arXiv subjects

H. Feng

Publications and source records attributed to H. Feng.

At least 19 recordsLinked to original sources

arXiv2026

LHAASO-WCDA observed a $\sim$ 5 days TeV-delayed flaring event in blazar 1ES 1959+650

We report a day-scale hard lag between GeV and TeV $\gamma$-ray emission from the HBL 1ES~1959+650 in early 2024. Since the LHAASO-WCDA real-time monitoring system began operation in late 2023, multiple TeV flares from this source have been triggered, including the 1st trigger flare on 2024 February 9. A Bayesian-block analysis of the WCDA light curve identifies three TeV flares in 2024. For the second triggered flare, a discrete cross-correlation analysis reveals a $>3\,\sigma$ correlation (relative to uncorrelated red-noise simulations) at a time delay of $\Delta t = 5.0_{-2.1}^{+2.1}$ days, with the TeV emission lagging the GeV. Time-resolved spectroscopy shows that this flare has the softest TeV spectrum among these flares (intrinsic spectral index $\Gamma=3.16\pm0.18$), while the 1st trigger flare is harder ($\Gamma=2.48\pm0.21$). The observed five-day hard lag is difficult to reconcile with a purely cooling-driven temporal ordering and is consistent with scenarios in which particle energization and/or transport may contribute to the evolution. However, the current data do not uniquely identify the underlying mechanism.

astro-ph.HE↗

arXiv2026

Anisotropic Particle Transport from a Pulsar Wind Nebula Revealed by Einstein Probe and LHAASO

Pulsar wind nebulae (PWNe) are major cosmic ray accelerators, yet the mechanisms transporting high-energy particles into the interstellar medium remain elusive. Building on the LHAASO discovery of an ultra-high-energy (UHE) $\gamma$-ray source near the bow-shock PWN powered by the pulsar PSR J1740+1000, we present a joint Einstein Probe (EP) and LHAASO study of this system. EP observations reveal an extended X-ray tail far exceeding the structure previously seen by XMM-Newton. Updated LHAASO observations show that the $\gamma$-ray emission is elongated, with its major axis aligned with the extended X-ray tail revealed by EP. This is the first detection of an X-ray pulsar tail associated with a spatially coincident extended UHE $\gamma$-ray emission. The X-ray and $\gamma$-ray spectrum can be well explained with a single population of relativistic electrons via synchrotron and inverse Compton radiation, respectively, removing the need for particle re-acceleration during propagation. The results unambiguously show that electrons/positrons above 100 TeV are escaping from the PWN. Instead of the immediate, isotropic diffusion into ambient interstellar medium that is typically assumed, these particles are transported anisotropically over at least $\sim$10 pc, either guided by the background magnetic field or carried by an advective outflow.

astro-ph.HE↗

arXiv2026

The Extended Ultrahigh-energy Gamma-Ray Emission in the Vicinity of PSR J2238+5903

We present a comprehensive analysis of the recently discovered TeV gamma-ray source, LHAASO J2238+5900. Based on data collected from the LHAASO, our fitting results suggest that the source is significantly extended with an angular extension of 0.54{\deg} \pm 0.01{\deg} and is spatially coincident with the pulsar PSR J2238+5903. Its spectrum is characterized by a power-law with a cutoff at 41.0\pm 3.5 TeV. Additionally, the source exhibits a significant signal of 7.9\sigma above 100 TeV, implying that it is a PeVatron candidate. While the gamma-ray emission is consistent with a pulsar wind nebula (PWN) scenario, the relatively large extension size also allows for a halo interpretation, potentially caused by electron-positron pairs escaping from the PWN.

astro-ph.HE↗

arXiv2026

EP-FXT Observations of Abell 1795: X-ray Properties and Structure out to $R_{200}$

