We measured the proper motion of a $γ$-ray radio-quiet pulsar J0633+0632 using Chandra observations performed in 2009 and 2017. The measured proper motion is $53\pm15$~mas~yr$^{-1}$. We found that the proper motion direction does not follow the extension of the J0633+0632 pulsar wind nebula. The J0633+0632 pulsar wind nebula therefore can be a jet-like feature or a misaligned outflow. We also discuss a possible birth cite of the pulsar.
We describe the first X-ray observations of binary millisecond pulsars PSRs J0023+0923, J1810+1744, J2215+5135, and J2256-1024. All four are Fermi gamma-ray sources and three are 'black-widow' pulsars, with companions of mass < 0.1 solar masses. Data were taken using the Chandra X-Ray Observatory and covered a full binary orbit for each pulsar. Two pulsars, PSRs J2215+5135 and J2256-1024, show significant orbital variability and X-ray flux minima at the times of eclipses observed at radio wavelengths. This phenomenon is consistent with intrabinary shock emission characteristic of black-widow p…
We have analyzed archival XMM-Newton and Chandra observations of the gamma-ray radio-quiet pulsar J1826-1256 and its pulsar wind nebula. The pulsar spectrum can be described by a power-law model with a photon index $Γ\approx1$. We find that the nebular spectrum softens with increasing distance from the pulsar, implying synchrotron cooling. The empirical interstellar absorption-distance relation gives a distance of $\approx3.5$ kpc to J1826-1256. We also discuss the nebula geometry and association between the pulsar, the very high energy source HESS J1826-130, the supernova remnant candidate G1…
We present spectral and timing analyses of the X-ray emission from the pulsar wind nebula DA 495 and its central object, J1952.2+2925, suggested to be the pulsar, using archival Chandra and XMM-Newton data. J1952.2+2925 has a pure thermal spectrum which is equally well fitted either by the blackbody model with a temperature of $\approx 215$ eV and an emitting area radius of $\approx 0.6$ km or by magnetized neutron star atmosphere models with temperatures of 80-90 eV. In the latter case the thermal emission can come from the entire neutron star surface which temperature is consistent with stan…
We report on the results of Chandra X-ray observations of the $γ$-ray radio-quiet pulsar J1932+1916. We confirm the previous detection of the pulsar counterpart and its pulsar wind nebula in X-rays from low spatial resolution data obtained by Suzaku and Swift. The Chandra data with much better spatial resolution resolved the fine structure of the nebula in the pulsar vicinity, which can be interpreted as jets bent by the ram pressure. The size of this compact part is about 30'', and it is surrounded by a weak asymmetric diffusive emission extended up to $\approx$ 2.8'. The X-ray spectra of the…
We report on Chandra X-ray and Gemini-North near-infrared K-band observations of the eclipsing accretion-powered millisecond X-ray pulsar SWIFT J1749.4-2807 in quiescence. Using the Chandra observation we derive a source position of Right Ascencion: 17:49:31.73 and Declination:-28:08:05.08. The position is accurate to 0.6" (90 per cent confidence). We find one source at a magnitude K=18.44+-0.03 with a position fully consistent with the accurate Chandra X-ray localization and a second source at K=19.2+-0.1 that falls close to the edge of the error circle in the deep K-band images. The presence…
High magnetic field (high-B) pulsars are key sources to bridge magnetars and conventional rotation powered pulsars, and thus to understand the origin of magnetar activities. We have estimated a tight upper-limit on the X-ray flux of one of the youngest high-B pulsars PSR J1208-6238 for the first time; a Chandra 10 ks observation shows no significant source. Depending on the emission models, the 3sigma upper-limit on the intrinsic 0.5-7 keV flux to (2.2-10.0)e-14 erg/s/cm2.
