Accepted Cycle 15 Observing Proposals

GALACTIC DIFFUSE EMISSION & SURVEYS

Proposal Number	Subject Category	PI Name	Type	Time (ks)	Title
15910352	GALACTIC DIFFUSE EMISSION AND SURVEYS	Mori	GO	24	Chandra Studies of Unidentified X-ray Sources in the Galactic Bulge
15910500	GALACTIC DIFFUSE EMISSION AND SURVEYS	Kobulnicky	GO	25	PROBING THE ENERGY THRESHOLD FOR TRIGGERED STAR FORMATION
15910506	GALACTIC DIFFUSE EMISSION AND SURVEYS	Wang	GO	60	An X-ray View of Hypervelocity Star HVS5
15910711	GALACTIC DIFFUSE EMISSION AND SURVEYS	Tomsick	TOO	20	Localizing NuSTAR-Discovered Sources in the Galactic Plane
15910826	GALACTIC DIFFUSE EMISSION AND SURVEYS	Soldi	GO	100	The Sgr C complex: a cosmic ray dominated region?

Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 15910352

Title: Chandra Studies of Unidentified X-ray Sources in the Galactic Bulge

Type: GO Total Time (ks): 24

PI Name: Hideyuki Mori

We propose to study a complete X-ray sample in the luminosity range of > 10^34 erg s^-1 in the Galactic bulge, including 5 unidentified sources detected in the ROSAT All Sky Survey. Our goal is to obtain a clear picture about X-ray populations in the bulge, by utilizing the excellent Chandra position accuracy leading to unique optical identification together with the X-ray spectral properties. This is a new step toward understanding the formation history of the bulge. Furthermore, because the luminosity range we observe corresponds to a ``missing link'' region ever studied for a neutron star or blackhole X-ray binary, our results are also unique to test accretion disk theories at intermediate mass accretion rates.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
17:08:56.90	-23:59:36.00	1RXS J170856.9-235936	ACIS-S	NONE	7
17:45:59.60	-37:00:55.00	1RXS J174559.6-370055	ACIS-S	NONE	4
18:11:19.40	-27:59:39.00	1RXS J181119.4-275939	ACIS-S	NONE	4
18:23:39.20	-34:54:12.00	1RXS J182339.2-345412	ACIS-S	NONE	2
17:22:31.60	-19:04:22.00	1RXS J172231.6-190422	ACIS-S	NONE	7

Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 15910500

Title: PROBING THE ENERGY THRESHOLD FOR TRIGGERED STAR FORMATION

Type: GO Total Time (ks): 25

PI Name: Chip Kobulnicky

Massive stars may trigger new generations of star formation (SF) in surrounding molecular clouds. The efficiency of triggering imay scale with the ionizing luminosity of the central stars, but there may also be a lower energy threshold. The intermediate-mass SF complex G38.9 offers a nearby and clean sightline to test this idea. The region contains four 0.5-3 Myr interstellar bubbles powered by, at most, a late-O star with N_LyC<10^47 ph/s. We request a 25 ks ACIS-I observation to complete the Spitzer IR YSO census by identifying the diskless young stars and mapping their distribution. Clusters of X-ray active young stars in and around the bubble rims would reveal triggering missed by IR surveys, and their absence would support the claim that triggering has not been effective.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
19:05:55.00	+05:47:48.00	G38.9-0.44	ACIS-I	NONE	25

Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 15910506

Title: An X-ray View of Hypervelocity Star HVS5

Type: GO Total Time (ks): 60

PI Name: Junfeng Wang

Hypervelocity stars (HVSs) are a new class of objects traveling in the Galactic halo at velocities ~400-750 km/s (unbound to the Milky Way), most of which are main sequence B-type stars. We identified an interesting hypervelocity star (HVS5; minimum velocity of 663 km/s in the Galactic rest frame) that shows cometary optical morphology, suggesting a tail behind a fast moving object. We propose a 60 ks Chandra ACIS-S observation of HVS5 to search for X-ray emission from gas swept by the star and shock heated to high temperature. Our goal is to learn about the shock speed and the ambient halo medium in which HVSs are traveling. In the case of non-detection, we can still place constraint on the mass loss rate.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
09:17:59.50	+67:22:38.30	HVS5	ACIS-S	NONE	60

Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 15910711

Title: Localizing NuSTAR-Discovered Sources in the Galactic Plane

Type: TOO Total Time (ks): 20

PI Name: John Tomsick

The NuSTAR satellite launched in 2012 June and operates in the hard X-ray band with unprecedented angular resolution. In addition to improved imaging and better hard X-ray source localizations, this leads to detection sensitivities that are orders of magnitude lower than previous hard X-ray satellites, and a main 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. This TOO proposal is to follow-up future transient or highly variable source discovered by NuSTAR in order to obtain a sub-arcsecond position and determine their nature.

Target Name	Det.	Grating	Exp.Time (ks)
NuSTAR Hard Transient #1	ACIS-S	NONE	5
NuSTAR Hard Transient #2	ACIS-S	NONE	5
NuSTAR Soft Transient #1	ACIS-S	NONE	5
NuSTAR Soft Transient #2	ACIS-S	NONE	5

Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 15910826

Title: The Sgr C complex: a cosmic ray dominated region?

Type: GO Total Time (ks): 100

PI Name: Simona Soldi

We propose a 100 ks Chandra observation of Sgr C to unveil the origin of the Fe Kalpha emission in the region. Different scenarios have been proposed based on cosmic-ray irradiation of the molecular clouds, or on illumination by a past flare of SgrA*. This observation offers the unique opportunity to study the variability of the 6.4 keV emission: stable emission in the vicinity of the supernova remnant G359.41-0.12 would suggest a cosmic ray dominated region. The excellent angular resolution of Chandra will also allow to characterize the apparent interaction of the SNR with dense molecular material, a candidate site for intense cosmic-ray production. Finally, we will be able to study the past emission from SgrA*, analysing the time behaviour of other clouds in the field of view.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
17:44:22.00	-29:24:53.60	Sgr C	ACIS-I	NONE	100

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