Search Publications
Finding Lensed Radio Sources with the Very Large Array Sky Survey
Martinez, Michael N.; Gordon, Yjan A.; Bechtol, Keith +3 more
Radio observations of strongly lensed objects are valuable as cosmological probes. Lensed radio sources have proven difficult to identify, in large part due to the limited depth and angular resolution of the previous generation of radio sky surveys, and, as such, only a few dozen lensed radio sources are known. In this work, we present the results…
GRB 241107A: A Giant Flare from a Close-by Extragalactic Magnetar?
Mereghetti, Sandro; Salvaterra, Ruben; Ubertini, Pietro +5 more
We report the results on the short gamma-ray burst GRB 241107A, obtained with the IBIS instrument on board the INTEGRAL satellite. The burst had a duration of about 0.2 s, a fluence of 8 × 10‑7 erg cm‑2 in the 20 keV–10 MeV range, and a hard spectrum, characterized by a peak energy of 680 keV. The position of GRB 241107A has …
Quasiperiodic Super-Alfvénic Slippage along Flare Ribbons Observed by the Interface Region Imaging Spectrograph
Hou, Yijun; Li, Ting; Zhou, Guiping +3 more
The apparent slipping motion of flare loops is regarded as a key feature of the 3D magnetic reconnection in the solar flares. The slippage with a super-Alfvénic speed could be defined as slipping–running reconnection, while the slippage with a sub-Alfvénic speed is called slipping reconnection. Due to the limitation of the observational instrument…
Understanding the Broad-line Region of Active Galactic Nuclei with Photoionization. I. The Moderate-accretion Regime
Brandt, W. N.; Shen, Yue; Ho, Luis C. +9 more
Over three decades of reverberation mapping (RM) studies on local broad-line active galactic nuclei (AGNs) have measured reliable black hole (BH) masses for >100 AGNs. These RM measurements reveal a significant correlation between the Balmer broad-line region (BLR) size and AGN optical luminosity (the R–L relation). Recent RM studies for AGN sa…
Revisiting the Fundamental Planes of Black Hole Activity for Strong Jet Sources
Long, Qing-Chen; Dong, Ai-Jun; Zhi, Qi-Jun +1 more
Whether the X-ray emissions of strong jet sources originate from disk+coronas or jets is still controversial. In this work, we constructed a strong jet sample containing 50 flat-spectrum radio quasars, 51 low-synchrotron-peaked BL Lac objects, and 18 intermediate-synchrotron-peaked BL Lac objects to explore the origin of X-ray emissions. Generally…
Fluctuations Driven by Multicomponent Pickup Ion Distributions in the Outer Heliosheath
Roytershteyn, Vadim; Mousavi, Ameneh; Fraternale, Federico +1 more
The stability of a realistic multicomponent pickup ion (PUI) velocity distribution derived from a global model of neutral atoms in the heliosphere, which treats hydrogen and helium atoms self-consistently and includes equations for electrons and helium ions, is investigated using linear instability analysis and hybrid simulations. Linear instabili…
Near- and Mid-ultraviolet Observations of X-6.3 Flare on 2024 February 22 Recorded by the Solar Ultraviolet Imaging Telescope on board Aditya-L1
Solanki, Sami K.; Tripathi, Durgesh; Nandy, Dibyendu +10 more
Solar flares are regularly observed in extreme-ultraviolet soft X-rays (SXRs) and hard X-rays (HXRs). However, those in near- and mid-ultraviolet are sparse. The Solar Ultraviolet Imaging Telescope (SUIT) on board the Aditya-L1, launched on 2023 September 2, provides regular observations in the 200–400 nm wavelength range through 11 filters. Here,…
Stellar X-Ray Variability and Planetary Evolution in the DS Tucanae System
Ramsay, Gavin; Wheatley, Peter J.; Bourrier, Vincent +5 more
We present an analysis of four Chandra observations of the 45 Myr old DS Tuc binary system. We observed X-ray variability of both stars on timescales from hours to months, including two strong X-ray flares from star A. The implied flaring rates are in agreement with past observations made with XMM-Newton, though these rates remain imprecise due to…
Ca II K Polar Network Index of the Sun: A Proxy for Historical Polar Magnetic Field
Chatzistergos, Theodosios; Ermolli, Ilaria; Banerjee, Dipankar +4 more
The Sun's polar magnetic field is pivotal in understanding solar dynamo processes and forecasting future solar cycles. However, direct measurements of the polar field have only been available since the 1970s. The chromospheric Ca II K polar network index (PNI; the fractional area of the chromospheric network regions above a certain latitude) has r…
Connecting Dust and Outflows in Active Galactic Nuclei: The Intriguing Case of NGC 6860
Costantini, E.; Mehdipour, M.; Rogantini, D. +4 more
Cosmic dust plays a crucial role in the evolution of galaxies, significantly influencing star formation and the interstellar medium. However, in active galactic nuclei (AGNs), the role and origin of dust remain poorly understood. High-resolution X-ray spectroscopy is a powerful tool for probing the properties of dust in AGN. NGC 6860, an X-ray bri…