Hongjun An

NuSTAR Observations of the Magnetar 1E 2259+586

Julia K. Vogel, Romain Hascoet, Victoria M. Kaspi +15

We report on new broad band spectral and temporal observations of the magnetar 1E 2259+586, which is located in the supernova remnant CTB 109. Our data were obtained simultaneously…

Multi-wavelength observations of 2HWC J1928+177: dark accelerator or new TeV gamma-ray binary?

Kaya Mori, Hongjun An, Qi Feng +9

2HWC J1928+177 is a Galactic TeV gamma-ray source detected by the High Altitude Water Cherenkov (HAWC) Observatory up to ~ 56 TeV. The HAWC source, later confirmed by H.E.S.S., sti…

NuSTAR observations of X-ray bursts from the magnetar 1E 1048.1-5937

Hongjun An, Victoria M. Kaspi, Andrei M. Beloborodov +13

We report the detection of eight bright X-ray bursts from the 6.5-s magnetar 1E 1048.1-5937, during a 2013 July observation campaign with the Nuclear Spectroscopic Telescope Array…

astro-ph.HE2018

Flux Relaxation after two outbursts of the magnetar SGR 1627 $-$ 41 and possible hard X-ray emission

Hongjun An, Andrew Cumming, Victoria M. Kaspi

We report on the long-term flux relaxation of the magnetar SGR 1627-41 after its 2008 outburst, and evidence for hard X-ray excess measured with NuSTAR. We use new observations mad…

Correlation study of temporal and emission properties of quiescent magnetars

Jiwoo Seo, Jaewon Lee, Hongjun An

We measured temporal and emission properties of quiescent magnetars using archival Chandra and XMM-Newton data, produced a list of the properties for 17 magnetars, and revisited pr…

astro-ph.HE2018

Signatures of Intra-binary shock emission in the black widow pulsar binary PSR J2241-5236

Hongjun An, Roger W. Romani, Matthew Kerr

We report on high-energy properties of the black widow pulsar PSR J2241 $-$ 5236 in the X-ray and the Fermi-LAT (GeV gamma-ray) bands. In the LAT band, the phase-averaged gamma-ray l…

astro-ph.HE2025

X-ray studies of PSR J1838 $-$ 0655 and its wind nebula associated with HESS J1837 $-$ 069 and 1LHAASO J1837 $-$ 0654u

Minseo Park, Jaegeun Park, Chanho Kim +1

We analyzed X-ray data from Chandra, XMM-Newton, NICER, and NuSTAR to characterize the properties of the pulsar PSR J1838 $-$ 0655 and its pulsar wind nebula (PWN) associated with HE…

Characterizing X-ray properties of the gamma-ray pulsar PSR J1418 $-$ 6058 in the Rabbit pulsar wind nebula

Minjun Kim, Hongjun An

We report on X-ray studies of the gamma-ray pulsar PSR J1418 $-$ 6058 in the Rabbit pulsar wind nebula (PWN) carried out using archival Chandra and XMM-Newton observations. A refined…

astro-ph.HE2022

Investigation of the broadband emission of the gamma-ray binary HESS J0632+057 using an intrabinary shock model

Jinyoung Kim, Hongjun An, Kaya Mori

We investigated a wealth of X-ray and gamma-ray spectral energy distribution (SED) and multi-band light curve (LC) data of the gamma-ray binary HESS J0632+057 using a phenomenologi…

SED modelling of broadband emission in the pulsar wind nebula 3C 58

Seungjong Kim, Hongjun An

We investigate broadband emission properties of the pulsar wind nebula (PWN) 3C 58 using a spectral energy distribution (SED) model. We attempt to match simultaneously the broadban…

eess.IV2025

Large model enhanced computational ghost imaging

Yifan Chen, Hongjun An, Zhe Sun +4

Ghost imaging (GI) achieves 2D image reconstruction through high-order correlation of 1D bucket signals and 2D light field information, particularly demonstrating enhanced detectio…

eess.IV2021

Deep reinforcement learning-designed radiofrequency waveform in MRI

Dongmyung Shin, Younghoon Kim, Chungseok Oh +4

Carefully engineered radiofrequency (RF) pulses play a key role in a number of systems such as mobile phone, radar, and magnetic resonance imaging. The design of an RF waveform, ho…

