X-ray observations of the supernova remnant W44

Smith, A.; Jones, L. R.; Watson, M. G.; Willingale, R.; Wood, Norman B.; Seward, F. D.

doi:10.1093/mnras/217.1.99

Cited by 25 publications

(26 citation statements)

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“…For example, the 267 ms radio pulsar PSR B 1853+01 associated with the SNR W 44 (Wolszczan et al 1991) has almost the same spin-down luminosity ( 4 × 10 35 erg s −1 ) as that derived above for the source N, while the characteristic age of the pulsar ( 2 × 10 4 yr; consistent with a range of ages derived for W 44 using the standard Sedov-Taylor model, see Smith et al 1985) points to its relative youth. On the other hand, the pulsar PSR B 1853+01 could be much older if its high spindown rate (Ṗ 0.2 × 10 −12 s s −1 ) is connected to the interaction between the pulsar's magnetosphere and the dense circumstellar matter 2 (cf.…”

Section: Power Law Modelsupporting

confidence: 73%

Point X-ray sources in the SNR G 315.4-2.30 (MSH 14-63, RCW 86)

Gvaramadze

Vikhlinin

2003

A&A

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Abstract.We report the results of a search for a point X-ray source (stellar remnant) in the southwest protrusion of the supernova remnant G 315.4−2.30 (MSH 14−63, RCW 86) using the archival data of the Chandra X-ray Observatory. The search was motivated by a hypothesis that G 315.4−2.30 is the result of an off-centered cavity supernova explosion of a moving massive star, which ended its evolution just near the edge of the main-sequence wind-driven bubble. This hypothesis implies that the southwest protrusion in G 315.4−2.30 is the remainder of a pre-existing bow shock-like structure created by the interaction of the supernova progenitor's wind with the interstellar medium and that the actual location of the supernova blast center is near the center of this hemispherical structure. We have discovered two point X-ray sources in the "proper" place. One of the sources has an optical counterpart with the photographic magnitude 13.38 ± 0.40, while the spectrum of the source can be fitted with an optically thin plasma model. We interpret this source as a foreground active star of late spectral type. The second source has no optical counterpart to a limiting magnitude ∼21. The spectrum of this source can be fitted almost equally well with several simple models (power law: photon index = 1.87; two-temperature blackbody: kT 1 = 0.11 keV, R 1 = 2.34 km and kT 2 = 0.71 keV, R 2 = 0.06 km; blackbody plus power law: kT = 0.07 keV, photon index = 2.3). We interpret this source as a candidate stellar remnant (neutron star), while the photon index and non-thermal luminosity of the source (almost the same as those of the Vela pulsar and the recently discovered pulsar PSR J 0205+6449 in the supernova remnant 3C 58) suggest that it can be a young "ordinary" pulsar.

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Section: Power Law Modelsupporting

confidence: 73%

Point X-ray sources in the SNR G 315.4-2.30 (MSH 14-63, RCW 86)

Gvaramadze

Vikhlinin

2003

A&A

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“…The X-ray emission from W44 has been investigated using the Einstein, EXOSAT, ROSAT, ASCA, and Chandra telescopes (Smith et al 1985;Jones et al 1993;Rho et al 1994;Harrus et al 1996;Shelton et al 2004). In Fig.…”

Section: Radio and X-ray Emissionmentioning

confidence: 99%

The low-frequency radio emission and spectrum of the extended SNR W44: new VLA observations at 74 and 324 MHz

Castelletti

Dubner

Brogan

et al. 2007

A&A

108

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Aims. We present new Very Large Array (VLA) radio images at 74 and 324 MHz of the SNR W44. The VLA images, obtained with unprecedented angular resolution and sensitivity for such low frequencies (HPBW 37 at 74 MHz, and 13 at 324 MHz), have been used in combination with existing 1442 MHz radio data, Spitzer IR data, and ROSAT and Chandra X-ray data to investigate morphological and spectral continuum properties of this SNR. Methods. The observations were carried out with the VLA simultaneously at 74 and 324 MHz in the A and B configurations and at 324 MHz in the C and D configurations. The radio continuum spectral index distribution was derived through direct comparison of the combined data at 74, 324, and 1442 MHz. In addition, to isolate and identify different spectral components, tomographic spectral analysis was performed. Results. We measured total flux densities of 634 Jy and 411 Jy at 74 and 324 MHz, respectively, for W44, and from a careful assessment of published values between 22 and 10 700 MHz derived a global integrated continuum spectral index α = −0.37 ± 0.02. The spatially resolved spectral index study revealed that the bright filaments, both around and across the SNR, have a straight spectrum between 74 and 1442 MHz, with α ∼ −0.5, with two clear exceptions: a short portion of the SNR limb to the southeast, with α varying between 0 and +0.4 and a bright arc to the west where the spectrum breaks around 300 MHz and becomes concave down. We conclude that at the shell and along the internal filaments, the electrons responsible for the synchrotron emission were accelerated at the shock according to a simple diffusive shock model. The positive spectrum corresponds to a location where the SN shock is running into a molecular cloud and the line of sight intersects the photo dissociation region of an HII region and a young stellar object is present. Such spectral inversion is a classic signature of thermal absorption, either from ionized gas in the postshock region, from the HII region itself, or both. The curved spectrum on the westernmost bright arc is explained as the consequence of strong post-shock densities and enhanced magnetic fields after the interaction of the SN shock with a coincident molecular cloud. No spectral index trace was found indicating any connection between the associated pulsar PSR B1953+0.1 and the surrounding shell, nor between the SNR and the 3EG 1853+0114 γ-ray source proposed to be associated with W44. The comparison of the 324 MHz image with a 4.5 µm IR image obtained with Spitzer underscored an impressive correspondence between emission both to the north and west sides of W44, while the comparison with ROSAT and Chandra images confirm that the synchrotron radio emission surrounds the thermal X-ray radiation.

