Accepted Cycle 15 Observing Proposals

BH & NS BINARIES

Proposal Number	Subject Category	PI Name	Type	Time (ks)	Title
15400074	BH AND NS BINARIES	Paizis	TOO	40	INVESTIGATING NEW INTEGRAL SOURCES WITH Chandra
15400089	BH AND NS BINARIES	Pottschmidt	TOO	24	Filling the gap in understanding the wind structure of HDE 226868 /Cyg X-1
15400135	BH AND NS BINARIES	Bogdanov	GO	200	A DEEP SUBARRAY EXPOSURE OF X7 IN 47 TUC: TOWARDS CONSTRAINING NEUTRON STAR STRUCTURE
15400162	BH AND NS BINARIES	Miller	GO	100	Chandra Spectroscopy of a Remarkable Neutron Star
15400216	BH AND NS BINARIES	Degenaar	GO	105	Observing a cooling neutron star crust in Terzan 5
15400240	BH AND NS BINARIES	Chakrabarty	TOO	4	Precise Localization of Transient Low-Mass X-ray Binaries
15400249	BH AND NS BINARIES	Diaz Trigo	TOO	100	A study of the relativistic jet of 4U 1630-47
15400260	BH AND NS BINARIES	Maccarone	GO	150	Searching for a Metallicity Effect in Field X-ray Binaries
15400298	BH AND NS BINARIES	Chomiuk	GO	87	A Black Hole in the Galactic Globular Cluster M62
15400302	BH AND NS BINARIES	Pooley	TOO	45	Transient LMXBs in Globular Clusters
15400308	BH AND NS BINARIES	Chakrabarty	GO	130	LETGS Spectroscopy of the Ultracompact Binary 4U 1626-67
15400315	BH AND NS BINARIES	GRENIER	TOO	30	ToO observation of a bright Galactic transient discovered by Fermi and Swift
15400317	BH AND NS BINARIES	Corbel	TOO	150	X-Ray Jets in Microquasars
15400330	BH AND NS BINARIES	Jonker	GO	13	Does Holmberg II X-1 harbor an intermediate-mass black hole?
15400346	BH AND NS BINARIES	Reig	TOO	450	X-ray pulsars at very low mass accretion rates
15400408	BH AND NS BINARIES	Marshall	GO	150	SS 433 Jet Formation
15400412	BH AND NS BINARIES	Cackett	LP	300	A Definitive Test of Relativistic Disk Lines in Neutron Stars
15400459	BH AND NS BINARIES	Plotkin	GO	26	A mutiwavelength probe of black hole accretion flows in quiescence
15400471	BH AND NS BINARIES	Heida	GO	60	CXOU J122518.6+144545: Type IIn supernova or hyperluminous X-ray source?
15400475	BH AND NS BINARIES	Oskinova	TOO	120	Chandra's study of the slow pulsar SXP1062 associated with a young SNR in the SMC
15400517	BH AND NS BINARIES	Tomsick	GO	50	The Nature of INTEGRAL Sources in the Galactic Plane
15400524	BH AND NS BINARIES	in 't Zand	TOO	100	Search for absorption edges in superexpansion bursts
15400528	BH AND NS BINARIES	Plotkin	TOO	135	Following a black hole X-ray transient as it transitions to quiescence
15400714	BH AND NS BINARIES	Hynes	GO	25	Confirmation of the Symbiotic Nature of CXOGBS J173620.2-293338
15400856	BH AND NS BINARIES	Homan	GO	115	The cooling neutron star in the super-Eddington accretor XTE J1701-462
15400867	BH AND NS BINARIES	Heinz	TOO	180	Turning Down the Noise on Circinus X-1: A Deep Look at the Jets, Shocks, and Lobes at Low Background
15400870	BH AND NS BINARIES	Chakrabarty	TOO	150	Narrow Lines from a Slowly Rotating Neutron Star
15400871	BH AND NS BINARIES	Steiner	GO	150	Confronting IC 10 X-1: Does the Most Massive Stellar Black Hole Also Have the Most Extreme Spin?
15400876	BH AND NS BINARIES	Farrell	GO	40	Resolving a New Hyper-luminous X-ray Source in NGC 1511
15400896	BH AND NS BINARIES	Canizares	GTO/TOO	150	High-resolution X-ray spectroscopy of the X-ray burster and 11 Hz pulsar IGR J17480-2446

