Symposium Proceedings

SN, SNR, and Isolated NS


Spectral and Temporal Monitoring of the INS RX J1308.6+2127 with XMM-Newton

Carol Airhart (Dynetics, Inc.) , P.M. Woods (Dynetics, Inc., NSSTC), V. Zavlin (NSSTC, Marshall Space Flight Center), M.H. Finger (NSSTC), D.L. Kaplan (MIT), C. Kouveliotou (NSSTC, Marshall Space Flight Center), G.G. Pavlov (Penn State University)

The isolated neutron star (INS) RX J1308.6+2127 has been observed with Chandra and XMM-Newton several times between 2001 and 2007. The six most recent XMM-Newton observations are part of a monitoring campaign we initiated to study the long-term temporal and spectral properties of INSs. The primary goal of this investigation is to better quantify the similarities and differences between INSs and magnetar candidates (i.e. Anomalous X-ray Pulsars and Soft Gamma Repeaters) in terms of their spectral and temporal variability. Here, we present our analysis of the current data set and show that (i) the energy spectrum is well modeled by a blackbody with two absorption lines, (ii) the spectral parameters do not show significant time variability over the last five years, (iii) the pulse profile is strongly energy dependent, but stationary, and (iv) the pulse frequency evolution is consistent with monotonic spin-down. Our spectral and temporal results are in agreement with earlier analyses by Schwope et al. (2007) and Kaplan & van Kerkwijk (2005), respectively. The inclusion of the new monitoring data provides more precise constraints on both spectral and temporal parameters of this INS. For isolated neutron stars whose X-ray emission is not powered by spin-down (INSs, AXPs and SGRs), RX J1308.6+2127 is among the most stable members.

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Nonthermal Bremsstrahlung vs. Synchrotron Radiation: Cas A

Glenn Allen (MIT) , Stage, M. D. (U. of Mass, Amherst), Houck, J. C. (MIT)

We performed a joint spectral analysis of some Chandra and RXTE data for the supernova remnant Cas A. A 1.1 Ms ACIS data set is used to identify regions dominated by synchrotron radiation. The best-fit spectral models for each of these regions are combined to obtain a composite synchrotron model for the entire remnant. The difference between this model and the observed RXTE flux is fitted with a nonthermal bremsstrahlung model. The results of this analysis can be used to determine (1) the ratio of the synchrotron radiation to nonthermal bremsstrahlung in the RXTE energy band, (2) the shape of the electron spectrum at energies just above the thermal Maxwellian distribution, (3) the fraction of the electrons that are nonthermal and (4) the balance of energy between thermal and nonthermal electrons.

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A search for X-ray counterparts of the millisecond pulsars in the globular cluster M28

Werner Becker (MPE-Garching) , C.Y. Hui, H.H. Huang, Steve Begin (University of British Columbia)

A recent radio survey of globular clusters has increased the number of millisecond pulsars drastically. M28 is now the globular cluster with the third largest population of known pulsars, after Terzan 5 and 47Tuc. This prompted us to revisit the archival Chandra data on M28 to evaluate whether the newly discovered millisecond pulsars find a counterpart among the various X-ray sources detected in M28 previously. The radio position of J1824-2452H is found to be in agreement with the position of CXC 182431-245217 while some faint unresolved X-ray emission near to the center of M28 is found to be coincident with the millisecond pulsars PSR J1824-2452G, J1824-2452J, J1824-2452I and J1824-2452E.

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Doppler Velocities of Knots and Filaments in the SNR N132D

Tracey DeLaney (MIT Kavli Institute) , Dan Dewey (MIT), Claude Canizares (MIT)

The oxygen-rich supernova remnant N132D in the Large Magellanic Cloud was observed with the High Energy Transmission Grating Spectrometer on board the Chandra X-ray Observatory. Individual emission lines of oxygen, neon, magnesium, and silicon are observed and Doppler shifts have been measured. We find Doppler velocities of knots and filaments of only a few hundred km/s supporting previous abundance studies that concluded that the X-ray emission is mostly swept-up ISM and not ejecta.

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X-ray Spectroscopic Diagnosis of a Wind-Collimated Blast Wave and Metal-Rich Ejecta from the 2006 Explosion of RS Ophiuchi

Jeremy Drake (SAO) , J. Martin Laming (NRL), Jan-Uwe Ness (Arizona State), Sumner Starrfield (Arizona State), Salvatore Orlando (Palermo) and the RS Oph Team

Chandra HETG observations of RS Ophiuchi at day 13.9 of the 2006 outburst reveal a rich spectrum of emission lines from abundant ions formed over a wide temperature range (  K) indicative of shock-heating of the circumstellar medium by the expanding blast wave. Lines are asymmetric and strongly broadened ($v\sim 2400$ km s-1 at zero intensity). Using simple analytical model profiles, we show how the lines are shaped by differential absorption in the red giant wind and explosion ejecta, and that shock heating to multi-million degree temperatures appears to have occurred preferentially in the direction perpendicular to the line-of-sight. We conclude that the asymmetric nature of the offset 1/r2 density profile and likely equatorial circumstellar density enhancement in which the explosion occurred is responsible for both the shock collimation and broad range in plasma temperature observed. The ejecta mass deduced from X-ray absorption is much more easily reconciled with the expected mass accretion rate for material enhanced in metals by about an order of magnitude.


Spectral Feature at 3.7 keV in the Slowly Rotating Central Compact Object in RCW 103

Gordon Garmire (Penn State University) , Audrey Garmire (Penn State)

A series of nineteen monitoring observations of the CCO in RCW 103 were carried out from 2000 to 2005. During these observations a large flare was observed to have occurred sometime before 2000 February 8. The following six years of observation revealed a very slow, but steady decline in the source intensity. About half way through the decline a significant absorption line appeared in the spectrum of the source at an energy of about 3.7 keV. It was observed during four of the nineteen observations. The line appears to be rather narrow, but it could be a proton cyclotron line. Another possibility is that it is from an excited state of ionized Calcium in the surrounding nebula. If it is a cyclotron line, it would imply a magnetic field of greater than 10^14 Gauss.

