H.E.S.S.银河平面扫描揭示了银河系中大量的甚高能量（VHE; E > 100 GeV）发射体。大多数的星系源都是延伸的，通常与脉冲星风星云（35%）和超新星遗迹（21%）有关，而一些源仍然无法识别（31%）。一小部分点状源（总共5个，相当于4%）被确定为伽马射线双星。位于银河平面后面的活动星系核也是一个潜在的源类。在VHE星系中，活动星系可以通过点状外观、高变率幅度（高达100倍）和典型的软光谱（由于被河外背景光吸收）来识别。在这里，我们报告的VERITAS观测HESS J1943+213，一个身份不明的点源，发现发射超过470 GeV的扩展H.E.S.S.银河平面扫描这个源被认为是银河系平面后面的一个遥远的BL Lac天体，虽然它表现出陡峭的光谱，但它是一个弱的GeV源，最近才使用5年的费米-LAT数据检测到。VERITAS在高海拔地区的深观测导致了迄今为止对该物体最重要的VHE探测，超过200 GeV的超过18个标准差。我们使用的变化和光谱分析的VERITAS数据HESS J1943+213在多波长的背景下，以解决源分类。
英文摘要：
The H.E.S.S. Galactic plane scan has revealed a large population of Galactic very high energy (VHE; E > 100 GeV) emitters. The majority of the galactic sources are extended and can typically be associated with pulsar wind nebulae (35%) and supernova remnants (21%), while some of the sources remain unidentified (31%). A much smaller fraction of point-like sources (5 in total, corresponding to 4%) are identified as gamma-ray binaries. Active galactic nuclei located behind the Galactic plane are also a potential source class. An active galaxy could be identified in the VHE regime by a point-like appearance, a high variability amplitude (up to a factor of 100) and a typically soft spectrum (due to absorption by the extra-galactic background light). Here we report on VERITAS observations of HESS J1943+213, an unidentified point source discovered to emit above 470 GeV during the extended H.E.S.S. Galactic plane scan. This source is thought to be a distant BL Lac object behind the Galactic plane and, though it exhibits a steep spectrum it is a weak GeV source, only recently detected using 5 years of Fermi-LAT data. Deep VERITAS observations at high elevations result in the most significant VHE detection of this object so far, with an excess above 200 GeV of more than 18 standard deviations. We use variability and spectral analyses of VERITAS data on HESS J1943+213 in a multi-wavelength context to address the source classification.
The gamma-ray binary HESSJ0632+057 (VERJ0633+057) has been observed at very-high energies for a decade by all major systems of imaging atmospheric Cherenkov telescopes. We present here new observations taken by the VERITAS observatory during the season 2015-2016. The observations cover now all phases of the binary orbit (with its period of about 315 days), showing clearly enhancements around phases 0.35 and 0.75. The results are discussed along with simultaneous observations with Swift's X-Ray Telescope.
The gamma-ray binary HESS J0632+057 has been observed at very-high energies (E $>$ 100 GeV) for more than ten years by the major systems of imaging atmospheric Cherenkov telescopes. We present a summary of results obtained with the H.E.S.S., MAGIC, and VERITAS experiments based on roughly 440 h of observations in total. This includes a discussion of an unusually bright TeV outburst of HESS J0632+057 in January 2018. The updated gamma-ray light curve now covers all phases of the orbital period with significant detections in almost all orbital phases. Results are discussed in context with simult…
HESS J1943+213 is a very high energy (VHE; 100 GeV) γ-ray source in the direction of the Galactic plane. 38 hours of deep VERITAS observations taken over two seasons detect the source with ~20 σ significance. Monitoring observations of HESS J1943+213 show a remarkably stable flux and spectrum in VHE γ-rays. Studies exploring the classification of HESS J1943+213 are converging towards accepting the source as an extreme synchrotron BL Lac object. Specifically, overall SED characteristics of the source, the detection of a potential host galaxy in near-IR imaging, and VLBI observations of the HESS…
HESS J0632+057 is a gamma-ray binary composed of a compact object and a Be star, with an orbital period of about 315 days. The actual nature of its non-thermal emission, spanning from radio to very-high-energy (VHE, >100 GeV) gamma-rays, is currently unknown. In this contribution we will present the results of a set of simultaneous observations performed by the NuSTAR X-ray telescope and the VERITAS observatory. The combination of hard X-rays (3-30 keV) and VHE gamma-rays (0.1-5 TeV) provide valuable information for the understanding of the radiative processes occurring in the system. The spec…
With 8 hours of observations, VERITAS confirms the detection of two very high energy gamma-ray sources. The gamma-ray binary LS 5039 is detected with a statistical significance of $8.8σ$. The measured flux above 1 TeV is $(2.5 \pm 0.4) \times 10^{-12} \rm \, cm^{-2} \, s^{-1}$ near inferior conjunction and $(7.8 \pm 2.8) \times 10^{-13} \rm \, cm^{-2} \, s^{-1}$ near superior conjunction. The pulsar wind nebula HESS J1825-137 is detected with a statistical significance of $6.7σ$ and a measured flux above 1 TeV of $(3.9 \pm 0.8) \times 10^{-12} \rm \, cm^{-2} \, s^{-1}$.
