Accepted Cycle 16 Observing Proposals

GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number	Subject Category	PI Name	Type	Time (ks)	Title
16910519	GALACTIC DIFFUSE EMISSION AND SURVEYS	Clavel	GO	480	Characterizing past outbursts from Sagittarius A*
16910568	GALACTIC DIFFUSE EMISSION AND SURVEYS	Tomsick	TOO	20	Localizing NuSTAR-Discovered Sources in the Galactic Plane
16910752	GALACTIC DIFFUSE EMISSION AND SURVEYS	Slavin	GO	150	The Local Leo Cold Cloud: Separating Solar Wind Charge Exchange from Local Bubble X-ray Emission
16910820	GALACTIC DIFFUSE EMISSION AND SURVEYS	Tomsick	GO	29	Follow-up of Serendipitous NuSTAR Sources in the Galactic Plane

Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 16910519

Title: Characterizing past outbursts from Sagittarius A*

Type: GO Total Time (ks): 480

PI Name: Maica Clavel

Abstract: We propose a Chandra three-cycle observation for a total of 480 ks to follow the echo of Sgr A*'s past flares in the molecular clouds of the region near Sgr A*. This observation with Chandra's unequaled spatial resolution is required to advance the characterization of both the temporal and spatial variations occurring in the region. It will permit us to significantly extend our recent analysis which suggests that at least two distinct events are propagating through the Galaxy's central molecular zone. The objective of this project is to reconstruct Sgr A*'s past lightcurve by measuring the intrinsic duration and luminosity of the distinct events. The additional time baseline will bring us closer to conclusively establishing the mechanisms at the origin of these past events.

R.A.	Dec.	Target Name	Det.	Grating	Exp. Time (ks)
+17:46:14.10	-28:54:52.50	Sgr A complex 1	ACIS-I	None	240.0
+17:46:09.60	-28:53:43.80	Sgr A complex 2	ACIS-I	None	240.0

Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 16910568

Title: Localizing NuSTAR-Discovered Sources in the Galactic Plane

Type: TOO Total Time (ks): 20

PI Name: John Tomsick

Abstract: The NuSTAR satellite operates in the 3-79 keV band with unprecedented angular resolution for a hard X-ray instrument. In addition to improved imaging and better source localizations, this leads to detection sensitivities that are orders of magnitude lower than previous hard X-ray satellites, and a main NuSTAR goal is to study populations of >10 keV sources in the Galaxy. Despite the improvement in source localization, the NuSTAR positions are still not sufficient for a unique identification of counterparts at other wavelengths (e.g., near-IR) especially in the Galactic Plane. Thus, we propose a Chandra TOO program to follow-up future sources discovered by NuSTAR in order to obtain a sub-arcsecond position and determine their nature.

R.A.	Dec.	Target Name	Det.	Grating	Exp. Time (ks)
		NuSTAR Transient #1	ACIS-S	None	10.0
		NuSTAR Transient #2	ACIS-S	None	10.0

Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 16910752

Title: The Local Leo Cold Cloud: Separating Solar Wind Charge Exchange from Local Bubble X-ray Emission

Type: GO Total Time (ks): 150

PI Name: Jonathan Slavin

Abstract: The Local Leo Cold Cloud is a dense and cold (T ~ 20 K) cloud that lies within 24 pc of the Sun, well within the Local Bubble. The cloud has been thoroughly mapped in HI and has column densities ranging up to 1.E20 cm^-2, thus making it a prime candidate to make shadows in the diffuse X-ray emission coming from more distant regions of the Local Bubble and the Galactic halo. In addition, the cloud lies near the ecliptic plane which allows for viewing it while looking through the enhanced region of solar wind charge exchange emission known as the helium focusing cone. We intend to exploit these characteristic of the cloud by observing toward it two times, once through the focusing cone and once not. In this way we aim to disentangle distant diffuse emission and heliospheric X-rays.

R.A.	Dec.	Target Name	Det.	Grating	Exp. Time (ks)
+09:42:42.00	+12:24:28.80	Local Leo Cold Cloud	ACIS-S	None	150.0

Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 16910820

Title: Follow-up of Serendipitous NuSTAR Sources in the Galactic Plane

Type: GO Total Time (ks): 29

PI Name: John Tomsick

Abstract: In order to study the populations of hard (3-79 keV) sources, we have carried out a search of NuSTAR observations that have been carried out during the first 1.5 years of the mission. Due to the sensitivity of NuSTAR, this is extending to lower flux levels than previous surveys. Once a serendipitous NuSTAR source is found, we are obtaining optical/NIR spectra for identifications. For high Galactic latitudes, we have been able to identify unique counterparts. However, close to the Galactic plane, source confusion is an issue. We have selected 4 serendips within 12 degrees of the Galactic Plane, which have multiple candidate counterparts. We propose Chandra observations of these serendips to localize the sources and to compare their fluxes to archival soft X-ray measurements.

R.A.	Dec.	Target Name	Det.	Grating	Exp. Time (ks)
+20:24:21.70	+33:50:51.00	3XMM J202421.7+335050	ACIS-S	None	13.0
+14:54:40.20	-51:35:18.60	Swift J145440.2-513518	ACIS-S	None	5.0
+17:28:05.70	-14:21:09.30	3XMM J172805.7-142109	ACIS-S	None	5.0
+17:27:51.40	-14:14:39.50	3XMM J172751.4-141439	ACIS-S	None	6.0

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