wide-Area Treasury from the Spitzer program. The Hα flux is derived from the offset betwee…
Center-to-limb Variation of Transition-region Doppler Shifts in Active Regions
Tripathi, Durgesh; Kashyap, Vinay L.; Ghosh, Avyarthana +2 more
Studying Doppler shifts provides deep insights into the flow of mass and energy in the solar atmosphere. We perform a comprehensive measurement of Doppler shifts in the transition region and its center-to-limb variation (CLV) in the strong-field regions (∣ B ∣ ≥ 50 G) of 50 active regions (ARs), using the Si IV 1394 Å line recorded by the Interfac…
White-light Superflare and Long-term Activity of the Nearby M7-type Binary EI Cnc Observed with GWAC System
Wang, Jing; Liang, En-Wei; Wang, Xiang-Gao +14 more
Stellar white-light flares are believed to play an essential role in the physical and chemical properties of the atmosphere of the surrounding exoplanets. Here we report an optical monitoring campaign on the nearby flaring system EI Cnc carried out by the Ground-based Wide Angle Camera (GWAC) and its dedicated follow-up telescope. A superflare, co…
Unusual Hard X-Ray Flares Caught in NICER Monitoring of the Binary Supermassive Black Hole Candidate AT2019cuk/Tick Tock/SDSS J1430+2303
Fabian, Andrew C.; Remillard, Ronald A.; Arzoumanian, Zaven +17 more
The nuclear transient AT2019cuk/Tick Tock/SDSS J1430+2303 has been suggested to harbor a supermassive black hole (SMBH) binary near coalescence. We report results from high-cadence NICER X-ray monitoring with multiple visits per day from 2022 January to August, as well as continued optical monitoring during the same time period. We find no evidenc…