Deep NuSTAR and Swift Monitoring Observations of the Magnetar 1E 1841-045

Hongjun An, Robert F. Archibald, Romain Hascoet +15

We report on a 350-ks NuSTAR observation of the magnetar 1E 1841-045 taken in 2013 September. During the observation, NuSTAR detected six bursts of short duration, with $T_{90} < 1$ …

cs.CL2026

Ruyi2 Technical Report

Huan Song, Shuyu Tian, Junyi Hao +5

Large Language Models (LLMs) face significant challenges regarding deployment costs and latency, necessitating adaptive computing strategies. Building upon the AI Flow framework, w…

astro-ph.HE2026

The Advanced X-ray Imaging Satellite (AXIS) Community Science Book

Michael Koss, Nafisa Aftab, Steven W. Allen +395

The AXIS Community Science Book represents the collective effort of 592 scientists worldwide to define the transformative science enabled by the Advanced X-ray Imaging Satellite (A…

astro-ph.HE2021

NuSTAR broad-band X-ray observational campaign of energetic pulsar wind nebulae in synergy with VERITAS, HAWC and Fermi gamma-ray telescopes

Kaya Mori, Hongjun An, Daniel Burgess +13

We report recent progress on the on-going NuSTAR observational campaign of 8 TeV-detected pulsar wind nebulae (PWNe). This campaign constitutes a major part of our NuSTAR study of…

astro-ph.HE2017

High-Energy Variability of PSR J1311-3430

Hongjun An, Roger W. Romani, Tyrel Johnson +2

We have studied the variability of the black-widow type binary millisecond pulsar PSR J1311 $-$ 3430 from optical to gamma-ray energies. We confirm evidence for orbital modulation in…

astro-ph.HE2013

NuSTAR observations of magnetar 1E 1841-045

Hongjun An, Romain Hascoet, Victoria M. Kaspi +18

We report new spectral and temporal observations of the magnetar 1E 1841-045 in the Kes 73 supernova remnant obtained with the Nuclear Spectroscopic Telescope Array (NuSTAR). Combi…

Measuring timing properties of PSR B0540-69

Minjun Kim, Hongjun An

We report on the timing properties of the `Crab twin' pulsar PSR~B0540 $-$ 69 measured with X-ray data taken with the Swift telescope over a period of 1100\,days. The braking index o…

The Synchrotron Emission Pattern of IntraBinary Shocks

D. Kandel, Roger W. Romani, Hongjun An

We model millisecond pulsars winds colliding with radiatively-driven companion winds in black widow and redback systems. For the redbacks, the geometry of this intrabinary shock (I…

Hard X-ray observation and multiwavelength study of the PeVatron candidate pulsar wind nebula "Dragonfly"

Jooyun Woo, Hongjun An, Joseph D. Gelfand +5

We studied the PeVatron nature of the pulsar wind nebula G75.2+0.1 ("Dragonfly") as part of our NuSTAR observational campaign of energetic PWNe. The Dragonfly is spatially coincide…

astro-ph.HE2026

New Hard X-Ray and Multiwavelength Study of the PeVatron Candidate PWN G0.9+0.1 in the Galactic Center Region

Giulia Brunelli, Kaya Mori, Jaegeun Park +12

We present a new X-ray study and multiwavelength spectral energy distribution (SED) modeling of the young pulsar wind nebula (PWN) powered by the energetic pulsar PSR J1747-2809, i…

astro-ph.HE2013

NuSTAR discovery of a 3.76-second transient magnetar near Sagittarius A*

Kaya Mori, Eric V. Gotthelf, Shuo Zhang +20

We report the discovery of 3.76-s pulsations from a new burst source near Sgr A* observed by the NuSTAR Observatory. The strong signal from SGR J1745-29 presents a complex pulse pr…

X-ray characterization of the pulsar PSR J1849 $-$ 0001 and its wind nebula G32.64+0.53 associated with TeV sources detected by H.E.S.S., HAWC, Tibet AS $I^^{3}$ , and LHAASO

