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## The Distances of SNRs Kes 69 and G21.5-0.9 from HI and 13CO Spectra

Tian, Wenwu; Leahy, Denis A.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We obtain new HI and $^{13}$CO images around Supernova Remnants (SNR) Kes 69 and G21.5-0.9. By comparing HI spectra with $^{13}$CO emission spectra, we significantly revise the kinematic distance for Kes 69 to $\sim$ 5.5 kpc, which was 11.2 kpc, and refine the kinematic distance for G21.5-0.9 to ~4.8 kpc. For Kes 69, the highest velocity of absorption is ~86 km/s and a prominent HI emission feature at ~ 112 km/s has no respective absorption. These new results suggest that Kes 69 is associated with a newly detected extended 1720 MHz OH maser at velocity of ~85 km/s that originates from within the bright southern radio shell of Kes 69. For G21.5-0.9, the highest velocity of absorption is ~67 km/s. The HI absorption spectra of the nearby bright source PMN J1832-1035 and of Kes 69 show a common absorption feature at velocity of ~69 km/s, which is not seen for G21.5-0.9. The resulting velocity of ~68 km/s gives the best distance estimate of ~4.8 kpc for G21.5-0.9 and associated young pulsar J1833-1034.; Comment: 5 page, 2 figs. Monthly Notices of the Royal Astronomical Society: Letters. in press

## Comparison of XMM-Newton EPIC, Chandra ACIS-S3, ASCA SIS and GIS, and ROSAT PSPC Results for G21.5-0.9, 1E0102.2-7219, and MS1-54.4-0321

Snowden, S. L.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.1%
This paper presents a man on the street'' view of the current status of the spectral cross calibration between the XMM-Newton EPIC, Chandra ACIS-S3, ASCA SIS and GIS, and ROSAT PSPC instruments. Using publicly released software for the extraction of spectra and the production of spectral redistribution response matrices and effective areas, the spectral fits of data from three astronomical objects are compared. The three sources are G21.5-0.9 (a heavily absorbed Galactic SNR with a power law spectrum), 1E0102.2-7219 (a SNR in the SMC with a line-dominated spectrum), and MS1054.4-0321 (a high redshift cluster with a thermal spectrum). The agreement between the measured fluxes of the various instruments is within the 10% range, and is better when just XMM-Newton and Chandra are compared. Fitted spectral parameters are also in relatively good agreement although the results are more limited.; Comment: 5 pages, 9 figures, from ESTEC Symposium 'New Visions of the X-ray Universe in the XMM-Newton and Chandra Era' 26-30 November 2001

## The Plerionic Supernova Remnant G21.5-0.9: In and Out

Matheson, Heather; Safi-Harb, Samar
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.4%
The absence of a supernova remnant (SNR) shell surrounding the Crab and other plerions (pulsar wind nebulae) has been a mystery for 3 decades. G21.5-0.9 is a particularly intriguing plerionic SNR in which the central powering engine is not yet detected. Early Chandra observations revealed a faint extended X-ray halo which was suggested to be associated with the SNR shell; however its spectrum was nonthermal, unlike what is expected from an SNR shell. On the other hand, a plerionic origin to the halo is problematic since the X-ray plerion would be larger than the radio plerion. We present here our analysis of an integrated 245 ksec of archival Chandra data acquired with the High-Resolution Camera (HRC) and 520 ksec acquired with the Advanced CCD Imaging Spectrometer (ACIS). This study provides the deepest and highest resolution images obtained to date. The resulting images reveal for the first time 1) a limb-brightened morphology in the eastern section of the halo, and 2) a rich structure in the inner (40"-radius) bright plerion including wisps and a double-lobed morphology with an axis of symmetry running in the northwest-southeast direction. Our spatially resolved spectroscopic study of the ACIS-I data indicates that the photon index steepens with increasing distance from the central point source out to a radius of 40" then becomes constant at ~2.4 in the X-ray halo (for a column density N_H=2.2E22/cm^2). No line emission was found from the eastern limb; however marginal evidence for line emission in the halo's northern knots was found. This study illustrates the need for deep Chandra observations to reveal the missing SNR material in Crab-like plerions.; Comment: 10 pages including 6 figures (2 in colour) and 2 tables...

