The Nearby Neutron Star RX J0720.4-3125 from Radio to X-rays

Abstract

We present radio, optical, ultraviolet, and X-ray observations of the isolated, thermally-emitting neutron star RX J0720.4-3125 using the Parkes radio telescope, the Very Large Array, the Hubble Space Telescope, and the Chandra X-ray Observatory. From these data we show that the optical/UV spectrum of RX J0720.4-3125 is not well fit by a Rayleigh-Jeans tail as previously thought, but is instead best fit by either a single non-thermal power-law or a combination of a Rayleigh-Jeans tail and a non-thermal power-law. Taken together with the X-ray spectrum, we find the best model for RX J0720.4-3125 to be two blackbodies plus a power-law, with the cool blackbody implying a radius of 11-13 km at an assumed distance of 300 pc. This is similar to many middle aged (10^{5-6} yr) radio pulsars such as PSR B0656+14, evidence supporting the hypothesis that RX J0720.4-3125 is likely to be an off-beam radio pulsar. The radio data limit the flux at 1.4 GHz to be <0.24 mJy, or a luminosity limit of 4*pi*d^2*F < 3e25*d_300^2 ergs/s, and we see no sign of extended nebulosity, consistent with expectations for a pulsar like RX J0720.4-3125.

13 pages, 9 figures. Uses emulateapj5.sty and onecolfloat5.sty. Accepted for publication in ApJ

References in corpus (3)

• RX J1856-3754: Evidence for a Stiff EOS
• A Probable Optical Counterpart for the Isolated Neutron Star RX J1308.6+2127
• Subaru optical observations of the old pulsar PSR B0950+08

Cited by in corpus (51)

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• A phase-dependent absorption line in the spectrum of the X-ray pulsar RX J0720.4-3125
• Constraining the Spin-down of the Nearby Isolated Neutron Star RX J2143.0+0654
• An X-ray Search for Compact Central Sources in Supernova Remnants I: SNRs G093.3+6.9, G315.4-2.3, G084.2+0.8, & G127.1+0.5
• Constraining the Spin-down of the Nearby Isolated Neutron Star RX J0806.4-4123, and Implications for the Population of Nearby Neutron Stars
• A Coherent Timing Solution for the Nearby Isolated Neutron Star RX J0720.4-3125
• A Coherent Timing Solution for the Nearby Isolated Neutron Star RX J1308.6+2127/RBS 1223
• Long-term variability in the X-ray emission of RX J0720.4-3125
• New Optical/UV Counterparts and the Spectral Energy Distributions of Nearby, Thermally Emitting, Isolated Neutron Stars
• The Distance to the Isolated Neutron Star RX J0720.4-3125
• The origin of RXJ1856.5-3754 and RXJ0720.4-3125 -- updated using new parallax measurements
• Cooling of Small and Massive Hyperonic Stars
• The proper motion of the isolated neutron star RX J1605.3+3249
• The Optical Counterpart of the Isolated Neutron Star RX J1605.3+3249
• Constraining Superfluidity in Dense Matter from the Cooling of Isolated Neutron Stars
• Models of magnetized neutron star atmospheres: thin atmospheres and partially ionized hydrogen atmospheres with vacuum polarization
• A self-consistent model of isolated neutron stars: the case of the X-ray pulsar RX J0720.4-3125
• The continued spectral evolution of the neutron star RX J0720.4-3125
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• Cooling Theory Faced with Old Warm Neutron Stars: Role of Non-Equilibrium Processes with Proton and Neutron Gaps
• Timing Analysis of the Isolated Neutron Star RX J0720.4-3125 Revisited
• XMM-Newton RGS spectrum of RX J0720.4-3125: An absorption feature at 0.57 keV
• Hard X-ray Excess from the Magnificent Seven Neutron Stars
• Long-term evolution of dim isolated neutron stars
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• The continued spectral and temporal evolution of RX J0720.4-3125
• An Optical Counterpart Candidate for the Isolated Neutron Star RBS1774
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• Updated phase coherent timing solution of the isolated neutron star RX J0720.4-3125 using recent XMM-Newton and Chandra observations
• Models of magnetized neutron star atmospheres
• New photometry and astrometry of the isolated neutron star RX J0720-3125 using recent VLT/FORS observations
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