We present deep X-ray observations of the nearby, X-ray luminous galaxy cluster Abell 1795 obtained with the Einstein Probe Follow-up X-ray Telescope (EP-FXT), with a total exposure time of 480 ks. Exploiting the large field of view and low particle background of EP-FXT, we directly measure the radial temperature profile of A1795 out to $R_{200}$ with full azimuthal coverage, which increases with radius within 6 arcmin and then gradually declines toward larger radii. The surface-brightness residual map and 2D thermodynamic maps reveal a clockwise spiral structure extending from the cluster core toward the southeast, which traces low-temperature, low-entropy gas and is consistent with sloshing-induced cold fronts. In the northwest, the surface-brightness-enhanced region exhibits an arc-like high-temperature feature, and both the temperature-derived and density-derived Mach numbers support that it is a weak shock. These substructures can be explained by a binary merger scenario: the perturbing subcluster induces sloshing during its first passage past the primary core, and its subsequent return passage through the ICM may drive the shock toward the northwest. Our results indicate that relaxed galaxy clusters such as A1795 can still retain signatures of dynamical activity.

astro-ph.HE↗

arXiv2026

Extreme PeV accelerator associated with GRS 1915+105

Microquasars, binary systems featuring relativistic jets, have emerged as sources for particle acceleration beyond PeV energies. We present a study of the broadband $\gamma$-ray emission from one of the most prominent Galactic microquasars GRS 1915+105 based on data accumulated by LHAASO and Fermi-LAT over 4 and 17 years, respectively. A joint analysis of LHAASO-WCDA and LHAASO-KM2A data reveals extended $\gamma$-ray emission whose centroid appears significantly shifted, by ~ 0.13{\deg}, from the binary system and its jets. The spectral energy distribution is well described by a curved spectrum with progressive steepening that can be described by a log-parabola function with no evidence for a sharp cutoff, consistent with parent particles reaching multi-PeV energies and an extreme acceleration efficiency approaching the limit set by the available potential drop across the source. Several features, most notably the shift of the emission and single-power-law spectrum down to GeV band, favor radiation by cosmic rays accelerated in the source interacting with the dense ambient medium. Our spectral modeling implies that at least a few percent of the jet mechanical power is transferred to protons, whose maximum energy reaches beyond 5 PeV. These results strengthen the case for microquasars as exceptionally efficient accelerators in our Galaxy.

astro-ph.HE↗

arXiv2026

The science of compressional heating on the LM26 magnetized target fusion experiment

The Lawson Machine 26 (LM26) at General Fusion has demonstrated compressional heating of a spherical tokamak deuterium plasma as it was compressed by an imploding solid lithium liner. Results from the first 11 compression shots on LM26 are presented, the highest-performing of which show more than a 3x increase in $T_e$, a 10x increase in $n_e$, and a 10x increase in $B_{pol}$ within the plasma driven by 3x radial compression. The experimental device and instrumentation are reviewed in detail, followed by observations about the liner trajectory and evolution of plasma properties, including increases in emission of neutrons, X-rays, and visible radiation. Observations from fast-camera images during compression provide context for interpreting the spatial structure of plasma-wall interaction. Overviews of relevant models and analysis are presented. Diagnostic data are used to reconstruct the experimental equilibrium state in computational framework as a function of time. The results build confidence in the stability and transport analyses that support the primary conclusions. Trends across the full set of 11 compression shots are presented, and detailed examinations of the high-performance shots are given individually. The central conclusions of the integrated physics model specifically indicate that compressional heating was achieved in this set of experiments, as evidenced by the balance of heating power from compression, Ohmic heating from plasma current, and losses to the boundary needed to match the experimental data. A majority of the temperature rise is attributable to compressional heating. An increase in neutron flux is also observed during compression. The results provide a basis for planned improvements to the LM26 facility that will enable the compression of magnetized plasma to increasingly higher densities and temperatures.

physics.plasm-ph↗

arXiv2026

A rare sextuple-merging brightest cluster galaxy system in a disturbed galaxy cluster observed with the Einstein Probe Follow-up X-ray Telescope

