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X-ray spectra of the PWN (crosses; 1-20 keV) extracted within an R 3 = ¢ circle, and those of the pulsar (empty circles; 1-30 keV). The best-fit instrumental Gaussian lines for the PWN spectra measured by XMM-Newton are presented in dashed black (MOS1) and red (MOS2) lines in the top panel. The pulsar spectrum measured by Chandra (cyan circles in the top panel) includes both the pulsed and off-pulse components, and those measured by NuSTAR are only for the pulsed component (blue and green circles). The bottom panel shows residuals after subtracting the best-fit power-law and instrumental Gaussian models.
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We report on broadband X-ray properties of the Rabbit pulsar wind nebula (PWN) associated with the pulsar PSR J1418−6058 using archival Chandra and XMM-Newton data, as well as a new NuSTAR observation. NuSTAR data above 10 keV allowed us to detect the 110 ms spin period of the pulsar, characterize its hard X-ray pulse profile, and resolve hard X-ra...
Contexts in source publication
Context 1
... XMM-Newton spectra constructed following the aforementioned procedure exhibited small but noticeable residuals around the instrumental line complex at 1.5-2 keV; the residuals (e.g., dashed black and red lines in Figure 5 top) show a structure that is broader than individual instrumental lines. This is possibly caused by temporal variation of the line emissions and likely imperfect subtraction of the FWC background (e.g., Kuntz & Snowden 2008). ...
Context 2
... characterize the R 3 = ¢ PWN emission better, we jointly fit the XMM-Newton, Chandra, and NuSTAR spectra, and inferred the best-fit parameters to be N H = (2.78 ± 0.11) × 10 22 cm −2 , Γ = 2.02 ± 0.05, and F 2-10keV = (3. (Figure 5 left). The cross-normalization factors (set to 1 for Chandra) were estimated to be 0.82 ± 0.02 and 1.17 ± 0.06 for MOS1 and FPMA, respectively. ...
Context 3
... we used the XMM-Newton measurements of the radial profiles for the pair scans. Because the broadband X-ray SED, especially the NuSTAR measurement, is crucial for the estimation of e,max g , we used all the spectral measurements in Figure 5 after normalizing the flux to the XMM-Newton flux of the R 40 3 < < ¢ region. ...
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We present the first spatially resolved, X-ray spectroscopic study of the 4-8 keV diffuse emission found in the central part of the nearby starburst galaxy M82 on a few arcsecond scales. The new details that we see allow a number of important conclusions to be drawn on the nature of the hot gas and its origin as well as feedback on the ISM. We use...
Citations
... In Scenario 1, the S1 size of R 1 » ¢ (∼4 pc for an assumed distance of 13 kpc scaled by N H ) may indicate a middle-aged PWN. Such a PWN could exhibit a TeV flux comparable to its X-ray flux (e.g., J. Park et al. 2023), which is an order of magnitude lower than the measured gamma-ray flux of the SNR shell (peaking at ∼100 GeV). IC emission from the electrons emitting synchrotron photons at ∼10 keV would appear at TeV energies, as observed in other middle-aged PWNe. ...
We present a detailed X-ray investigation of a region (S1) exhibiting nonthermal X-ray emission within the supernova remnant (SNR) CTB 37B hosting the magnetar CXOU J171405.7−381031. Previous analyses modeled this emission with a power law (PL), inferring various values for the photon index (Γ) and absorbing column density ( N H ). Based on these, S1 was suggested to be an SNR shell, a background pulsar wind nebula, or an interaction region between the SNR and a molecular cloud. Our analysis of a larger data set favors a steepening (broken or curved PL) spectrum over a straight PL, with the best-fit broken power-law (BPL) parameters of Γ = 1.23 ± 0.23 and 2.24 ± 0.16 below and above a break at 5.57 ± 0.52 keV, respectively. However, a simple PL or srcut model cannot be definitively ruled out. For the BPL model, the inferred N H = (4.08 ± 0.72) × 10 ²² cm ⁻² towards S1 is consistent with that of the SNR, suggesting a physical association. The BPL-inferred spectral break ΔΓ ≈ 1 and hard Γ can be naturally explained by a nonthermal bremsstrahlung (NTB) model. We present an evolutionary NTB model that reproduces the observed spectrum, which indicates the presence of subrelativistic electrons within S1. However, alternate explanations for S1, an unrelated PWN or the SNR shock with unusually efficient acceleration, cannot be ruled out. We discuss these explanations and their implications for gamma-ray emission from CTB 37B and describe future observations that could settle the origin of S1.