Gamma-ray binaries are variable sources of GeV-to-TeV photons with the peak in their spectral energy distributions above 100 MeV. There are only five Galactic gamma-ray binaries known and the processes which govern particle acceleration, non-thermal emission and the variability patterns are not well understood. We present here for the first time results of the VERITAS binary discovery program at VHE energies and a summary of eleven years of observations of the gamma-ray binary HESS J0632+057. VERITAS has acquired more than 220 hours of observations on HESS J0632+057. The results are discussed …
The H.E.S.S. Galactic Plane Survey (HGPS) revealed 78 TeV sources among which 47 are not clearly associated with a known object. We present a multiwavelength approach to constrain the origin of the emission from unidentified HGPS sources. We present a generic pipeline that explores a large database of multiwavelength archival data toward any region in the Galactic plane. Along with a visual inspection of the retrieved multiwavelength observations to search for faint and uncataloged counterparts, we derive a radio spectral index that helps disentangle thermal from nonthermal emission and a mean…
The search for Dark Matter (DM) has great potential to reveal physics beyond the Standard Model. As such, searches for evidence of DM particles are being carried out using a wide range of techniques, such as direct searches for DM particles, searches for DM produced with colliders, and indirect searches for the Standard Model annihilation products of DM. Dwarf spheroidal galaxies (dSphs) are excellent targets for indirect Dark Matter searches due to their relatively high DM content and negligible expected astrophysical background. A collaboration was formed to maximise the sensitivity of DM se…
HESS J1614$-$518 and HESS J1616$-$508 are two tera-electron volt (TeV) $γ$-ray sources that are not firmly associated with any known counterparts at other wavelengths. We investigate the distribution of interstellar medium towards the TeV $γ$-ray sources using results from a 7 mm-wavelength Mopra study, the Mopra Southern Galactic Plane CO Survey, the Millimetre Astronomer's Legacy Team - 45 GHz survey and [CI] data from the HEAT telescope. Data in the CO(1$-$0) transition lines reveal diffuse gas overlapping the two TeV sources at several velocities along the line of sight, while observations…
The Galactic TeV $γ$-ray source HESS$\,$J1804$-$216 is currently an unidentified source. In an attempt to unveil its origin, we present here the most detailed study of interstellar gas using data from the Mopra Southern Galactic Plane CO Survey, 7 and 12$\,$mm wavelength Mopra surveys and Southern Galactic Plane Survey of HI. Several components of atomic and molecular gas are found to overlap HESS$\,$J1804$-$216 at various velocities along the line of sight. The CS(1-0) emission clumps confirm the presence of dense gas. Both correlation and anti-correlation between the gas and TeV $γ$-ray emis…
HESS J0632+057 belongs to a rare subclass of binary systems which emits gamma-rays above 100 GeV. It stands out for its distinctive high-energy light curve, which features a sharp ``primary'' peak and broader ``secondary'' peak. We present the results of contemporaneous observations by NuSTAR and VERITAS during the secondary peak between Dec. 2019 and Feb. 2020, when the orbital phase ($ϕ$) is between 0.55 and 0.75. NuSTAR detected X-ray spectral evolution, while VERITAS detected TeV emission. We fit a leptonic wind-collision model to the multi-wavelength spectra data obtained over the four Nu…
A Multiwavelength Interpretation of HESS J1857+026 Emission Using the Fermi-LAT, VERITAS, and HAWC Observatories
NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；University of Maryland（马里兰大学）；DePauw University（迪堡大学）；Temple University（天普大学）；University of Utah（犹他大学）；University College Dublin（都柏林大学学院）；University of California, Los Angeles（加州大学洛杉矶分校）；California Polytechnic State University（加州州立理工大学）
We report the detection, with the CANGAROO-III imaging atmospheric Cherenkov telescope array, of a very high energy gamma-ray signal from the unidentified gamma-ray source HESS J1614-518, which was discovered in the H.E.S.S. Galactic plane survey. Diffuse gamma-ray emission was detected above 760 GeV at the 8.9 sigma level during an effective exposure of 54 hr from 2008 May to August. The spectrum can be represented by a power-law: 8.2+-2.2_{stat}+-2.5_{sys}x10^{-12}x (E/1TeV)^{-Gamma} cm^{-2} s^{-1} TeV^{-1} with a photon index Gamma of 2.4+-0.3_{stat}+-0.2_{sys}, which is compatible with tha…
