As part of a multiwavelength study of the unusual radio supernova remnant DA 495, we present observations made with the Chandra X-ray Observatory. Imaging and spectroscopic analysis confirms the previously detected X-ray source at the heart of the annular radio nebula, establishing the radiative properties of two key emission components: a soft unresolved source with a blackbody temperature of 1 MK consistent with a neutron star, surrounded by a nonthermal nebula 40'' in diameter exhibiting a power-law spectrum with photon index Gamma = 1.6+/-0.3, typical of a pulsar wind nebula. The implied spin-down luminosity of the neutron star, assuming a conversion efficiency to nebular flux appropriate to Vela-like pulsars, is ~10^{35} ergs/s, again typical of objects a few tens of kyr old. Morphologically, the nebular flux is slightly enhanced along a direction, in projection on the sky, independently demonstrated to be of significance in radio polarization observations; we argue that this represents the orientation of the pulsar spin axis. At smaller scales, a narrow X-ray feature is seen extending out 5'' from the point source, a distance consistent with the sizes of resolved wind termination shocks around many Vela-like pulsars. Finally, we argue based on synchrotron lifetimes in the estimated nebular magnetic field that DA 495 represents a rare pulsar wind nebula in which electromagnetic flux makes up a significant part, together with particle flux, of the neutron star's wind, and that this high magnetization factor may account for the nebula's low luminosity.
We present observations with the Chandra X-ray Observatory of the pulsar wind nebula (PWN) within the supernova remnant G0.9+0.1. At Chandra's high resolution, the PWN has a clear axial symmetry; a faint X-ray point source lying along the symmetry axis possibly corresponds to the pulsar itself. We argue that the nebular morphology can be explained in terms of a torus of emission in the pulsar's equatorial plane and a jet directed along the pulsar spin axis, as is seen in the X-ray nebulae powered by other young pulsars. A bright clump of emission within the PWN breaks the axisymmetry and may c…
We have studied the nearby old pulsar PSR B1929+10 and its surrounding interstellar medium utilizing the sub-arcsecond angular resolution of the Chandra X-ray Observatory. The Chandra data are found to be fully consistent with the results obtained from deep XMM-Newton observations as far as the pulsar is concerned. We confirm the non-thermal emission nature of the pulsar's X-radiation. In addition to the X-ray trail already seen in previous observations by the ROSAT and XMM-Newton X-ray observatories, we discovered an arc-like nebula surrounding the pulsar. We interpret the feature as a bow-sh…
Pulsar winds shocked in the ambient medium produce spectacular nebulae observable from the radio through gamma-rays. The shape and the spectrum of a pulsar wind nebula (PWN) depend on the angular distribution, magnetization and energy spectrum of the wind streaming from the pulsar magnetosphere, as well as on the pulsar velocity and the properties of the ambient medium. The advent of Chandra, with its unprecedented angular resolution and high sensitivity, has allowed us not only to detect many new PWNe, but also study their spatial and spectral structure and dynamics, which has significantly a…
SBS 1150+599A is a blue stellar object at high galactic latitude discovered in the Second Byurakan Survey. New high-resolution images of SBS 1150+599A are presented, demonstrating that it is very likely to be an old planetary nebula in the galactic halo, as suggested by Tovmassian et al (2001). An H-alpha image taken with the WIYN 3.5-m telescope and its "tip/tilt" module reveals the diameter of the nebula to be 9.2", comparable to that estimated from spectra by Tovmassian et al. Lower limits to the central star temperature were derived using the Zanstra hydrogen and helium methods to determin…
We present a Chandra and HST study of IC 10 X-1, the most luminous X-ray binary in the closest starburst galaxy to the Milky Way. Our new hard X-ray observation of X-1 confirms that it has an average 0.5-10 keV luminosity of 1.5e38 erg/s, is strongly variable (a factor of ~2 in >3 ks), and is spatially coincident (within 0.'23 +/-0.'30) with the Wolf-Rayet (WR) star [MAC92] 17A in IC 10. The spectrum of X-1 is best fit by a power law with photon index of ~1.8 and a thermal plasma with kT~1.5 keV, although systematic residuals hint at further complexity. Taken together, these facts suggest that…
