http://arxiv.org/abs/1701.00002
We observed a nearby millisecond pulsar J2124–3358 with the {\sl Hubble Space Telescope} in broad far-UV (FUV) and optical filters. The pulsar is detected in both bands with fluxes $F(1250$-$2000\,{\rm \AA})= (2.5\pm 0.3)\times10^{-16}$\,erg\,s$^{-1}$\,cm$^{-2}$ and $F(3800-6000\,{\rm \AA})=(6.4\pm0.4)\times10^{-17}$\,erg\,s$^{-1}$\,cm$^{-2}$, which correspond to luminosities of $\approx 5.8\times 10^{27}$ and $1.4\times 10^{27}$ erg s$^{-1}$, for $d=410$ pc and $E(B-V)=0.03$. The optical-FUV spectrum can be described by a power-law model, $f_\nu\propto \nu^{\alpha}$, with slope $\alpha=0.18$–0.48 for a conservative range of color excess, $E(B-V)=0.01$–0.08. Since a spectral flux rising with frequency is unusual for pulsar magnetospheric emission in this frequency range, it is possible that the spectrum is predominantly magnetospheric (power law with $\alpha <0$) in the optical while it is dominated by thermal emission from the neutron star surface in the FUV. For a neutron star radius of 12 km, the surface temperature would be between $0.5\times 10^5$ and $2.1\times 10^5$ K, for $\alpha$ ranging from $-1$ to 0, $E(B-V)=0.01$–0.08, and $d=340$–500 pc. In addition to the pulsar, the FUV images reveal extended emission spatially coincident with the known H$\alpha$ bow shock, making PSR J2124–3358 the second pulsar (after PSR J0437$-$4715) with a bow shock detected in FUV.
B. Rangelov, G. Pavlov, O. Kargaltsev, et. al.
Tue, 3 Jan 17
52/55
Comments: Accepted to ApJ
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