The results from a systematic study of eleven pulsar wind nebulae with a torus structure observed with the Chandra X-ray observatory are presented. A significant observational correlation is found between the radius of the tori, r, and the spin-down luminosity of the pulsars, Edot. A logarithmic linear fit between the two parameters yields log r = (0.57 +- 0.22) log Edot -22.3 +- 8.0 with a correlation coefficient of 0.82, where the units of r and Edot are pc and ergs s^-1, respectively. The value obtained for the Edot dependency of r is consistent with a square root law, which is theoreticall…
The nearby, middle-aged PSR B1055-52 has many properties in common with the Geminga pulsar. Motivated by the Geminga's enigmatic and prominent pulsar wind nebula (PWN), we searched for extended emission around PSR B1055-52 with Chandra ACIS. For an energy range 0.3-1 keV, we found a 4 sigma flux enhancement in a 4.9-20 arcsec annulus around the pulsar. There is a slight asymmetry in the emission close, 1.5-4 arcsec, to the pulsar. The excess emission has a luminosity of about 10^{29} erg s^{-1} in an energy range 0.3-8 keV for a distance of 350 pc. Overall, the faint extended emission around P…
We report the Chandra/HRC-S and Swift/XRT observations for the 2015 outburst of the high-mass X-ray binary (HMXB) pulsar in the Small Magellanic Cloud, SMC X-2. While previous studies suggested that either an O star or a Be star in the field is the high-mass companion of SMC X-2, our Chandra/HRC-S image unambiguously confirms the O-type star as the true optical counterpart. Using the Swift/XRT observations, we extracted accurate orbital parameters of the pulsar binary through a time of arrivals (TOAs) analysis. In addition, there were two X-ray dips near the inferior conjunction, which are pos…
High-magnetic-field pulsars represent an important class of objects for studying the relationship between magnetars and radio pulsars. Here we report on four Chandra observations of the high-magnetic-field pulsar J1718-3718 ($B=7.4\times10^{13}$\,G) taken in 2009 as well as on a re-analysis of 2002 Chandra observations of the region. We also report an improved radio position for this pulsar based on ATCA observations. We detect X-ray pulsations at the pulsar's period in the 2009 data, with pulsed fraction 52%$\pm$13% in the 0.8--2.0 keV band. We find that the X-ray pulse is aligned with the ra…
We present the results of {\it Chandra} observations of two non-accreting millisecond pulsars, PSRs J1640$+$2224 (J1640) and J1709$+$2313 (J1709), with low inferred magnetic fields and spin-down rates in order to constrain their surface temperatures, obtain limits on the amplitude of unstable $r$-modes in them, and make comparisons with similar limits obtained for a sample of accreting low-mass X-ray binary (LMXB) neutron stars. We detect both pulsars in the X-ray band for the first time. They are faint, with inferred soft X-ray fluxes ($0.3-3$ keV) of $\approx$ $6\times10^{-15}$ and $3\times …
We report the timing analysis results of X-ray pulsars from a recent deep Chandra survey of the Small Magellanic Cloud (SMC). We have analyzed a total exposure of 1.4 Ms from 31 observations over a 1.2 deg$^2$ region in the SMC under a Chandra X-ray Visionary Program. Using the Lomb-Scargle and epoch folding techniques, we have detected periodic modulations from 20 pulsars and a new candidate pulsar. The survey also covers 11 other pulsars with no clear sign of periodic modulation. The 0.5-8 keV X-ray luminosity ($L_X$) of the pulsars ranges from $10^{34}$ to $10^{37}$ erg s$^{-1}$ at 60 kpc. …
