Multi-wavelength observations of 2HWC J1928+177: dark accelerator or new TeV gamma-ray binary?
Kaya Mori, Hongjun An, Qi Feng, Kelly Malone, Raul R. Prado, Yve E. Schutt, Brenda L. Dingus, E. V. Gotthelf, Charles J. Hailey, Jeremy Hare, Oleg Kargaltsev, Reshmi Mukherjee
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., still remains unidentified as a dark accelerator since there is no apparent supernova remnant or pulsar wind nebula detected in the lower energy bands. The radio pulsar PSR J1928+1746, coinciding with the HAWC source position, has no X-ray counterpart. Our SED modeling shows that inverse Compton scattering in the putative pulsar wind nebula can account for the TeV emission only if the unseen nebula is extended beyond r ~ 4 [arcmin]. Alternatively, TeV gamma rays may be produced by hadronic interactions between relativistic protons from an undetected supernova remnant associated with the radio pulsar and a nearby molecular cloud G52.9+0.1. NuSTAR and Chandra observations detected a variable X-ray point source within the HAWC error circle, potentially associated with a bright IR source. The X-ray spectra can be fitted with an absorbed power-law model with $N_{\rm H} = (9\pm3)\times10^{22}$ cm$^{-2}$ and $Γ_X = 1.6\pm0.3$ and exhibit long-term X-ray flux variability over the last decade. If the X-ray source, possibly associated with the IR source (likely an O star), is the counterpart of the HAWC source, it may be a new TeV gamma-ray binary powered by collisions between the pulsar wind and stellar wind. Follow-up X-ray observations are warranted to search for diffuse X-ray emission and determine the nature of the HAWC source.
The Cygnus Cocoon is the first gamma-ray superbubble powered by a massive stellar association, the OB2 association. It was postulated that the combined effects of the stellar winds of all the massive O-type stars of the OB2 association can accelerate the cosmic rays to PeV energy in the Cocoon. The conclusive proof of acceleration to PeV energy in the Cocoon will identify the stellar association as a PeV cosmic-ray accelerator, known as PeVatron. However, the Cocoon has been previously studied only up to 10 TeV. In this contribution, using 1343 days of High Altitude Water Cherenkov (HAWC) obse…
Ultrahigh energy protons and nuclei from extragalactic cosmic ray sources initiate intergalactic electromagnetic cascades, resulting in observable fluxes of $γ$-rays in the GeV-TeV energy domain. The total spectrum of such cascade $γ$-rays of hadronic nature is significantly harder than the one usually expected from blazars. The spectra of some sources known as "extreme TeV blazars" could be well-described by this "intergalactic hadronic cascade model" (IHCM). We calculate the shape of the observable point-like spectrum, as well as the observable angular distibution of $γ$-rays, for the first …
Since the discovery of cosmic rays (CRs) over a century ago, their origin remains an open question. Galactic CRs with energy up to the knee ($10^{15}$ eV) are considered to originate from supernova remnants, but this scenario has recently been questioned due to lack of TeV $γ$-ray counterparts in many cases. Extragalactic CRs on the other hand, are thought to be associated with accelerated particles in the relativistic jets launched by supermassive accreting black holes at the center of galaxies. Scaled down versions of such jets have been detected in X-ray binaries hosting a stellar black hol…
It is generally held that >100 TeV emission from astrophysical objects unambiguously demonstrates the presence of PeV protons or nuclei, due to the unavoidable Klein-Nishina suppression of inverse Compton emission from electrons. However, in the presence of inverse Compton dominated cooling, hard high-energy electron spectra are possible. We show that the environmental requirements for such spectra can naturally be met in spiral arms, and in particular in regions of enhanced star formation activity, the natural locations for the most promising electron accelerators: powerful young pulsars. Our…
Fossil shell in 3C 84 as TeV $γ$-ray emitter and cosmic-ray accelerator
我们探索了受冲击的外部介质的物理特性（即，3C 84中与1960年左右出生的周期性射电瓣有关的一个壳）。在Ito等人先前的工作中，我们研究了在中央发动机停止喷气发射后这种壳层的动力学和辐射演化，我们发现化石壳层的辐射与快速衰落的射电瓣的辐射相似。我们将这个模型应用于3C 84，发现：（1）由数密度为0.3 cm $^{-3}$的冲击扩散环境物质构成的化石壳层，以来自中心致密区的射电辐射种子光子为辐射源，辐射出明亮的逆康普顿（IC）辐射，IC辐射超过切伦科夫望远镜阵列（CTA）的灵敏度阈值。(ii)当化石壳产生于数密度为$10^{3}$ cm $^{-3}$的几何厚电离等离子体中时，壳中的场强在磁场放大的存在下可达到约17 mG，射电发射变得与深成像VLBI观测的灵敏度相当。超高能宇宙射线（UHECRs）的可能产生的致密冲击等离子体也被认为是。
Constraining the Diffusion Coefficient with HAWC TeV Gamma-Ray Observations of Two Nearby Pulsar Wind Nebulae
附近的电子/正电子加速器，主要是脉冲星风星云（PWNe），被认为是超过10 GeV的正电子过剩的潜在来源。HAWC天文台揭示了两个非常扩展的源，它们在空间上与附近的两个中年恒星重合：Geminga和PSR B 0656 +14，这表明超相对论电子/正电子在我们的后院加速。对这两种PWNe的形态学研究提供了在HAWC能量下扩散系数的约束。在这张海报中，我们将介绍这些PWNe的模型开发和形态学研究，以及最适合数据的衍生扩散系数。
An ALMA view of the Jet-Arc CO clouds toward the TeV $γ$-ray source HESS J1023-575 and Westerlund 2; Evidence for the footprints of microquasar jets, the very powerful cosmic-ray accelerator in the Galactic disk
Nagoya University（名古屋大学）；Gifu University（岐阜大学）；Chiba University（千叶大学）；University of Tsukuba（筑波大学）；Konan University（神户学院大学）；Deutsches Elektronen-Synchrotron DESY（德国电子同步辐射中心）
The most powerful persistent accelerators in the Universe are jetted active galaxies. Blazars, galaxies whose jets are directed towards Earth, dominate the extragalactic gamma-ray sky. Still, most of the highest-energy particle accelerators likely elude detection. These extreme blazars, whose radiated energy can peak beyond 10 TeV, are ideal targets to study particle acceleration and radiative processes, and may provide links to cosmic rays and astrophysical neutrinos. The growing number of extreme blazars observed at TeV energies has been critical for the emergence of gamma-ray cosmology, inc…
Observations of the Milky Way at TeV-PeV energies reveal a bright diffuse flux of hadronic cosmic rays and also bright point sources of gamma rays. If the gamma-ray sources are hadronic cosmic-ray accelerators, then they must also be neutrino sources. However, no neutrino sources have been detected. Where are they? We introduce a new population-based approach to probe Milky Way hadronic PeVatrons, demanding consistency between diffuse and point-source PeV-range data on cosmic rays, gamma rays, and neutrinos. For the PeVatrons, two extreme scenarios are allowed: (1) the hadronic cosmic-ray acce…
