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We report on the X-ray emission properties of the pulsar PSR J1849−0001 and its wind nebula (PWN), as measured by Chandra, XMM-Newton, NICER, Swift, and NuSTAR. In the X-ray data, we detected the 38 ms pulsations of the pulsar up to ∼60 keV with high significance. Additionally, we found that the pulsar's on-pulse spectral energy distribution displa...
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... the PL fit was acceptable, adopting the logpar model resulted in an improved fit ( Table 2 and Figure 4). The latter model was favored with an F-test probability of 5 × 10 −5 . ...Context 2
... factors were found to be consistent with 1 at 1σ confidence levels. The results are presented in Table 2. ...Context 3
... we have measured the on−off spectrum of the pulsar using the multimission data in the previous section, we fit the XMM-Newton/PN on−off spectrum with a PL model for a comparison with the on+off spectrum measured with MOS+PN. The results are presented in Table 2. The best-fit parameter values for this on−off spectrum are in complete agreement with those derived from the on+off spectrum (Table 2). ...Context 4
... results are presented in Table 2. The best-fit parameter values for this on−off spectrum are in complete agreement with those derived from the on+off spectrum (Table 2). By comparing the on−off and on+off spectra, we find that the off-pulse flux is ≈23% of the on−off flux, which is in accord with the finding in our image analysis (panel (c)). ...Context 5
... we linked the N H of the PL model to that of the logpar model. The PL+logpar model was acceptable, with the best-fit PL parameter values reported in Table 2. ...Context 6
... in the case of the Chandra analysis (see above), the logpar model accounts for the off-pulse emission. For this model, we used point-source response files and adopted the logpar parameters listed in Table 2, along with an additional normalization factor suitable for the lower flux of the off-pulse emission (22%); these pulsar parameters were frozen. The second PL model was introduced to take into account the contamination from S1 to 11; its parameters were held fixed at the Chandra-inferred values. ...Context 7
... second PL model was introduced to take into account the contamination from S1 to 11; its parameters were held fixed at the Chandra-inferred values. The best-fit parameters for the first PL model (i.e., PWN emission) are presented in Table 2. At face value, the NuSTAR spectra are softer than the Chandra spectrum, possibly indicating a spectral break. ...Context 8
... held the parameters of the second PL component (emission from S1 to S11) in the NuSTAR model fixed at the Chandrainferred values. The model adequately fit the spectra (Figure 4, right), and the best-fit parameter values are presented in Table 2. The cross-normalization factors of the two instruments agreed within the 1σ level. ...Context 9
... performed spectral analysis using various background estimations (e.g., regions) and logpar and point-source model parameter values (within their uncertainties). We then quantified the 1σ changes of the PWN model parameters, which are presented as the additional uncertainty in Table 2. ...Citations
... ± 0.379) × 10 −15 cm −2 s −1 MeV −1 , and the energy scale E 0 is fixed to 20,000 MeV. Kim et al. (2024) To investigate the systematic errors in the local γ-ray Galactic background and the effective area, we altered the normalization of the diffuse background by ±5% and used the isotropic diffuse background version P8R3_SOURCE_V2 instead of P8R3_SOURCE_V3 (Acero et al. 2013). The spectral points we obtained are shown in Figure 3, and they are well connected to the TeV spectrum of HESS J1849-000 and ASγ. ...
... We assumed that the nebula has an age of 21 kyr in order to make the synchrotron spectra coincide with the observations of X-ray data, and we found that the detected multiwavelength data can be well reproduced by combining the parameters α 1 = 1.0, α 2 = 2.0, γ b = 6.0 × 10 7 , η = 0.3, ò = 0.4, and τ 0 = 5000. The fitting parameters used for our model are summarized in Table 4, and the resulting SED is shown in Figure 4. Furthermore, in comparison with other research, we found that while Kim et al. (2024) used a multizone emission model to determine a lower magnetic field strength within the PWN of approximately 7 μG, based on our research model and constrained by the X-ray flux, the calculated magnetic field is even lower, estimated at around 3.69 μG. This is significantly lower than the magnetic field strength observed in the Crab Nebula, which is estimated to be about 100 μG (Martín et al. 2012;Torres et al. 2014;Wen et al. 2021;Martin & Torres 2022). ...
