We report the discovery of 70.5 ms pulsations from the X-ray source AX J1838.0-0655 using the Rossi X-ray Timing Explorer (RXTE). PSR J1838-0655 is a rotation-powered pulsar with spin-down luminosity Edot = 5.5e36 ergs/s, characteristic age tau = P/2Pdot = 23 kyr, and surface dipole magnetic field strength Bs = 1.9e12 G. It coincides with an unresolved INTEGRAL source and the extended TeV source HESS J1837-069. At an assumed distance of 6.6 kpc by association with an adjacent massive star cluster, the efficiency of PSR J1838-0655 converting spin-down luminosity to radiation is 0.8% for the 2-10 keV ASCA flux, 9% for the 20-300 keV INTEGRAL flux and ~3% for the >200 GeV emission of HESS J1837-069, making it a plausible power source for the latter. A Chandra X-ray observation resolves AX J1838.0-0655 into a bright point source surrounded by a ~2' diameter, centrally peaked nebula. The spectra of the pulsar and nebula are each well fitted by power laws, with photon indices Gamma = 0.5(0.3-0.7) and Gamma = 1.6(1.1-2.0), respectively. The 2-10 keV X-ray luminosities of the pulsar and nebula are L(PSR) = 4.6e34 d(6.6)^2 ergs/s and L(PWN) = 5.2e33 d(6.6)^2 ergs/s. A second X-ray source adjacent to the TeV emission, AX J1837.3-0652, is resolved into an apparent pulsar/PWN; it may also contribute to HESS J1837-069. The star cluster RSGC1 may have given birth to one or both pulsars, while fueling TeV emission from the extended PWN with target photons for inverse Compton scattering.
Motivated by recent detections of pulsar wind nebulae in very-high-energy (VHE) gamma rays, a systematic search for VHE gamma-ray sources associated with energetic pulsars was performed, using data obtained with the H.E.S.S. (High Energy Stereoscopic System) instrument. The search for VHE gamma-ray sources near the pulsar PSR J1718-3825 revealed the new VHE gamma-ray source HESS J1718-385. We report on the results from the HESS data analysis of this source and on possible associations with the pulsar and at other wavelengths. We investigate the energy spectrum of HESS J1718-385 that shows a cl…
Context: We investigate the possible theoretical properties of the putative pulsar associated with the pulsar wind nebula IGR J18135-1751/HESS J1813-178 based upon recent gamma-ray observations and archival multi-wavelength observations. Aims: We show that when using the standard equations for magnetic dipole radiation with recent soft gamma-ray observations leads to deriving an extreme set of parameters (magnetic field, period and spin down rate) for the putative pulsar. Alternative scenarios that generate more typical parameter values are explored. Methods: The properties of the putative pul…
We report on a possible association of the recently discovered very high-energy $γ$-ray source HESS J1825--137 with the pulsar wind nebula (commonly referred to as G 18.0--0.7) of the $2.1\times 10^{4}$ year old Vela-like pulsar PSR B1823--13. HESS J1825--137 was detected with a significance of 8.1 $σ$ in the Galactic Plane survey conducted with the H.E.S.S. instrument in 2004. The centroid position of HESS J1825--137 is offset by 11\arcmin south of the pulsar position. \emph{XMM-Newton} observations have revealed X-ray synchrotron emission of an asymmetric pulsar wind nebula extending to the …
We present the discovery of the Vela-like radio pulsar J1856+0245 in the Arecibo PALFA survey. PSR J1856+0245 has a spin period of 81ms, a characteristic age of 21kyr, and a spin-down luminosity Edot = 4.6 x 10^36 ergs/s. It is positionally coincident with the TeV gamma-ray source HESS J1857+026, which has no other known counterparts. Young, energetic pulsars create wind nebulae, and more than a dozen pulsar wind nebulae have been associated with very-high-energy (100GeV-100TeV) gamma-ray sources discovered with the HESS telescope. The gamma-ray emission seen from HESS J1857+026 is potentially…