Subject Category: BH AND NS BINARIES

Proposal Number: 15400074

Title: INVESTIGATING NEW INTEGRAL SOURCES WITH Chandra

Type: TOO Total Time (ks): 40

PI Name: Adamantia Paizis

We propose to trigger a maximum of 2 Chandra fast (4-15 days) ToO observations on new sources discovered by INTEGRAL. We ask for 20 ksec per observation, using HETGS. The scientific aims are: 1) determine the source position with Chandra unique sub-arcsecond accuracy, which will allow our team to perform source identification and multi-wavelength follow-up observations, crucial in the crowded Galactic plane and center regions; 2) obtain the high resolution HETGS X-ray spectrum, free from pile-up distortions, crucial to determine the nature of the new source. We aim to continue our successful INTEGRAL-Chandra monitoring program begun in Chandra AO 5.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
		New INTEGRAL source 1	ACIS-S	HETG	20
		New INTEGRAL source 2	ACIS-S	HETG	20

Subject Category: BH AND NS BINARIES

Proposal Number: 15400089

Title: Filling the gap in understanding the wind structure of HDE 226868 /Cyg X-1

Type: TOO Total Time (ks): 24

PI Name: Katja Pottschmidt

We propose to observe the BH HMXB system HDE 226868 /Cyg X-1 as a ToO with Chandra-HETGS for 24 ks (corresponding to Delta phi=0.05 in orbital phase) between orbital phases phi=0.25 and phi =0.4. The spectroscopic analysis of the highly photoionized wind during this phase will improve our understanding of the wind, its implications for the accretion flow onto the black hole, and also of the conditions necessary for the formation of a narrow Fe K fluorescence line. In addition, during this phase dipping, which is very prominent at phi=0, is expected to cease. The morphology and spectral signatures of the very last observed dips will constrain the location and kinematics of the wind structures responsible for these absorption events.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
19:58:21.70	+35:12:05.80	Cyg X-1	ACIS-S	HETG	24

Subject Category: BH AND NS BINARIES

Proposal Number: 15400135

Title: A DEEP SUBARRAY EXPOSURE OF X7 IN 47 TUC: TOWARDS CONSTRAINING NEUTRON STAR STRUCTURE

Type: GO Total Time (ks): 200

PI Name: Slavko Bogdanov

X-ray spectroscopic observations of thermally-emitting quiescent low-mass X-ray binaries (qLMXBs) have been used to constrain the neutron star (NS) equation of state (EoS). The qLMXB X7 in 47 Tuc is the best target for constraints of the NSs EoS, due to its known distance, high countrate, and simple single-temperature hydrogen atmosphere spectrum. In our previous 270-ks full-frame ACIS-S observation, X7 suffered from significant pile-up (~15%), degrading the spectrum and introducing large statistical and systematic uncertainties in the measurement. We propose a 200-ks 1/8 subarray ACIS-S exposure in order to minimize the deleterious effects of pile-up, thereby dramatically improving the constraints on the structure of this NS and yielding the best such measurement for any qLMXB.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
00:24:05.40	-72:04:53.20	47 Tuc	ACIS-S	NONE	200

Subject Category: BH AND NS BINARIES

Proposal Number: 15400162

Title: Chandra Spectroscopy of a Remarkable Neutron Star

Type: GO Total Time (ks): 100

PI Name: Jon Miller

IGR J17062-6143 is one of only 5 sources that have displayed a super-expansion burst. This requires a special mode of continuous low-level accretion that allows material to accumulate on the stellar surface, without triggering smaller bursts. Swift spectroscopy of a super-expansion burst in IGR J17062-6143 revealed the only strong detections of atomic emission and absorption lines in a burst observed at CCD or gratings resolution. Whereas atomic features from the stellar surface have not been detected in other neutron stars, the accretion mode in IGR J17062-6143 may provide the right conditions. To search for lines from the surface, and to better understand the nature of low-level accretion, we request a 100 ksec HETGS observation of IGR J17062-6143.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
17:06:13.80	-61:43:44.70	IGR J17062-6143	ACIS-S	HETG	100

