Search Publications
The AstroSat UV Deep Field North: The IRX–β Relation for the UV-selected Galaxies at z ∼ 0.5‑0.7
Saha, Kanak; Mondal, Chayan
The relation between the observed UV continuum slope (β) and the infrared excess (IRX) is used as a powerful probe to understand the nature of dust attenuation law in high-redshift galaxies. We present a study of 83 UV-selected galaxies between a redshift of 0.5 and 0.7 from the AstroSat UV Deep Field north that encloses the GOODS-North field. Usi…
The Spatial Correlation between CN-line- and Dust-continuum-emitting Regions in High-mass Star-forming Clouds
Hwang, Jihye; Chung, Eun Jung; Kim, Jongsoo +2 more
Measuring the strength of a three-dimensional (3D) magnetic field vector is challenging as it is not easy to recognize whether its line-of-sight (LOS) and plane-of-sky (POS) components are obtained from the same region. CN (N = 1–0) emission has been used to get the LOS component of a magnetic field (B LOS) from its Zeeman splitting lin…
A Multiwavelength Machine-learning Approach to Classifying X-Ray Sources in the Fields of Unidentified 4FGL-DR4 Sources
Kargaltsev, Oleg; Yang, Hui; Hare, Jeremy
A large fraction of Fermi-Large Area Telescope (LAT) sources in the fourth Fermi-LAT 14 yr catalog (4FGL) still remain unidentified (unIDed). We continued to improve our machine-learning pipeline and used it to classify 1206 X-ray sources with signal-to-noise ratios >3 located within the extent of 73 unIDed 4FGL sources with Chandra X-ray Obser…
Embedded Young Stellar Objects near H72.97-69.39: A Forming Super Star Cluster in N79
Hirschauer, Alec S.; Lenkić, Laura; Meixner, Margaret +10 more
We present 102 embedded young stellar object (YSO) candidates associated with the H72.97-69.39 super star cluster (SSC) in the Large Magellanic Cloud (LMC). With the use of the James Webb Space Telescope Mid-Infrared Instrument (MIRI) imaging mode, we utilize an F770W – F1000W versus F1000W color–magnitude diagram to select 70 YSO candidates. An a…
Local Transition of Electron Pitch Angle Distribution within Flux Pileup Region behind Dipolarization Front
Cao, J. B.; Liu, Y. Y.; Liu, C. M. +2 more
Dipolarization fronts (DFs), earthward-propagating magnetic transients with a strong magnetic field, are important regions favorable for energetic electron acceleration in the magnetotail. The DF-driven electron acceleration usually generates coherent pitch angle distributions (PADs) inside flux pileup regions (FPRs), i.e., strong magnetic field r…
On the Nature of Nonthermal Broadening of Spectral Lines Observed by IRIS
Testa, Paola; De Pontieu, Bart; Cho, Kyuhyoun
The origin of nonthermal broadening in solar spectra is one of the long-standing questions in solar physics. Various processes have been invoked—including unresolved flows, waves, and turbulent processes—but definitive answers are lacking. To investigate the physical processes responsible for nonthermal broadening, we examine its relation with the…
Longitudinal Extent of 3He-rich Solar Energetic Particle Events Near 1 au
Kouloumvakos, Athanasios; Wimmer-Schweingruber, Robert F.; Allen, Robert C. +3 more
Multispacecraft observations of 3He-rich solar energetic particle (SEP) events are scarce, but much needed in order to understand and properly constrain the source and transport of these remarkably enriched 3He SEP events. In this paper, we report 15 3He-rich SEP events that were detected by the Advanced Compositio…
Rapid Dimming Followed by a State Transition: A Study of the Highly Variable Nuclear Transient AT 2019avd over 1000+ Days
Gandhi, Poshak; Miller, Jon M.; Ji, Long +16 more
The tidal disruption of a star around a supermassive black hole (SMBH) offers a unique opportunity to study accretion onto an SMBH on a human timescale. We present results from our 1000+ days monitoring campaign of AT 2019avd, a nuclear transient with tidal-disruption-event-like properties, with NICER, Swift, and Chandra. Our primary finding is th…
Comprehensive Analysis of a Filament-embedding Solar Active Region at Different Stages of Evolution
Li, Hui; Su, Yang; Li, Chuan +9 more
Active regions are the brightest structures seen in the solar corona, so their physical properties hold important clues to the physical mechanisms underlying coronal heating. In this work, we present a comprehensive study for a filament-embedding active region as determined from observations from multiple facilities including the Chinese Hα Solar …
Center-to-limb Variations in Solar Plage Using IRIS Observations
Young, Peter R.; Kayshap, Pradeep
The center-to-limb variations (CLV) of transition region line Gaussian fit parameters in solar plage are reported for the first time. The Si IV 1402.77 Å line observed by the Interface Region Imaging Spectrograph is used. The spectral intensity increases linearly from the disk center to the solar limb. Similarly, the nonthermal velocity also incre…