The high resolution capabilities of the High Energy Stereoscopic System (HESS) introduced a new era in Gamma-Ray Astronomy, and opens a new window on pulsar wind nebula (PWN) research. A rotationally induced jet (associated with PSR B1509-58) is resolved for the first time in gamma-rays, allowing us to trace the particle transport directly, without having the complicating effect of spatially varying field distributions on the synchrotron emissivity. For PWN older or more extended than Crab (i.e. those with lower field strengths), HESS also reveals the properties of electrons contributing to th…
HESS J1825-137 was detected with a significance of 8.1 $σ$ in the Galactic Plane survey conducted with the H.E.S.S. instrument in 2004. Both HESS J1825-137 and the X-ray pulsar wind nebula G18.0--0.7 (associated with the Vela-like pulsar PSR B1823-13) are offset south of the pulsar, which may be the result of the SNR expanding into an inhomogeneous medium. The TeV size ($\sim 35$ pc, for a distance of 4 kpc) is $\sim 6$ times larger than the X-ray size, which may be the result of propagation effects as a result of the longer lifetime of TeV emitting electrons, compared to the relatively short …
Detailed morphological and spatially resolved spectral studies reveal the very high-energy (VHE) gamma-ray aspects of this object with unprecedented precision. We confirm previous results obtained in a survey of the Galactic Plane in 2004. The gamma-ray emission extends asymmetrically to the south and south-west of the energetic pulsar PSR J1826-1334, that is thought to power the pulsar wind nebula. The differential gamma-ray spectrum of the whole emission region is measured over more than two orders of magnitude, from 270 GeV to 35 TeV, and shows indications for a deviation from a pure power …
H.E.S.S. is currently the most sensitive instrument in the very-high-energy gamma-ray domain and has revealed many new sources along the Galactic Plane, a significant fraction of which seems to be associated with energetic pulsars. HESS J1825-137 and Vela X are considered to be the prototypes of such sources in which the large VHE nebula results from the whole history of the pulsar wind and the supernova remnant host, both evolving in a complex interstellar medium. These nebulae are seen to be offset from the pulsar position and, for HESS J1825-137, a spectral steepening at increasing distance…
We detected X-ray emission from the 50-kyr-old pulsar J1809-1917 and resolved its pulsar wind nebula (PWN) with Chandra. The pulsar spectrum fits PL+BB model with the photon index of 1.2 and the BB temperature of 2 MK for n_{H}=0.7\times 10^{22} cm^{-2}. The luminosities are(4\pm 1)\times 10^{31} ergs s^{-1} for the PL component (in the 0.5-8 keV band) and ~1\times 10^{32} ergs s^{-1} for the BB component (bolometric) at a plausible distance of 3.5 kpc. The bright inner PWN component of a 3''\times12'' size is elongated in the north-south direction, with the pulsar close to its south end. This…
We present a Chandra X-ray observation of G12.82-0.02, a shell-like radio supernova remnant coincident with the TeV gamma-ray source HESS J1813-178. We resolve the X-ray emission from the co-located ASCA source into a compact object surrounded by structured diffuse emission that fills the interior of the radio shell. The morphology of the diffuse emission strongly resembles that of a pulsar wind nebula. The spectrum of the compact source is well-characterized by a power-law with index approx. 1.3, typical of young and energetic rotation-powered pulsars. For a distance of 4.5 kpc, consistent wi…
Compact astrophysical objects produce some of the highest energy light in the universe. The challenge is to determine what mechanism produces these photons.