The evolutionary processes of galaxy clusters influence the properties of their member galaxies. We present a joint X-ray--optical analysis of the galaxy cluster WHY J050106.2+013714 at $z_{\rm c}=0.151$. X-ray observations with the Einstein Probe Follow-up X-ray Telescope indicate that the cluster is dynamically young. The cluster displays an average X-ray temperature of $2.8^{+0.4}_{-0.3}$ keV and a total luminosity of 9.4$\pm0.3\times10^{43}$ erg s$^{-1}$, consistent with the scaling relation of typical disturbed clusters. Remarkably, the cluster hosts a multi-merging brightest cluster galaxy (BCG) system composed of six massive galaxies, with a total stellar mass of $1.16\times10^{12}M_{\odot}$. We detected a well-defined intracluster light component extending to a size of 310 kpc. A systematic search for merging BCGs in the DESI Legacy Surveys reveals that this sextuple-merging BCG is extremely rare in the local Universe. Additionally, other merging BCGs are also likely to form in moderately disturbed clusters, which provides valuable insights into the formation of BCGs.

astro-ph.CO↗

arXiv2026

Discovery of EP J175257.3-351923 as a Candidate Black Hole Low-Mass X-ray Binary

We report the discovery of a new X-ray transient, EP J175257.3-351923 (EP250916a), by the Einstein Probe (EP) near the Galactic plane. The outburst lasted for at least 250\,days, reached a peak 2--10 keV flux of $\sim 4 \times 10^{-10}$~erg~cm$^{-2}$~s$^{-1}$, and exhibited a fast-rise exponential-decay (FRED) profile typical of X-ray binary outbursts. The source remained in the hard state throughout the outburst, with only modest variations in the photon index ($\sim 1.6$--$2.2$) and no evidence for a spectral state transition. Broadband spectral modeling suggests a truncated disk, a weak reflection component, and a high-energy cutoff at $\sim 217$~keV, consistent with hard-state accretion in black-hole systems. No reliable optical or radio counterpart is detected within the Swift/XRT error circle. The inferred X-ray-to-optical and X-ray-to-radio flux ratios are consistent with a low-mass X-ray binary classification. Neither pulsations nor significant aperiodic variability are detected. Although the compact object cannot yet be firmly identified, the timing, spectral, and multiwavelength evidence favors EP~J175257.3--351923 as a black-hole low-mass X-ray binary candidate, highlighting EP's potential to uncover a faint, previously hidden population of X-ray binaries.

astro-ph.HE↗

arXiv2026

Demonstrating CBM Capabilities by $\Lambda$ Baryon Reconstruction in Ni+Ni Collisions with the mCBM Experiment at SIS18 of GSI/FAIR

The Compressed Baryonic Matter (CBM) experiment at the upcoming Facility for Antiproton and Ion Research (FAIR) is a high-rate fixed-target experiment designed to investigate nuclear matter at extreme baryon densities in relativistic nucleus-nucleus collisions. To enable high-statistics measurements of rare probes, CBM is designed to operate at event rates up to 10 MHz. This necessitates the development of fast and radiation-tolerant detectors, self-triggered front-end electronics, a free-streaming data acquisition architecture, and real-time event reconstruction capabilities. Prototype versions and pre-series productions of the CBM detector systems have been deployed in the mini-CBM demonstrator setup mCBM - an experimental precursor comprising sub-components of all major CBM systems, installed at the SIS18 facility of GSI/FAIR within the FAIR Phase-0 program. In 2024, Ni+Ni collisions at a kinetic beam energy of 1.93 AGeV and an average interaction rate of about 250 kHz were successfully recorded. This dataset enables a detailed evaluation of the operational performance of the detector systems as well as the complete CBM data chain, while the reconstruction of rare $\Lambda$ baryons serves as a natural benchmark. This paper presents the first results on $\Lambda$ signal reconstruction with the mCBM experiment, demonstrating the readiness of the detector technologies and the data chain for the upcoming full-scale CBM experiment.

physics.ins-det↗

arXiv2026

Multi-wavelength outburst activity from EP J174942.2-384834: a very faint X-ray transient discovered by Einstein Probe