... The radio band data are from Aliu et al. (2013), the X-ray band data from Martín et al. (2016), the TeV γ-ray band data from Aliu et al. (2013). Roberts et al. (1999), the X-ray band from Park et al. (2023), the GeV band from Acero et al. (2013), the TeV γ-ray band from Aharonian et al. (2006). Murphy et al. (2007), the X-ray band from Fujinaga et al. (2013), the GeV γ-ray band from Guo et al. (2017), the TeV γ-ray band from Aharonian et al. (2008). ...
In this paper, we analyze the spectral energy distributions (SEDs) of 17 powerful (with a spin-down luminosity greater than erg/s) young (with an age less than 15000 yrs) Pulsar Wind Nebulae (PWNe) using a simple time-independent one-zone emission model. Our aim is to investigate correlations between model parameters and the ages of the corresponding PWNe, thereby revealing the evolution of high-energy electron distributions within PWNe. Our findings are as follows: (1) The electron distributions in PWNe can be characterized by a double power-law with a superexponential cutoff; (2) As PWNe evolve, the high-energy end of the electron distribution spectrum becomes harder with the index decreasing from approximately 3.5 to 2.5, while the low-energy end spectrum index remains constant near 1.5; (3) There is no apparent correlation between the break energy or cutoff energy and the age of PWNe. (4) The average magnetic field within PWNe decreases with age, leading to a positive correlation between the energy loss timescale of electrons at the break energy or the high-energy cutoff, and the age of the PWN.
(5) The total electron energy within PWNe remains constant near erg, while the total magnetic energy decreases with age.
... However, the injection rates and energetics of electrons remain unclear. These quantities depend on the flow properties and energy-loss mechanisms within PWNe (e.g., Reynolds 2016), which can be investigated by modeling spatially varying properties and broadband SEDs of PWNe (e.g., Park et al. 2023a) across different evolutionary stages. Of particular significance is investigating the most energetic electrons (>100 TeV), which is most effectively accomplished by analyzing their synchrotron X-ray emission, while the IC emission in TeV energies is suppressed by the Klein-Nishina effect. ...
... For the NuSTAR data, we use the nuskybgd simulations (Wik et al. 2014). More detailed explanations of these background estimation processes can be found in Park et al. (2023a). ...
... We extracted spectra from annular regions of R = 30″-75″ and 75″-150″, excluding contaminating sources within the regions. For background estimation, we followed the same procedure employed in the Chandra analysis (Section 2.4.3) using the quiescence particle background data generated by the evqpb of SAS instead of the blank-sky data used for Chandra (see Park et al. 2023a, for more detail). We then fit the spectra with the PL+logpar model, where the logpar model accounts for the contamination from the pulsar. ...
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 displays significant curvature, peaking at ≈60 keV. Comparing the phase-averaged and on-pulse spectra of the pulsar, we found that the pulsar's off-pulse emission exhibits a spectral shape that is very similar to its on-pulse emission. This characterization of the off-pulse emission enabled us to measure the >10 keV spectrum of the faint and extended PWN using NuSTAR's off-pulse data. We measured both the X-ray spectrum and the radial profiles of the PWN’s brightness and photon index, and we combined these X-ray measurements with published TeV results. We then employed a multizone emission scenario to model the broadband data. The results of the modeling suggest that the magnetic field within the PWN is relatively low (≈7 μ G) and that electrons are accelerated to energies ≳400 TeV within this PWN. The electrons responsible for the TeV emission outside the X-ray PWN may propagate to ∼30 pc from the pulsar in ∼10 kyr.
... In direct CR observations, electrons have been robustly detected up to 5 TeV and possibly 20 TeV [14][15][16][17][18][19]. However, we have indirect indications that electrons are accelerated to much higher energies, based on observations of the emission they produce due to synchrotron losses and inverse-Compton scattering [66][67][68][69][70][71][72][73]. For example, luminous sources like the Crab accelerate electrons up to at least 1 PeV [66] and less luminous (but more common) sources like Geminga accelerate electrons up to at least 100 TeV [67]. ...
Detecting the end of the cosmic-ray (CR) electron spectrum would provide important new insights. While we know that Milky Way sources can accelerate electrons up to at least 1~PeV, the observed CR electron spectrum at Earth extends only up to 5~TeV (possibly 20~TeV), a large discrepancy. The question of the end of the CR electron spectrum has received relatively little attention, despite its importance. We take a comprehensive approach, showing that there are multiple steps at which the observed CR electron spectrum could be cut off. At the highest energies, the accelerators may not have sufficient luminosity, or the sources may not allow sufficient escape, or propagation to Earth may not be sufficiently effective, or present detectors may not have sufficient sensitivity. For each step, we calculate a rough range of possibilities. Although all of the inputs are uncertain, a clear vista of exciting opportunities emerges. We outline strategies for progress based on CR electron observations and auxiliary multi-messenger observations. In addition to advancing our understanding of CRs in the Milky Way, progress will also sharpen sensitivity to dark matter annihilation or decay.