Subject Category: BH AND NS BINARIES

Proposal Number: 15400216

Title: Observing a cooling neutron star crust in Terzan 5

Type: GO Total Time (ks): 105

PI Name: Nathalie Degenaar

We propose a 105 ks Chandra observation of the globular cluster Terzan 5, to continue our study of the thermal evolution of the transiently accreting neutron star IGR J17480-2446. Previous Chandra observations have revealed that the crust of the neutron star was severely heated during a 10-week long accretion outburst in 2010, and is currently cooling in quiescence. Monitoring this crustal cooling yields valuable information about the heat generation and thermal transport properties of the neutron star crust. Following the first instance where crust cooling has been observed after a short accretion outburst poses a breakthrough opportunity in neutron star research.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
17:48:05.20	-24:46:47.30	Terzan 5	ACIS-S	NONE	105

Subject Category: BH AND NS BINARIES

Proposal Number: 15400240

Title: Precise Localization of Transient Low-Mass X-ray Binaries

Type: TOO Total Time (ks): 4

PI Name: Deepto Chakrabarty

We propose to observe up to four neutron star or black hole X-ray transients in outburst to obtain accurate source positions, continuing a successful multi-year and multiwavelength program in place since Cycle 6. These positions and their prompt dissemination will allow re-observation of these sources in the X-ray, optical, IR, and radio bands in order to study their quiescent emission and to enable detailed follow-up (e.g., orbital radial velocity spectroscopy). This program will increase the number of accurately positioned X-ray transients, providing a more uniform sample for future studies. We will only trigger our program for sources in crowded or highly obscured fields where a position from another mission (e.g., Swift) is insufficiently precise

Target Name	Det.	Grating	Exp.Time (ks)
X-ray transient 1	ACIS-S	NONE	1
X-ray transient 2	ACIS-S	NONE	1
X-ray transient 3	ACIS-S	NONE	1
X-ray transient 4	ACIS-S	NONE	1

Subject Category: BH AND NS BINARIES

Proposal Number: 15400249

Title: A study of the relativistic jet of 4U 1630-47

Type: TOO Total Time (ks): 100

PI Name: Maria Diaz Trigo

We propose one 100~ks observation of the black hole (BH) low mass X-ray binary (LMXB) 4U 1630-47 in a very high state of accretion. We will investigate the presence of the narrow emission features observed in a recent XMM spectrum of the source that we interpret as Doppler-shifted lines from a relativistic, bipolar jet. Chandra/HETGS spectra have proven invaluable to study the jet in the supercritical accreting source SS 433. The detection of such features in a canonical BH LMXB transient opens a new window for the understanding of jets and launching mechanisms via the detection of baryons, and precise measurements of speed and opening angle of the jet. With simultaneous radio observations we will test models for jet expansion and ejections in transitional states.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
16:34:01.60	-47:23:34.00	4U 1630-47	ACIS-S	HETG	100

Subject Category: BH AND NS BINARIES

Proposal Number: 15400260

Title: Searching for a Metallicity Effect in Field X-ray Binaries

Type: GO Total Time (ks): 150

PI Name: Thomas Maccarone

Recent work has shown a strong color gradient in the halo of NGC 4472, indicating a metallicity which falls off sharply outside a few effective radii. The surface brightness of this region of NGC 4472, while small, is large enough to provide a large sample of stars at low metallicity. This sample can be used to test whether the metallicity effect seen in globular clusters, that metal rich clusters are about 3 times more likely than metal poor clusters to host X-ray binaries, is present in field star populations as well. This can then be used to help distinguish between models where the metallicity effect is due primarily to stellar evolution versus those where it is due primarily or partially to dynamical effects.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
12:29:04.40	+07:49:24.10	NGC 4472 Halo-1	ACIS-I	NONE	30
12:28:45.00	+08:03:48.00	NGC 4472 Halo-2	ACIS-I	NONE	30
12:29:43.20	+08:15:12.30	NGC 4472 Halo-3	ACIS-I	NONE	30
12:30:43.80	+08:05:21.60	NGC 4472 Halo-4	ACIS-I	NONE	30
12:30:14.20	+07:50:00.20	NGC 4472 Halo-5	ACIS-I	NONE	30