## X-Ray Observations of the supernova remnant G21.5-0.9

Safi-Harb, S.; Harrus, I. M.; Petre, R.; Pavlov, G. P.; Koptsevich, A. B.; Sanwal, D.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.59%
We present the analysis of archival X-ray observations of the supernova remnant (SNR) G21.5-0.9. Based on its morphology and spectral properties, G21.5-0.9 has been classified as a Crab-like SNR. In their early analysis of the CHANDRA calibration data, Slane et al. (2000) discovered a low-surface-brightness, extended emission. They interpreted this component as the blast wave formed in the supernova (SN) explosion. In this paper, we present the CHANDRA analysis using a total exposure of ~150 ksec. We also include ROSAT and ASCA observations. Our analysis indicates that the extended emission is non-thermal -- a result in agreement with XMM observations. The entire remnant of radius ~ 2'.5 is best fitted with a power law model with a photon index steepening away from the center. The total unabsorbed flux in the 0.5-10 keV is 1.1E-10 erg/cm2/s with an 85% contribution from the 40" radius inner core. Timing analysis of the High-Resolution Camera (HRC) data failed to detect any pulsations. We put a 16% upper limit on the pulsed fraction. We derive the physical parameters of the putative pulsar and compare them with those of other plerions (such as the Crab and 3C 58). G21.5-0.9 remains the only plerion whose size in X-rays is bigger than in the radio. Deep radio observations will address this puzzle.; Comment: 23 pages including 11 figures and 3 tables; accepted by ApJ June 22...

## The Expansion and Radio Spectral Index of G21.5-0.9: Is PSR J1833-1034 the Youngest Pulsar?

Bietenholz, M. F.; Bartel, N.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
27.59%
We report on new 5-GHz VLA radio observations of the pulsar-powered supernova remnant G21.5-0.9. These observations have allowed us to make a high-quality radio image of this remnant with a resolution of ~0.7". It has a filamentary structure similar to that seen in the Crab Nebula. Radio structure suggestive of the torus seen around the Crab pulsar is tentatively identified. We also compared the new image with one taken ~15 yr earlier at 1.5 GHz, both to find the expansion speed of the remnant and to make a spectral index image. Between 1991 and 2006, we find that the average expansion rate of the remnant is 0.11 +/- 0.02 %/year, corresponding, for a distance of 5 kpc, to a speed of 910 +/- 160 km/s wrt. the centre of the nebula. Assuming undecelerated expansion, this expansion speed implies that the age of G21.5-0.9 is 870 (+200,-150) yr, which makes PSR J1833-1034 one of the youngest, if not the youngest, known pulsars in the Galaxy.; Comment: Accepted for publication in the MNRAS. 8 pages; For an animation showing the expansion of G21.5-0.9, see http://www.yorku.ca/bartel/G21new.html . (The only change in V3 of the preprint is to add the above url)

## Chandra Observations of the Crab-like Supernova Remnant G21.5-0.9

Slane, Patrick; Chen, Yang; Schulz, Norbert S.; Seward, Frederick; Hughes, John P.; Gaensler, Bryan M.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.4%
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.; Comment: 4 pages, 2 figures, formatted with emulateapj, submitted to ApJL

## Cross-calibration of the X-ray Instruments onboard the Chandra, INTEGRAL, RXTE, Suzaku, Swift, and XMM-Newton Observatories using G21.5-0.9

