Search Publications
SKYSURF-3: Testing Crowded Object Catalogs in the Hubble eXtreme Deep Field Mosaics to Study Sample Incompleteness from an Extragalactic Background Light Perspective
Pirzkal, Nor; Windhorst, Rogier A.; Koekemoer, Anton +6 more
Extragalactic background light (EBL) studies have revealed a significant discrepancy between direct measurements-via instruments measuring "bare" sky from which Zodiacal and Galactic light models are subtracted-and measurements of the integrated galaxy light (IGL). This discrepancy could lie in either method, whether it be an incomplete Zodiacal m…
A Star-sized Impact-produced Dust Clump in the Terrestrial Zone of the HD 166191 System
Rieke, G. H.; Kennedy, Grant M.; Su, Kate Y. L. +2 more
We report on five years of 3-5 µm photometry measurements obtained by warm Spitzer to track the dust debris emission in the terrestrial zone of HD 166191 in combination with simultaneous optical data. We show that the debris production in this young (~10 Myr) system increased significantly in early 2018 and reached a record high level (almos…
Radio Observations of Four Active Galactic Nuclei Hosting Intermediate-mass Black Hole Candidates: Studying the Outflow Activity and Evolution
Ho, Luis C.; Zhang, Shaohua; Yang, Jun +5 more
Observational searches for intermediate-mass black holes (IMBHs; 102-106 M ⊙) include relatively isolated dwarf galaxies. For those that host active galactic nuclei (AGNs), the IMBH nature may be discerned through the accretion-jet activity. We present radio observations of four AGN-hosting dwarf galaxies, which po…
Far-ultraviolet Flares on Accreting Protostars: Weak and Classical T Tauri Stellar Pair Analysis
Kowalski, Adam F.; France, Kevin; Hinton, P. C. +5 more
The far-ultraviolet (FUV) emission of classical T Tauri stars (CTTSs) is known to play an important role in protoplanetary disk dispersal and giant planet formation, yet the role played by protostellar flares in these processes is largely unknown. We use nearby star-forming regions as laboratories to probe the FUV flare characteristics of CTTSs an…
First Report of a Solar Energetic Particle Event Observed by China's Tianwen-1 Mission in Transit to Mars
Zhao, Lingling; Sun, Zhiyu; Yu, Yuhong +15 more
Solar energetic particles (SEPs) associated with flares and/or coronal mass ejection (CME)-driven shocks can impose acute radiation hazards on space explorations. To measure energetic particles in near-Mars space, the Mars Energetic Particle Analyzer (MEPA) instrument on board China's Tianwen-1 (TW-1) mission was designed. Here, we report the firs…
Relationship between Total Solar Irradiance and Magnetic Flux during Solar Minima
Lean, Judith L.; Marchenko, Sergey V.; DeLand, Matthew T.
What drives the small total solar irradiance (TSI) changes of ~50-100 parts per million (compared with >1000 ppm solar-cycle amplitudes) during a deep solar minimum, i.e., in the practical absence of detectable sunspots and long-lasting active regions? We consider the epoch 2008 June-October and investigate multiple data sets (TSI; various Mg I…
A Very Long Baseline Array Trigonometric Parallax for RR Aql and the Mira Period-Luminosity Relation
Sun, Yan; Reid, Mark J.; Zhang, Bo +4 more
We report Very Long Baseline Array observations of 22 GHz H2O and 43 GHz SiO masers toward the Mira variable RR Aql. By fitting the SiO maser emission to a circular ring, we estimate the absolute stellar position of RR Aql and find agreement with Gaia astrometry to within the joint uncertainty of ≈1 mas. Using the maser astrometry we me…
On the Evolution of Rotational Modulation Amplitude in Solar-mass Main-sequence Stars
Masuda, Kento
We investigate the relation between rotation periods P rot and photometric modulation amplitudes R per for ≈4000 Sun-like main-sequence stars observed by Kepler, using P rot and R per from McQuillan et al., effective temperature T eff from LAMOST DR6, and parallax data from Gaia EDR3. As has b…
Radio Emission from Binary Ultracool Dwarf Systems
Kao, Melodie M.; Pineda, J. Sebastian
Well-characterized binary systems will provide valuable opportunities to study the conditions that are necessary for the onset of both auroral and nonauroral magnetospheric radio emission in the ultracool dwarf regime. We present new detections of nonauroral "quiescent" radio emission at 4-8 GHz of the three ultracool dwarf binary systems GJ 564 B…
Discovery of Nine Super Li-rich Unevolved Stars from the LAMOST Survey
Wang, L.; Shi, J. -R.; Zhou, Y. -T. +7 more
Based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) medium-resolution spectroscopic survey (MRS), we report the discovery of nine super Li-rich unevolved stars with A(Li) > 3.8 dex. These objects show unusually high levels of lithium abundances, up to three times higher than the meteoritic value of 3.3 dex, which ind…