Subject Category: BH AND NS BINARIES

Proposal Number: 15400298

Title: A Black Hole in the Galactic Globular Cluster M62

Type: GO Total Time (ks): 87

PI Name: Laura Chomiuk

Following our discovery of the first strong candidate black holes in a Milky Way globular cluster, we pursued additional clusters with the Karl G. Jansky Very Large Array (VLA). We have now discovered a candidate stellar-mass black hole in a second Milky Way globular cluster: M62. This candidate is unique in that, unlike the earlier-discovered sources in M22, it has an associated Chandra X-ray source. We request 87 ksec of Chandra imaging, along with joint VLA observations, to measure simultaneous X-ray and radio luminosities and assess the nature of this candidate. Confirmation of a black hole in M62 constitutes a critical step in establishing a population of black holes in globular clusters and developing a new technique for discovering Galactic black holes.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
17:01:12.80	-30:06:49.40	M62	ACIS-S	NONE	87

Subject Category: BH AND NS BINARIES

Proposal Number: 15400302

Title: Transient LMXBs in Globular Clusters

Type: TOO Total Time (ks): 45

PI Name: David Pooley

Since the discovery of globular cluster LMXBs in the 1970s, it was assumed that there was only one luminous LMXB per cluster. Deep Chandra observations of several globular clusters have revealed that they contain numerous quiescent LMXB systems, any of which could go into outburst. Our observations will determine the precise locations of new outbursts from transient LMXBs in globular clusters, enabling the important study of their quiescent counterparts.

Target Name	Det.	Grating	Exp.Time (ks)
GC Transient 1	ACIS-S	NONE	15
GC Transient 2	ACIS-S	NONE	15
GC Transient 3	ACIS-S	NONE	15

Subject Category: BH AND NS BINARIES

Proposal Number: 15400308

Title: LETGS Spectroscopy of the Ultracompact Binary 4U 1626-67

Type: GO Total Time (ks): 130

PI Name: Deepto Chakrabarty

A strong Ne/O emission line complex near 1 keV gives this object one of the most unusual known LMXB X-ray spectra. The X-ray source recently entered a prolonged, multi-year bright state. We propose to obtain the first LETGS spectrum of this rich line source, in order to search for the predicted X-ray lines of C near 0.3 keV and measure the known lines of Ne and O. We will use these lines to constrain the exotic composition of the WD donor and to explore the ionization and velocity structure of the accretion disk as a function of radius and compare to theoretical predictions.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
16:32:16.70	-67:27:42.00	4U 1626-67	HRC-S	LETG	130

Subject Category: BH AND NS BINARIES

Proposal Number: 15400315

Title: ToO observation of a bright Galactic transient discovered by Fermi and Swift

Type: TOO Total Time (ks): 30

PI Name: Isabelle GRENIER

We propose a TOO observation of one bright Galactic transient detected by the Fermi large area telescope, and followed by a Swift-XRT detection. Our goal is to determine the nature of an event similar to the intense, non-blazar, transient that EGRET has detected near the Galactic plane once in its lifetime. The lack of a radio-loud blazar counterpart and of a spacially coincident X-ray binary indicates either a new manifestation of a non-blazar active galaxy lying behind the Milky Way, capable of producing massive gamma-ray flares, or a new facet of Galactic compact objects. A significant XRT detection of an X-ray counterpart will trigger the proposed 30 ks Chandra observation to locate precisely this counterpart, to constrain the X-ray decay time, and to measure the source spectrum.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
		Fermi Transient	ACIS-S	NONE	30

Subject Category: BH AND NS BINARIES

Proposal Number: 15400317

Title: X-Ray Jets in Microquasars

Type: TOO Total Time (ks): 150

PI Name: Stephane Corbel

We propose Target of Opportunity (ToO) observations for detailed studies of X-ray jets from microquasars. We describe our discovery of radio/X-ray jets in three microquasars, why X-ray jets are probably much more common than previously thought, and transient X-ray jets offer an exciting new way to probe the physics of relativistic jets from black holes. The proposed ToO observations are optimized to discover and study (flux evolution, morphology, SED, proper motion, ...) of new X-ray jets from microquasars, triggered by their detection as radio lobes. This will have implications not only for the study of jets from Galactic X-ray binaries, but also for our understanding of relativistic jets from active galactic nuclei (AGN).

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
		X-ray Jets	ACIS-S	NONE	150

Subject Category: BH AND NS BINARIES

Proposal Number: 15400330

Title: Does Holmberg II X-1 harbor an intermediate-mass black hole?