We report on a timing and spectral analysis of the young, high magnetic field rotation-powered pulsar (RPP) B1509-58 using Chandra continuous-clocking mode observation. The pulsar's X-ray light curve can be fit by the two Gaussian components and the pulsed fraction shows moderate energy dependence over the Chandra band. The pulsed X-ray spectrum is well described by a power law with a photon index 1.16(4), which is harder than the values measured with RXTE PCA and NuSTAR. This result supports the log-parabolic model for the broadband X-ray spectrum. With the unprecedented angular resolution of…
PSR B0656+14 is a middle-aged pulsar with a characteristic age $τ_c=110$ kyr and spin-down power $\dot{E}= 3.8\times 10^{34}$ erg s$^{-1}$. Using Chandra data, we searched for a pulsar wind nebula (PWN) and found evidence of extended emission in a 3.5-15 arcsec annulus around the pulsar, with a luminosity $L_{\rm 0.5-8\,keV}^{\rm ext} \sim 8\times 10^{28}$ erg s$^{-1}$ (at the distance of 288 pc), which is a fraction of $\sim 0.05$ of the non-thermal pulsar luminosity. If the extended emission is mostly due to a PWN, its X-ray efficiency, $η_{\rm pwn} = L_{\rm 0.5-8\,keV}^{\rm ext}/\dot{E} \si…
PSR J1813-1749 is one of the most energetic rotation-powered pulsars known, producing a pulsar wind nebula (PWN) and gamma-ray and TeV emission, but whose spin period is only measurable in X-ray. We present analysis of two Chandra datasets that are separated by more than ten years and recent NICER data. The long baseline of the Chandra data allows us to derive a pulsar proper motion mu_R.A.=-(0.067"+/-0.010") yr^-1 and mu_decl.=-(0.014"+/-0.007") yr^-1 and velocity v_perp~900-1600 km/s (assuming a distance d=3-5 kpc), although we cannot exclude a contribution to the change in measured pulsar p…
Taking advantage of the high sensitivity of the Chandra Advanced CCD Imaging Spectrometer, we have conducted a snap-shot survey of pulsars previously undetected in X-rays. We detected 12 pulsars and established deep flux limits for 11 pulsars. Using these new results, we revisit the relationship between the X-ray luminosity, L_psr_x, and spin-down power, Edot. We find that the obtained limits further increase the extremely large spread in the non-thermal X-ray efficiencies, eta_psr_x=L_psr_x/Edot, with some of them being now below 1e-5. Such a spread cannot be explained by poorly known distanc…
We combined Chandra ACIS observations of the globular cluster 47 Tucanae (hereafter, 47 Tuc) from 2000, 2002, and 2014-15 to create a deeper X-ray source list, and study some of the faint radio millisecond pulsars (MSPs) present in this cluster. We have detected 370 X-ray sources within the half-mass radius (2$'$.79) of the cluster, 81 of which are newly identified, by including new data and using improved source detection techniques. The majority of the newly identified sources are in the crowded core region, indicating cluster membership. We associate five of the new X-ray sources with chrom…
We present a deep Chandra X-ray Observatory study of the peculiar binary radio millisecond pulsar PSR J1740--5340 and candidate millisecond pulsars (MSPs) in the globular cluster NGC 6397. The X-rays from PSR J1740--5340 appear to be non-thermal and exhibit variability at the binary period. These properties suggest the presence of a relativistic intrabinary shock formed due to interaction of a relativistic rotation-powered pulsar wind and outflow from the unusual "red-straggler/sub-subgiant" companion. We find the X-ray source U18 to show similar X-ray and optical properties to those of PSR J1…
We report on Chandra X-ray Observatory (CXO) observations of the pulsar wind nebula (PWN) associated with PSR B0355+54 (eight observations with a 395 ks total exposure, performed over an 8 month period). We investigated the spatial and spectral properties of the emission coincident with the pulsar, compact nebula (CN), and extended tail. We find that the CN morphology can be interpreted in a way that suggests a small angle between the pulsar spin axis and our line-of-sight, as inferred from the radio data. On larger scales, emission from the 7' (2 pc) tail is clearly seen. We also found hints …
