2002/05/24 by J. P. Halpern, E. V. Gotthelf, N. Mirabal +1 · 2 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Black-body radiation #Egret #Gamma ray #Hubble space telescope #Neutron star #Optics #Physics #Pulsar #Pulsars and Gravitational Waves Research #Radiation #Space Telescope Imaging Spectrograph #Stars #Telescope #astro-ph
paper · pdf · doi:10.1086/341967
4 pages, 4 figures, accepted for publication in ApJ Letters
arxiv created 2002/05/24 · openalex publication_date 2002/07/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We describe Chandra , Hubble Space Telescope ( HST ), and radio observations that reveal a radio-quiet but magnetospherically active neutron star in the error circle of the high-energy γ-ray source 3EG J1835+5918, the brightest of the unidentified EGRET sources at high Galactic latitude. A Chandra ACIS-S spectrum of the ultrasoft X-ray source RX J1836.2+5925, suggested by Mirabal & Halpern as the neutron star counterpart of 3EG J1835+5918, requires two components: a blackbody of T ∞ ≈ 3 × 10 5 K and a hard tail that can be parameterized as a power law of photon index Γ ≈ 2. An upper limit of d < 800 pc can be derived from the blackbody fit under an assumption of R ∞ = 10 km. Deep optical imaging with the HST Space Telescope Imaging Spectrograph CCD failed to detect this source to a limit of V > 28.5, and thus f X / f V > 6000 and d > 250 pc assuming the X-ray-fitted temperature for the full surface. Repeated observations with the 76 m Lovell telescope at Jodrell Bank place an upper limit of less than 0.1 mJy on the flux density at 1400 MHz for a pulsar with P > 0.1 s and less than 0.25 mJy for a ~10 ms pulsar at the location of RX J1836.2+5925. All of this evidence points to an older, possibly more distant version of the highly efficient γ-ray pulsar Geminga as the origin of the γ-rays from 3EG J1835+5918.