Tsujimoto, Masahiro; Guainazzi, Matteo; Plucinsky, Paul P.; Beardmore, Andrew P.; Ishida, Manabu; Natalucci, Lorenzo; Posson-Brown, Jennifer L. L.; Read, Andrew M.; Saxton, Richard D.; Shaposhnikov, Nikolai V.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.4%
Context. The Crab nebula has been used as a celestial calibration source of the X-ray flux and spectral shape for many years by X-ray astronomy missions. However, the object is often too bright for current and future missions equipped with instruments with improved sensitivity. Aims. We use G21.5-0.9 as a viable, fainter substitute to the Crab, which is another pulsar-wind nebula with a time-constant powerlaw spectrum with a flux of a few milli Crab in the X-ray band. Using this source, we conduct a cross-calibration study of the instruments onboard currently active observatories: Chandra ACIS, Suzaku XIS, Swift XRT, XMM-Newton EPIC (MOS and pn) for the soft-band, and INTEGRAL IBIS-ISGRI, RXTE PCA, and Suzaku HXD-PIN for the hard band. Methods. We extract spectra from all the instruments and fit them under the same astrophysical assumptions. We compare the spectral parameters of the G21.5-0.9 model: power-law photon index, H-equivalent column density of the interstellar photoelectric absorption, flux in the soft (2-8 keV) or hard (15-50 keV) energy band. Results. We identify the systematic differences in the best-fit parameter values unattributable to the statistical scatter of the data alone. We interpret these differences as due to residual cross-calibration problems. The differences can be as large as 20% and 9% for the soft-band flux and power-law index...

## PSR J1833-1034: Discovery of the Central Young Pulsar in the Supernova Remnant G21.5-0.9

Camilo, F.; Ransom, S. M.; Gaensler, B. M.; Slane, P. O.; Lorimer, D. R.; Reynolds, J.; Manchester, R. N.; Murray, S. S.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We have discovered the pulsar associated with the supernova remnant G21.5-0.9. PSR J1833-1034, with spin period P = 61.8 ms and dispersion measure 169 pc/cc, is very faint, with pulse-averaged flux density of approximately 70 microJy at a frequency of 1.4 GHz, and was first detected in a deep search with the Parkes telescope. Subsequent observations with Parkes and the Green Bank Telescope have confirmed this detection, and yield a period derivative dP/dt = 2.02e-13. These spin parameters imply a characteristic age tau_c = 4.8 kyr and a spin-down luminosity dE/dt = 3.3e37 ergs/s, the latter value exceeded only by the Crab pulsar among the rotation-powered pulsars known in our Galaxy. The pulsar has an unusually steep radio spectrum in the 0.8-2.0 GHz range, with power law index ~3.0, and a narrow single-peaked pulse profile with full-width at half maximum of 0.04P. We have analyzed 350 ks of archival Chandra X-ray Observatory High Resolution Camera (HRC) data, and find a point-like source of luminosity approximately 3e-5dE/dt, offset from the center of an elliptical region of size ~7"x5" and luminosity approximately 1e-3dE/dt within which likely lies the pulsar wind termination shock. We have searched for X-ray pulsations in a 30 ks HRC observation without success...

## Detection of thermal X-ray emission in the halo of the plerionic supernova remnant G21.5-0.9

Bocchino, F.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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The detection of a soft thermal X-ray component in the spectrum of a bright knot in the halo of the plerion G21.5-0.9 is reported. Using a collisional ionization equilibrium model for an hot optically thin plasma, a temperature $kT=0.12-0.24$ kev, a mass of 0.3--1.0 M$_\odot$ and a density of 1.6-6 cm$^{-3}$ is derived. The spectral analysis suggests a possible overabundance of Silicon with respect to the solar value in the knot; if this will be confirmed this object may be a clump of shocked ejecta.; Comment: 6 pages, 4 figures, Adv.Sp.Res. in press, proc of COSPAR Session E1.4 "Young Neutron Stars and Supernova Remnants", http://www.astropa.unipa.it/Library/OAPA_preprints/ns.ps.gz