We present the results of a deep study of the neutron star (NS) population in the globular cluster M28 (NGC 6626), using the full 330-ks 2002-2015 ACIS dataset from the Chandra X-ray Observatory and coordinated radio observations taken with the Green Bank Telescope (GBT) in 2015. We investigate the X-ray luminosity (Lx), spectrum, and orbital modulation of the 7 known compact binary millisecond pulsars (MSPs) in the cluster. We report two simultaneous detections of the redback PSR J1824-2452I (M28I) and its X-ray counterpart. We discover a double-peaked X-ray orbital flux modulation in M28I du…
PSR J1509-5850 is a middle-aged pulsar with the period P ~ 89 ms, spin-down power Edot = 5.1 x 10^35 erg/s, at a distance of about 3.8 kpc. We report on deep Chandra X-ray Observatory observations of this pulsar and its pulsar wind nebula (PWN). In addition to the previously detected tail extending up to 7' southwest from the pulsar (the southern outflow), the deep images reveal a similarly long, faint diffuse emission stretched toward the north (the northern outflow) and the fine structure of the compact nebula (CN) in the pulsar vicinity. The CN is resolved into two lateral tails and one axi…
We report the discovery of a bright X-ray source in the XMM-Newton and Chandra X-ray Observatory (CXO) images of the unidentified Fermi-LAT source 3FGL J1016.5-6034. The XMM-Newton spectrum of the source is well fit by an absorbed blackbody+power-law model with a temperature, $kT=0.20\pm0.02$ keV, and photon index $Γ=1.8\pm0.1$. The CXO resolves the same source into a point source (CXOU J101546.0-602939) and a surrounding compact nebula seen up to about $30''$ from the point source. The CXO spectrum of the nebula can be described by an absorbed power-law with $Γ=1.7\pm0.3$ and is partly respon…
We present a Chandra X-ray Observatory ACIS-S variability, spectroscopy, and imaging study of the peculiar binary containing the millisecond pulsar J1023+0038. The X-ray emission from the system exhibits highly significant (12.5 sigma) large-amplitude (factor of 2-3) orbital variability over the five consecutive orbits covered by the observation, with a pronounced decline in the flux at all energies at superior conjunction. This can be naturally explained by a partial geometric occultation by the secondary star of an X-ray--emitting intrabinary shock, produced by the interaction of outflows fr…
One of the most unique phenomena in the Galactic center region is the existence of numerous long and narrow filamentary structures within a few hundred parsecs of Sgr A$^{\star}$. While more than one than one hundred radio filaments have been revealed by MeerKAT, about two dozens X-ray filaments have been discovered so far. In this article, we report our analysis on the deep Chandra and NuSTAR observations of a non-thermal X-ray filament, G0.13-0.11, which is located adjacent to the Radio arc. Chandra revealed a unique morphology of G0.13-0.11, which is an elongated (0.1 pc in width and 3.2 pc…
We report on X-ray studies of the gamma-ray pulsar PSR J1418$-$6058 in the Rabbit pulsar wind nebula (PWN) carried out using archival Chandra and XMM-Newton observations. A refined timing analysis performed with the 120-ks XMM-Newton data finds significant ($p\approx10^{-7}$) pulsation at $P\approx110$ ms which is consistent with that measured with the Fermi large area telescope (LAT). In the Chandra image, we find extended emission around the pulsar similar to those seen around other pulsars in young PWNe, which further argues for association between PSR J1418$-$6058 and the Rabbit PWN. The X…