We present preliminary results from a systematic spectral study of pulsars and their wind nebulae using the Chandra X-Ray Observatory. The superb spatial resolution of Chandra allows us to differentiate the compact object's spectrum from that of its surrounding nebulae. Specifically, for six Crab-like pulsars, we compare spectral fits of the averaged pulsar wind nebulae (PWN) emission to that of the central core using an absorbed power-law model. These results suggest an empirical relationship between the bulk averaged photon indicies (Gamma) for the PWNe and the pulsar cores; Gamma_PWN = 0.8 …
We report the detection of well resolved, extended X-ray emission from the young planetary nebula BD+303639 using the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-ray Observatory. The X-ray emission from BD+303639 appears to lie within, but is concentrated to one side of, the interior of the shell of ionized gas seen in high-resolution optical and IR images. The relatively low X-ray temperature (Tx ~ 3x10^6 K) and asymmetric morphology of the X-ray emission suggests that conduction fronts are present and/or mixing of shock-heated and photoionized gas has occurred and, furtherm…
We present a series of monitoring observations of the Crab Nebula with the Chandra X-ray Observatory, focusing on the temporal evolution of the structure. This series of 8 observations, spanning a period of approximately six months, shows the dynamic nature of the inner X-ray structures. We detected outward moving ``wisps'' from the recently discovered inner ring seen in optical observations. We also find that the inner ring itself shows temporal variations in structure. The torus also appears to be expanding. Such temporal variations generally match the canonical scenario that an expanding sy…
We present a {\it Chandra} ACIS observation of SNR G54.1+0.3. This supernova remnant is resolved into several distinct X-ray emitting components: a central bright point-like source (CXOU J193030.13+185214.1), a surrounding ring, bipolar elongations, plus low surface brightness diffuse emission. The spectra of these components are all well described by power-law models; the spectral index steepens with increasing distance from the point-like source. We find no evidence for any thermal plasma emission that would correspond to shocked interstellar medium or ejecta. The observed morphological and …
The observations of the pulsar-wind nebula (PWN) around the Vela pulsar with the Advanced CCD Imaging Spectrometer aboard the Chandra X-ray Observatory, taken on 2000 April 30 and November 30, reveal its complex morphology reminiscent of that of the Crab PWN. Comparison of the two observations shows changes up to 30% in the surface brightness of the PWN features. Some of the PWN elements show appreciable shifts, up to a few arcseconds (about 10^{16} cm), and/or spectral changes. To elucidate the nature of the observed variations, further monitoring of the Vela PWN is needed.
We report on Chandra ACIS and XMM-Newton MOS/PN imaging observations of two pulsar wind nebulae (K3/PSR J1420-6048 and G313.3+0.1=`the rabbit') associated with the Galactic unidentified gamma-ray source GeV J1417-6100. With the excellent ACIS imaging, the very energetic pulsar PSR J1420-6048 is separated from its surrounding nebula. This nebula has surprisingly little compact structure, although a faint arc is seen near the pulsar. Similarly, two point sources are resolved in the rabbit nebula. The large XMM-Newton collecting area provides useful spectral constraints on the rabbit and the asso…
We present results from a statistical analysis of 173 bright radio-quiet AGNs selected from the Chandra Deep Field-North and Chandra Deep Field-South surveys (hereafter, CDFs) in the redshift range of 0.1 < z < 4. We find that the X-ray power-law photon index (Gamma) of radio-quiet AGNs is correlated with their 2-10 keV rest-frame X-ray luminosity (L_X) at the > 99.5 percent confidence level in two redshift bins, 0.3 < z < 0.96, and 1.5 < z < 3.3 and is slightly less significant in the redshift bin 0.96 < z < 1.5. We investigate the redshift evolution of the correlation between the power-law p…