... The TS map shows a ∼4σ significance γ-ray emission located on the position of G32.64+0.53. No significant variability in the light curve is found with (Amenomori et al. 2023), and X-ray data obtained from Chandra and NuSTAR (Kim et al. 2024). The observation conducted with the Giant Metrewave Radio Telescope at 610 MHz revealed a radio flux density upper limit of 3.5 mJy for LHAASO J1848-0001u (Pandey et al. 2006). ...
In this study, we report the likely GeV γ -ray emissions originating from the pulsar PSR J1849-0001's pulsar wind nebula (PWN) G32.64+0.53. Our analysis covers approximately 14.7 yr of data from the Fermi Large Area Telescope Pass 8. The position of the source and its spectrum matches those in X-ray and TeV energy bands, so we propose that the GeV γ -ray source is indicative of PWN G32.64+0.53. We interpret the broadband spectral energy distribution (SED) using a time-dependent one-zone model, which assumes that the multiband nonthermal emission of the target source can be generated by synchrotron radiation and inverse Compton scattering (ICS) of the electrons/positrons. Our findings demonstrate that the model substantially elucidates the observed SED. These results lend support to the hypothesis that the γ -ray source originates from the PWN G32.64+0.53 powered by PSR J1849-0001. Furthermore, the γ -rays in TeV bands are likely generated by electrons/positrons within the nebula through ICS.
... When T S 100 > 20, the source was claimed as an Ultra High Energy (UHE) source. Kim et al. (2024) The UHE source 1LHAASO J1848-0001u was associated with IGR J18490-0000 and HESS J1849-000. In GeV energy band, γ-ray radiation corresponding to the PWN is still lacking. ...
... Photon Energy (MeV) (Amenomori et al. 2023) and X-ray data obtained from Chandra and NuSTAR (Kim et al. 2024). The observation conducted with Giant Metrewave Radio Telescope at 610 MHz revealed a radio flux density upper limit of 3.5 mJy for LHAASO J1848-0001u (Pandey et al. 2006). ...
... The fitting parameters used for our model are summarized in Table. 4 and the resulting SED is shown in Fig. 4. Furthermore, in comparison with other research, we found that (Kim et al. 2024) used a multi-zone emission model to determine a lower magnetic field strength within the PWN, approximately 7 µG. However, based on our research model and constrained by the X-ray flux, the calculated magnetic field is even lower, estimated at around 3.69 µG. ...
In this study, we report the likely GeV {\gamma}-ray emissions originating from the pulsar PSR J1849-0001's pulsar wind nebula (PWN) G32.64+0.53. Our analysis covers approximately 14.7 years of data from the Fermi Large Area Telescope (Fermi-LAT) Pass 8. The position of the source and its spectrum matches those in X-ray and TeV energy bands, so we propose that the GeV {\gamma}-ray source is indicative of PWN G32.64+0.53. We interpret the broadband spectral energy distribution (SED) using a time-dependent one-zone model, which assumes that the multi-band non-thermal emission of the target source can be generated by synchrotron radiation and inverse Compton scattering (ICS) of the electrons/positrons. Our findings demonstrate that the model substantially elucidates the observed SED. These results lend support to the hypothesis that the {\gamma}-ray source originates from the PWN G32.64+0.53 powered by PSR J1849-0001. Furthermore, the {\gamma}-rays in TeV bands are likely generated by electrons/positrons within the nebula through Inverse Compton Scattering.
... In addition, a short 23 ks Chandra observation was obtained in 2012 (ObsID 13291) to explore the compact structure of the PWN. Kuiper & Hermsen (2015) and Kim et al. (2024) used this observation to analyze the PSR J1849-0001 and its PWN spectra. For the PWN, 7 Kuiper & Hermsen (2015) fitted an absorbed PL model, fixing n H to 4.5 × 10 22 cm −2 , and found a photon index of Γ = 1.18 ± 0.05 and an unabsorbed flux f X = (0.71 ± 0.05) × 10 −12 erg cm −2 s −1 in 2-10 keV. ...