We present a Chandra X-ray Observatory investigation of the millisecond pulsars (MSPs) in the globular cluster M28 (NGC 6626). In what is one of the deepest X-ray observations of a globular cluster, we firmly detect seven and possibly detect two of the twelve known M28 pulsars. With the exception of PSRs B1821-24 and J1824-2452H, the detected pulsars have relatively soft spectra, with X-ray luminosities 10^30-31 ergs s^-1 (0.3-8 keV),similar to most "recycled" pulsars in 47 Tucanae and the field of the Galaxy, implying thermal emission from the pulsar magnetic polar caps. We present the most d…
We present an analysis of 745.6 ks of archival Chandra X-ray Observatory Advanced CCD Imaging Spectrometer data accumulated between 2000 and 2016 of the millisecond pulsar (MSP) population in the rich Galactic globular cluster Terzan 5. Eight of the 37 MSPs with precise positions are found to have plausible X-ray source matches. Despite the deep exposure, the remaining MSPs are either marginally detected or have no obvious X-ray counterparts, which can be attributed to the typically soft thermal spectra of rotation-powered MSPs, which are strongly attenuated by the high intervening absorbing c…
We present 35 ks Chandra ACIS observations of the 42 Myr old radio pulsar PSR B1451-68. A point source is detected 0.32" +/- 0.73" from the expected radio pulsar position. It has ~200 counts in the 0.3-8 keV energy range. We identify this point source as the X-ray counterpart of the radio pulsar. PSR B1451-68 is located close to a 2MASS point source, for which we derive 7% as the upper limit on the flux contribution to the measured pulsar X-ray flux. The pulsar spectrum can be described by either a power-law model with photon index Gamma=2.4 (+0.4/-0.3) and a unrealistically high absorbing col…
No apparent correlation was found between giant pulses (GPs) and X-ray photons from the Crab pulsar during 5.4 hours of simultaneous observations with the Green Bank Telescope at 1.5 GHz and Chandra X-Ray Observatory primarily in the energy range 1.5-4.5 keV. During the Crab pulsar periods with GPs the X-ray flux in radio emission phase windows does not change more than by +-10% for main pulse (MP) GPs and +-30% for interpulse (IP) GPs. During giant pulses themselves, the X-ray flux does not change more than by two times for MP GPs and 5 times for IP GPs. All limits quoted are compatible with …
PSR J1809-1917 is a young ($τ=51$ kyr) energetic ($\dot{E}=1.8\times10^{36}$ erg s$^{-1}$) radio pulsar powering an X-ray pulsar wind nebula (PWN) that exhibits morphological variability. We report on the results of a new monitoring campaign by the Chandra X-ray Observatory (CXO), carried out across 6 epochs with a $\sim$7-week cadence. The compact nebula can be interpreted as a jet-dominated outflow along the pulsar's spin axis. Its variability can be the result of Doppler boosting in the kinked jet whose shape changes with time (akin to the Vela pulsar jet). The deep X-ray image, composed of…
PSR B1259-63 is a middle-aged radio pulsar (P=48 ms, tau=330 kyr, Edot=8.3*10^{35} erg/s) in an eccentric binary (P_orb =3.4 yr, e=0.87) with a high-mass Be companion, SS 2883. We observed the binary near apastron with the Chandra ACIS detector on 2009 May 14 for 28 ks. In addition to the previously studied pointlike source at the pulsar's position, we detected extended emission on the south-southwest side of this source. The pointlike source spectrum can be described by the absorbed power-law model with the hydrogen column density N_H = (2.5+/-0.6)*10^{21} cm^{-2}, photon index Gamma = 1.6+/-…
Transitional millisecond pulsars are millisecond pulsars that switch between a rotation-powered millisecond pulsar state and an accretion-powered X-ray binary state, and are thought to be an evolutionary stage between neutron star low-mass X-ray binaries and millisecond pulsars. So far, only three confirmed systems have been identified in addition to a handful of candidates. We present the results of a multi-wavelength study of the low-mass X-ray binary NGC 6652B in the globular cluster NGC 6652, including simultaneous radio and X-ray observations taken by the Karl G. Jansky Very Large Array a…