An axisymmetric model for the Crab Nebula is constructed to examine the flow dynamics in the nebula. The model is based on that of Kennel and Coroniti (1984), although we assume that the kinetic-energy-dominant wind is confined in an equatorial region. The evolution of the distribution function of the electron-positron plasma flowing out in the nebula is calculated. Given viewing angles, we reproduce an image of the nebula and compare it with Chandra observation. The reproduced image is not a ring-like but rather 'lip-shaped'. It is found that the assumption of toroidal field does not reproduc…
We have observed the young Galactic supernova remnant Kes 75 with the Chandra X-ray Observatory. This object is one of an increasing number of examples of a shell-type remnant with a central extended radio core harboring a pulsar. Here we present a preliminary spatially resolved spectroscopic analysis of the Kes~75 system. We find that the spectrum of the pulsar is significantly harder than that of the wind nebula, and both of these components can be isolated from the diffuse thermal emission that seems to follow the same distribution as the extended radio shell. When we characterize the therm…
This paper deals with the Crab Nebula problem to suggest that particle acceleration takes place not only at the inner shock but also over a larger region in the nebula with disordered magnetic field. Kennel and Cornoniti (1984) constructed a spherically symmetric model of the Crab Nebula and concluded that the pulsar wind which excites the nebular is kinetic-energy dominant (KED) because the nebula flow induced by KED wind is favorable to explain the nebula spectrum and expansion speed. This is true even with new Chandra observation, which provides newly the spatially resolved spectra. We have…
Chu et al (2001; ApJ, 533, L69) report that they find the diffuse X-ray emission from the Cat's Eye Nebula, NGC 6543, to be inconsistent with nebular abundances but consistent with abundances expected for the stellar wind although the location of the emission and the temperature they derive for the X-ray emitting region of NGC 6543 require that a significant fraction of the X-ray emitting material be nebular. A recent, refined, determination by Bernard-Salus et al (personal communication) of nebular abundances in NGC 6543 incorporating infrared, optical, and ultraviolet observations provides a…
We report the discovery of X-ray emission from NGC 7027, a prototypical object for the study of the formation and evolution of planetary nebulae (PNs). Observations with the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-ray Observatory show that the X-ray emission from NGC 7027 is extended and is bipolar in morphology. The ACIS spectrum displays strong emission from highly ionized Ne and weaker emission features which we attribute to O, Mg, and Si. Model fits to this spectrum suggest a characteristic temperature T_x ~ 3x10^6 K and an intrinsic (unabsorbed) X-ray luminosity of L…
We report the serendipitous detection of the planetary nebula NGC 5315 by the Chandra X-ray Observatory. The Chandra imaging spectroscopy results indicate that the X-rays from this PN, which harbors a Wolf-Rayet (WR) central star, emanate from a T_X ~ 2.5x10^6 K plasma generated via the same wind-wind collisions that have cleared a compact (~8000 AU radius) central cavity within the nebula. The inferred X-ray luminosity of NGC 5315 is ~2.5x10^{32} erg s^{-1} (0.3-2.0 keV), placing this object among the most luminous such ``hot bubble'' X-ray sources yet detected within PNe. With the X-ray dete…
3C58 is a young Crab-like supernova remnant. Historical evidence strongly suggests an association of the remnant with supernova SN 1181, which would make 3C58 younger than the Crab Nebula. Recent Chandra observations have identified the young 65 ms pulsar J0205+6449 at its center, embedded in a compact nebula which, we show here, appears to be confined by the pulsar wind termination shock. We present new Chandra observations of this compact nebula and embedded pulsar which set strong upper limits on thermal emission originating from the neutron star surface. These limits fall far below predict…
V407 Vul is a candidate double-degenerate binary with a putative 1.756 mHz (9.5 min) orbital frequency. In a previous timing study using archival ROSAT and ASCA data we reported evidence for an increase of this frequency at a rate consistent with expectations for gravitational radiation from a detached ultracompact binary system. Here we report the results of new CHANDRA timing observations which confirm the previous indications of spin-up of the X-ray frequency, and provide much tighter constraints on the frequency derivative. We obtained with CHANDRA a total of 90 ksec of exposure in two epo…