... For the pulsar spectrum fitted with absorbed PL, Kuiper & Hermsen (2015) obtained the best-fit Γ = 1.08 ± 0.02 for the same fixed n H and the unabsorbed flux of ≈4.1 × 10 −12 rg cm −2 s −1 in 2-10 keV. Kim et al. (2024) fit the PWN with a PL + logpar model with a fixed n H = 6.4 × 10 22 cm −2 and found Γ = 1.96 ± 0.33 and an unabsorbed flux f X = (1.44 ± 0.18) × 10 −12 erg cm −2 s −1 in 2-10 keV. In this study, we analyzed the data from the first short CXO observation together with the data from our new CXO observations. ...
... Finally, we note that although Amenomori et al. (2023) discussed an alternative hadronic scenario, where the TeV γ-rays are produced by neutral pion decay, no evidence of a radio SNR is seen in the radio images (see Figure 9). The paper of Kim et al. (2024), which appeared nearly simultaneously with our paper, offers a more detailed modeling of multiwavelength emission from this source, including the comparison between one-zone and more physical multizone models. ...
We obtained a 108 ks Chandra X-ray Observatory (CXO) observation of PSR J1849-0001 and its pulsar wind nebula (PWN) coincident with the TeV source HESS J1849-000. By analyzing the new and old (archival) CXO data, we resolved the pulsar from the PWN, explored the PWN morphology on arcsecond and arcminute scales, and measured the spectra of different regions of the PWN. Both the pulsar and the compact inner PWN spectra are hard with power-law photon indices of 1.20 ± 0.07 and 1.49 ± 0.20, respectively. The jet-dominated PWN has a relatively low luminosity, lack of γ -ray pulsations, relatively hard and nonthermal spectrum of the pulsar, and sine-like pulse profile, which indicates a relatively small angle between the pulsar’s spin and magnetic dipole axis. In this respect, it shares similar properties with a few other so-called MeV pulsars. Although the joint X-ray and TeV spectral energy distribution can be roughly described by a single-zone model, the obtained magnetic field value is unrealistically low. A more realistic scenario is the presence of a relic PWN, no longer emitting synchrotron X-rays but still radiating in TeV via inverse-Compton upscattering. We also serendipitously detected surprisingly bright X-ray emission from a very wide binary whose components should not be interacting.
... To date, there is no known radio PWN coincident with HESS J1849-000 (Green 2014;Anderson et al. 2017;Green 2019). Very recently, Kim et al. (2024) used Chandra, XMM-Newton, NICER, Swift, and NuSTAR to measure both the X-ray spectrum and the radial profiles of the PWN's brightness and photon index, and then employed a spatially dependent emission scenario to explain the broadband data. In addition, Gagnon et al. (2023) also explored the PWN morphology on arcsecond and arcminute scales and measured the spectra of different regions of the PWN by analyzing the new and old Chandra data. ...
... Here, the value of δ depends on the property of turbulence in the ambient medium, and the different values of δ represent different diffusion forms (for details, see Zhu et al. 2021Zhu et al. , 2023. Following Kim et al. (2024), we assumed that the turbulence is a classical Kolmogorov turbulence within the nebula, and so the value of δ was chosen to be one-third. According to Parker (1965), the diffusion timescale of particles τ diff is described by ...
... Consequently, it must be relatively young. Following Kim et al. (2024), the age of the system is estimated as t age = 9000 yr. For the measured P and P values of the pulsar, the corresponding characteristic age is τ c = 4.31 × 10 4 yr and the current spin-down luminosity is L(t age ) = 9.77 × 10 36 erg s −1 . ...
Pulsar wind nebula HESS J1849-000 is one of the sources that may emit PeV γ -ray photons based on the recent measurement by the Tibet Air Shower Array and the Large High Altitude Air Shower Observatory. We use a time-dependent model to investigate the nonthermal radiative properties of HESS J1849-000. Observed multiband data are produced well by relativistic leptons through synchrotron radiation and inverse Compton processes, and the particle transport and cooling processes are analyzed. Our results show that the particle adiabatic loss dominates over the synchrotron loss and inverse Compton losses, and the particle advection dominates over diffusion for the low-energy band. On the other hand, the particle synchrotron loss dominates over the adiabatic loss and inverse Compton losses, and the diffusion dominates over advection for the high-energy band. Furthermore, particle transport would be playing a significant role in the low-energy band, whereas the particle cooling processes may play a more important role in the high-energy band. The current diffusion coefficient 3.4 × 10 ²⁶ cm ² s ⁻¹ at an electron energy of 1 TeV is derived, which implies a slow diffusion mechanism may occur within the nebula. More importantly, our model suggests that the particle's maximum energy is 3.6 PeV, which makes HESS J1849-000 a PeVatron candidate.