In an effort to better understand the evolution of composite supernova remnants (SNRs) and the eventual fate of relativistic particles injected by their pulsars, we present a multifaceted investigation of the interaction between a pulsar wind nebula (PWN) and its host SNR G327.1-1.1. Our 350 ks Chandra X-ray observations of SNR G327.1-1.1 reveal a highly complex morphology; a cometary structure resembling a bow shock, prong-like features extending into large arcs in the SNR interior, and thermal emission from the SNR shell. Spectral analysis of the non-thermal emission offers clues about the o…
We report on the temporal properties of the ULX pulsar M51 ULX-7 inferred from the analysis of the 2018-2020 Swift/XRT monitoring data and archival Chandra data obtained over a period of 33 days in 2012. We find an extended low flux state, which might be indicative of propeller transition, lending further support to the interpretation that the NS is rotating near equilibrium. Alternatively, this off state could be related to a variable super-orbital period. Moreover, we report the discovery of periodic dips in the X-ray light curve that are associated with the binary orbital period. The presen…
Previous observations of the middle-aged pulsar Geminga with XMM-Newton and Chandra have shown an unusual pulsar wind nebula (PWN), with a 20" long central (axial) tail directed opposite to the pulsar's proper motion and two 2' long, bent lateral (outer) tails. Here we report on a deeper (78 ks) Chandra observation and a few additional XMM-Newton observations of the Geminga PWN. The new Chandra observation has shown that the axial tail, which includes up to three brighter blobs, extends at least 50" (i.e., 0.06 d_{250} pc) from the pulsar. It also allowed us to image the patchy outer tails and…
We present coordinated Chandra X-ray Observatory and Karl G. Jansky Very Large Array observations of the transitional millisecond pulsar PSR J1023+0038 in its low-luminosity accreting state. The unprecedented five hours of strictly simultaneous X-ray and radio continuum coverage for the first time unambiguously show a highly reproducible, anti-correlated variability pattern. The characteristic switches from the X-ray high mode into a low mode are always accompanied by a radio brightening with duration that closely matches the X-ray low mode interval. This behavior cannot be explained by a cano…
The recent discovery by Bachetti et al. (2014) of a pulsar in M82 that can reach luminosities of up to 10^40 ergs s^-1, a factor of ~100 the Eddington luminosity for a 1.4 Msol compact object, poses a challenge for accretion physics. In order to better understand the nature of this source and its duty cycle, and in the light of several physical models that have been subsequently published, we conduct a spectral and temporal analysis of the 0.5-8 keV X-ray emission from this source from 15 years of Chandra observations. We fit the Chandra spectra of the pulsar with a power-law model and a disk …
We report on a new Chandra exposure of PSR J1809-2332, the recently discovered pulsar powering the bright EGRET source 3EG J1809-2328. By registration of field X-ray sources in an archival exposure, we measure a significant proper motion for the pulsar point source over an ~11 year baseline. The shift of 0.30+/-0.06" (at PA= 153.3+/-18.4) supports an association with proposed SNR parent G7.5-1.7. Spectral analysis of diffuse emission in the region also supports the interpretation as a hard wind nebula trail pointing back toward the SNR.