The young and energetic pulsar B1509-58 powers a bright X-ray synchrotron nebula, embedded in the unusual supernova remnant G320.4-1.2. We present observations of this system with the Chandra X-ray Observatory, which show a spectacularly complicated source. The nebula is dominated by a bright collimated feature which we interpret as a relativistic jet directed along the pulsar spin axis. Several compact knots can be seen in the immediate vicinity of the pulsar. While many of these features are similar to those seen around the Crab pulsar, the nebula surrounding PSR B1509-58 shows important dif…
A Chandra observation of the isolated hard X-ray source XMMU J061804.3+222732, located in the region of apparent interaction of the supernova remnant IC 443 with a molecular cloud, resolved the complex structure of the source in a few bright clumps embedded in an extended emission of a ~ 30 arcsec size. The X-ray spectra of the clumps and the extended emission are dominated by a hard power-law component with a photon index of 1.2--1.4. In addition, we see some indications of an optically thin thermal plasma of a ~ 0.3 keV temperature. The observed X-ray morphology and spectra are consistent wi…
Two Chandra observations have been used to search for thermal X-ray emission from within and around the Crab Nebula. Dead-time was minimized by excluding the brightest part of the Nebula from the field of view. A dust-scattered halo comprising 5% of the strength of the Crab is clearly detected with surface brightness measured out to a radial distance of 18 arcminutes. Coverage is 100% at 4 arcminutes, 50% at 12 arcminutes, and 25% at 18 arcminutes. The observed halo is compared with predictions based on 3 different interstellar grain models and one can be adjusted to fit the observation. This …
While supernova remnants (SNRs) have long been considered prime candidates as sources of cosmic rays, it is only recently that X-ray observations have identified several shell-type SNRs dominated by nonthermal emission, thus revealing shock-accelerated electrons with energies extending far beyond the typical thermal spectrum. Two of these SNRs have been detected as sources of VHE gamma-rays.In other remnants, discrepancies between the shock velocity and the electron temperature point to a strong cosmic ray component that has thrived at the expense of the thermal gas. Modeling of the radio, X-r…
We have obtained Chandra ACIS-S observations of NGC 6543, the Cat's Eye Nebula. The X-ray emission from NGC 6543 is clearly resolved into a point source at the central star and diffuse emission confined within the central elliptical shell and two extensions along the major axis. Spectral analysis of the diffuse component shows that the abundances of the X-ray-emitting gas are similar to those of the fast (1,750 km/s) stellar wind but not those of the nebula. Furthermore, the temperature of this gas is ~1.7 million K, which is 100 times lower than the expected post-shock temperature of the fast…
We present the results of detailed spatial and spectral analysis of the pulsar wind nebula (PWN) in supernova remnant Kes 75 (G29.7-0.3) using a deep exposure with Chandra X-ray observatory. The PWN shows a complex morphology with clear axisymmetric structure. We identified a one-sided jet and two bright clumps aligned with the overall nebular elongation, and an arc-like feature perpendicular to the jet direction. Further spatial modeling with a torus and jet model indicates a position angle $207\arcdeg\pm8 \arcdeg$ for the PWN symmetry axis. We interpret the arc as an equatorial torus or wisp…
We present and analyze the first high-resolution X-ray images ever obtained of the Eagle Nebula star-forming region. On 2001 July 30 the Chandra X-ray Observatory obtained a 78 ks image of the Eagle Nebula (M 16) that includes the core of the young galactic cluster NGC 6611 and the dark columns of dust and cold molecular gas in M 16 known as the Pillars of Creation. We find a total of 1101 X-ray sources in the 17'x17' ACIS-I field of view. Most of the X-ray sources are low mass pre-main-sequence or high-mass main-sequence stars in this young cluster. A handful of hard X-ray sources in the pill…