We report the discovery and multi-wavelength characterization of the Galactic transient EP J174942.2$-$384834, first detected by the Einstein Probe during a faint X-ray outburst in March 2025. Coordinated follow-up observations revealed two major outbursts and a rebrightening over a seven-month period. Broadband X-ray spectral modeling shows that the outburst emission was dominated by thermal Comptonization of very soft seed photons. The absence of a detected thermal disk component, together with the low inferred seed-photon temperature, is consistent with a cool and possibly truncated accretion disk. The X-ray spectrum remained consistently hard throughout the outburst activity, with a power-law photon index of $\Gamma \approx 1$-2, gradually softening as the flux declined. The optical/UV counterpart brightened in tandem with the X-ray emission and exhibited a blue continuum with broad Balmer absorption features. Together with the optical/UV - X-ray luminosity correlation, this supports a disk-dominated origin of the optical/UV outburst emission, with viscous heating likely playing a major role and irradiation possibly contributing, especially in the UV. No radio counterpart was detected, implying at most very faint jet activity. Taken together, the observed properties support the classification of EP J174942.2$-$384834 as a very faint X-ray transient black hole candidate. This study demonstrates the ability of Einstein Probe to uncover and characterize the faintest accreting compact objects in the Galaxy.

astro-ph.HE↗

arXiv2026

Ultra-high-energy $\gamma$-ray imprints from PeV particles accelerated by supernova remnants

The quest for the origin of cosmic ray (CRs) is a fundamental issue in astrophysics. Shocks of supernova remnants (SNRs) have been considered as the dominant contributors to Galactic CRs below the spectral knee near $\sim 3$ petaelectronvolt (PeV). Whether SNRs are efficient accelerators of particles beyond PeV energies has long been debated. Here we report observations of very-high-energy $\gamma$-ray emission up to hundreds of TeV from two middle age shell-type SNRs, G150.3$+$4.5 and $\gamma$-Cygni, with the Large High Altitude Air Shower Observatory (LHAASO). Two (or three) distinct morphological/spectral components with convex spectral shapes are observed in both sources, with the low-energy one being more extended than the high-energy one. %Although it is possible that these high-energy components may be driven by powerful pulsars, The likely association of the high-energy component with molecular clouds at similar distances, and the weakness/absence of pulsar wind nebulae (PWNe) inside these SNRs clearly indicate for the first time that the highest energy emission is produced by collision of hadronic CRs up to PeV energies with the clouds. These results are compatible with the classic model prediction that PeV particles accelerated near the end of the free expansion phase of SNR evolution can illuminate nearby molecular clouds (MCs) to produce strong $\gamma$-ray emission.

astro-ph.HE↗

arXiv2026

Energy Correlators Within Jets in Transversely Polarized Proton-Proton Collisions at $\sqrt{s} = 200$ GeV

We report the first measurement of one- and two-point energy correlators within jets in transversely polarized proton-proton collisions at $\sqrt{s}=200$ GeV, using the STAR detector at RHIC. These observables quantify the energy-weighted angular distribution of single hadrons and hadron pairs within jets, respectively. Sizable spin-dependent asymmetries are observed for $\pi^+$, $\pi^-$, and $\pi^+\pi^-$ pairs, revealing the onset of nonperturbative dynamics at specific angular scales. By projecting the fragmentation dynamics onto Mellin moments, these measurements provide sensitivity to the nucleon's transversity while minimizing uncertainties from nonperturbative fragmentation functions. These results establish energy correlators as a novel and precise probe of nucleon structure and open a promising avenue for three-dimensional nucleon tomography at the future Electron-Ion Collider.