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“…The ROSAT PSPC (Rho et al 1994) and Einstein IPC (Smith et al 1985) X-ray maps show centrally concentrated thermal emission whose dim outer edge extends as far as the radio-continuum shell in the north, south, and west (Rho et al 1994). The X-rayÈemitting region may similarly extend to the eastern edge where it is absorbed by a foreground molecular cloud that covers irregularly from a(1950)018h53m40s to 18h54m55s and d(1950)001¡10@ to 01¡20@ (Wootten 1977).…”

Section: X-ray Observationsmentioning

confidence: 99%

“…Working from the Ðtted results is somewhat misleading, however, as Figure 7 of Rho et al (1994) clearly shows that the spectral hardness is signiÐcantly greater in the center, where the X-rays are brightest. Smith et al (1985), Jones et al (1993), andRho et al (1994) calculated the X-ray luminosity for the remnant interior from the Einstein, EXOSAT , and ROSAT data, respectively. Their estimates should be reduced by about 25%È30% at our revised distance.…”

Section: X-ray Observationsmentioning

confidence: 99%

Modeling W44 as a Supernova Remnant in a Density Gradient with a Partially Formed Dense Shell and Thermal Conduction in the Hot Interior. I. The Analytical Model

Cox

Shelton

Maciejewski

et al. 1999

ApJ

163

222

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We show that many observations of W44, a supernova remnant in the Galactic plane at a distance of about 2500 pc, are remarkably consistent with the simplest realistic model. The model remnant is evolving in a smooth ambient medium of fairly high density, about 6 cm~3 on average, with a substantial density gradient. At the observed time it has an age of about 20,000 yr, consistent with the age of the associated pulsar, and a radius of 11È13 pc. Over most of the outer surface, radiative cooling has become important in the postshock gas ; on the denser end there has been sufficient compression of the cooled gas to develop a very thin dense half-shell of about 450 supported against further compression by M _ , nonthermal pressure. The half-shell has an expansion velocity of about 150 km s~1 and is bounded on the outer surface by a radiative shock with that speed. The deep interior of the remnant has a substantial and fairly uniform pressure, as expected from even highly idealized adiabatic models ; our model, however, is never adiabatic. Thermal conduction, while the remnant is young and hot, reduces the need for expansion cooling and prevents formation of the intensely vacuous cavity characteristic of adiabatic evolution. It radically alters the interior structure from what one might expect from familiarity with the Sedov solution. At the time of observation, the temperature in the center is about 6 ] 106 K, the density about 1 cm~3. The temperature decreases gradually away from the center, while the density rises. Farther out, where cooling is becoming important, the pressure drops precipitously, and the temperature in the denser gas there is quite low. We provide several analytic tools for the assembly of models of this type. We review the early evolution and shell formation analyses and their generalizations to evolution in a density gradient. We also calculate the density and temperature that should be present in the hot interior of a remnant with thermal conduction. We supply the van der Laan mechanism in a particularly useful form for the calculation of radio continuum from radiative remnants. Finally, we estimate the optical emission that should be present from Ñuorescence of UV light, emitted by the forming shell and the radiative shock and absorbed in the cold shell and the ambient medium, and the associated 63 km [O I] emission. Both are in agreement with the intensity and spatial structures found in recent observations. Neither requires interaction with a dense molecular cloud for its generation. We calculate the gamma rays that should be emitted by cosmic-ray electrons and ions in the shell, interacting with the cold material, and Ðnd each capable of generating about 25% of the Ñux reported by EGRET for the vicinity.

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X-ray observations of the supernova remnant W44

Cited by 25 publications

References 0 publications

Point X-ray sources in the SNR G 315.4-2.30 (MSH 14-63, RCW 86)

Point X-ray sources in the SNR G 315.4-2.30 (MSH 14-63, RCW 86)

The low-frequency radio emission and spectrum of the extended SNR W44: new VLA observations at 74 and 324 MHz

Modeling W44 as a Supernova Remnant in a Density Gradient with a Partially Formed Dense Shell and Thermal Conduction in the Hot Interior. I. The Analytical Model

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