Located in southern Arizona, VERITAS is amongst the most sensitive detectors for astrophysical very high energy (VHE; E>100 GeV) gamma rays and has been operational since April 2007. We highlight some recent results from VERITAS observations. These include the long-term observations of the gamma-ray binaries HESS J0632+057 and LS I +61° 303, the observations of the Galactic Center region, and of the supernova remnant Cas~A. We discuss the results from a decade of multi-wavelength observations of the blazar 1ES 1215+303, the EHT 2017 campaign on the M87 galaxy, the discovery of 3C 264 in VHE, a…
HESS J0632+057 is a gamma-ray binary composed of a compact object orbiting a Be star with a period of about $315$ days. Extensive X-ray and TeV gamma-ray observations have revealed a peculiar light curve containing two peaks, separated by a dip. We present the results of simultaneous observations in hard X-rays with NuSTAR and in TeV gamma-rays with VERITAS, performed in November and December 2017. These observations correspond to the orbital phases $ϕ\approx0.22$ and $0.3$, where the fluxes are rising towards the first light-curve peak. A significant variation of the spectral index from 1.77$…
We present a catalog of results of gamma-ray observations made by VERITAS, published from 2008 to 2020. VERITAS is a ground based imaging atmospheric Cherenkov telescope observatory located at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona, sensitive to gamma-ray photons with energies in the range of ~100 GeV - 30 TeV. Its observation targets include galactic sources such as binary star systems, pulsar wind nebulae, and supernova remnants, extragalactic sources like active galactic nuclei, star forming galaxies, and gamma-ray bursts, and some unidentified objects. The catalog…
Resolving the origin of the unidentified TeV source HESS J1626-490 as a relic of the ancient cosmic-ray factory SNR G335.2+0.1
Ritsumeikan University（立命馆大学）；Research Organization of Science and Technology, Ritsumeikan University（立命馆大学科学技术研究院）；Kyoto University（京都大学）；Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所）；Tohoku University（东北大学）；Gifu University（岐阜大学）；University of Miyazaki（宫崎大学）；Konan University（神户女学院大学）
Lower limits on the energy cutoff for unidentified gamma-ray sources detected in the HESS galactic plane survey are derived. Additional public data from the VERITAS, HESS and Milagro experiments are used for MGRO J1908+06 to confirm the limit derived from the HESS galactic plane survey data and to enable further conclusions on the presence of spectral breaks. Five Pevatron candidates are identified in the HESS galactic plane survey. The cutoff of the gamma-ray spectrum for these sources is larger than 20 TeV at 90% confidence level. The gamma-ray sources MGRO J1908+06 and HESS J1641-463, found…
The Galactic Center region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of non-thermal radiation. We present the analysis of the very-high-energy gamma-ray emission above 2 TeV of the region around the Galactic Center known as the Central Molecular Zone using 125 hours of data taken with the VERITAS imaging-atmospheric Cherenkov telescope between 2010 and 2018. This analysis employs new shower reconstruction algorithms and instrument response functions optimized for data taken at large zenith angles such as the Galactic Center sources…
The High Energy Stereoscopic System (H.E.S.S.) observatory has carried a deep survey of the Galactic plane, in the course of which the existence of a significant number of ($\sim$ 78) TeV $γ$-ray sources was confirmed, many of which remain unidentified. HESS J1828-099 is a point-like (Gaussian stand. dev. $<$ 0.07$^{\circ}$) unidentified source among the 17 confirmed point-like sources in the H.E.S.S. Galactic Plane Survey (HGPS) catalog. This source is also unique because it does not seem to have any apparent association with any object detected at other wavelengths. We investigate the nature…
Supernova remnants (SNRs), star formation regions (SFRs), and pulsar wind nebulae (PWNe) are prime candidates for Galactic PeVatrons. The nonthermal high-energy (HE, $\varepsilon>100 \textrm{ MeV}$) and very high-energy (VHE, $\varepsilon>100 \textrm{ GeV}$) $γ$-ray emission from these sources should be a promising manifestation of acceleration processes. We investigate the possibility to explain the HE and VHE $γ$-ray emission from the sky region of the magnetar SGR 1900+14 as a signature of cosmic rays accelerated in above mentioned sources. To this end, we simulate the $γ$-ray emission from…