hep-ex↗

arXiv2026

Inclusive jet cross section in $pp$ collisions at $\sqrt{s} = 200$ and $510$ GeV

Jets are collimated clusters of particles formed by the hadronization of partons following a hard interaction. In proton-proton ($pp$) collisions at the Relativistic Heavy Ion Collider (RHIC), jet production is dominated by $gg$ and $qg$ partonic processes, allowing us to directly probe the gluon parton distribution function (PDF) in the proton in a way complementary to deep inelastic scattering. In this paper, we report the double-differential inclusive-jet cross sections as a function of jet transverse momentum, $p_{\rm T}$, and pseudorapidity, $\eta$, at center-of-mass energies $\sqrt{s} = 200$ and $510$~GeV, from $pp$ collisions studied with the STAR detector. The jet $p_{\rm T}$ is corrected for underlying event contributions by applying an off-axis cone method. At mid-pseudorapidity, $|\eta| < 0.9$, the kinematic coverage of our data extends to $0.07 < x_{\rm T} \text{ (}= 2p_{\rm T}{} / \sqrt{s} \text{)} < 0.5$ and $0.03 < x_{\rm T} < 0.31$ at $\sqrt{s} = 200$~and 510 GeV, respectively, where the gluon PDF is poorly constrained by the TeV-scale $pp$~($p\bar{p}$) colliders. The inclusive jet cross sections are compared to the next-to-next-to-leading order perturbative quantum chromodynamics calculations using several recent PDF sets as inputs. These results will further constrain the gluon PDF, help tune Monte Carlo generators, and provide critical reference data needed to study the quark-gluon plasma.

hep-ex↗

arXiv2026

High-Precision Mass Measurements of Proton-Rich Rh, Pd, Cd isotopes in the vicinity of 100Sn and Impact on X-Ray Burst and Supernova Nucleosynthesis

Using the ZeroDegree multi-reflection time-of-flight mass spectrograph of the CRISMASS project at RIKEN Radioactive Isotope Beam Factory, we performed high-precision mass measurements of proton-rich nuclei near the doubly magic nucleus 100Sn, achieving uncertainties on the order of 10 keV. The masses of 91Rh, 92Pd, and 96Cd were determined for the first time with high precision, and the accuracy of several additional masses was substantially improved. Incorporating the new data into X-ray burst simulations significantly reduces the abundance uncertainties in the $A$ = 90-100 region, shifting the reaction flow toward $A$ = 90 production and suppressing the synthesis of heavier nuclei. Further investigation of the $\nu p$-process indicates that 99Rh plays a significant role in the reaction flow within the mass region studied. These high-precision mass measurements refine the mass surface near 100Sn and provide critical constraints on models of proton-rich nucleosynthesis.

nucl-ex↗

arXiv2026

LHAASO observation of Mrk 421 during 2021 March - 2024 March: a comprehensive VHE catalog of multi-timescale outbursts and its time average behavior

The Large High Altitude Air Shower Observatory (LHAASO) monitors sources within its field of view for up to 7 hours daily, achieving a duty cycle exceeding 98% and an annual point-source sensitivity of 1.5% Crab Units (CU) in the very high energy (VHE) band. This unbiased sky-survey mode facilitates systematic monitoring and investigation of outburst phenomena. In this paper, we present results from an unprecedented three-year monitoring campaign (March 2021--March 2024) of Mrk421 using LHAASO, spanning energies from 0.4 TeV to 20 TeV. We find that the blazar stayed in a quiescent state in 2021 and became active starting in 2022 with a total of 23 VHE outburst events identified, where the highest observed daily significance reaches $20\,\sigma$ with a flux equivalent to approximately 3.3~CU. LHAASO's continuous monitoring suggests the flaring occupancy of Mrk~421 to be around 14%. During long-term monitoring, multiwavelength (MWL) variability and correlation analyses are conducted using complementary data from Fermi-LAT, MAXI-GSC, Swift-XRT, and ZTF. A significant correlation ($>3\,\sigma$) is observed between X-ray and VHE bands with no detectable time lag, while the correlation between GeV and TeV bands is weaker. The flux distribution of the TeV emission during the quiescent state is different from that in the active state, implying the existence of two modes of energy dissipation in the blazar jet. Using simultaneous MWL data, we also analyzed both the long-term and outburst-period SEDs, and discussed the possible origin of the outburst events.

astro-ph.HE↗

arXiv2026

Probing Late-Stage Hadronic Interactions at High Baryon Density via $K^{*0}$ Production in the RHIC Beam Energy Scan Program

