Dr. Peter L. Gonthier joined the department in 1983. Since 1992, he mentors students in the Astro Group, which is trying to improve our understanding of the high-energy emission from magnetars. Magnetars are neutron stars that have the strongest magnetic fields in the known universe. In such strong magnetic fields quantum electrodynamics (QED) describes processes believed to be taking place in magnetar magnetospheres like pair production, photon splitting, and Compton scattering. Compton upscattering of the soft X-ray photons from the surface scattering with relativistic electrons and positrons accelerated within the magnetosphere. The upscattering boost the soft photons to higher energies appearing as high-energy tails in the X-ray spectra that have been observed by many magnetars. We are seeking to provide concise analytics of the correct QED spin-dependent and polarization-dependent cross section for the astrophysics community. We are also developing efficient multiprocessing computer codes.

Dr. Gonthier played a key role in getting Hope College in the Michigan Space Grant Consortium (MSGC) in 1994. Hope was the only liberal arts college in the consortium with the 10 big universities in Michigan. He has served as the affiliate representative of Hope in MSCG since then until the present, currently sharing the duties with Dr. Brian Yurk, who will take the reins in 2023.

Dr. Gonthier is a member of the American Astronomical Society (High Energy Astrophysics Division).

Areas of research

• Radio, x-ray and gamma-ray astrophysics
• Neutron stars
• Pulsars

EDUCATION

• Ph.D., nuclear chemistry, Texas A&M University, 1980
• B.A., chemistry, Texas A&M University, College Station, Texas, 1975

Previous positions

• Associate professor, Hope College, 1989–1999
• Interim chairperson of the Hope College Department of Physics, 1991–1992 and 2007–2008
• Guest professor, II Physikalisches Institut, Giessen, Germany, 1990–1991
• Assistant professor, Hope College, 1983–1989
• Visiting assistant professor, Texas A&M University, College Station, Texas, 1981–1983
• Post-doctoral fellow, Max-Planck-Institut für Kernphysik, Heidelberg, Germany, 1980–1981

Selected Publications

Download full citations and a complete list of Dr. Gonthier’s publications and presentations (PDF).

• “Compton scattering in strong magnetic fields: Spin-dependent influences at the cyclotron resonance,” with M.G. Baring, M.T. Eiles, Z. Wadiasingh, C.A. Taylor and C.J. Fitch, Physical Review D, 90, 2014
• “Cooling rates for relativistic electrons undergoing Compton scattering in strong magnetic fields,” with M.G. Baring and Z. Wadiasingh, The Astrophysics Journal, 733, 2011
• “Population Synthesis of Radio and Gamma-ray Millisecond Pulsars from the Galactic Disk,” with S.A. Story and A.K. Harding, The Astrophysics Journal, 671, 2007
• “Spin-Dependent Cyclotron Decay Rates in Strong Magnetic Fields,” with M.G. Baring, and A.K. Harding, The Astrophysics Journal, 630, 2005
• “Radio-loud and radio-quiet, gamma-ray pulsars from the Galaxy and the Gould Belt,” with R. Van Guilder, A.K. Harding, I.A. Grenier and C.A. Perrot, Astrophysics and Space Science, 297, 2005
• “Role of Beam Geometry in Population Statistics and Pulse Profiles of Radio and Gamma-Ray Pulsars,” with R. Van Guilder and A.K. Harding, The Astrophysics Journal, bf 604, 2004
• “Galactic Populations of Radio and Gamma-Ray Pulsars in the Polar Cap Model,” with M.S. Ouellette, J. Berrier, S. OBrien and A.K. Harding, The Astrophysics Journal, 565, 2002
• “Compton Scattering in Ultra-Strong Magnetic Fields: Numerical and Analytical Behavior in the Relativistic Regime,” with A.K. Harding, M.G. Baring, R.M. Costello and C.L. Mercer, The Astrophysics Journal, 540, 2000
• “Photon Splitting Cascades in Gamma-Ray Pulsars and the Spectrum of PSR1509-58,” with A.K. Harding and M.G. Baring, The Astrophysics Journal, 476, 1997
• “General relativistic corrections in the gamma-ray emission from pulsars,” with A. K. Harding, The Astrophysics Journal, 425, 1994

Outside the College

Dr. Gonthier loves to go scuba diving on the island of Cozumel, Mexico, off the coast of the Yucatan peninsula. He was a scuba instructor from 1994 until 2021. He used to co-teach a course in marine biology and biophysics with Dr. Greg Murray, professor of biology. The course was taught in the spring beginning in 2006 and included a volunteer field trip to Cozumel. Dr. Gonthier would certify the students for their scuba open waters. To this day, he continues to go as often as he can.