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Observations of pulsar wind nebulae

C.Y. Hui (MPE, Germany) , Werner Becker (MPE, Germany), Hsiu-Hui Huang (MPE, Germany)

In searching for diffuse X-ray emission around a variety of pulsars, we have discovered trail-like nebulae associated with PSRs J2124-3358 and J1509-5850. Examining the diffuse emission, we found that the observed X-rays are non-thermal in nature. Modeling the nebular emission with the one-zone model, we found that the observed X-rays are inline with the emission originating from accelerated particles in the post shock flow. In searching for radio counterparts, we have discovered a radio nebula associated with PSR J1509-5850 which is apparantly longer than its X-ray counterpart. This is consistent with the scenario of sychrotron cooling. The X-ray nebula of PSR J2124-3358 is the first time that extended emission from a solitary millisecond pulsar is detected. In contrast to a typical pulsar wind nebula, the X-ray nebula of PSR J2124-3358 appears to be highly asymmetric and significantly deviated from the direction of the pulsar's velocity.


X-ray observations of the pulsar B1929+10 and its environment

Zdenka Misanovic (Pennstate University) , George Pavlov (Pennstate), Gordon Garmire (Pennstate)

We report on two Chandra observations of B1929+10, which reveal a PWN with a torus bent in the direction opposite to the pulsar's proper motion and possibly a small jet in the immediate vicinity of this 3-Myr-old pulsar. There is also a long tail behind the pulsar, extending up to 2' in Chandra images and 15' in the XMM-Newton data, with a luminosity of 10e30 ergs/s in the 0.3-8 keV band. However, the PWN morphology does not seem to be entirely consistent with the existing MHD simulations for bow-shock PWNe, suggesting that the intrinsic anisotropy of the pulsar wind must be taken into account when modelling such objects. Contrary to previous results, our spectral analysis suggests that, in addition to the magnetospheric emission, there is a strong thermal component ( 40-500f the total emission in the 0.3-10 keV band) in the pulsar's spectrum. The combined Chandra and XMM-Newton data suggest that the thermal emission emerges from a polar cap region with an apparent radius of 30-40 m and a temperature of about 0.3 keV.

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X-ray observations of PSR J1740+1000

Zdenka Misanovic (Pennstate University) , George Pavlov (Pennstate), Oleg Kargaltsev (Pennstate)

Extremely long parsec-scale tails associated with pulsars have been detected in recent X-ray and radio observations. We present XMM-Newton and Chandra observations of the middle-aged pulsar J1740+1000, with a tail extending up to 3 pc. The tail has a relatively hard spectrum with a photon index of 1.4-1.5 and a luminosity of 1-2e30 ergs/s in the 0.3-10 keV band. The pulsar spectrum is best fit by a combination of two black-body models with temperatures of 0.16 and 0.08 keV, and a power-law component with a photon index of 1.4. The X-ray data shows 154-ms sinusoidal-shaped pulsations with the pulsed fraction of 20-30

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The X-ray Spectrum of the Galactic Supernova Remnant RCW 103

Daniel Patnaude (SAO)

I present a spectral analysis of archival observations of the Galactic supernova remnant RCW 103. The X-ray spectrum is dominated by thermal X-ray emission and shows little evidence for a nonthermal synchrotron component. Furthermore, the thermal X-ray emission is dominated by shocked ISM and does not appear to have appreciable emission from the ejecta component.


Synchrotron-Dominated X-ray Emission from the Galactic SNR G1.9+0.3

Stephen Reynolds (North Carolina State University) , K.J. Borkowski (NC State U), U. Hwang (NASA/GSFC), I. Harrus (NASA/GSFC), R. Petre (NASA/GSFC)

The shell supernova remnant G1.9+0.3 has the smallest angular diameter of any Galactic SNR, at about 1.2 arcmin at radio wavelengths (Green 2004). Our 50 ks Chandra observation of G1.9+0.3 shows a complete shell structure with strong bilateral symmetry. The mean diameter is about 100", though fainter extensions on opposite sides extend about 10" further on each side. The azimuthal brightness variations around the shell are quite different from the single bright maximum in radio. The spectrum is featureless and well-described by the exponentially cut off synchrotron model srcut, with a very high absorbing column of (6.0 +/- 0.3) x 10^22 cm^-2. With the radio flux at 1 GHz fixed at 0.9 Jy, we find a spectral index of 0.65 +/- 0.02 and a rolloff frequency of 1.1 (0.5, 2.5) x 10^18 Hz, one of the highest values known. (All errors are 90onfidence intervals.) There are no indications of spectral lines. The high column implies that G1.9+0.3 is at least as far as the Galactic center, and perhaps far across the Galaxy. At 8.5 kpc, the diameter is 4.4 pc, comparable to Kepler's SNR; even at 20 kpc, it would be only half the size of SN 1006. Simple age estimates give values between 200 and 1000 yr. The high rolloff frequency requires shock velocities of several thousand km/s. G1.9+0.3 thus becomes the fourth clear member of the class of Galactic synchrotron-dominated shell supernova remnants.


X-ray emission from the young pulsar J1357-6429 and similar objects

Vyacheslav Zavlin (NASA/MSFC/USRA)

The first Chandra and XMM-Newton observations of the young and energetic pulsar J1357-6429 provided strong indications of a tail-like pulsar-wind nebula associated with this object, as well as pulsations of its X-ray flux with a pulsed fraction above 50

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