Thermal and nonthermal emission in the optical-UV spectrum of PSR B0950+08

Abstract

Based on recent Hubble Space Telescope (HST) observations in far-UV and groundbased observations in optical bands, Pavlov and colleagues have revealed a thermal component in the spectrum of the old pulsar B0950+08 (spin-down age 17.5 Myr) and estimated a neutron star (NS) surface temperature of $(1$--$3)\times 10^5$ K. Our new HST observations in the optical have allowed us to resolve the pulsar from a close-by galaxy and measure the optical fluxes more accurately. Using the newly measured fluxes and a new calibration of the HST's far-UV detector, we fit the optical-UV pulsar's spectrum with a model that consists of a nonthermal power-law ($f_{\nu }\propto {\nu }^{\alpha }$) and a thermal blackbody components. We obtained the spectral slope $\alpha =-0.3\pm 0.3$, considerably flatter than found from groundbased observations, and the best-fit temperature in the range of $(6$--$12)\times 10^4$ K (as seen by a distant observer), depending on interstellar extinction and NS radius. The temperature is lower than reported previously, but still much higher than predicted by NS passive cooling scenarios for such an old pulsar. This means that some heating mechanisms operate in NSs, e.g., caused by interaction of the faster rotating neutron superfluid with the slower rotating normal matter in the inner crust of the NS.

10 pages, 3 figures, 3 tables. Accepted to ApJ

References in corpus (5)

• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• Creation of magnetic spots at the neutron star surface
• Hubble Space Telescope non-detection of PSR J2144-3933: the coldest known neutron star
• Magnetic Axis Drift and Magnetic Spot Formation in Neutron Stars with Toroidal Fields
• Old but still warm: Far-UV detection of PSR B0950+08

Cited by in corpus (8)

• Capture of Electroweak Multiplet Dark Matter in Neutron Stars
• On the Peculiar Rotational Evolution of PSR B0950+08
• Timing and Evolution of PSR B0950+08
• X-ray and near-infrared observations of the middle-aged pulsar B1055-52, its multiwavelength spectrum, and proper motion
• The middle-aged pulsar PSR J1741-2054 and its bow-shock nebula in far ultraviolet
• Axion Emission from Proton Cooper Pairs in Neutron Stars
• Initial periods and magnetic fields of neutron stars
• Neutron star heating vs. HST observations