We present a Chandra observation of the H II region RCW89. The nebula lies on 10' north from the central pulsar PSR B1509-58, and it has been suggested that the nebula is irradiated by the pulsar jet. We performed a spectral analysis of the seven brightest emitting regions aligned in a ``horse-shoe'' shape, and found that the temperature of the knots increases along the ``horse-shoe'' in the clockwise direction, while, in contrast, the ionization parameter decreases. This strongly supports a picture of energy transfer via the precessing pulsar jet. We examined the energy budget assuming that R…
In this first of two companion papers on the Orion Nebula Cluster (ONC), we present our analysis of a 63 Ksec Chandra HRC-I observation that yielded 742 X-ray detections within the 30'x30' field of view. To facilitate our interpretation of the X-ray image, here we collect a multi-wavelength catalog of nearly 2900 known objects in the region by combining 17 different catalogs from the recent literature. We define two reference groups: an infrared sample, containing all objects detected in the K band, and an optical sample comprising low extinction, well characterized ONC members. We show for bo…
We present observations with the Chandra X-ray Observatory of the pulsar wind nebula (PWN) powered by the energetic young pulsar B1509-58. These data confirm the complicated morphology of the system indicated by previous observations, and in addition reveal several new components to the nebula. The overall PWN shows a clear symmetry axis oriented at a position angle 150 degrees (N through E), which we argue corresponds to the pulsar spin axis. We show that a previously identified radio feature matches well with the overall extent of the X-ray PWN, and propose the former as the long-sought radi…
We report the detection of a point source CXO J172337.5-373442 in a Chandra field with a high significance (26.7 sigma), and the discovery (4 sigma) of a 48" long X-ray tail emanating from the point source. The X-ray spectra of both the point source and the tail are well described with a single absorbed powerlaw, and the tail is harder (powerlaw index Gamma = 0.14^{+0.59}_{-0.68}) than the point source (Gamma = 1.78^{+0.13}_{-0.11}). From this first detailed spatial, spectral and timing X-ray analysis of CXO J172337.5-373442, and from a plausible optical counterpart found from the archives, we…
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…
The Chandra Orion Ultradeep project (COUP) observation described in a companion paper by Getman et al. provides an exceptionally deep X-ray survey of the Orion Nebula Cluster and associated embedded young stellar objects. Membership of the region is important for studies of the stellar IMF, cluster dynamics, and star formation. The COUP study detected 1616 X-ray sources. In this study we confirm cloud membership for 1315 stars, identify 16 probable foreground field stars having optical counterparts with discrepant proper motions, and classify the remaining 285 X-ray sources, of which 51 are li…
Chandra observations of the Crab-like supernova remnant G21.5-0.9 reveal a compact central core and spectral variations indicative of synchrotron burn-off of higher energy electrons in the inner nebula. The central core is slightly extended, perhaps indicating the presence of an inner wind-shock nebula surrounding the pulsar. No pulsations are observed from the central region, yielding an upper limit of ~40% for the pulsed fraction. A faint outer shell may be the first evidence of the expanding ejecta and blast wave formed in the initial explosion, indicating a composite nature for G21.5-0.9.
We report the discovery, by the Chandra X-ray Observatory, of X-ray emission from the bipolar planetary nebula Menzel 3. In Chandra CCD imaging, Mz 3 displays hot (3-6x10^6 K) gas within its twin, coaxial bubbles of optical nebulosity, as well as a compact X-ray source at the position of its central star(s). The brightest diffuse X-ray emission lies along the polar axis of the optical nebula, suggesting a jet-like configuration. The observed combination of an X-ray-emitting point source and possible X-ray jet(s) is consistent with models in which accretion disks and, potentially, magnetic fiel…
We have discovered a long radio trail at 843 MHz which is apparently associated with middle age pulsar PSR J1509-5850. The radio trail has a length of ~7 arcmin. In X-rays, Chandra observations of PSR J1509-5850 reveal an associated X-ray trail which extends in the same orientation as the radio trail. Moreover, two clumpy structures are observed along the radio trail. The larger one is proposed to be the supernova remnant (SNR) candidate MSC 319.9-0.7. Faint X-ray enhancement at the position of the SNR candidate is found in the Chandra data.