Chanho Kim, Jaegeun Park, Jooyun Woo +6

We report on the X-ray emission properties of the pulsar PSR J1849 $-$ 0001 and its wind nebula (PWN), as measured by Chandra, XMM-Newton, NICER, Swift, and NuSTAR. In the X-ray data…

Orbital Modulation of Gamma Rays from PSR~J2339 $-$ 0533

Hongjun An, Roger W. Romani, Matthew Kerr

We report on orbital modulation of the 100-600 MeV gamma-ray emission of the $P_{B} = 4.6$ hr millisecond pulsar binary PSR J2339 $-$ 0533 using 11 yr of Fermi Large Area Telescope…

astro-ph.IM2014

In-flight PSF calibration of the NuSTAR hard X-ray optics

Hongjun An, Kristin K. Madsen, Niels J. Westergaard +7

We present results of the point spread function (PSF) calibration of the hard X-ray optics of the Nuclear Spectroscopic Telescope Array (NuSTAR). Immediately post-launch, NuSTAR ha…

astro-ph.HE2012

Chandra observations of SGR 1627-41 near quiescence

Hongjun An, Victoria M. Kaspi, John A. Tomsick +4

We report on an observation of SGR 1627-41 made with the Chandra X-ray Observatory on 2011 June 16. Approximately three years after its outburst activity in 2008, the source's flux…

astro-ph.HE2017

Light curve and SED modeling of the gamma-ray binary 1FGL J1018.6 $-$ 5856: constraints on the orbital geometry and relativistic flow

Hongjun An, Roger W. Romani

We present broadband spectral energy distributions (SEDs) and light curves of the gamma-ray binary 1FGL J1018.6 $-$ 5856 measured in the X-ray and the gamma-ray bands. We find that t…

eess.IV2021

DIFFnet: Diffusion parameter mapping network generalized for input diffusion gradient schemes and bvalues

Juhung Park, Woojin Jung, Eun-Jung Choi +4

In MRI, deep neural networks have been proposed to reconstruct diffusion model parameters. However, the inputs of the networks were designed for a specific diffusion gradient schem…

cs.CR2026

Are LLMs Vulnerable to Preference-Undermining Attacks (PUA)? A Factorial Analysis Methodology for Diagnosing the Trade-off between Preference Alignment and Real-World Validity

Hongjun An, Yiliang Song, Jiangan Chen +3

Large Language Model (LLM) training often optimizes for preference alignment, rewarding outputs that are perceived as helpful and interaction-friendly. However, this preference-ori…

astro-ph.SR2013

NuSTAR and Swift observations of the fast rotating magnetized white dwarf AE Aquarii

Takao Kitaguchi, Hongjun An, Andrei M. Beloborodov +11

AE Aquarii is a cataclysmic variable with the fastest known rotating magnetized white dwarf (P_spin = 33.08 s). Compared to many intermediate polars, AE Aquarii shows a soft X-ray…

astro-ph.HE2021

XMM-Newton Observes the Intrabinary Shock of PSR J1959+2048

D. Kandel, Roger W. Romani, Hongjun An

In a multi-orbit (100 ks) $XMM - Newton$ exposure of the original black widow pulsar, PSR J1959+2048, we measure the strong orbital modulation caused by intrabinary shoc…

astro-ph.HE2024

Investigation of the non-thermal X-ray emission from the supernova remnant CTB 37B hosting the magnetar CXOU J171405.7 $-$ 381031

Chanho Kim, Jaegeun Park, Hongjun An +4

We present a detailed X-ray investigation of a region (S1) exhibiting non-thermal X-ray emission within the supernova remnant (SNR) CTB 37B hosting the magnetar CXOU J171405.7 $-$ 38…