Type: GO Total Time (ks): 13

PI Name: Peter Jonker

The nature of ULXs remains unclear. The emission of some of these ULXs is shown to be isotropic (not strongly beamed), meaning that either they accrete above the Eddington limit or they harbor intermediate-mass BHs. In the latter case, they are probably accreting in the ULX equivalent of the low-hard state and as such they should fall on the Fundamental Plane of BH activity. We propose to test using a simultaneous Chandra and VLA-A configuration observation if Holmberg II X-1 falls on this Fundamental Plane. If so, it would establish the ULX as a strong IMBH candidate.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
08:19:29.00	+70:42:19.30	Holmberg II X-1	ACIS-S	NONE	13

Subject Category: BH AND NS BINARIES

Proposal Number: 15400346

Title: X-ray pulsars at very low mass accretion rates

Type: TOO Total Time (ks): 450

PI Name: Pablo Reig

Accretion-powered pulsars are predicted to enter a centrifugally inhibited state at low mass accretion rates due to the propeller effect. In this state, accretion is halted. However, three Be/X-ray binaries show pulsations at low luminosities (< 10^{34} erg s^{-1}). At least in one occasion X-ray pulse emission was detected when the reservoir of matter that fuels the X-rays was exhausted. We propose to observe a maximum of two accreting pulsars as ToO (50 ksec each) when mass transfer from the donor has presumably stopped i order to characterise this low-luminosity state and to distinguish between alternative models to accretion.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
01:18:31.90	+63:44:24.00	4U 0115+63	ACIS-S	NONE	50
03:34:59.90	+53:10:23.30	V0332+53	ACIS-S	NONE	50
04:40:59.30	+44:31:49.30	RX J0440.9+4431	ACIS-S	NONE	50
06:58:17.30	-07:12:35.20	XTE J0658-073	ACIS-S	NONE	50
19:45:39.40	+27:21:55.50	XTE J1946+274	ACIS-S	NONE	50
19:49:35.50	+30:12:31.80	KS 1947+300	ACIS-S	NONE	50
20:32:15.30	+37:38:14.90	EXO 2030+375	ACIS-S	NONE	50
20:58:47.50	+41:46:37.30	GRO J2058+42	ACIS-S	NONE	50
21:03:35.70	+45:45:05.50	SAX J2103.5+4545	ACIS-S	NONE	50

Subject Category: BH AND NS BINARIES

Proposal Number: 15400408

Title: SS 433 Jet Formation

Type: GO Total Time (ks): 150

PI Name: Herman Marshall

Our goal is to determine how the SS 433 jets are reoriented. In a 75 ks HETGS data set, we found a Doppler shift change on a time scale of 20 ks, much smaller than the known dynamical times. The shift may have triggered the ejection of a radio-emitting knot. If the rapid changes result from interaction with an accretion disk wind, then we predict that all Doppler shift changes are abrupt, that the jets will shift independently, and that the Doppler shifts would only follow the known periods in a general way. We will test this model with 150 ks of HETGS data and joint VLBA data, so two knot ejections are expected in both jets. This test can only be done with high resolution X-ray spectra because the X-ray emission originates at the base of the jet, unlike the optical and radio emission.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
19:11:49.50	+04:58:58.00	SS 433	ACIS-S	HETG	150

Subject Category: BH AND NS BINARIES

Proposal Number: 15400412

Title: A Definitive Test of Relativistic Disk Lines in Neutron Stars

Type: LP Total Time (ks): 300

PI Name: Edward Cackett

Accretion disks around neutron stars must be truncated at the stellar surface. If neutron star spectra contain relativistic lines from the inner disk, these lines could then give constraints on stellar radii and the neutron star equation of state. Such lines have recently been claimed in many sources. However, other work has brought the nature of these lines into question, largely owing to instrumental effects such as photon pile-up. The resolution of the HETG is ideally suited to testing the nature of such lines, and it is uniquely resistant to photon pile-up when the ACIS array is run in 'CC' mode. As a unified group of six teams, we request a 300 ksec observation of Serpens X-1 to definitively resolve the nature of iron lines in neutron star low-mass X-ray binaries.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
18:39:57.60	+05:02:09.60	Serpens X-1	ACIS-S	HETG	300