... Combined with modeling of the multiwavelength (MW) spectral energy distribution (SED) of the PWNe over 20 decades of energy range, it allows the deduction of the key physical parameters that define the systems, such as the maximum particle energy and magnetic field. Our NuSTAR observation and MW SED modeling have functioned as powerful probes of PWNe as energetic leptonic cosmic-ray accelerators in our galaxy (e.g., Burgess et al. 2022;Park et al. 2023aPark et al. , 2023b. ...
... Ohira et al. (2018) proposed using a Monte Carlo simulation that particles may be accelerated to 1 PeV during the compression of a PWN by the collision with the reverse shock of its host SNR. Some of the above properties are in contrast to those of other TeV PWNe in our NuSTAR observational campaign, such as G313.54+0.23 ("K3" or "Kookaburra"; Park et al. 2023b) and G313.3+0.1 ("Rabbit"; Park et al. 2023a). These southern sources are invisible to HAWC and LHAASO, the telescopes that operate in the highest-energy regime (> 100 TeV). ...
... These features include a compact hard X-ray inner nebula undergoing SC burnoff, a large diffuse outer nebula in lower energy, and the absence of a GeV nebula. Opposite patterns are observed in two of our target PWNe, K3 (Park et al. 2023b) and Rabbit (Park et al. 2023a). These PWNe exhibit extended hard X-ray nebulae without a sign of SC burnoff, energy-insensitive morphologies, and bright GeV nebulae. ...
We studied the PeVatron nature of the pulsar wind nebula (PWN) G75.2+0.1 (“Dragonfly”) as part of our NuSTAR observational campaign of energetic PWNe. The Dragonfly is spatially coincident with LHAASO J2018+3651, whose maximum photon energy is 0.27 PeV. We detected a compact (radius 1 ′ ) inner nebula of the Dragonfly without a spectral break in 3–20 keV using NuSTAR. A joint analysis of the inner nebula with archival Chandra and XMM-Newton (XMM) observations yields a power-law spectrum with Γ = 1.49 ± 0.03. Synchrotron burnoff is observed from the shrinkage of the NuSTAR nebula at higher energies, from which we infer the magnetic field in the inner nebula of 24 μ G at 3.5 kpc. Our analysis of archival XMM data and 13 yr of Fermi-LAT data confirms the detection of an extended ( ∼ 10 ′ ) outer nebula in 2–6 keV (Γ = 1.82 ± 0.03) and the nondetection of a GeV nebula, respectively. Using the VLA, XMM, and HAWC data, we modeled a multiwavelength spectral energy distribution of the Dragonfly as a leptonic PeVatron. The maximum injected particle energy of 1.4 PeV from our model suggests that the Dragonfly is likely a PeVatron. Our model prediction of the low magnetic field (2.7 μ G) in the outer nebula and recent interaction with the host supernova remnant’s reverse shock (4 kyr ago) align with common features of PeVatron PWNe. The origin of its highly asymmetric morphology, pulsar proper motion, PWN–supernova remnant (SNR) interaction, and source distance will require further investigations in the future, including a multiwavelength study using radio, X-ray, and gamma-ray observations.
... Combined with modeling the multi-wavelength (MW) spectral energy distribution (SED) of the PWNe over 20 decades of energy range, it allows deducing the key physical parameters that define the systems, such as the maximum particle energy and magnetic field. Our NuSTAR observation and MW SED modeling have functioned as powerful probes of PWNe as energetic leptonic cosmic ray accelerators in our Galaxy (e.g., Burgess et al. (2022), Park et al. (2023a), and Park et al. (2023b)). ...
... Ohira et al. (2018) proposed using a Monte Carlo simulation that particles may be accelerated to 1 PeV during the compression of a PWN by the collision with the reverse shock of its host SNR. Some of the above properties are in contrast to those of other TeV PWNe in our NuSTAR observational campaign, such as G313.54+0.23 ("K3" or "Kookaburra", Park et al. (2023b)) and G313.3+0.1 ("Rabbit", Park et al. (2023a)). These southern sources are invisible to HAWC and LHAASO, the telescopes that operate in the highest energy regime (> 100 TeV). ...
... These features include a compact hard X-ray inner nebula undergoing synchrotron burnoff, a large diffuse outer nebula in lower energy, and an absence of a GeV nebula. Opposite patterns are observed in two of our target PWNe, the K3 (Park et al. (2023b)) and Rabbit (Park et al. (2023a)). These PWNe exhibit extended hard X-ray nebulae without a sign of synchrotron burnoff, energy-insensitive morphologies, and bright GeV nebulae. ...