X-ray timing studies of the low-field magnetar CXOU J164710.2-455216

Hongjun An, Robert Archibald

We report results of X-ray timing analyses for the low-field magnetar CXOU~J164710.2 $-$ 455216 which exhibited multiple outbursts. We use data taken with NICER, NuSTAR, Chandra, and…

astro-ph.HE2013

Swift observations of 1FGL J1018.6-5856

Hongjun An, Francois Dufour, Victoria M. Kaspi +1

We report on X-ray properties of the gamma-ray binary 1FGL J1018.6-5856 using observations obtained with the Swift X-ray telescope. Using 54 observations made between MJD 55575 and…

astro-ph.HE2018

SED constraints on the highest- $z$ blazar jet: QSO J0906+6930

Hongjun An, Roger W. Romani

We report on Gemini, NuSTAR and 8-year Fermi observations of the most distant blazar QSO~J0906 $+$ 6930 ( $z = 5.48$ ). We construct a broadband spectral energy distribution (SED) and mo…

NuSTAR study of Hard X-Ray Morphology and Spectroscopy of PWN G21.5-0.9

Melania Nynka, Charles J. Hailey, Stephen P. Reynolds +16

We present NuSTAR high energy X-ray observations of the pulsar wind nebula (PWN)/supernova remnant G21.5-0.9. We detect integrated emission from the nebula up to ~40 keV, and resol…

Broadband X-ray Imaging and Spectroscopy of the Crab Nebula and Pulsar with NuSTAR

Kristin K. Madsen, Stephen Reynolds, Fiona Harrison +12

We present broadband (3 -- 78 keV) NuSTAR X-ray imaging and spectroscopy of the Crab nebula and pulsar. We show that while the phase-averaged and spatially integrated nebula + puls…

{\it NuSTAR} hard X-ray studies of the pulsar wind nebula 3C~58

Hongjun An

We report on new NuSTAR and archival Chandra observations of the pulsar wind nebula (PWN) 3C 58. Using the X-ray data, we measure energy-dependent morphologies and spatially-resolv…

Spectral variability of the blazar 3C 279 in the optical to X-ray band during 2009-2018

Sungmin Yoo, Hongjun An

We report on spectral variability of the blazar 3C 279 in the optical to X-ray band between MJD 55100 and 58400 during which long-term radio variability was observed. We construct…

cs.CV2026

Single-Pixel Vision-Language Model for Intrinsic Privacy-Preserving Behavioral Intelligence

Hongjun An, Yiliang Song, Jiawei Shao +2

Adverse social interactions, such as bullying, harassment, and other illicit activities, pose significant threats to individual well-being and public safety, leaving profound impac…

astro-ph.HE2021

Gamma-ray orbital modulation of the transitioning millisecond pulsar binary XSS J12270-4859

Hongjun An

We report on gamma-ray orbital modulation of the transitioning millisecond pulsar binary XSS J12270-4859 detected in the Fermi Large Area Telescope (LAT) data. We use long-term opt…

cs.LG2026

Theoretical Foundations of Scaling Law in Familial Models

Huan Song, Qingfei Zhao, Ting Long +4

Neural scaling laws have become foundational for optimizing large language model (LLM) training, yet they typically assume a single dense model output. This limitation effectively…

cs.LG2024

Physics in Next-token Prediction

Hongjun An, Yiliang Song, Xuelong Li

We discovered the underlying physics in Next-token Prediction (NTP). We identified the law of information conservation within NTP and proposed the First Law of Information Capacity…

cs.AI2025

AI Flow: Perspectives, Scenarios, and Approaches

Hongjun An, Wenhan Hu, Sida Huang +11

Pioneered by the foundational information theory by Claude Shannon and the visionary framework of machine intelligence by Alan Turing, the convergent evolution of information and c…

cs.AI2026

Sequence Search: Automated Sequence Design using Neural Architecture Search

Rokgi Hong, Hongjun An, Sooyeon Ji +1

Developing an MR sequence is challenging and remains largely constrained by human intuition. Recently, AI-driven approaches have been proposed; however, most require an initial seq…

The High Energy X-ray Probe (HEX-P): Supernova remnants, pulsar wind nebulae, and nuclear astrophysics

Stephen Reynolds, Hongjun An, Moaz Abdelmaguid +29

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging ( $< 10"$ full width at half maximum) and broad spectral coverage (0.2--80 keV) with an…