Subject Category: BH AND NS BINARIES

Proposal Number: 15400459

Title: A mutiwavelength probe of black hole accretion flows in quiescence

Type: GO Total Time (ks): 26

PI Name: Richard Plotkin

We request coordinated Chandra and Jansky VLA observations of the black hole X-ray binary Swift J1357.2-0933 in quiescence. At a distance of 1.6 kpc, this is the only remaining system, out of three total, with a confirmed black hole for which we can realistically hope to secure simultaneous X-ray and radio detections at highly sub-Eddington accretion rates, thereby probing empirical radio/X-ray correlations for hard state sources to the lowest observable luminosities. Swift J1357.2-0933 is also the only one of these three systems known to once be `radio-underluminous' at higher Eddington ratios. These observations will allow us to place new constraints on accretion flows and their outflows deep in quiescence, and to break some degeneracies between different accretion models.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
13:57:16.90	-09:32:38.90	Swift J1357.2-0933	ACIS-S	NONE	26

Subject Category: BH AND NS BINARIES

Proposal Number: 15400471

Title: CXOU J122518.6+144545: Type IIn supernova or hyperluminous X-ray source?

Type: GO Total Time (ks): 60

PI Name: Marianne Heida

In 2010 we reported the discovery of CXOU J122518.6+144545. A new Chandra observation in 2012 showed that it varies by more than a factor 10 in X-ray flux. This leaves us with two options: we either discovered a rare type IIn SN, or the second most luminous HLX thus far. Deeper Chandra observations combined with a new HST visit will decide between these scenarios. If CXO J1225 was a supernova, with these new data we will be able to identify the progenitor star. This will be only the second type IIn SN for which this is done. If instead the source is an HLX it is a strong candidate to contain an intermediate mass black hole. In this case the new Chandra data will give us information about its variability and the HST image will give us stronger constraints on the size of the optical source.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
12:25:18.60	+14:45:45.70	CXOU J122518.6+144545	ACIS-S	NONE	60

Subject Category: BH AND NS BINARIES

Proposal Number: 15400475

Title: Chandra's study of the slow pulsar SXP1062 associated with a young SNR in the SMC

Type: TOO Total Time (ks): 120

PI Name: Lidia Oskinova

SXP1062 is an exceptional case of a young neutron star with known age in a BeXRB. A unique combination of measured spin period, its derivative, luminosity and young age makes this source a key probe for the physics of accretion and neutron star evolution. All current accretion scenarios encounter major difficulties explaining the properties of this accretion-powered pulsar. This joint Swift and Chandra study will allow us to construct a spin period-luminosity relation as a powerful tool for distinguishing between different accretion and evolution models and thus shed new light on the physics of accreting neutron stars.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
01:27:45.90	-73:32:56.30	SXP 1062	ACIS-I	NONE	120

Subject Category: BH AND NS BINARIES

Proposal Number: 15400517

Title: The Nature of INTEGRAL Sources in the Galactic Plane

Type: GO Total Time (ks): 50

PI Name: John Tomsick

The INTEGRAL satellite is continuing to discover new hard X-ray sources in the Galactic plane. The few arcminute INTEGRAL positions do not allow for identification of these IGR sources at other wavelengths, leaving their nature unclear. Chandra can make a major contribution to studies of IGR sources by localizing the sources to allow for the identification of counterparts and by constraining the soft X-ray spectrum. We propose for relatively short Chandra observations of ten unidentified IGR sources in the Galactic plane. In previous cycles, this program has identified new High-Mass X-ray Binaries with interesting properties, Catalysmic Variables, Supernova Remnants, and Pulsar Wind Nebulae.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
17:16:29.50	-38:02:24.00	IGR J17164-3803	ACIS-I	NONE	5
14:09:05.80	-61:08:31.20	IGR J14091-6108	ACIS-I	NONE	5
15:33:29.50	-54:21:28.80	IGR J15335-5420	ACIS-I	NONE	5
18:38:09.10	-09:24:54.00	IGR J18381-0924	ACIS-I	NONE	5
08:29:48.00	-42:50:52.80	IGR J08297-4250	ACIS-I	NONE	5
18:09:01.00	-27:42:14.40	IGR J18088-2741	ACIS-I	NONE	5
20:10:34.30	+45:34:04.80	IGR J20107+4534	ACIS-I	NONE	5
17:17:20.40	-24:36:21.60	IGR J17174-2436	ACIS-I	NONE	5
04:05:59.80	+54:16:33.60	IGR J04059+5416	ACIS-I	NONE	5
17:30:24.20	-20:16:19.20	IGR J17306-2015	ACIS-I	NONE	5