We observed the young energetic pulsar J1617-5055 with the Chandra ACIS detector for 60 ks. In addition to the pulsar, the X-ray images show a faint pulsar-wind nebula (PWN) seen up to ~1' from the pulsar. Deconvolution and reconstruction of the image reveal a brighter compact PWN component of ~1'' size, possibly with a jet-torus morphology. The PWN spectrum fits an absorbed power-law (PL) model with the photon index Gamma=1.5. The total PWN luminosity in the 0.5-8 keV band, L_{pwn}=3.2\times10^{33} ergs s^{-1} for d=6.5 kpc, is a fraction of 2\times 10^{-4} of the pulsar's spin-down power and…
We present a Chandra X-ray observation of G12.82-0.02, a shell-like radio supernova remnant coincident with the TeV gamma-ray source HESS J1813-178. We resolve the X-ray emission from the co-located ASCA source into a point source surrounded by structured diffuse emission that fills the interior of the radio shell. The morphology of the diffuse emission strongly resembles that of a pulsar wind nebula. The spectrum of the compact source is well-characterized by a power-law with index Gamma approx 1.3, typical of young and energetic rotation-powered pulsars. For a distance of 4.5 kpc, consistent…
HESS J1616-508 is one of the brightest emitters in the TeV sky. Recent observations with the IBIS/ISGRI telescope on board the INTEGRAL spacecraft have revealed that a young, nearby and energetic pulsar, PSR J1617-5055, is a powerful emitter of soft gamma-rays in the 20-100 keV domain. In this paper we present an analysis of all available data from the INTEGRAL, Swift, BeppoSAX and XMM-Newton telescopes with a view to assessing the most likely counterpart to the HESS source. We find that the energy source that fuels the X/gamma-ray emissions is derived from the pulsar, both on the basis of the…
We present the ASCA and Suzaku studies of the TeV source HESS J1837--069, which has not been identified in other wave-lengths. We confirm the presence of two X-ray sources in the Suzaku XIS image, AX J1838.0--0655 and AX J1837.3--0652, near both ends of the elongated TeV emission region. The XIS spectra of the two sources are reproduced by an absorbed power-law model, whose parameters are all consistent with those determined by the ASCA data. Recently, 70.5 ms X-ray pulsation has been detected with RXTE in the sky region including HESS J1837--069 (2008, ApJ, 681, 515). Using the ASCA GIS data …
The observed population of young radio pulsars has grown substantially in recent years due to a combination of large-scale surveys and deep targeted searches. Many of the pulsars are associated with supernova remnants and/or unidentified gamma-ray sources. This review summarises the state of play and looks ahead to likely advances in the near future.
Combined X-ray synchrotron and inverse-Compton gamma-ray observations of pulsar wind nebulae (PWN) may help to elucidate the processes of acceleration and energy loss in these systems. In particular, such observations provide constraints on the particle injection history and the magnetic field strength in these objects. The newly discovered TeV gamma-ray source HESS J1718-385 has been proposed as the likely PWN of the high spin-down luminosity pulsar PSR J1718-3825. The absence of previous sensitive X-ray measurements of this pulsar, and the unusual energy spectrum of the TeV source, motivated…
We observed the brightest part of HESS J1825-137 with the Suzaku XIS, and found diffuse X-rays extending at least up to 15' (~ 17 pc) from the pulsar PSR J1826-1334. The spectra have no emission line, and are fitted with an absorbed power-law model. The X-rays, therefore, are likely due to synchrotron emission from a pulsar wind nebula. The photon index near at the pulsar (r<1.5') is 1.7 while those in r=1.5-16 are nearly constant at Gamma=2.0. The spectral energy distribution of the Suzaku and H.E.S.S. results are naturally explained by a combined process; synchrotron X-rays and gamma-rays by…
Young radio pulsars shed vast amounts of rotational energy, sometimes as high as 100,000 times the total energy loss rate from the sun. The wide range of phenomena resulting from this energy loss include: glitches, timing noise, jets, bow shocks, bullets and plerions and are be reviewed from an observational perspective. Past and proposed surveys for young radio pulsars are summarised along with pulsar birth velocities and associations with supernova remnants. There are now 4 radio pulsars with measured braking indices. The resulting constraints on the evolution of young radio pulsars are disc…
In this review paper on pulsar wind nebulae (PWN) we discuss the properties of such nebulae within the context of containment against cross-field diffusion (versus normal advection), the effect of reverse shocks on the evolution of offset ``Vela-like'' PWN, constraints on maximum particle energetics, magnetic field strength estimates based on spectral and spatial properties, and the implication of such field estimates on the composition of the wind. A significant part of the discussion is based on the High Energy Stereoscopic System ({\it H.E.S.S.} or {\it HESS}) detection of the two evolved p…