A broadband X-ray study of the Geminga pulsar with NuSTAR and XMM-Newton

Kaya Mori, Eric V. Gotthelf, Francois Dufour +14

We report on the first hard X-ray detection of the Geminga pulsar above 10 keV using a 150 ks observation with the NuSTAR observatory. The double-peaked pulse profile of non-therma…

Phase-resolved NuSTAR and Swift-XRT Observations of Magnetar 4U 0142+61

Shriharsh P. Tendulkar, Romain HascÃ¶et, Chengwei Yang +12

We present temporal and spectral analysis of simultaneous 0.5-79 keV Swift-XRT and NuSTAR observations of the magnetar 4U 0142+61. The pulse profile changes significantly with phot…

NuSTAR results and future plans for magnetar and rotation-powered pulsar observations

Hongjun An, Victoria M. Kaspi, Robert Archibald +27

The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing hard X-ray mission in orbit and operates in the 3-79 keV range. NuSTAR's sensitivity is roughly two orders…

A Spatially Resolved Study of the Synchrotron Emission and Titanium in Tycho's Supernova Remnant with NuSTAR

Laura A. Lopez, Brian W. Grefenstette, Stephen P. Reynolds +12

We report results from deep observations (~750 ks) of Tycho's supernova remnant (SNR) with NuSTAR. Using these data, we produce narrow-band images over several energy bands to iden…

cs.CV2025

StreakNet-Arch: An Anti-scattering Network-based Architecture for Underwater Carrier LiDAR-Radar Imaging

Xuelong Li, Hongjun An, Haofei Zhao +6

In this paper, we introduce StreakNet-Arch, a real-time, end-to-end binary-classification framework based on our self-developed Underwater Carrier LiDAR-Radar (UCLR) that embeds Se…

astro-ph.HE2025

Multi-wavelength Study of HESS J0632+057: New Insights into Pulsar-Disk Interaction

Jaegeun Park, Hongjun An, Chanho Kim +60

We present an analysis of new multi-wavelength observations of the TeV gamma-ray binary HESS J0632+057, conducted using SALT, Swift, NuSTAR, and VERITAS in 2023--2024. By combining…

X-ray studies of the pulsar PSR J1420-6048 and its TeV pulsar wind nebula in the Kookaburra region

Jaegeun Park, Chanho Kim, Jooyun Woo +4

We present a detailed analysis of broadband X-ray observations of the pulsar PSR J1420-6048 and its wind nebula (PWN) in the Kookaburra region with Chandra, XMM-Newton, and NuSTAR.…

NuSTAR observations of the young, energetic radio pulsar PSR B1509-58

Ge Chen, Hongjun An, Victoria M. Kaspi +3

We report on Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of the young rotation-powered radio pulsar PSR B1509 $-$ 58 in the supernova remnant MSH 15 $-$ 52.…

A broadband X-ray study of the Rabbit pulsar wind nebula powered by PSR J1418-6058

Jaegeun Park, Chanho Kim, Jooyun Woo +4

We report on broadband X-ray properties of the Rabbit pulsar wind nebula (PWN) associated with the pulsar PSR J1418-6058 using archival Chandra and XMM-Newton data, and a new NuSTA…

X-ray constraints on the spectral energy distribution of the $z = 5.18$ blazar SDSS J013127.34-032100.1

Hongjun An, Roger W. Romani

We report on X-ray measurements constraining the spectral energy distribution (SED) of the high-redshift $z = 5.18$ blazar SDSS J013127.34 $-$ 032100.1 with new XMM-Newton and NuSTAR e…

astro-ph.HE2024

Modeling X-ray and gamma-ray emission from redback pulsar binaries

Minju Sim, Hongjun An, Zorawar Wadiasingh

We investigated the multiband emission from the pulsar binaries XSS J12270-4859, PSR J2039-5617, and PSR J2339-0533, which exhibit orbital modulation in the X-ray and gamma-ray ban…

eess.IV2020

DeepResp: Deep learning solution for respiration-induced B0 fluctuation artifacts in multi-slice GRE

Hongjun An, Hyeong-Geol Shin, Sooyoen Ji +5

Respiration-induced B $_{0}$ fluctuation corrupts MRI images by inducing phase errors in k-space. A few approaches such as navigator have been proposed to correct for the artifacts at…

