Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2501.02397

Multi-wavelength Emission of Gamma-ray Burst Prompt Phase. II. Spectral Polarimetry

Jia-Sheng Li·Mi-Xiang Lan
View original source ↗Read source document ↗Export metadata ↓

Abstract

Polarization spectra had been predicted within the photosphere model. For the purpose of seeking more clues to distinguish between the models, both the time-resolved and time-integrated polarization spectra from optical band to MeV gamma-rays of the magnetic reconnection model are studied here. There are two newly found differences between the two models. First, the time-integrated polarization degree (PD) of the magnetic reconnection model would in general increase with frequency for on-axis observations, while it is not monotonous for the photosphere model. Second, the variations of both the time-integrated and the time-resolved polarization angles (PAs) with frequency of the magnetic reconnection model is not random, while the time-integrated PA varies randomly with frequency for the photosphere model. Therefore, future energy-resolved polarization analysis could distinguish between the two models. In addition, the PA rotation spectra are studied for the first time. The rotation value of PA within the burst duration will decrease with the increase of the observational energy band. Most significant PA rotation would happen for slightly off-axis observations in each energy band. The PA would rotate even for on-axis observations in optical band. Compared with the aligned magnetic field case, the PA rotation is quite rare in the gamma-ray band for the case with a toroidal field in the radiation region.

Explore related subjects

astro-ph.HE

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Jia-Sheng Li, Mi-Xiang Lan. 2025-01-04. Multi-wavelength Emission of Gamma-ray Burst Prompt Phase. II. Spectral Polarimetry. https://arxiv.org/abs/2501.02397

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

GW231109_235456: A Sub-threshold Binary Neutron Star Merger in the LIGO-Virgo-KAGRA O4a Observing Run?

We present a sub-threshold search for gravitational-wave inspirals from binary neutron stars using data from the first part of the fourth LIGO--Virgo--KAGRA observing run. To enhance sensitivity to this targeted population, we adopt a population prior informed by the Galactic double neutron star population observed via radio pulsar surveys and by the confirmed GW170817 event. The search, with a sensitivity ~60% higher than standard GWTC-4.0 searches, recovers the previously sub-threshold candidate GW231109_235456 (reported in GWTC-4.0) with a network signal-to-noise ratio of 9.7 and an improved false-alarm rate of 1 per 60 years. Accounting for a trials factor of five, arising from the four previous searches and this new search, the false-alarm rate of the candidate is approximately 1 per 12 years. If the event is of astrophysical origin, the inferred source properties indicate component masses of 1.40 to 2.24 solar masses for the primary and 0.97 to 1.49 solar masses for the secondary, yielding a total mass of 2.95 solar masses with an uncertainty of plus 0.38 and minus 0.07 solar masses. The event is localized to a region of 430 square degrees (90% probability) at a luminosity distance of 165 megaparsecs with an uncertainty of plus 70 and minus 69 megaparsecs. Assuming the signal arises from a binary neutron star merger, this event would contribute a local merger rate of 53 to 342 per cubic gigaparsec per year (90% credible interval).

astro-ph.HE↗
arXiv2026

Gaussian-process evidence for a stochastic-variability transition in the recovering corona of 1ES 1927+654

We investigate the stochastic X-ray variability of the changing-look active galactic nucleus 1ES 1927+654 during its 2018--2024 evolution, focusing on the recovery of the X-ray corona after its 2018 collapse. Using XMM-Newton EPIC-pn light curves in the 0.3--2.0 keV and 2.0--10.0 keV bands, we model the variability with Gaussian process (GP) covariance components including Matérn-3/2, damped-random-walk (DRW), stochastically driven damped simple-harmonic-oscillator (SHO), and white-noise terms. Bayesian model comparison reveals an X-ray stochastic-variability transition during the changing-look recovery phase. In the 2019 May 5 observation, the preferred covariance changes from a Matérn-3/2-like state to a DRW-like state within a single continuous exposure. A phenomenological gated-kernel estimate localizes this transition sharply in the hard band at $t_c\simeq23.5~{\rm ks}$, while the soft band shows the same qualitative change over a broader interval. This transition occurs after the X-ray corona had reappeared but before the later pronounced hardening and brightening of the coronal emission, suggesting an early timing-domain signature of disk--corona reconfiguration. Phenomenologically, the dominant variability evolves from a smoother, finite-memory correlated process to a rougher, shorter-memory red-noise process. In the later 2022--2024 observations, SHO-like components associated with the known millihertz QPO show increasing characteristic frequency and quality factor, indicating a faster and more coherent oscillatory component during the QPO-plus-jet phase. GP-based time-domain inference therefore provides a sensitive probe of stochastic-variability changes in recovering AGN coronae.

astro-ph.HE↗
arXiv2026

Exploring the dynamics of the Coma galaxy cluster by mapping its X-ray emission line profiles with XRISM

The intracluster medium (ICM) in merging galaxy clusters exhibits turbulence and bulk flows. Unraveling these components is crucial not only for elucidating the geometry of the cluster mergers, but also for understanding the physics of magnetic field amplification and relativistic particle acceleration. XRISM/Resolve data for two $3'\times3'$ fields in the core of the Coma cluster reveales that the ICM in the central field moves with $Δcz = -430$~km~s$^{-1}$ relative to the cluster galaxy average, while that in the southern field moves with $Δcz = -730$~km~s$^{-1}$ (see \cite{2025ApJ...985L..20X}, hereinafter ``Paper I''). In this paper, we perform a more detailed analysis of these data sets to search for non-Gaussian features in the Fe-K line complex profiles. In the spectra from the northwest (NW) quadrant of the central field, in addition to the main and redshifted ICM components ($Δcz = -40$ km s$^{-1}$) reported in Paper I, we find evidence of another, blueshifted component, moving with $Δcz = -1250$ km s$^{-1}$. For a systematic search for other significant velocity components, we perform a bias-free 3 eV step multi-component fit to the Resolve full-array spectra from the central and southern fields. This search uncovers another redshifted component in the southern field, moving with $Δcz \sim +1230$ km s$^{-1}$. We estimate the energy densities of the ICM turbulence and bulk motion to be similar to each other and several times greater than the energy density of the cluster's $B\sim 5~μ$G magnetic field.

astro-ph.HE↗