At least one massive binary system containing an energetic pulsar, PSR B1259-63/SS2883, has been recently detected in the TeV gamma-rays by the HESS telescopes. These gamma-rays are likely produced by particles accelerated in the vicinity of the pulsar and/or at the pulsar wind shock, in comptonization of soft radiation from the massive star. However, the process of gamma-ray production in such systems can be quite complicated due to the anisotropy of the radiation field, complex structure of the pulsar wind termination shock and possible absorption of produced gamma-rays which might initiate …
Many of the recently discovered TeV gamma-ray sources are associated with pulsar wind nebulae (PWNe). In fact, they represent the most populous class of Galactic sources at TeV energies. In addition, HESS has also discovered, in a survey of the Galactic plane, a population of TeV gamma-ray sources that are still without definitive counterparts at longer wavelengths. For a number of these sources, a pulsar is an evident association, which is often located within an extended region of the TeV gamma-ray emission. These particular HESS sources are promising candidates for yet not resolved pulsar w…
We present the discovery of PSR J1410-6132, a 50-ms pulsar found during a high-frequency survey of the Galactic plane, using a 7-beam 6.3-GHz receiver on the 64-m Parkes radio telescope. The pulsar lies within the error box of the unidentified EGRET source 3EG J1410-6147, has a characteristic age of 26 kyr and a spin-down energy of 10^37 erg s^-1. It has a very high dispersion measure of 960+/-10 cm^-3 pc and the largest rotation measure of any pulsar, RM=+2400 +/- 30 rad m^-2. The pulsar is very scatter-broadened at frequencies of 1.4 GHz and below, making pulsed emission almost impossible to…
Some massive binaries should contain energetic pulsars which inject relativistic leptons from their inner magnetospheres and/or pulsar wind regions. If the binary system is compact enough, then these leptons can initiate inverse Compton (IC) $e^\pm$ pair cascades in the anisotropic radiation field of a massive star. $γ$-rays can be produced in the IC cascade during its development in a pulsar wind region and above a shock in a massive star wind region where the propagation of leptons is determined by the structure of a magnetic field around the massive star. For a binary system with specific p…
The Crab Nebula demonstrates that neutron stars can interact with their environments in spectacular fashion, their relativistic winds generating nebulae observable across the electromagnetic spectrum. At many previous conferences, astronomers have discussed, debated and puzzled over the complicated structures seen in the Crab, but have been limited to treating most other pulsar wind nebulae (PWNe) as simple calorimeters for a pulsar's spin-down energy. However, with the wealth of high-quality data which have now become available, this situation has changed dramatically. I here review some of t…
We present recent X-ray and radio observations of pulsar wind nebulae discovered in EGRET error boxes. Two XMM-Newton observations show the X-ray extent of the rapidly moving PWN associated with the variable gamma-ray source 3EG J1809-2328, and a trail coming from the new millisecond pulsar PSR J1614-2230 at high Galactic z. We also briefly discuss three PWN that are HESS TeV sources including a new HESS source we argue is associated with the Eel nebula in 3EG J1826-1302.
In this paper we compare the characteristics of pulsars with a high spin-down energy loss rate (Edot) against those with a low Edot. We show that the differences in the total intensity pulse morphology between the two classes are in general rather subtle. A much more significant difference is the fractional polarization which is very high for high Edot pulsars and low for low Edot pulsars. The Edot at the transition is very similar to the death line predicted for curvature radiation. This suggests a possible link between high energy and radio emission in pulsars and could imply that gamma-ray …
We present high-resolution X-ray images taken with the Chandra X-ray Observatory of the field that contains the unidentified TeV gamma-ray source HESS J1804-216. A total of eleven discrete sources were detected with a posteriori significance of > 5 sigma over the entire field of view. Among them, only one, designated as CXOU J180351.4-213707, is significantly extended. The source is about 40" away from the radio pulsar PSR J1803-2137, which was the target of the Chandra observation but was not detected in X-rays. A natural question is whether the two sources are physically related. While it is…
