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OBSID:
27954
 Title:
TRACKING THE NE X ACCRETION DISK LINE EMISSION OF ULTRACOMPACT X-RAY BINARY 4U 1626-67 ACROSS A TORQUE REVERSAL
Investigator:
Ng
 Observer:
Ng, Mason
 Phone:
8573205973
 Email:
mason.ng@mcgill.ca
Target Name:
4U 1626-67
 Sequence Number:
402459
 Instrument:
ACIS-S
 Grating:
HETG
 SI Mode:
TE_0092EB
 Raster Scan:
N
 Annotated DOT:
JUL2423a

Proposal Number:
24408915
 Right Ascension:
248.07
 Declination:
-67.4609
 Status:
archived
 Start Date:
2023-07-29 14:55:01
Category:
BH AND NS BINARIES
 Type:
DDT
 AO Cycle:
24
 Dither Flag:
Y
 Y Offset:
0
 Z Offset:
0
Est. Count Rate:
2.17
 Order-1 Count Rate:
1.2
 Exposure Time:
30
 Time Remaining:
30.045
 Reqd Start Time:

 Reqd Stop Time:
Period:

 Epoch:

 Start of Period:

 End of Period:

 PS Margin:

 PE Margin:

 Max Segments:
0

ACIS Mode:
TE
 Standard?:
No
 BEP Mode:
F
 Dropped Chip Count:
0
 Optional Chips:
S0 S5
On-Chip Summing?:
No
 Row Sum:

 Column Sum:

 Frame Time:
Subarray Mode:
CUSTOM
 Starting Row:
1
 Row Count:
512
 Subarray Frame Time:

Duty Cycle?:
No
 Cycle Count:
0
 Primary Exp Time:

 Secondary Exp Time:
Event Filter?:
No
 Filter Threshold:

 Filter Range:

 Bias Requested?:
No
 Bias Frequency:

 Bias After?:
No
 Spatial Window?:
No

Abstract:
We propose a 60 ks HETGS observation of the ultracompact X-ray binary 4U 1626-67 that will, for the first time, characterize the Ne X accretion disk line emission so close in time to a torque reversal. 4U 1626-67 is an unusual ultracompact X-ray binary that hosts a highly magnetized (B ~ 3x10^(12) G) slowly rotating pulsar (P ~ 7.7 s) and a low-mass companion (M_c ~ 0.02x solar mass). It is one of the two low mass X-ray binaries that has exhibited long-term torque reversals (the other being GX 1+4). Since its discovery in the 1970s, it has exhibited three torque reversals. The pulse profiles have very different morphologies between the two spin states, suggesting significant changes in the accretion geometry. Our proposed observation will be the closest to a torque reversal of 4U 1626-67, which will provide us the unique opportunity to track the evolution of the Ne X line emission across a torque reversal episode and trace the inner disk location.

psci Run:
24
 Processing Date:
Aug 15 2023
 psci Directory:
/nfs/maaxnew/r3/fk/acis125a/acis125.log
OBSID:
27954
 SIM Mode:
ACIS-S
 OTG Mode:
HETG
 Seq Number:
402459
 Target Name:
4U_1626-67
 AO:
24
Start VCDU:
34795:064
 Start Time (UTC):
210:54801.142
 Stop Time (UTC):
210:84853.218
 Kilosecs:
30.1
 % Frames:
100.0
 # CCDs:
S6
# Frames:
17261
 # Events:
677093
 Events/sec:
22
 PSCI errors:
0
 % drops:
0.0
 Bias Errs:
0
 FP Temp:
-115.3
Parameter Block:
0x0092e024
 Window Block:
-
 # Windows:
0
 FEP Mode:
Te3x3
 BEP Mode:
F
 Start Row:
0
 # Rows:
512
Primary Exposure:
17
 Secondary Exposure:
0
 Duty Cycle:
0
 Summing?:
No
 Bias?:
Yes
 Trickle?:
Yes
 Bias Run:
24

pgf@space.mit.edu Tue Apr 8 9:48:31 EST 2025