... It has been discussed that the nonthermal X-ray emission is produced by the synchrotron radiation from the secondary electron/positron pairs that are produced by the pair-creation process of the GeV gamma rays (Kisaka & Tanaka 2017). For MeV pulsars, on the other hand, previous X-ray studies have collected evidence that the broadband X-ray spectrum is described by a single power law with a photon index of Γ 1 < 1.5 or by a power law with a turnover in the 1-10 keV bands (see, e.g., Chen et al. 2016;Hu et al. 2017; and references therein for PSR B1509-58; Kargaltsev et al. 2009 for PSR J1617-5055; Madsen et al. 2020 for PSR J1811-1925Kuiper & Hermsen 2015 for PSR J1813-1749; Lin et al. 2009 and references therein for PSR J1838-0655; Gotthelf et al. 2021 for PSR J1846-0258; Gotthelf et al. 2011 andKim et al. 2024 for PSR J1849-0001; and Lu et al. 2007 for PSR J1930+1852). We also refer to Kuiper & Hermsen (2015) for a comprehensive observational study of the hard X-ray/soft gamma-ray emission of the young pulsars. ...
... The s-pl model provides an acceptable fitting result ( Table 2), and its parameters are N H = 5.1(3) × 10 22 cm 2 and Γ 1 = 1.48(5). Although the obtained N H is smaller than N H = 8.1(2) × 10 22 cm 2 reported in Kim et al. (2024), who use the same XMM-Newton and NuSTAR data as we did, the photon index is consistent with their Γ 1 = 1.42(3) within the error. The bk-pl model improves the fitting results with an Fstatistic value of 8.2 (p = 0.00031), and the photon index (Γ 1 = 0.8(4)) below the break energy (E b = 4.9(8) keV) is consistent with ∼1.1 in previous studies (Gotthelf et al. 2011;Kuiper & Hermsen 2015), in which XMM-Newton data were fit by an s-pw model. ...
... Assuming a distance of 7 kpc to the source (Gotthelf et al. 2011), the efficiency in the 0.3-150 keV bands is estimated to be η X ∼ 0.025. Kim et al. (2024) suggest the existence of a peak in the spectrum at ∼60 keV, which is lower than the ∼1-5 MeV of PSRs B1509-58 and J1846-0258. As the left panel in Figure B4 shows, on the other hand, our extracted spectrum may indicate an absorption feature at around 40 keV rather than a peaking of the spectrum. ...
We report on the properties of pulsed X-ray emission from eight MeV pulsars using XMM-Newton, NICER, NuSTAR, and HXMT data. For five of the eight MeV pulsars, the X-ray spectra can be fit by a broken power-law model with a break energy of ∼5–10 keV. The photon indices below and above the break energy are ∼1 and ∼1.5, respectively. In comparison with the X-ray emission of the Fermi-LAT pulsars, the MeV pulsars have a harder spectrum and a higher radiation efficiency in the 0.3–10 keV energy bands. When isotropic emission is assumed, the emission efficiency in the keV–MeV bands is estimated to be η MeV ∼ 0.01–0.1, and this is similar to the efficiency of the GeV emission of the Fermi-LAT pulsars with a similar spin-down power. To explain the observed efficiency of the MeV pulsars, we estimate the required pair multiplicity as 10 4–7 , which depends on the emission process (curvature radiation or synchrotron radiation) and on the location in the magnetosphere. The high multiplicity indicates that the secondary pairs that are created by a pair-creation process of the GeV photons produce the X-ray/soft gamma-ray emission of the MeV pulsars. We speculate that the difference between MeV pulsars and Fermi-LAT pulsars can be attributed to the difference in viewing angle measured from the spin axis if the emission originates from a region inside the light cylinder (canonical gap model) or to the difference in the inclination angle of the magnetic axis if the emission is produced in the equatorial current sheet outside the light cylinder.