We present a new survey for pulsars in the error boxes of the low-latitude EGRET sources 3EG J1027-5817, 3EG J1800-2338 and 3EG J1810-1032. Although all of these sources have been covered by previous pulsar surveys, the recent discovery of the young, energetic pulsar PSR J1410-6132 at 6.7 GHz has shown that pulsars of this type can be hidden from low frequency surveys. Using an observing frequency of 3.1 GHz we discovered a 91-ms pulsar, PSR J1028-5819, which observations made at the Parkes telescope and the Australia Telescope Compact Array have shown to be young and energetic. We believe thi…
We investigate the conditions required for the production of electron-positron pairs above a pulsar polar cap (PC) and the influence of pair production on the energetics of the primary particle acceleration. Assuming space-charge limited flow acceleration including the inertial frame-dragging effect, we allow both one-photon and two-photon pair production by either curvature radiation (CR) photons or photons resulting from inverse-Compton scattering of thermal photons from the PC by primary electrons. We find that, while only the younger pulsars can produce pairs through CR, nearly all known r…
We report the discovery with the Parkes radio telescope of a pulsar associated with the ~ 1700 yr-old oxygen-rich composite supernova remnant G292.0+1.8. PSR J1124-5916 has period 135 ms and period derivative 7.4e-13, implying characteristic age 2900 yr, spin-down luminosity 1.2e37 erg/s, and surface magnetic field strength 1.0e13 G. Association between the pulsar and the synchrotron nebula previously identified with Chandra within this supernova remnant is confirmed by the subsequent detection of X-ray pulsations by Hughes et al. The pulsar's flux density at 1400 MHz is very small, S ~ 0.08 m…
We report the discovery and follow-up timing observations of the 63 ms radio pulsar, PSR J1105-6107. The pulsar is young, having a characteristic age of only 63 kyr and, from its dispersion measure, is estimated to be at a distance of ~7 kpc from the Sun. We consider its possible association with the nearby supernova remnant G290.1-0.8 (MSH 11-61A); an association requires that the pulsar's proper motion be ~22 mas/yr (corresponding to ~650 km/s for a distance of 7 kpc) directed away from the remnant center, assuming that the characteristic age is the true age. The pulsar's spin-down luminosit…
We present new results on the recently discovered 69 ms X-ray pulsar AXS J161730-505505, the sixth youngest sample of all known pulsars. We have undertaken a comprehensive X-ray observing campaign of AXS J161730-505505 with the ASCA, SAX, and XTE observatories and follow its long term spin-down history between 1989 and 1999, using these, archival GINGA and ASCA data sets, and the radio ephemeris. The spin-down is not simply described by a linear function as originally thought, but instead we find evidence of a giant glitch (|Delta P/P| > 10E-6) between 1993 August and 1997 September, perhaps t…
Observations with H.E.S.S. revealed a new source of very high-energy (VHE) gamma-rays above 100 GeV - HESS J1825-137 - extending mainly to the south of the energetic pulsar PSR B1823-13. A detailed spectral and morphological analysis of HESS J1825-137 reveals for the first time in VHE gamma-ray astronomy a steepening of the energy spectrum with increasing distance from the pulsar. This behaviour can be understood by invoking radiative cooling of the IC-Compton gamma-ray emitting electrons during their propagation. In this scenario the vastly different sizes between the VHE gamma-ray emitting r…
The source HESS J1809-193 was discovered in 2006 in data of the Galactic Plane survey, followed by several re-observations. It shows a hard gamma-ray spectrum and the emission is clearly extended. Its vicinity to PSR J1809-1917, a high spin-down luminosity pulsar powerful enough to drive the observed gamma-ray emission, makes it a plausible candidate for a TeV Pulsar Wind Nebula (PWN). On the other hand, in this region of the sky a number of faint, radio-emitting supernova remnants can be found, making a firm conclusion on the source type difficult. Here we present a detailed morphological stu…
We present X-ray observations of the as of yet unidentified very high-energy (VHE) gamma-ray source HESSJ1640-465 with the aim of establishing a counterpart of this source in the keV energy range, and identifying the mechanism responsible for the VHE emission. The 21.8 ksec XMM-Newton observation of HESSJ1640-465 in September 2005 represents a significant improvement in sensitivity and angular resolution over previous ASCA studies in this region. These new data show a hard-spectrum X-ray emitting object at the centroid of the H.E.S.S. source, within the shell of the radio Supernova Remnant (SN…
