Accepted Cycle 16 Observing Proposals

WD BINARIES AND CV

Proposal Number	Subject Category	PI Name	Type	Time (ks)	Title
16300107	WD BINARIES AND CV	Kilic	GO	48	Extremely Low-Mass White Dwarfs with Massive Companions
16300574	WD BINARIES AND CV	Karovska	GO	80	The Elusive Soft Emission from Hard X-ray Symbiotic System RT Cru
16300839	WD BINARIES AND CV	Orio	GO	100	V794 Aql: evolution at high mass transfer rate
16300874	WD BINARIES AND CV	Nelson	TOO	100	Probing mass ejection in novae with X-ray grating spectroscopy
16300876	WD BINARIES AND CV	Mukai	GO	20	Is the Nova V2672 Oph a Luminous X-ray Source in Quiescence?
16300891	WD BINARIES AND CV	Sokoloski	GO	150	Mutual influence between the two stars in T Pyxidis

Subject Category: WD BINARIES AND CV

Proposal Number: 16300107

Title: Extremely Low-Mass White Dwarfs with Massive Companions

Type: GO Total Time (ks): 48

PI Name: Mukremin Kilic

Abstract: After spending several dozen nights on the 6.5m MMT and the Kitt Peak 4m telescopes as part of the ELM Survey, we have identified 54 short period binary white dwarf (WD) systems, including half a dozen WDs with massive unseen companions. In cycle 14, we obtained Chandra observations of two of these targets and identified the first progenitors of underluminous supernovae .Ia. Here, we propose to obtain Chandra observations of the three remaining WD binary systems with massive companions. These systems have the best chance of containing neutron star companions among the 54 systems found in our survey, with a 42-65% likelihood of M>1.4 Msun companions. Our proposed three targets will provide an opportunity to study either new WD + NS systems or double WD progenitors of supernovae .Ia and Ia.

R.A.	Dec.	Target Name	Det.	Grating	Exp. Time (ks)
+14:43:42.70	+15:09:38.60	SDSS J144342.74+150938.6	ACIS-S	None	1.3
+21:32:28.40	+07:54:28.20	SDSS J213228.36+075428.2	ACIS-S	None	11.7
+08:11:33.60	+02:25:56.80	SDSS J081133.56+022556.8	ACIS-S	None	35.0

Subject Category: WD BINARIES AND CV

Proposal Number: 16300574

Title: The Elusive Soft Emission from Hard X-ray Symbiotic System RT Cru

Type: GO Total Time (ks): 80

PI Name: Margarita Karovska

Abstract: RT Cru is a fascinating member of a new class of hard X-ray emitting symbiotic binaries showing X-ray emission extending to over 50keV. While its hard X-ray emission has been studied in detail, the soft component of the spectrum, including flares, remains elusive, since previous observations have focused on the high-energy regime. We propose Chandra HRC-S/LETG observations to determine the spatial, spectral, and temporal characteristics of the source of the soft X-ray emission with a goal to establish the origin of the soft component, and determine whether and how it is tied to the hard component. Determining the origin of the soft emission is a crucial piece of the puzzle to understanding the geometry, energetics, and the environment of WD accretion in this class of symbiotic systems.

R.A.	Dec.	Target Name	Det.	Grating	Exp. Time (ks)
+12:34:53.70	-64:33:56.00	RT Cru	HRC-S	LETG	80.0

Subject Category: WD BINARIES AND CV

Proposal Number: 16300839

Title: V794 Aql: evolution at high mass transfer rate

Type: GO Total Time (ks): 100

PI Name: Marina Orio

Abstract: V794 Aql, a VYScl or nova-like star in which a white dwarf, accretes at very high mass transfer rate mdot (~10(-8) solar masses) from a main sequence binary companion. Very few interacting white dwarf binaries show clear physical manifestation of such high mass transfer rate, which is very important to understand how recurrent novae and type I supernovae occur. Periodic "low states" at all wavelengths from optical to X-rays can be explained with a limit cycle that regulates the mdot through a physical mechanisms that could be due to a number of root causes: irradiation induced wind from the secondary and its periodic halt, spots on the secondary, the magnetic field of the WD. We propose to obtain a HETG spectrum that will clarify how these systems evolve.

R.A.	Dec.	Target Name	Det.	Grating	Exp. Time (ks)
+20:17:33.90	-03:39:50.90	V794 Aql	ACIS-S	HETG	100.0

Subject Category: WD BINARIES AND CV

Proposal Number: 16300874

Title: Probing mass ejection in novae with X-ray grating spectroscopy

Type: TOO Total Time (ks): 100

PI Name: Thomas Nelson

Abstract: We request a Chandra target-of-opportunity observation of the next X-ray bright nova discovered in outburst that is visible to the Very Large Array radio observatory. The resulting high resolution X-ray spectra will be used in conjunction with detailed multiwavelength light curves (especially in the radio regime) and photoionization modeling to study the mass ejection process in novae. The X-ray and radio data in tandem will enable us to estimate the mass ejected by the nova, and to characterize the mass loss evolution over the course of the outburst.

R.A.	Dec.	Target Name	Det.	Grating	Exp. Time (ks)
		Bright nova	HRC-S	LETG	100.0

Subject Category: WD BINARIES AND CV

Proposal Number: 16300876

Title: Is the Nova V2672 Oph a Luminous X-ray Source in Quiescence?

Type: GO Total Time (ks): 20

PI Name: Koji Mukai

Abstract: The very fast nova V2672 Oph had one of the shortest decay times (t2=2.3 d) and the broadest emission lines (FWZI up to 12,000 km/s) ever observed in novae. It may well be a recurrent nova with a near Chandrasekhar mass white dwarf. There is also a ROSAT all-sky survey Faint Source Catalog source consistent with its position: if confirmed, V2672 Oph would be only the third nova to have been detected in X-rays before the nova eruption. We therefore propose an ACIS-S imaging observation to provide the precise location, and rough timing and spectral characteristics of the ROSAT source. V2672 Oph may join V2487 Oph and V2491 Cyg as novae with quiescent X-ray luminosities not seen in normal cataclysmic variables.

R.A.	Dec.	Target Name	Det.	Grating	Exp. Time (ks)
+17:38:19.70	-26:44:13.90	V2672 Oph	ACIS-S	None	20.0

Subject Category: WD BINARIES AND CV

Proposal Number: 16300891

Title: Mutual influence between the two stars in T Pyxidis

Type: GO Total Time (ks): 150

PI Name: Jennifer Sokoloski

Abstract: In 2011, the recurrent nova T Pyx erupted for the first time in 45 years, providing the ideal opportunity to determine how the companion star influences, and is influenced by, a nearby nova. Because the ejecta from the 2011 explosion are now large enough and still X-ray bright enough to be detectable, we propose a 150-ks ACIS-S observation to image the young remnant. The orientation of extended X-ray emission with respect to morphological structures detected by HST provides a clear test of the influence of the companion star. Moreover, the X-ray emission from the central binary will reveal the affect of past novae on the accretion flow from the companion. This work has implications for fundamental aspects of novae, binary stellar evolution, and the progenitors of type Ia supernovae.

R.A.	Dec.	Target Name	Det.	Grating	Exp. Time (ks)
+09:04:41.50	-32:22:47.50	T Pyx	ACIS-S	None	150.0

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