## ESO 603-G21: A strange polar-ring galaxy

Reshetnikov, V. P.; Faundez-Abans, M.; de Oliveira-Abans, M.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.59%
We present the results of B, V, R surface photometry of ESO603-G21 - a galaxy with a possible polar ring. The morphological and photometric features of this galaxy are discussed. The central round object of the galaxy is rather red and presents a nearly exponential surface brightness distribution. This central structure is surrounded by a blue warped ring or disk. The totality of the observed characteristics (optical and NIR colors, strong color gradients, HI and H_2 content, FIR luminosity and star-formation rate, rotation-curve shape, global mass-to-luminosity ratio, the agreement with the Tully-Fisher relation, etc.) shows that ESO603-G21 is similar to late-type spiral galaxies. We suppose that morphological peculiarities and the possible existence of two large-scale kinematically-decoupled subsystems in ESO603-G21 can be explained as being a result of dissipative merging of two spiral galaxies or as a consequence of a companion accretion onto a pre-existing spiral host.; Comment: 8 pages, Astron. Astrophys, accepted

## The Intriguing Plerionic Supernova Remnant: G21.5-0.9

Safi-Harb, S.; Harrus, I. M.; Petre, R.; Pavlov, G. G.; Koptsevitch, A. B.; Sanwal, D.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.4%
G21.5-0.9 is a plerionic supernova remnant (SNR) whose properties hint at the presence of a pulsar -- yet no pulsations have been found at any wavelength. Early observations with Chandra led to the discovery of an extended component, making the SNR at least twice as big as originally thought. Our analysis indicates that this low-surface brightness extended component is non-thermal. We perform a spatially resolved spectroscopy using a 72 ksec exposure with ACIS-S, and find no evidence of line emission. The 5-arcminute diameter remnant is well fitted with a power law with a photon index steepening from 1.5 (central core) to 2.7 (extended component) and a column density N_H=2.2 10^22 cm^-2. Using a 76 ksec exposure with the HRC, we derive an upper limit of 16% on the pulsed fraction from a putative pulsar. We also infer the parameters of the hidden pulsar' in G21.5-0.9 in comparison with the Crab and 3C 58 pulsars. This remnant remains unique and intriguing since it is, to date, the only candidate whose size is bigger in X-rays than in the radio.; Comment: 4 pages including 2 color figures and a table, newpasp.sty. To Appear in Neutron Stars in Supernova Remnants' (ASP Conference proceedings), eds. P. O. Slane and B. M. Gaensler

## Timing analysis of the core of the Crab-like SNR G21.5-0.9

La Palombara, N.; Mereghetti, S.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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The Crab-like SNR G21.5-0.9 was observed in the X-ray band (0.5-10 keV) by the XMM-Newton satellite for over 100 ks. The large effective area of the EPIC instrument has allowed us to to perform a deep search for pulsations from the central core of G21.5-0.9. No pulsations were found with upper limits on the pulsed fraction between 7.5 % and 40 % (depending on frequency and energy range).; Comment: 3 pages, latex, 2 tables, no figures, accepted for publication by A&A

## The Extended X-ray Halo of the Crab-like SNR G21.5-0.9

Warwick, R. S.; Bernard, J-P.; Bocchino, F.; Decourchelle, A.; Ferrando, P.; Griffiths, R. G.; Haberl, F.; La Palombara, N.; Lumb, D.; Mereghetti, S.; Read, A. M.; Schaudel, D.; Schurch, N.; Tiengo, A.; Willingale, R.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.4%
Recent XMM-Newton observations reveal an extended (150") low-surface brightness X-ray halo in the supernova remnant G21.5-0.9. The near circular symmetry, the lack of any limb brightening and the non-thermal spectral form, all favour an interpretation of this outer halo as an extension of the central synchrotron nebula rather than as a shell formed by the supernova blast wave and ejecta. The X-ray spectrum of the nebula exhibits a marked spectral softening with radius, with the power-law spectral index varying from Gamma = 1.63 +/- 0.04 in the core to Gamma = 2.45 +/- 0.06 at the edge of the halo. Similar spectral trends are seen in other Crab-like remnants and reflect the impact of the synchrotron radiation losses on very high energy electrons as they diffuse out from the inner nebula. A preliminary timing analysis provides no evidence for any pulsed X-ray emission from the core of G21.5-0.9.; Comment: 6 pages. Accepted for publication in the Astronomy and Astrophysics Special Issue on 1st science with XMM-Newton