Subject Category: BH AND NS BINARIES

Proposal Number: 15400524

Title: Search for absorption edges in superexpansion bursts

Type: TOO Total Time (ks): 100

PI Name: Jean in 't Zand

Our goal is to measure with the LETGS a series of bright type-I X-ray bursts with strong photospheric radius expansion ('superexpansion') to search for absorption edges due to the ashes of nuclear burning. We request a quick TOO, to be triggered by ISS-MAXI and Swift-BAT, with a total exposure time of 100 ks to obtain the detection of about 10 bursts.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
18:23:40.50	-30:21:40.00	4U 1820-30	ACIS-S	LETG	100

Subject Category: BH AND NS BINARIES

Proposal Number: 15400528

Title: Following a black hole X-ray transient as it transitions to quiescence

Type: TOO Total Time (ks): 135

PI Name: Richard Plotkin

There is increasing evidence that the quiescent state of black hole X-ray binaries (BHXBs) is different from the canonical hard state at higher luminosities. Quiescent BHXB X-ray spectra are generally softer, and it has recently been realized that not every system takes the same path through the radio-X-ray luminosity plane during the decay into quiescence. We request six (nearly) simultaneous Chandra/VLA TOO observations to monitor a BHXB during an outburst decay between 3e-7 -- 1e-4 L_edd, a crucial luminosity regime that represents the transition into quiescence for many systems, but still has sparse data coverage. From these coordinated observations we will place new constraints on jet-dominated and radiatively inefficient accretion flow models.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
		TOO	ACIS-S	HETG	135

Subject Category: BH AND NS BINARIES

Proposal Number: 15400714

Title: Confirmation of the Symbiotic Nature of CXOGBS J173620.2-293338

Type: GO Total Time (ks): 25

PI Name: Robert Hynes

The Galactic Bulge Survey (GBS) detected 1640 faint bulge X-ray sources. CX332 lies within 1" of an asymptotic giant branch carbon star. Bulge carbon stars are extremely rare, so we estimate only a 0.1% of chance coincidence within 1" with ANY GBS source, so it is likely to be a symbiotic. The X-ray hardness and optical spectrum suggest it might be neutron star symbiotic X-ray binary (SyXB). It would be only the second SyXB with a carbon star, and the first based on a secure X-ray detection. A deeper observation will i) obtain a precise, on-axis X-ray position to confirm or refute the positional assocation; ii) obtain an X-ray spectrum to classify the symbiotic type; iii) search for the large amplitude variability typical of symbiotics, and possibly measure a neutron star spin period.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
17:36:20.20	-29:33:38.30	CXOGBS J173620.2-293338	ACIS-I	NONE	25

Subject Category: BH AND NS BINARIES

Proposal Number: 15400856

Title: The cooling neutron star in the super-Eddington accretor XTE J1701-462

Type: GO Total Time (ks): 115

PI Name: Jeroen Homan

Observing the cooling of neutron stars reheated by accretion provides new insights into neutron star structure. Using Chandra and XMM-Newton we have followed in unprecedented detail the cooling of the neutron star transient XTE J1701-462, which accreted at super- and near-Eddington rates for 1.6 years before returning to quiescence. A recent observation indicates that the source has now entered a phase of more rapid cooling after an extended period of much slower evolution. Here we propose to continue our successful monitoring of the source with a 115 ks observation early in Cycle 15, thus extending our tracking of the source from 5.2 to 6.5 years into quiescence. This will serve to constrain the current phase of rapid cooling and thereby the properties of the neutron star inner crust.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
17:00:58.50	-46:11:08.60	XTE J1701-462	ACIS-S	NONE	115

Subject Category: BH AND NS BINARIES

Proposal Number: 15400867

Title: Turning Down the Noise on Circinus X-1: A Deep Look at the Jets, Shocks, and Lobes at Low Background

Type: TOO Total Time (ks): 180

PI Name: Sebastian Heinz

We propose to observe Circinus X-1 in a 180ksec TOO at very low point source flux. This will allow us to (a) unambiguously determine the nature of the tentative excess X-ray emission from the edges of the radio lobes, (b) map synchrotron aging across the shocks detected in a 2009 observation (c) search for thermal emission from the forward shock, (d) search for X-ray evidence of jet bending, and (e) determine the nature of the compact X-ray emission along the radio jets. The observation will allow us to measure the jet power and the age of the synchrotron nebula and to constrain the dynamics of the jet. We ask for 11 ksec of joint Swift time to verify our trigger criteria.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
15:20:40.90	-57:10:00.20	Circinus X-1	ACIS-S	NONE	180