We studied the PeVatron nature of the pulsar wind nebula G75.2+0.1 ("Dragonfly") as part of our NuSTAR observational campaign of energetic PWNe. The Dragonfly is spatially coincident with LHAASO J2018+3651 whose maximum photon energy is 0.27 PeV. We detected a compact (radius 1') inner nebula of the Dragonfly without a spectral break in 3 20 keV using NuSTAR. A joint analysis of the inner nebula with the archival Chandra and XMM-Newton observations yields a power-law spectrum with . Synchrotron burnoff is observed from the shrinkage of the NuSTAR nebula at higher energies, from which we infer the magnetic field in the inner nebula of 24 G at 3.5 kpc. Our analysis of archival XMM data and 13 years of Fermi-LAT data confirms the detection of an extended (~10') outer nebula in 2 6 keV () and non-detection of a GeV nebula, respectively. Using the VLA, XMM, and HAWC data, we modeled a multi-wavelength spectral energy distribution of the Dragonfly as a leptonic PeVatron. The maximum injected particle energy of 1.4 PeV from our model suggests that the Dragonfly is likely a PeVatron. Our model prediction of the low magnetic field (2.7 G) in the outer nebula and recent interaction with the host supernova remnant's reverse shock (4 kyrs ago) align with common features of PeVatron PWNe. The origin of its highly asymmetric morphology, pulsar proper motion, PWN-SNR interaction, and source distance will require further investigations in the future including a multi-wavelength study using radio, X-ray, and gamma-ray observations.
To date, over 4000 pulsars have been detected. In this study, we identify 231 X-ray counterparts of Australia Telescope National Facility (ATNF) pulsars by performing a spatial cross match across the Chandra, XMM-Newton observational catalogs. This data set represents the largest sample of X-ray counterparts ever compiled, including 98 normal pulsars (NPs) and 133 millisecond pulsars (MSPs). Based on this significantly expanded sample, we re-establish the correlation between X-ray luminosity and spin-down power, given by L X ∝ E ̇ 0.85 ± 0.05 across the whole X-ray band. The strong correlation is also observed in hard X-ray band, while in soft X-ray band there is no significant correlation. Furthermore, L X shows a strong correlation with spin period and characteristic age for NPs. For the first time, we observe a strongly positive correlation between L X and the light cylinder magnetic field ( B lc ) for MSPs, with both NPs and MSPs following the relationship L X ∝ B lc 1.14 , consistent with the outer-gap model of pulsars that explains the mechanism of X-ray emission. Additionally, we investigate potential X-ray counterparts for Galactic Plane Pulsar Snapshot pulsars, finding a lower likelihood of detection compared to ATNF pulsars.
To date, over 4,000 pulsars have been detected. In this study, we identify 231 X-ray counterparts of {\it ATNF} pulsars by performing a spatial cross-match across the {\it Chandra}, {\it XMM-Newton} observational catalogs. This dataset represents the largest sample of X-ray counterparts ever compiled, including 98 normal pulsars (NPs) and 133 millisecond pulsars (MSPs). Based on this significantly expanded sample, we re-establish the correlation between X-ray luminosity and spin-down power, given by across the whole X-ray band. The strong correlation is also observed in hard X-ray band, while in soft X-ray band there is no significant correlation. Furthermore, shows a strong correlation with spin period and characteristic age for NPs. For the first time, we observe a strongly positive correlation between and the light cylinder magnetic field () for MSPs, with both NPs and MSPs following the relationship , consistent with the outer-gap model of pulsars that explains the mechanism of X-ray emission. Additionally, we investigate potential X-ray counterparts for GPPS pulsars, finding a lower likelihood of detection compared to {\it ATNF} pulsars.
Detecting the end of the cosmic-ray (CR) electron spectrum would provide important new insights. While we know that Milky Way sources can accelerate electrons up to at least ∼1 PeV, the observed CR electron spectrum at Earth extends only up to 5 TeV (possibly 20 TeV), a large discrepancy. The question of the end of the CR electron spectrum has received relatively little attention, despite its importance. We take a comprehensive approach, showing that there are multiple steps at which the observed CR electron spectrum could be cut off. At the highest energies, the accelerators may not have sufficient luminosity, or the sources may not allow sufficient escape, or propagation to Earth may not be sufficiently effective, or present detectors may not have sufficient sensitivity. For each step, we calculate a rough range of possibilities. Although all of the inputs are uncertain, a clear vista of exciting opportunities emerges. We outline strategies for progress based on CR electron observations and auxiliary multimessenger observations. In addition to advancing our understanding of CRs in the Milky Way, progress will also sharpen sensitivity to dark matter annihilation or decay.
