We observed PSR J0437-4715 with the FUV-MAMA detector of the Space Telescope Imaging Spectrometer (STIS) to measure the pulsar's spectrum and pulsations. For the first time, UV emission from a millisecond pulsar has been detected. The measured flux, (2.0+/-0.2)×10-15 ergs s-1 cm-2 in the 1150-1700 Å range, corresponds to the luminosity LFUV=(4.7+/-0.5)×1027 ergs s-1, for the distance of 140 pc and negligible interstellar extinction. The shape of the observed spectrum suggests thermal emission from the neutron star surface with a surprisingly high temperature of about 1×105 K, above the upper limit on the surface temperature of the younger ``ordinary'' pulsar J0108-1431. For the few-Gigayear-old J0437-4715, such a temperature requires a heating mechanism to operate. The spectrum of J0437-4715 shows marginal evidence of an emission line at 1372 Å, which might be a gravitationally redshifted Zeeman component of the hydrogen Lyα line in a magnetic field of ~7×108 G. No pulsations are detected, with a 3 σ upper limit of 50% on the pulsed fraction.Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-9098.
The Astrophysical Journal
- Pub Date:
- February 2004
- Stars: Pulsars: Individual: Alphanumeric: PSR J0437-4715;
- Stars: Neutron;
- Ultraviolet: Stars;
- 26 pages, 7 figures, to appear in ApJ, v602, February 10, 2004 issue