We analyse 55 ks of Chandra X-ray observations of the Galactic globular cluster M13. Using the latest radio timing positions of six known millisecond pulsars (MSPs) in M13 from Wang et al. (2020), we detect confident X-ray counterparts to five of the six MSPs at X-ray luminosities of $L_X$(0.3-8 keV)$\sim 3 \times 10^{30} - 10^{31}~{\rm erg~s^{-1}}$, including the newly discovered PSR J1641+3627F. There are limited X-ray counts at the position of PSR J1641+3627A, for which we obtain an upper limit $L_X<1.3 \times 10^{30}~{\rm erg~s^{-1}}$. We analyse X-ray spectra of all six MSPs, which are we…
IGR J17511-3057 is a low mass X-ray binary hosting a neutron star and is one of the few accreting millisecond X-ray pulsars with X-ray bursts. We report on a 20ksec Chandra grating observation of IGR J17511-3057, performed on 2009 September 22. We determine the most accurate X-ray position of IGR J17511-3057, alpha(J2000) = 17h 51m 08.66s, delta(J2000) = -30deg 57' 41.0" (90% uncertainty of 0.6"). During the observation, a ~54sec long type-I X-ray burst is detected. The persistent (non-burst) emission has an absorbed 0.5-8keV luminosity of 1.7 x 10^36 erg/sec (at 6.9kpc) and can be well descri…
Using the Chandra X-ray Observatory, we have pinpointed the location of a faint X-ray point source (CXOUJ182913.1-125113) and an associated diffuse nebula in the composite supernova remnant G18.95-1.1. These objects appear to be the long-sought pulsar and its wind nebula. The X-ray spectrum of the point source is best described by an absorbed powerlaw model with Gamma=1.6 and an N_H of ~1x10^(22) cm^(-2). This model predicts a relatively low unabsorbed X-ray luminosity of about L_X (0.5-8.0keV) = 4.1x10^(31)D_2^2 erg s^(-1), where D_2 is the distance in units of 2kpc. The best-fitted model of …
We present X-ray observations of CU Vir performed with XMM-Newton and Chandra. With Lx = 3 x 10^28 erg/s the source is moderately X-ray bright, but its spectrum is extremely hard compared to other Ap stars. Spectral modelling requires multi-component models with predominant hot plasma at temperatures of about Tx = 25 MK or, alternatively, a nonthermal spectral component. The Chandra observations was performed six years later than the one by XMM-Newton, yet the source has similar X-ray flux and spectrum, suggesting a steady and persistent X-ray emission. To explain its full X-ray properties, a …
Redback millisecond pulsars (MSPs) typically show pronounced orbital variability in their X-ray emission due to our changing view of the intrabinary shock (IBS) between the pulsar wind and stellar wind from the companion. Some redbacks ("transitional" MSPs) have shown dramatic changes in their multiwavelength properties, indicating a transition from a radio pulsar state to an accretion-powered state. The redback MSP 47 Tuc W showed clear X-ray orbital variability in the Chandra ACIS-S observations in 2002, which were not detectable in the longer Chandra HRC-S observations in 2005-06, suggestin…
The millisecond pulsar PSR J1740-5340 in the globular cluster NGC 6397 shows radio eclipses over ~40% of its binary orbit. A first Chandra observation revealed indications for the X-ray flux being orbit dependent as well. In this work we analysed five data sets of archival Chandra data taken between 2000 and 2007 in order to investigate the emission across the pulsar's binary orbit. Utilizing archival Chandra observations of PSR J1740-5340, we have performed a systematic timing and spectral analysis of this binary system. Using a chi-square-test the significance for intra-binary orbital modula…
IGR J17591-2342 is an accreting millisecond X-ray pulsar discovered in 2018 August in scans of the Galactic bulge and center by the INTEGRAL X-ray and gamma-ray observatory. It exhibited an unusual outburst profile with multiple peaks in the X-ray, as observed by several X-ray satellites over three months. Here we present observations of this source performed in the X-ray/gamma-ray and near infrared domains, and focus on a simultaneous observation performed with the Chandra-High Energy Transmission Gratings Spectrometer (HETGS) and the Neutron Star Interior Composition Explorer (NICER). HETGS …
(abridged) PSR J1048-5832 is a young Vela-like pulsar that was recently detected in gamma-rays with Fermi, and also in X-rays with Chandra and XMM-Newton. It powers a compact PWN visible in X-rays. We present deep optical observations with the ESO Very Large Telescope to search for optical counterparts of the pulsar and its nebula and to explore their multi-wavelength emission properties. The data were obtained in V and R bands and compared with archival data in other spectral domains. We do not detect the pulsar in the optical and derive informative upper limits of R > 28.1 mag and V > 28.4 m…