The Trifid Nebula, a young star-forming HII region, was observed for 16 hours by the Chandra X-ray Observatory. We detected 304 X-ray sources, thirty percent of which are hard sources and seventy percent of of which have near-infrared counterparts. Chandra resolved the HD164492 multiple system into a number of discrete X-ray sources. X-ray emission is detected from components HD164492A (an O7.5III star which ionizes the nebula), B and C (a B6V star), and possibly D (a Be star). HD164492A has a soft spectrum (kT ~ 0.5 keV) while the component C blend shows much harder emission (kT ~ 6 keV). The…
About 1000 X-ray emitting young pre-main sequence (PMS) stars distributed in mass from 0.05 to 50 solar masses are detected in an image of the Orion Nebula obtained with the Advanced CCD Imaging Spectrometer on board the Chandra X-ray Observatory. This is the richest field of sources ever obtained in X-ray astronomy. ACIS sources include 85-90% of V<20 stars, plus a substantial fraction of deeply embedded stars with extinctions as high as A_V~60. The relationships between X-ray and other PMS stellar properties suggest that X-ray luminosity of lower-mass PMS stars depends more on mass, and poss…
We report on a 19 ks observation of the pulsar J1016-5857 with the Chandra X-ray Observatory. This "Vela-like" pulsar has rotation period 107 ms, characteristic age 21 kyr, and spin-down power 2.6e36 ergs/s. A relatively bright centrally peaked source of radius ~25" around the radio pulsar position has a spectrum that is well fitted by an absorbed power law with photon index 1.32+-0.25. We regard this as a newly identified pulsar wind nebula that we designate PWN G284.0-1.8. We do not detect the pulsar either as a point X-ray source or as a pulsed source in a 55 ks observation with the Rossi X…
We report on an observation of the Vela-like pulsar B1823-13 and its synchrotron nebula with Chandra.The pulsar's spectrum fits a power-law model with a photon index Gamma_PSR=2.4 for the plausible hydrogen column density n_H=10^{22} cm^{-2}, corresponding to the luminosity L_PSR=8*10^{31} ergs s^{-1} in the 0.5-8 keV band, at a distance of 4 kpc. The pulsar radiation likely includes magnetospheric and thermal components, but they cannot be reliably separated because of the small number of counts detected and strong interstellar absorption. The pulsar is surrounded by a compact, 25''x 10'', pu…
It is shown that the nonlinear kinetic model of cosmic ray (CR) acceleration in supernova remnants (SNRs) fits the shell-type nonthermal X-ray morphology, obtained in Chandra observations, in a satisfactory way. The set of empirical parameters is the same which reproduces the dynamical properties of the SNR and the spectral characteristics of the emission produced by CRs. The extremely small spatial scales of the observed X-ray distribution are due to the large effective magnetic field $B_{\mathrm d}\sim 100$ $μ$G in the interior, which is also required to give a good fit for the spatially int…
The young pulsar PSR B0540-69 was one of the first targets observed with the Chandra X-Ray Observatory. The high angular resolution of Chandra allows us to resolve the compact nebula surrounding the pulsar. We have determined a position for PSR B0540-69 of R.A. = 05h 40m 11s.221, decl. = -69o 19' 54".98 (J2000) with a 1-sigma radial uncertainty of 0.7". Combining our measurements of the pulsar period with previous measurements covering a span of 12 years, we derive a braking index of 2.08. The spectrum of the pulsed emission is consistent with a power-law with a photon index of 1.83 +/- 0.13. …
We report on two Chandra observations of the 3-Myr pulsar B1929+10, which reveal a faint compact (~9"x5") nebula elongated in the direction perpendicular to the pulsar's proper motion, two patchy wings, and a possible short (~3") jet emerging from the pulsar. In addition, we detect a tail extending up to at least 4' in the direction opposite to the pulsar's proper motion, aligned with the 15'-long tail detected in ROSAT and XMM-Newton observations. The overall morphology of the nebula suggests that the shocked pulsar wind is confined by the ram pressure due to the pulsar's supersonic speed. Th…