## The Crab-like Supernova Remnant G21.5-0.9 at Millimeter Wavelengths

Bock, Douglas C. -J.; Wright, Melvyn C. H.; Dickel, John R.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We present a BIMA image of the supernova remnant G21.5-0.9 at 94 GHz with angular resolution 8.6" x 4.5". On scales larger than our synthesized beam, our results do not indicate any radial or local variations in the acceleration or synchrotron loss processes for the relativistic particles emitting at radio wavelengths. However, the FWHM size of the radio remnant is significantly greater than that of the X-ray remnant. Either any low-frequency spectral break is distributed across the remnant, or more probably the break frequency is in fact higher than ~100 GHz.; Comment: 5 pages including 2 figures; ApJL, in press

## The discovery of PSR J1833-1034 : the pulsar associated with the supernova remnant G21.5-0.9

Gupta, Y.; Mitra, D.; Green, D. A.; Acharyya, A.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
27.1%
We report the discovery of a young pulsar associated with the supernova remnant G21.5-0.9, using the Giant Metrewave Radio Telescope (GMRT) located near Pune, India. Discovered at a frequency of 610 MHz, J1833-1034 has a period of 61.86 ms and a period derivative of $2.0 \times 10^{-13}$, making it similar to other known young pulsars. The characteristic age of the pulsar is $\approx 4900$ yr, somewhat higher than estimates for the age of the remnant, but not incompatible with it. The pulsar has a spin-down luminosity of $3.3 \times 10^{37}$ erg s$^{-1}$, which is the second highest amongst all the known Galactic pulsars.; Comment: 5 pages, with 1 figure and 1 table; published in Current Science

## Infrared imaging and polarimetric observations of the pulsar wind nebula in SNR G21.5-0.9

Zajczyk, A.; Gallant, Y. A.; Slane, P.; Reynolds, S. P.; Bandiera, R.; Gouiffès, C.; Floc'h, E. Le; Comerón, F.; Miramond, L. Koch
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
27.4%
We present infrared observations of the supernova remnant G21.5-0.9 with the Very Large Telescope, the Canada-France-Hawaii Telescope and the Spitzer Space Telescope. Using the VLT/ISAAC camera equipped with a narrow-band [FeII] 1.64um filter the entire pulsar wind nebula in SNR G21.5-0.9 was imaged. This led to detection of iron line-emitting material in the shape of a broken ring-like structure following the nebula's edge. The detected emission is limb-brightened. We also detect the compact nebula surrounding PSR J1833-1034, both through imaging with the CFHT/AOB-KIR instrument (K' band) and the IRAC camera (all bands) and also through polarimetric observations performed with VLT/ISAAC (Ks band). The emission from the compact nebula is highly polarised with an average value of the linear polarisation fraction $P_{L}^{avg} \simeq 0.47$, and the swing of the electric vector across the nebula can be observed. The infrared spectrum of the compact nebula can be described as a power law of index $\alpha_{IR} = 0.7 \pm 0.3$, and suggests that the spectrum flattens between the infrared and X-ray bands.; Comment: 11 pages, 13 figures, accepted by A&A; more detailed discussion of the reduction and analysis of the narrow-band imaging data added in Sect. 2.4...