We present the discovery of two very-high-energy gamma-ray sources in an ongoing systematic search for emission above 100 GeV from pulsar wind nebulae in survey data from the H.E.S.S. telescope array. Imaging Atmospheric Cherenkov Telescopes are ideal tools for searching for extended emission from pulsar wind nebulae in the very-high-energy regime. H.E.S.S., with its large field of view of 5 degrees and high sensitivity, gives new prospects for the search for these objects. An ongoing systematic search for very-high-energy emission from energetic pulsars over the region of the Galactic plane b…
We report on a sensitive survey for radio pulsar wind nebulae (PWN) towards 27 energetic and/or high velocity pulsars. Observations were carried out at 1.4 GHz using the Very Large Array and the Australia Telescope Compact Array, and utilised pulsar-gating to search for off-pulse emission. These observing parameters resulted in a considerably more sensitive search than previous surveys, and could detect PWN over a much wider range of spatial scales (and hence ambient densities and pulsar velocities). However, no emission clearly corresponding to a PWN was discovered. Based on these non-detecti…
We present an X-ray study of the field containing the extended TeV source HESS J1834-087 using data obtained with the XMM-Newton telescope. Previously, the coincidence of this source with both the shell-type supernova remnant (SNR) W41 and a giant molecular cloud (GMC) was interpreted as favoring pi^0-decay gamma-rays from interaction of the old SNR with the GMC. Alternatively, the TeV emission has been attributed to inverse Compton scattering from leptons deposited by PSR J1833-0827, a pulsar assumed to have been born in W41 but now located 24' from the center of the SNR (and the TeV source).…
We present spatially resolved spectroscopy of the supernova remnant (SNR) G292.0+1.8 with the Chandra X-ray observatory. This SNR contains the 135 ms pulsar, J1124-5916. We apply non-equilibrium ionization (NEI) models to the data. By comparing the derived abundances with those predicted from nucleosynthesis models, we estimate a progenitor mass of 30-40 solar masses. We also derive the intrinsic parameters of the supernova explosion such as its energy, the age of the SNR, the blast wave velocity, and the swept-up mass. In the Sedov interpretation, our estimated SNR age of 2,600 years is close…
The field of the extended TeV source HESS J1804-216 was serendipitously observed with the Chandra ACIS detector. The data reveal several X-ray sources within the bright part of HESS J1804-216. The brightest of these objects, CXOU J180432.4-214009, which has been also detected with Swift and Suzaku, is consistent with being a point-like source, with the 0.3-7 keV flux of (1.7\pm0.2)\times10^{-13} ergs s^{-1} cm^{-2}. Its hard and strongly absorbed spectrum can be fitted by the absorbed power-law model with the best-fit photon index of 0.45 and hydrogen column density of 4\times10^{22} cm^{-2}, …
We present results of Compton Gamma-Ray Observatory EGRET observations of the unidentified high-energy gamma-ray sources 2EG J1049-5847 (GEV J1047-5840, 3EG J1048-5840) and 2EG J1103-6106 (3EG J1102-6103). These sources are spatially coincident with the young, energetic radio pulsars PSRs B1046-58 and J1105-6107, respectively. We find evidence for an association between PSR B1046-58 and 2EG J1049-5847. The gamma-ray pulse profile, obtained by folding time-tagged photons having energies above 400 MeV using contemporaneous radio ephemerides, has probability of arising by chance of 1.2E-4 accordi…
We present the discovery of non-thermal radio and X-ray emission positionally coincident with the TeV $γ$-ray source HESS J1813--178. We demonstrate that the non-thermal radio emission is due to a young shell-type supernova remnant (SNR) G12.8--0.0, and constrain its distance to be greater than 4 kpc. The X-ray emission is primarily non-thermal and is consistent with either an SNR shell or unidentified pulsar/pulsar wind nebula origin; pulsed emission is not detected in archival ASCA data. A simple synchrotron+inverse Compton model for the broadband emission assuming that all of the emission a…
The existence of hot, two-temperature accretion flows is essential to the recent discussions of the low luminosity, hard X-ray emission from accreting neutron stars and black holes in Galactic binaries and massive black holes in low luminosity galactic nuclei. In these flows, protons are essentially virialized and relativistic energies for non-thermal protons are likely. Observational confirmation of the energetic protons' presence could further support the two-temperature accretion flow models. We point out that synchrotron emission from nonthermal relativistic protons could provide an observ…
We report the detection of radio and X-ray pulsations at a period of 51.6 ms from the X-ray source RX/AX J2229.0+6114 in the error box of the EGRET source 3EG J2227+6122. An ephemeris derived from a single ASCA observation and multiple epochs at 1412 MHz from Jodrell Bank indicates steady spin-down with P-dot = 7.83 x 10^(-14) s/s. From the measured P and P-dot we derive spin-down power E-dot = 2.2 x 10^(37) erg/s, magnetic field B = 2.0 x 10^(12) G, and characteristic age P/2P-dot = 10,460 yr. An image from the Chandra X-ray Observatory reveals a point source surrounded by centrally peaked di…