High-Energy X-ray Imaging of the Pulsar Wind Nebula MSH~15-52: Constraints on Particle Acceleration and Transport

Hongjun An, Kristin K. Madsen, Stephen P. Reynolds +11

We present the first images of the pulsar wind nebula (PWN) MSH 15-52 in the hard X-ray band (>8 keV), as measured with the Nuclear Spectroscopic Telescope Array (NuSTAR). Overall,…

astro-ph.HE2012

Spectral and timing properties of the magnetar CXOU~J164710.2-455216

Hongjun An, Victoria M. Kaspi, Robert Archibald +1

We report on spectral and timing properties of the magnetar CXOU J164710.2-455216 in the massive star cluster Westerlund 1. Using 11 archival observations obtained with Chandra and…

cs.AI2026

CreditAudit: 2 $^{nd}$ Dimension for LLM Evaluation and Selection

Yiliang Song, Hongjun An, Jiangong Xiao +3

Leaderboard scores on public benchmarks have been steadily rising and converging, with many frontier language models now separated by only marginal differences. However, these scor…

cs.AI2024

SentenceVAE: Enable Next-sentence Prediction for Large Language Models with Faster Speed, Higher Accuracy and Longer Context

Hongjun An, Yifan Chen, Zhe Sun +1

Current large language models (LLMs) primarily utilize next-token prediction method for inference, which significantly impedes their processing speed. In this paper, we introduce a…

The Hard X-Ray View of the Young Supernova Remnant G1.9+0.3

Andreas Zoglauer, Stephen P. Reynolds, Hongjun An +12

NuSTAR observed G1.9+0.3, the youngest known supernova remnant in the Milky Way, for 350 ks and detected emission up to $\sim$ 30 keV. The remnant's X-ray morphology does not change…

astro-ph.IM2013

The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission

Fiona A. Harrison, William W. Craig, Finn E. Christensen +77

The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 13 June 2012, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates in the band from 3…

Broadband X-ray Properties of the Gamma-ray Binary 1FGL J1018.6-5856

Hongjun An, Eric Bellm, Varun Bhalerao +11

We report on NuSTAR, XMM-Newton and Swift observations of the gamma-ray binary 1FGL J1018.6-5856. We measure the orbital period to be 16.544+/-0.008 days using Swift data spanning…

astro-ph.GA2022

Machine-guided Exploration and Calibration of Astrophysical Simulations

Boon Kiat Oh, Hongjun An, Eun-jin Shin +2

We apply a novel method with machine learning to calibrate sub-grid models within numerical simulation codes to achieve convergence with observations and between different codes. I…

cs.AI2026

Silicon Bureaucracy and AI Test-Oriented Education: Contamination Sensitivity and Score Confidence in LLM Benchmarks

Yiliang Song, Hongjun An, Jiangan Chen +4

Public benchmarks increasingly govern how large language models (LLMs) are ranked, selected, and deployed. We frame this benchmark-centered regime as Silicon Bureaucracy and AI Tes…

astro-ph.HE2024

Revisiting the Intrabinary Shock Model for Millisecond Pulsar Binaries: Radiative Losses and Long-Term Variability

Jaegeun Park, Chanho Kim, Hongjun An +1

Spectrally hard X-ray emission with double-peak light curves (LCs) and orbitally modulated gamma rays have been observed in some millisecond pulsar binaries, phenomena attributed t…

The High Energy X-ray Probe (HEX-P): Galactic PeVatrons, star clusters, superbubbles, microquasar jets, and gamma-ray binaries

Kaya Mori, Stephen Reynolds, Hongjun An +32

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10" FWHM) and broad spectral coverage (0.2-80 keV) with an effective area far super…

The Norma Arm Region Chandra Survey: X-ray Populations in the Spiral Arms

Francesca M. Fornasini, John A. Tomsick, Arash Bodaghee +6

We present a catalog of 1415 X-ray sources identified in the Norma arm region Chandra survey (NARCS), which covers a 2 deg x 0.8 deg region in the direction of the Norma spiral arm…