Jules P. Halpern Teaching: Fall 2007 e-mail: jules@astro.columbia.edu Telephone: (212) 854-2554

Research Interests:

Pulsars - I am investigating the extreme physical properties of neutron stars through timing and spectroscopy in X-rays and radio. This reveals their strongest magnetic fields, found in Anomalous X-ray Pulsars (AXPs), as well as their weakest, found in Central Compact Objects (CCOs). Monitoring the transient outbursts of AXPs is leading to an understanding of how their enormous magnetic field energy is converted to X-ray luminosity. In contrast, the relatively inconspicuous CCOs seem to have been born with very weak magnetic fields, and not much rotational energy either. This work makes use of the X-ray observatories Chandra, XMM-Newton, and Swift.

Gamma-ray Sources - The elusive unidentified high-energy gamma-ray sources originally discovered by the EGRET experiment on the Compton Gamma-Ray Observatory (CGRO) turn out to be pulsars and pulsar wind nebulae, supernova remnants, and maybe new classes as well. This subject has expanded into the very high-energy regime with the detection of TeV sources in the Galaxy by the ground-based Cerenkov telescopes H.E.S.S., MAGIC, Milagro. and VERITAS, and will literally "take off" with the planned 2008 launch of the Gamma-ray Large Area Space Telescope (GLAST). I will search for and study the counterparts of the gamma-ray sources at other wavelengths.

Background:

Selected Publications:

• "The Next Geminga: Search for Radio and X-ray Pulsations from the Neutron Star Identified with 3EG J1835+5918," J.P. Halpern, F. Camilo, & E.V. Gotthelf, Ap. J. 668, 1154 (2007)
  
• "1E 15470-5408: A Radio-Emitting Magnetar with a Rotation Period of 2 Seconds," F. Camilo, S.M. Ransom, J.P. Halpern, & J. Reynolds, Ap. J. (Letters) 666, L93 (2007)
  
• "X-ray Timing of PSR J1852+0040 in Kesteven 79: Evidence of Neutron Stars Weakly Magnetized at Birth," J.P. Halpern, E.V. Gotthelf, F. Camilo, & F.D. Seward, Ap. J. 665, 1304 (2007)
  
• "Discovery of the Putative Pulsar and Wind Nebula Associated with the TeV Gamma-ray Source HESS J1813-178," D.J. Helfand, E.V. Gotthelf, J.P. Halpern, F. Camilo, D.R. Semler, R.H. Becker, & R.L. White, Ap. J. 665, 1297 (2007)
  
• "Precise Timing of the X-ray Pulsar 1E 1207.4-5209: A Steady Neutron Star Weakly Magnetized at Birth," E.V. Gotthelf & J.P. Halpern, Ap. J. (Letters) 664, L35 (2007)
• More publications . . .