A precision measurement of the $K^{*0}$ meson yield is reported in Au+Au collisions at $\sqrt{s_{NN}} = 7.7,\; 11.5,\; 14.6,\; 19.6,$ and $27~\mathrm{GeV}$ using the high-statistics data sample collected by the STAR experiment during the Beam Energy Scan II (BES-II) program at RHIC. The transeverse momentum ($p_{T}$)-integrated yield ratios $(K^{*0} + \overline{K^{*0}})/(K^{+} + K^{-})$ in central collisions show a suppression relative to peripheral collisions at the $(1.7\text{-}3.6)\,\sigma$ level, while a thermal model without final-stage rescattering overpredicts this ratio with a deviation of $(6.9\text{-}8.2)\,\sigma$. These results indicate a loss of the measured $K^{*0}$ signal in central collisions due to re-scattering of its hadronic decay products in the hadronic phase. The $p_{T}$-integrated yield of charged kaons exhibits an approximate scaling with charged-particle multiplicity, independent of collision energy and system size. A similar trend is observed for the short-lived $K^{*0}$ resonance, although significant deviations emerge at lower energies. At BES energies, the $K^{*0}/K$ ratio shows stronger suppression than at the highest RHIC and LHC energies within a given multiplicity bin, particularly in central and mid-central collisions. This behavior is consistent with changes in the effective hadronic interaction cross section and is supported by transport model calculations, which indicate dominant meson-baryon interactions at lower energies and meson-meson interactions at higher energies.

nucl-ex↗

arXiv2026

Einstein Probe discovery of EP J171159.4-333253: an eclipsing neutron star low-mass X-ray binary with clocked bursts

EP J171159.4-333253 is a new neutron-star low-mass X-ray binary discovered in outburst by the Einstein Probe (EP) on 2025 June 23, exhibiting clocked type-I X-ray bursts, eclipses and dips. In this paper, we report on the results of the X-ray spectral and timing analyses for EP J171159.4-333253 using data collected by EP and NuSTAR during the first 21 days of the outburst. The X-ray burst recurrence time can be characterized over a subset of nine bursts spanning 1.6 days around the NuSTAR observation, and the result is $t_{\rm rec}=8196 \pm 177\,$s with indications of a possible decreasing trend. From the X-ray eclipse events, the binary orbital period and the eclipse duration are estimated to be $P_{\rm orb}=6.48301 \pm 0.00003\,$hr and $D_{\star,X} = 1245.5^{+6.9}_{-6.5}\,$s, respectively. These enable an estimate of the mass and radius of the companion star and the binary inclination, which are $M_2\approx0.6-0.8\,M_\odot$, $R_2\approx0.7-0.8\,R_\odot$ and $i\approx73-75^\circ$, respectively. We also report on joint ULTRACAM and EP observations on 2025 July 21--22, detecting the source optical counterpart and covering an eclipse in both X-ray and optical bands. The optical eclipse is wavelength-dependent and broader than in X-rays, indicating that part of the optical emission arises from an extended region in the accretion flow. Despite a moderate variation in the source flux, the properties of the persistent X-ray emission are typical of a hard spectral state. We further evaluated the ratio of the accretion energy to the thermonuclear energy to be 120--130, implying helium bursts with the accreted hydrogen being depleted in-between bursts.

astro-ph.HE↗

arXiv2026

The X-ray properties and structure of A3571 up to $R_{500}$

Abell 3571 is a nearby, X-ray bright galaxy cluster located in the Shapley Supercluster. Although it appears morphologically relaxed in X-ray images, multiwavelength observations reveal subtle indications of residual dynamical activity, likely associated with past merger events. Using wide-field ($1^{\circ} \times 1^{\circ}$) data from the Einstein Probe Follow-up X-ray Telescope (EP-FXT), we extend measurements of the cluster's properties beyond its $R_{500}$ radius. We detect surface-brightness excesses on both the northern and southern sides, consistent with previous XMM-Newton results. The temperature, pressure, and entropy in the northern excess region are lower than the average values, whereas those on the southern side are slightly higher. However, we find no evidence for cold fronts or shocks. These features can be interpreted as sloshing motions triggered by an off-center minor merger. Our findings suggest that, despite its symmetric appearance, A3571 is still recovering from a minor merger and is currently in a post-merger phase. This work also demonstrates the excellent capability of EP-FXT for probing the outskirts of galaxy clusters.

astro-ph.HE↗