Hubble Space Telescope Nondetection of PSR J2144-3933: The Coldest Known Neutron Star
Abstract
We report nondetections of the ∼3 × 108 yr old, slow, isolated, rotation-powered pulsar PSR J2144-3933 in observations with the Hubble Space Telescope in one optical band (F475X) and two far-ultraviolet bands (F125LP and F140LP), yielding upper bounds {F}{{F}475{{X}}}< 22.7 {nJy}, {F}{{F}125{LP}}< 5.9 {nJy}, and {F}{{F}140{LP}}< 19.5 {nJy}, at the pivot wavelengths 4940 Å, 1438 Å and 1528 Å, respectively. Assuming a blackbody spectrum, we deduce a conservative upper bound on the surface (unredshifted) temperature of the pulsar of T< 42,000 K. This makes PSR J2144-3933 the coldest known neutron star, allowing us to study thermal evolution models of old neutron stars. This temperature is consistent with models with either direct or modified Urca reactions including rotochemical heating, and, considering frictional heating from the motion of neutron vortex lines, it puts an upper bound on the excess angular momentum in the neutron superfluid, J < 1044 erg s.
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 #13783.- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2019
- DOI:
- 10.3847/1538-4357/ab0f38
- arXiv:
- arXiv:1901.07998
- Bibcode:
- 2019ApJ...874..175G
- Keywords:
-
- pulsars: individual: PSR J2144–3933;
- stars: neutron;
- ultraviolet: stars;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 5 Figure. 3 Tables. Accepted for publication in ApJ