## The nature of the X-ray halo of the plerion G21.5-0.9 unveiled by XMM-Newton and Chandra

Bocchino, F.; van der Swaluw, E.; Chevalier, R.; Bandiera, R.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.4%
The nature of the radio-quiet X-ray halo around the plerionic SNR G21.5-0.9 is under debate. On the basis of spatial and spectral analysis of a large Chandra and XMM-Newton dataset of this source, we have developed a self-consistent scenario which explains all the observational features. We found that the halo is composed by diffuse extended emission due to dust scattering of X-rays from the plerion, by a bright limb which traces particle acceleration in the fast forward shock of the remnant, and by a bright spot (the North Spur'') which may be a knot of ejecta in adiabatic expansion. By applying a model of interaction between the PWN, the SNR and supernova environment, we argue that G21.5-0.9 progenitor may be of Type IIP or Ib/Ic, and that the remnant may be young (200-1000 yr).; Comment: 11 pages, 10 figures, accepted by A&A, also avalaible at http://www.astropa.unipa.it/Library/OAPA_preprints/fb2870.ps.gz

## The Deepest Radio Study of the Pulsar Wind Nebula G21.5-0.9: Still No Evidence for the Supernova Shell

Bietenholz, Michael F.; Matheson, Heather; Safi-Harb, Samar; Brogan, Crystal; Bartel, Norbert
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
27.59%
We report on sensitive new 1.4-GHz VLA radio observations of the pulsar wind nebula G21.5-0.9, powered by PSR J1833-1034, and its environs. Our observations were targeted at searching for the radio counterpart of the shell-like structure seen surrounding the pulsar wind nebula in X-rays. Some such radio emission might be expected as the ejecta from the <~ 1000 yr old supernova expand and interact with the surrounding medium. We find, however, no radio emission from the shell, and can place a conservative 3-sigma upper limit on its 1-GHz surface brightness of 7 x 10^-22 W/m^2/Hz/sr, comparable to the lowest limits obtained for radio emission from shells around other pulsar-wind nebulae. Our widefield radio image also shows the presence of two extended objects of low-surface brightness. We re-examine previous 327-MHz images, on which both the new objects are visible. We identify the first, G21.64-0.84, as a new shell-type supernova remnant, with a diameter of ~13' and an unusual double-shell structure. The second, G21.45-0.59, ~1' in diameter, is likely an HII region.; Comment: 8 Pages, submitted to MNRAS

## The Plerionic Supernova Remnant G21.5-0.9 Powered by PSR J1833-1034: New Spectroscopic and Imaging Results Revealed with the Chandra X-ray Observatory

Matheson, Heather; Safi-Harb, Samar
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
27.71%
(Abridged) In 1999, Chandra revealed a 150"-radius X-ray halo surrounding the 40"-radius PWN G21.5-0.9. A 2005 imaging study showed that the halo is limb-brightened, and suggested this feature is a candidate for the long-sought SNR shell. We present a spectral analysis of G21.5-0.9, using the longest effective observation to date (578.6 ks with ACIS, 278.4 ks with HRC) to study unresolved questions about the spectral nature of remnant features, such as the limb-brightening of the X-ray halo and the bright knot in the northern part of the halo. The Chandra analysis favours the non-thermal interpretation of the limb. Its spectrum is well fit with a power-law model with a photon index $\Gamma$ = 2.13 (1.94-2.33) and a luminosity of L_x (0.5-8 keV) = (2.3 +/- 0.6) x 10^33 erg/s (at an assumed distance of 5.0 kpc). An srcut model was also used to fit the spectrum between radio and X-ray energies. We find that the maximum energy to which electrons are accelerated at the shock ranges from ~60-130 TeV (B/10$\mu$G)^(-1/2), where B is the magnetic field in units of $\mu$G. For the northern knot, we constrain previous models and find that a two-component power-law (or srcut) + pshock model provides an adequate fit, with the pshock model requiring a very low ionization timescale and solar abundances for Mg and Si. Our spectroscopic study of J1833-1034...

## The X-ray Halo of G21.5-0.9

Bandiera, R.; Bocchino, F.