Subject Category: BH AND NS BINARIES

Proposal Number: 15400870

Title: Narrow Lines from a Slowly Rotating Neutron Star

Type: TOO Total Time (ks): 150

PI Name: Deepto Chakrabarty

The detection and identification of photospheric absorption lines from a neutron star would allow measurement of their gravitational redshift and hence the neutron star compactness. In principle, the line shape would allow unique determination of M and R. X-ray bursters are, in most respects, the ideal targets for this search, but most rotate so rapidly that any lines are too broadened to detect. However, the recently discovered X-ray burster Terzan 5 X-2 spins at only 11 Hz, 20x slower than the next slowest rotator. We propose a TOO observation with HETGS to search for narrow lines of ionized Fe when this X-ray transient next becomes active. This is the best chance ever to detect a narrow atomic line in a neutron star.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
17:48:04.80	-24:46:48.80	IGR J17480-2446	ACIS-S	HETG	150

Subject Category: BH AND NS BINARIES

Proposal Number: 15400871

Title: Confronting IC 10 X-1: Does the Most Massive Stellar Black Hole Also Have the Most Extreme Spin?

Type: GO Total Time (ks): 150

PI Name: James Steiner

IC 10 X-1 shattered all mass records for stellar black holes. The fact that it eclipses significantly constrains its inclination and its distance is known because it resides in IC 10. These three quantities, mass, inclination and distance, are the key input parameters needed to derive spin from the thermal spectrum of a black hole. However, at a flux of 0.1 mCrab, we are stymied by a lack of signal at the highest energies, which prevents us from measuring its spin. Only through a coordinated effort combining NuSTAR's high energy sensitivity and Chandra pristine optics and low energy sensitivity can this be done. At the core of this study is a question: will IC 10 X-1, like the other HMXBs have a high spin?

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
00:20:29.10	+59:16:51.90	IC 10 X-1	ACIS-I	NONE	150

Subject Category: BH AND NS BINARIES

Proposal Number: 15400876

Title: Resolving a New Hyper-luminous X-ray Source in NGC 1511

Type: GO Total Time (ks): 40

PI Name: Sean Farrell

We have recently discovered a new candidate hyper-luminous X-ray source coincident with the starburst galaxy NGC 1511 in archival XMM-Newton data. At the galaxy's distance the luminosity is ~1E42 erg/s, equivalent to the brightest known ULX and strongest intermediate mass black hole candidate ESO 243-49 HLX-1. However, the source is confused in the XMM images, leading to a high level of uncertainty in both the spectral shape and luminosity. We request observations with Chandra in order to disentangle this source from the other sources of emission, pin-point its position, and accurately constrain the spectrum and luminosity. We will also seek simultaneous radio observations of a possible radio counterpart in order to constrain the black hole mass using the black hole fundamental plane.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
03:59:41.70	-67:38:20.00	XMMU J035941.7-673820	ACIS-S	NONE	40

Subject Category: BH AND NS BINARIES

Proposal Number: 15400896

Title: High-resolution X-ray spectroscopy of the X-ray burster and 11 Hz pulsar IGR J17480-2446

Type: GTO/TOO Total Time (ks): 150

PI Name: Claude Canizares

The detection and identification of photospheric absorption lines from a neutron star would allow measurement of their gravitational redshift and hence the neutron star compactness. In principle, the line shape would allow unique determination of M and R. X-ray bursters are, in most respects, the ideal targets for this search, but most rotate so rapidly that any lines are too broadened to detect. However, the recently discovered X-ray burster Terzan 5 X-2 spins at only 11 Hz, 20x slower than the next slowest rotator. We propose a TOO observation with HETGS to search for narrow lines of ionized Fe when this X-ray transient next becomes active. This is the best chance ever to detect a narrow atomic line in a neutron star.

R.A.	Dec.	Target Name	Det.	Grating	Exp.Time (ks)
17:48:04.80	-24:46:48.80	IGR J17480-2446	ACIS-S	HETG	150

The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA. Email: cxchelp@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2024. All rights reserved.