PI: David Kaplan, University of Wisconsin at Milwaukee, firstname.lastname@example.org
Address: 1900 E. Kenwood Blvd, Milwaukee, WI 53211, USA
CoI: Varun Bhalerao, The Inter-University Centre for Astronomy and Astrophysics
CoI: Marten van Kerkwijk, University of Toronto
CoI: Kevin Stovall, University of Texas at Brownsville
Title: Understanding the Strange Metal-Rich Companion to PSR J1816
Abstract: We discovered the eclipsing millisecond pulsar J1816+4510 in a radio survey toward an unidentified Fermi source. Since then we have identified its companion in optical/ultraviolet data, and its multi-wavelength properties place it apart from all other sources: we see strong absorption from hydrogen, helium, and metals, but while significantly larger than a white dwarf it is much smaller than a B star. The companion could be evolving into a helium white dwarf, although the mass loss required for the radio eclipses is surprising, and the (a priori) likelihood of finding an object in this phase is rather small. Independently, though, PSR J1816 appears to be a unique transition object, with implications for studies of white dwarf evolution, relativistic winds, and neutron star masses. We request Gemini GMOS-N observations of this system. With 3 blocks of 3 hours in relatively poor conditions we can measure the orbit of the companion and hence measure the masses, and greatly improve the abundances. This will be a first crucial step toward detailed understanding of the system.
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