Radio, X-ray, and HESS gamma-ray observations of the Galactic Center (GC) composite supernova remnant SNR G0.9+0.1 are used to constrain a time-dependent injection model of the downstream electron spectrum responsible for the total multiwavelength spectrum. The effect of spindown power evolution aswell as nebular field evolution is employed to reproduce the present-day multiwavelength spectrum. Assuming a nebular magnetic field decay model of typical HESS-type pulsar wind nebulae (PWN), ending with a present-day field strength of 6muG, we obtain an initial spindown power of ~ 10E+38 ergs/s if …
HESS J1745-303 is an extended, unidentified VHE (very high energy) gamma-ray source discovered using HESS in the Galactic Plane Survey. Since no obvious counterpart has previously been found in longer-wavelength data, the processes that power the VHE emission are not well understood. Combining the latest VHE data with recent XMM-Newton observations and a variety of source catalogs and lower-energy survey data, we attempt to match (from an energetic and positional standpoint) the various parts of the emission of HESS J1745-303 with possible candidates. Though no single counterpart is found to f…
Based on a Chandra ACIS observation, we report the detection of an extended X-ray feature close to the center of the remnant DA 530 with 5.3 sigma above the background within a circle of 20'' radius. This feature, characterized by a power-law with the photon index gamma=1.6+-0.8 and spatially coinciding with a nonthermal radiosource, most likely represents a pulsar wind nebula. We have further examined the spectrum of the diffuse X-ray emission from the remnant interior with a background-subtracted count rate of ~0.06 counts s^-1 in 0.3-3.5 keV. The spectrum of the emission can be described by…
We propose that there possibly exists a population of millisecond pulsars in the Galactic center region. Millisecond pulsars (MSPs) could emit GeV gamma-rays through synchrotron-curvature radiation as predicted by outer gap models. In the same time, the compact wind nebulae around millisecond pulsars can emit X-rays though synchrotron radiation and TeV photons through inverse Compton processes. Besides, millisecond pulsar winds provide good candidates for the electron-positrons sources in the Galactic center. Therefore, we suggest that the millisecond pulsar population could contribute to the …
A systematic X-ray survey of the most energetic rotation-powered pulsars known, based on spin-down energy loss rate, $\dot E$ = $Iω\dotω$, shows that all energetic pulsars with $\dot E > \dot E_{c} \approx 3.4 \times\ 10^{36}$ erg s$^{-1}$ are X-ray bright, manifest a distinct pulsar wind nebula (PWN), and are associated with a supernova event, either historically or via a thermal remnant, with over half residing in shell-like supernova remnants. Below $\dot E_c$, the 2-10 keV PWN flux ratio $F_{PWN}/F_{PSR}$ decreases by an order-of-magnitude. This threshold is predicted by the lower limit on…
We observed the unidentified TeV gamma-ray source HESS J1804-216 with the CANGAROO-III atmospheric Cerenkov telescopes from May to July in 2006. We detected very high energy gamma rays above 600 GeV at the 10 sigma level in an effective exposure of 76 hr. We obtained a differential flux of (5.0+/-1.5_{stat}+/-1.6_{sys})\times 10^{-12}(E/1 TeV)^{-α} cm^{-2}s^{-1}TeV^{-1} with a photon index αof 2.69 +/- 0.30_{stat} +/- 0.34_{sys}, which is consistent with that of the H.E.S.S. observation in 2004. We also confirm the extended morphology of the source. By combining our result with multi-wavelengt…
Amongst the sources seen in very high gamma-rays several are associated with Pulsar Wind Nebulae (``TeV plerions''). The study of hard X-ray/soft gamma-ray emission is providing an important insight into the energetic particle population present in these objects. The unpulsed emission from pulsar/pulsar wind nebula systems in the energy range accessible to the INTEGRAL satellite is mainly synchrotron emission from energetic and fast cooling electrons close to their acceleration site. Our analyses of public INTEGRAL data of known TeV plerions detected by ground based Cherenkov telescopes indica…
We propose that a nearby gamma-ray burst (GRB) or GRB-like (old, single and short-lived) pulsar/supernova remnant/microquasar about 10^{5-6} years ago may be responsible for the excesses of cosmic-ray positrons and electrons recently observed by the PAMELA, ATIC/PPB-BETS, Fermi and HESS experiments. We can reproduce the smooth Fermi/HESS spectra as well as the spiky ATIC/PPB-BETS spectra. The spectra have a sharp cutoff that is similar to the dark matter predictions, sometimes together with a line (not similar), since higher energy cosmic-rays cool faster where the cutoff/line energy marks the…
