Accepted Cycle 14 Observing Proposals

WD BINARES & CV

Proposal Number	Subject Category	PI Name	Title
14300296	WD BINARIES AND CV	Smith	AG Dra: High-Resolution Spectra of the Brightest Supersoft Source
14300573	WD BINARIES AND CV	Kilic	Extremely Low-Mass White Dwarfs with Neutron Star Companions

Subject Category: WD BINARIES AND CV

Proposal Number: 14300296

Title: AG Dra: High-Resolution Spectra of the Brightest Supersoft Source

PI Name: Randall Smith

Supersoft sources (SSS) are a fundamental type of binary evolution that may be key to understanding Type Ia supernovae, but they remain difficult to study due to their rarity. AG Dra is the brightest SSS with an X-ray spectrum that peaks in the LETG bandpass. Our proposed observation will address the many questions that have arisen about this source based on observations in other bandpasses, including the origin of its high bolometric luminosity and whether or not the soft X-rays arise purely from the photosphere of the white dwarf. By combining LETG and HST STIS spectra, both of which could contain lines from the same ions, we will determine not only the primary emission mechanisms but also the velocities and perhaps origins of these ions.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time
16:01:41.00	+66:48:10.10	AG Dra	HRC-S	LETG	100

Subject Category: WD BINARIES AND CV

Proposal Number: 14300573

Title: Extremely Low-Mass White Dwarfs with Neutron Star Companions

PI Name: Mukremin Kilic

We have recently discovered three remarkable binary systems containing extremely low-mass white dwarfs with unseen massive companions. Based on the mass function alone, there is a 42%-62% chance that the companions are more massive than 1.4 Msun. To distinguish between a neutron star and a massive white dwarf companion, we propose a search for X-ray emission from these three white dwarfs. These three systems have the best chance of containing neutron star companions among the 40+ systems found in the ELM survey. New milli-second pulsars with companions amenable to spectroscopy are of great interest, as they allow for a measurement of the neutron star mass, while ruling out neutron star companions will indicate that these systems are strong candidates for Type Ia supernova progenitors.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time
17:41:40.50	+65:26:38.70	J1741+6526	ACIS-S	NONE	6
07:51:41.20	-01:41:20.90	J0751-0141	ACIS-S	NONE	4

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