The luminous unstable star (star system) eta Carinae is surrounded by an optically bright bipolar nebula, the Homunculus and a fainter but much larger nebula, the so-called outer ejecta. As images from the EINSTEIN and ROSAT satellites have shown, the outer ejecta is also visible in soft X-rays, while the central source is present in the harder X-ray bands. With our CHANDRA observations we show that the morphology and properties of the X-ray nebula are the result of shocks from fast clumps in the outer ejecta moving into a pre-existing denser circumstellar medium. An additional contribution to…
Using the results of our first paper on the Chandra HRC observation of the Orion Nebula Cluster (ONC), here we explore the relation between the coronal activity of its 1-Myr-old pre-main sequence population and stellar parameters. We find that median X-ray luminosities of low mass stars (M/M_sun < 3) increase with increasing mass and decreasing stellar age. Brown dwarfs (0.03 < M/M_sun < 0.08) follow the same trend with mass. From M~0.1 to M~0.5M_sun, median L_X/L_bol values increase by about half an order of magnitude and then remain constant at ~10^-3.5 for the mass range from 0.5 to 3.0 M/M…
We report the discovery of a galaxy overdensity at z=1.11 associated with the z=1.110 high-redshift radio galaxy MG0442+0202. The group, CL0442+0202, was found in a near-infrared survey of z>1 radio galaxies undertaken to identify spatially-coincident regions with a high density of objects red in I-K' color, typical of z>1 elliptical galaxies. Spectroscopic observations from the Keck telescope reveal five galaxies within 35" of MG0442+0202 at 1.10<z<1.11. These member galaxies have broad-band colors and optical spectra consistent with passively-evolving elliptical galaxies formed at high redsh…
We present Chandra observations of the massive star-forming region S106, a prominent HII region in Cygnus, associated with an extended molecular cloud and a young cluster. The nebula is excited by a single young massive star located at the center of the molecular cloud and the embedded cluster. The prominence of the cluster in the Chandra observation presented here confirms its youth and allows some of its members to be studied in more detail. We detect X-ray emission from the young massive central source S106 IRS 4, the deeply embedded central object which drives the bipolar nebula with a mas…
We report the Chandra Advanced CCD Imaging Spectrometer detection of the X-ray counterpart of the high magnetic field, ~1600 year-old, 407 ms radio pulsar J1119-6127 associated with the supernova remnant G292.2-0.5. The powerful imaging capability of Chandra also unveiled, for the first time, a faint 3"x6" pulsar wind nebula (PWN) at energies above ~1.2 keV. The X-ray emission from the pulsar and its associated nebula is well described by an absorbed power law model with a photon index of 2.2 (1.9-2.8). The corresponding 0.5-10 keV unabsorbed X-ray luminosity is 5.5(2.2-15.5)x10^32 ergs/s (at …
The globular cluster M15 was observed on three occasions with the High Resolution Camera on board Chandra in 2001 in order to investigate the X-ray source population in the cluster centre. After subtraction of the two bright central sources, four faint sources were identified within 50 arcsec of the core. One of these sources is probably the planetary nebula, K648, making this the first positive detection of X-rays from a planetary nebula inside a globular cluster. Another two are identified with UV variables (one previously known), which we suggest are cataclysmic variables (CVs). The nature …
We interpret the observed X-ray morphology of the central part of the Crab Nebula (torus + jets) in terms of the standard theory by Kennel and Coroniti (1984). The only new element is the inclusion of anisotropy in the energy flux from the pulsar in the theory. In the standard theory of relativistic winds, the Lorentz factor of the particles in front of the shock that terminates the pulsar relativistic wind depends on the polar angle as $γ=γ_0+γ_m\sin^2θ$, where $γ_0 \sim 200$ and $γ_m \sim 4.5\times 10^6$. The plasma flow in the wind is isotropic. After the passage of the pulsar wind through …