We combine new and archival Chandra observations of the globular cluster NGC 6752 to create a deeper X-ray source list, and study the faint radio millisecond pulsars (MSPs) of this cluster. We detect four of the five MSPs in NGC 6752, and present evidence for emission from the fifth. The X-rays from these MSPs are consistent with thermal emission from the neutron star surfaces, with significantly higher fitted blackbody temperatures than other globular cluster MSPs (though we cannot rule out contamination by nonthermal emission or other X-ray sources). NGC 6752 E is one of the lowest-L_X MSPs …
We analyzed two Chandra observations of PSR J2055+2539 (for a total integration time of $\sim$130 ks) in order to measure its proper motion and study its two elongated nebular features. We did not detect the proper motion, setting an upper limit of 240 mas yr$^{-1}$ (3$σ$ level), that translates into an upper limit on the transverse velocity of $\sim$700 km s$^{-1}$, for an assumed distance of 600 pc. A deep H$α$ observation did not reveal the bow-shock associated with a classical pulsar wind nebula, thus precluding an indirect measurement of the proper motion direction. We determined the main…
Chandra observation of the relativistic binary J1906+0746
PSR J1906+0746 is a 112-kyr-old radio pulsar in a tight relativistic binary with a compact high-mass companion, at the distance of about 5 kpc. We observed this unique system with the Chandra ACIS detector for 31.6 ks. Surprisingly, not a single photon was detected within the 3" radius from the J1906+0746 radio position. For a plausible range of hydrogen column densities, n_H=(0.5-1) \times 10^{22} cm^{-2}, the nondetection corresponds to the 90% upper limit of (3-5) \times 10^{30} erg s^{-1} on the unabsorbed 0.5-8 keV luminosity for the power-law model with Gamma=1.0-2.0, and ~10^{32} erg s^…
A Chandra X-ray study of millisecond pulsars in the globular cluster Omega Centauri: a correlation between spider pulsar companion mass and X-ray luminosity
We summarize here the results, most of which are preliminary, of a number of recent observations of the Crab nebula system with the Chandra X-Ray Observatory. We discuss four different topics: (1) The motion on long (> 1yr) time scales of the southern jet. (2) The discovery that pulsar is not at the center of the projected ring on the sky and that the ring may well lie on the axis of symmetry but appears to be displaced at a latitude of about 5 degrees. (Note that this deprojection is by no means unique.) (3) The results and puzzling implications of the Chandra phase-resolved spectroscopy of t…
We report on a 10 ks simultaneous Chandra/HETG-NuSTAR observation of the Bursting Pulsar, GRO J1744-28, during its third detected outburst since discovery and after nearly 18 years of quiescence. The source is detected up to 60 keV with an Eddington persistent flux level. Seven bursts, followed by dips, are seen with Chandra, three of which are also detected with NuSTAR. Timing analysis reveals a slight increase in the persistent emission pulsed fraction with energy (from 10% to 15%) up to 10 keV, above which it remains constant. The 0.5-70 keV spectra of the persistent and dip emission are th…
Optical observations of pulsars are crucial to study the neutron star properties, from the structure and composition of the interior, to the properties and geometry of the magnetosphere. Historically, X and gamma-ray observations have paved the way to the pulsar optical identifications. The launch of Fermi opened new perspectives in the optical-to-gamma-ray studies of neutron stars, with the detection of more than 80 pulsars. Here, we aim to search for optical emission from two Fermi pulsars which are interesting targets on the basis of their spin-down age, energetics, and distance: PSR J1357-…
We present a detailed analysis of broadband X-ray observations of the pulsar PSR J1420-6048 and its wind nebula (PWN) in the Kookaburra region with Chandra, XMM-Newton, and NuSTAR. Using the archival XMM-Newton and new NuSTAR data, we detected 68 ms pulsations of the pulsar and characterized its X-ray pulse profile which exhibits a sharp spike and a broad bump separated by ~0.5 in phase. A high-resolution Chandra image revealed a complex morphology of the PWN: a torus-jet structure, a few knots around the torus, one long (~7') and two short tails extending in the northwest direction, and a bri…
