Identification of HESS J1303−631 as a pulsar wind nebula throughγ-ray, X-ray, and radio observations

Abstract

Aims. The previously unidentified very high-energy (VHE; E > 100 GeV) γ-ray source HESS J1303−631, discovered in 2004, is re-examined including new data from the H.E.S.S. Cherenkov telescope array in order to identify this object. Archival data from the XMM-Newton X-ray satellite and from the PMN radio survey are also examined. Methods. Detailed morphological and spectral studies of VHE γ-ray emission as well as of the XMM-Newton X-ray data are performed. Radio data from the PMN survey are used as well to construct a leptonic model of the source. The γ-ray and X-ray spectra and radio upper limit are used to construct a one zone leptonic model of the spectral energy distribution (SED). Results. Significant energy-dependent morphology of the γ-ray source is detected with high-energy emission (E > 10 TeV) positionally coincident with the pulsar PSR J1301−6305 and lower energy emission (E < 2 TeV) extending ∼0.4• to the southeast of the pulsar. The spectrum of the VHE source can be described with a power-law with an exponential cut-off N 0 = (5.6 ± 0.5) × 10 −12 TeV −1 cm −2 s −1 , Γ = 1.5 ± 0.2) and E cut = (7.7 ± 2.2) TeV. The pulsar wind nebula (PWN) is also detected in X-rays, extending ∼2−3 from the pulsar position towards the center of the γ-ray emission region. A potential radio counterpart from the PMN survey is also discussed, showing a hint for a counterpart at the edge of the X-ray PWN trail and is taken as an upper limit in the SED. The extended X-ray PWN has an unabsorbed flux of F 2−10 keV ∼ 1.6and is detected at a significance of 6.5σ. The SED is well described by a one zone leptonic scenario which, with its associated caveats, predicts a very low average magnetic field for this source.Conclusions. Significant energy-dependent morphology of this source, as well as the identification of an associated X-ray PWN from XMM-Newton observations enable identification of the VHE source as an evolved PWN associated to the pulsar PSR J1301−6305. This identification is supported by the one zone leptonic model, which suggests that the energetics of the γ-ray and X-ray radiation are such that they may have a similar origin in the pulsar nebula. However, the large discrepancy in emission region sizes and the low level of synchrotron radiation suggest a multi-population leptonic nature. The low implied magnetic field suggests that the PWN has undergone significant expansion. This would explain the low level of synchrotron radiation and the difficulty in detecting counterparts at lower energies, the reason this source was originally classified as a "dark" VHE γ-ray source.

Constraints on axion-like particle properties with TeV gamma-ray observations of Galactic sources

“…where N 0 , α, β and E cut are independently set free in both fits for the background and ALP models. For each source, the function type of the intrinsic spectrum is chosen as that in the literature [48,[50][51][52][53][55][56][57]. The spectral types and the corresponding parameter values a The distances d are extracted from the TeVCat http://tevcat.uchicago.edu/.…”

Connecting the ISM to TeV PWNe and PWN candidates

“…However, energy-dependent morphology of the TeV source (see Abramowski et al 2012b) unambiguously highlighted its association with the pulsar PSR J1301−6305 (P1 in Figure 8) with spin down energyĖ SD = 2.6 × 10 36 erg s −1 , a rotation period P = 184 ms, and a characteristic age τ c = 11 kyr. Follow-up observations with XMM-Newton revealed diffuse Xray emission towards the pulsar with a power-law spectral index X = 2.0 +0.6 −0.7 (Abramowski et al 2012b). Acero et al (2013) detected a GeV counterpart with a gamma-ray spectral index γ = 1.7.…”

“…Consequently, at this distance, the effect of the ISM on the morphology of HESS J1418−609 is also not significant. HESS J1303−631 HESS J1303−631 has clearly been identified as a PWN based on energy dependent morphology at TeV energies (Abramowski et al 2012b). We here check the potential contribution of the molecular regions 'A' to 'D' to the observed TeV gamma-ray emission.…”

“…HESS J1303−631 has clearly been identified as a PWN based on energy dependent morphology at TeV energies (Abramowski et al 2012b). We here check the potential contribution of the molecular regions ' A' to 'D' to the observed TeV gamma-ray emission.…”

“…HESS J1303−631 was first classified as a 'dark source' due to its lack of any counterparts at other wavelengths (Aharonian et al 2005;Acero et al 2013). However, energy-dependent morphology of the TeV source (see Abramowski et al 2012b) unambiguously highlighted its association with the pulsar PSR J1301−6305 (P1 in Figure 8) with spin down energyĖ SD = 2.6 × 10 36 erg s −1 , a rotation period P = 184 ms, and a characteristic age τ c = 11 kyr. Follow-up observations with XMM-Newton revealed diffuse Xray emission towards the pulsar with a power-law spectral index X = 2.0 +0.6 −0.7 (Abramowski et al 2012b).…”