C H A N D R A   S C I E N C E   C E N T E R
O B S E R V A T I O N   C A T A L O G

OBSID:
25550
 Title:
A Systematic Survey of Extreme X-ray Variability of Weak-Line Quasars  
Investigator:
Brandt
 Observer:
Brandt, William
 Phone:
814-865-3509
 Email:
wnbrandt@gmail.com
Target Name:
SDSS J163810.07+115103.9
 Sequence Number:
704531
 Instrument:
ACIS-S
 Grating:
NONE
 SI Mode:
TE_005C6B
 Raster Scan:
N
 Annotated DOT:
JAN0923a

Proposal Number:
23700162
 Right Ascension:
249.542
 Declination:
11.8511
 Status:
archived
 Start Date:
2023-01-09 14:45:39
Category:
ACTIVE GALAXIES AND QUASARS
 Type:
GO
 AO Cycle:
23
 Dither Flag:
Y
 Y Offset:
0
 Z Offset:
0
Est. Count Rate:
0.0009
 Order-1 Count Rate:

 Exposure Time:
3.4
 Time Remaining:
3.814
 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:
VF
 Dropped Chip Count:
0
 Optional Chips:
S4
On-Chip Summing?:
No
 Row Sum:

 Column Sum:

 Frame Time:
Subarray Mode:
NONE
 Starting Row:
0
 Row Count:
1023
 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:
X-ray observations of weak-line quasars (WLQs) suggest that, among luminous quasars, they may preferentially show extreme large-amplitude X-ray variability events, perhaps due to variations in the height of a thick inner accretion disk. We thus propose a three-cycle Chandra program to monitor 10 luminous WLQs with the main aim of exploring such extreme X-ray variability events systematically. We will determine robustly if WLQs indeed more frequently show large-amplitude X-ray variability than typical quasars. The Chandra observations, combined with supporting HET spectra of rest-frame UV line/continuum emission, will also test if extreme X-ray variability events are best described by the thick inner-disk model, constraining the size of variations of inner-disk height.

Remarks:
We request one Chandra observation per cycle. We increase exposure times in subsequent cycles by 10% to allow for the expected degradation in full-band efficiency. As described in the proposal text, near-simultaneous supporting spectroscopy will be obtained with the queue-scheduled Hobby-Eberly Telescope (HET) - no Chandra time constraint is needed for this HET support. This is the first observation of a sequence of 3, with the next one following between 6-12 months after, and the third one following on after another 6-12 months.

psci Run:
35
 Processing Date:
Jan 18 2023
 psci Directory:
/nfs/maaxnew/r3/fi/acis123a/acis123.log
OBSID:
25550
 SIM Mode:
ACIS-S
 OTG Mode:
NONE
 Seq Number:
704531
 Target Name:
SDSS_J163810.07
 AO:
23
Start VCDU:
76803:040
 Start Time (UTC):
009:54326.437
 Stop Time (UTC):
009:58152.217
 Kilosecs:
3.8
 % Frames:
100.0
 # CCDs:
S3
# Frames:
1218
 # Events:
81212
 Events/sec:
21
 PSCI errors:
0
 % drops:
0.1
 Bias Errs:
0
 FP Temp:
-112.0
Parameter Block:
0x005c6024
 Window Block:
-
 # Windows:
0
 FEP Mode:
Te5x5
 BEP Mode:
F
 Start Row:
0
 # Rows:
1024
Primary Exposure:
31
 Secondary Exposure:
0
 Duty Cycle:
0
 Summing?:
No
 Bias?:
Yes
 Trickle?:
Yes
 Bias Run:
35

pgf@space.mit.edu Mon Mar 31 10:36:39 EST 2025