Observations of the Vela pulsar region with the Chandra X-ray observatory have revealed the fine structure of its synchrotron pulsar-wind nebula (PWN), which showed an overall similarity with the Crab PWN. However, contrary to the Crab, no firm detection of the Vela PWN in optical has been reported yet. To search for the optical counterpart of the X-ray PWN, we analyzed deep optical observations performed with different telescopes. We compared the optical images with those obtained with the Chandra ACIS to search for extended emission patterns which could be identified as counterparts of the X…
We present the results of the first X-ray gratings spectroscopy observations of a planetary nebula (PN), the X-ray-bright, young BD+30 3639. We observed BD+30 3639 for a total of 300 ks with the Chandra X-ray Observatory's Low Energy Transmission Gratings in combination with its Advanced CCD Imaging Spectrometer(LETG/ACIS-S). The LETG/ACIS-S spectrum of BD+30 3639 is dominated by H-like resonance lines of O viii and C sc vi and the He-like triplet line complexes of Ne ix and O vii. Other H-like resonance lines, such as N vii, as well as lines of highly ionized Fe, are weak or absent. Continuum…
We present a spatially resolved spectroscopic analysis of the young Galactic supernova remnant Kes 75 (SNR G29.7-0.3) using the Chandra X-ray Observatory. Kes 75 is one of an increasing number of examples of a shell-type remnant with a central pulsar powering an extended radio/X-ray core. We are able to pinpoint the location of the recently discovered pulsar, PSR J1846-0258, and confirm that X-rays from the remnant's core component are consistent with non-thermal power-law emission from both the pulsar and its surrounding wind nebula. We find that the spectrum of the pulsar is significantly ha…
We report on Chandra imaging observations of the Galactic Unidentified $γ$-ray source GEV J1809-2327, comparing the X-ray images with new VLA 1.46 GHz and 4.86 GHz maps. The X-ray images reveal a point source connected to a non-thermal X-ray/radio nebula, supporting a pulsar/wind model for the $γ$-ray emitter. We also detect numerous X-ray sources from the young stellar association in the adjacent HII region S32.
We present here an overview of the status of the Chandra X-ray Observatory which has now been operating for five years. The Observatory is running smoothly, and the scientific return continues to be outstanding. We provide some details on the molecular contamination of the ACIS filters and its impact on observations. We review the observations with Chandra of the pulsar in the Crab Nebula and add some general comments as to the analysis of X-ray spectra. We conclude with comments about the future directions for the study of neutron stars with Chandra.
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…
An early analysis of Chandra observations of the planetary nebula NGC 6543 suggested that the location and the derived temperature for the X-ray emitting region is inconsistent with the abundances measured for this object (Chu et al. 2001). We revisit observations of this source (following significant updates to both the reprocessing and extraction software) in order to propose a resolution to this apparent anomaly. Our re-analysis using abundances found from observations in the infrared, optical, and ultraviolet suggests that the location and temperature of the X-ray emission from NGC 6543 is…
We present an X-ray tour of diffuse emission in the 30 Doradus star-forming complex in the Large Magellanic Cloud using high-spatial-resolution X-ray images and spatially-resolved spectra obtained with the Advanced CCD Imaging Spectrometer aboard the Chandra X-ray Observatory. The dominant X-ray feature of the 30 Doradus nebula is the intricate network of diffuse emission generated by interacting stellar winds and supernovae working together to create vast superbubbles filled with hot plasma. We construct maps of the region showing variations in plasma temperature (T = 3--9 million degrees), a…
We present Chandra X-ray Observatory imaging observations of the young Galactic supernova remnant G11.2-0.3. The image shows that the previously known young 65-ms X-ray pulsar is at position (J2000) RA 18h 11m 29.22s, DEC -19o 25' 27.''6, with 1 sigma error radius 0.''6. This is within 8'' of the geometric center of the shell. This provides strong confirming evidence that the system is younger, by a factor of ~12, than the characteristic age of the pulsar. The age discrepancy suggests that pulsar characteristic ages can be poor age estimators for young pulsars. Assuming conventional spin down …
