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LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY …
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LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY
- LIGO -
CALIFORNIA INSTITUTE OF TECHNOLOGY
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
LSC Proposal LIGO-T010019-A - D 3/8/01
LIGO Engineering Run: Periodic Gravitational
Wave Flux Upper Limit Analysis Proposal
LIGO Science Collaboration Periodic Upper Limit Analysis
Working Group (page 5)
Distribution of this draft:
LIGO Laboratory and LIGO Science Collaboration
This is a working document.
All data should be considered preliminary.
California Institute of Technology Massachusetts Institute of Technology
LIGO Project - MS 51-33 LIGO Project - MS 20B-145
Pasadena CA 91125 Cambridge, MA 01239
Phone (818) 395-2129 Phone (617) 253-4824
Fax (818) 304-9834 Fax (617) 253-7014
E-mail: info@ligo.caltech.edu E-mail: info@ligo.mit.edu
WWW: http://www.ligo.caltech.edu/
Table of Contents
Index
file Macintosh HD:Z_Docs:UpperLimits01:PULG-proposal-01.fm5 - printed March 8, 2001
LIGO-T010019-A
1 ABSTRACT
We propose to conduct a preliminary search for periodic gravitational waves using data from
the LIGO Hanford 2 km and 4 km and Livingston 4 km interferometers, the GEO600 interferom-
eter, and perhaps collaborating acoustic gravitational wave detectors which are active during the
scheduled Fall 2001 LIGO Engineering Data Run. The principal objectives of this search are:
· to discover or establish new upper limits on sources of continuous periodic gravitational radi-
ation flux, from electromagnetically known objects and classes of objects as well as from
unmodeled sources;
· to discover and mitigate detector background artifacts which may limit search sensitivity;
· to exercise and test the LIGO Data Analysis System (LDAS) infrastructure, and;
· to build and test software components of the LIGO Analysis Library (LAL).
We will pursue these objectives with the constraint of being fully prepared in the required time
frame and without a substantial increase in available resources. As a result, some investigations
may not yet exploit the full sensitivity, coverage or refinement available in principle. Nevertheless,
it is fair to expect that even a suboptimal analysis of data from these newly commissioned instru-
ments of unprecedented sensitivity will substantially advance our state of knowledge and will
pave the way for more ambitious searches in the future.
2 PROPOSED APPROACH
We propose to apply the following analyses to all detector data sets which are viable during the
appointed engineering data run, to whatever extent this proves feasible. Each task description lists
a spokesperson who has offered to organize and coordinate software and hardware preparations
for the analysis, and who will report progress to the group at regular intervals.
While members of this group will continue to contribute to global preparatory activities (com-
missioning the detectors, building LDAS, and generic data conditioning functions such as line
removal and calibration, to name a few) we discuss here only those activities specific to the hunt
for periodic signals. Stuart Anderson (LIGO Laboratory/Caltech) and Michael Zucker (LIGO
Laboratory/MIT) co-chair this analysis team and report jointly to the LIGO Science Collaboration
Spokesperson and the LIGO Laboratory Director.
All software generated under this proposal will conform to the standards of the LIGO Algo-
rithm Library (LAL). Analysis products and results will be made accessible through LDAS using
that system's standard query and retrieval tools.
2.1 Infrastructure functions
The following functions enable subsequent analyses and provide future infrastructure. Results
will be the subject of technical report(s) to the Collaboration; some may also result in method
publications.
2.1.1 Characterization of periodic detector artifacts
We will assemble a database comprising known local periodic artifacts in the strain and
selected auxiliary channels for each instrument. This is currently in progress for the LHO 2 km
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LIGO-T010019-A
interferometer. Comparable databases for the LHO 4km and LLO machine and (if possible)
GEO600, as well as tools to install and access these data in the LDAS system, remain to be devel-
oped. This catalog will be used by subsequent analysts to determine "deadbands" and reject
known local disturbances.
Keith Riles (Michigan) has responsibility for comparable activities in connection with the LSC
Detector Characterization Working Group, and has agreed to spearhead this task for the present
effort as well.
2.1.2 Earth Doppler/GR correction & AM antenna pattern removal
Mechanisms will be provided to correct time series for amplitude and phase modulation due to
the Earth's acceleration and general relativistic effects, as well as to synthesize test signals which
mimic physical extrasolar sources.
Curt Cutler (GEO/AEI) will lead on removal of Doppler and GR phase perturbations; Keith
Riles (Michigan) will lead on removal of amplitude modulation due to rotating detector antenna
patterns.
2.1.3 Detection efficiency analysis
Assuming there are no unequivocal detections, setting a useful upper limit on GR flux depends
on knowing the probability that a real signal would have been missed by each attempted analysis,
as a function of that signal's amplitude. We propose to approach this question by a combination of
direct calculation and Monte Carlo simulation, using test signals introduced in early analysis as
well as in the detector itself (see below). Because many of the proposed searches are in fact lim-
ited by computational resources, a traditional "brute force" Monte Carlo approach may not be
efficient or even feasible; we will investigate methods to extend to the full parameter space effi-
ciency results obtained for limited parameter samplings.
Patrick Brady (UWM) will report on this task.
2.1.4 Test signal injection
To support the Monte Carlo efficiency analysis, and also to provide end-to-end test of the anal-
ysis system with the detector, artificial test signals will be injected into each detector electrome-
chanically by a semi-autonomous system unaffiliated with the data analysis machinery. Some
portion of these signal injections will be performed in a blind fashion (with respect to starting
time, barycentric signal frequency, direction, amplitude and other search parameters) to reduce
the possibility of experimenter bias.
Michael Zucker (LIGO Laboratory/MIT) will report on this function, with Harry Ward (GEO/
Glasgow) serving as liaison for the GEO600 machine.
2.2 Astrophysics analysis products
Each of these analyses is expected to result in a Collaboration technical report and astrophysics
publication.
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LIGO-T010019-A
2.2.1 Short-transform all sky search
The transforms developed for task 2.1.1 and/or the preparatory initial transforms for task 2.2.3
below permit a straightforward search for lines which are correlated in two or more detectors and
yet cannot be ruled out as local interference. This search will be confined to data vectors short
enough to be unaffected by Earth Doppler or antenna pattern effects (order of tens of minutes) and
thus addresses the whole sky, albeit at limited sensitivity. Additional binary cuts based on detec-
tion in successive epochs and physically plausible frequency evolution between epochs may also
be applied.
The spokesperson for this task will be assigned at the March, 2001 LSC meeting.
2.2.2 Known radio pulsar search
The radio pulse phase evolution for some number (order 10) of known, nearby fast pulsars will
be used to perform a direct coherent search for gravitational waves from these objects, using
folded periodogram and/or demodulation methods. The full time series spanning the engineering
run will be used if possible.
Stuart Anderson (LIGO Lab/Caltech) will report on this task.
2.2.3 Semi-coherent wide area search with spindown
A prototype implementation of the Hough transform semi-coherent area search algorithm will
be employed to exploit the full length of the engineering run (approximately one week). Certain
specific sky patches (e.g., near the galactic center) may be selected to initially reduce the compu-
tational burden. A limited search over source spindown (first period derivative) is also proposed to
allow detection of young objects (less than a few My in age) over this timespan. Parameter space
gridding and coverage functions will be developed to insure adequate coverage without redun-
dancy. Depending on locked stretch durations attained by the various interferometers, bridging of
data dropouts and turn-on transients will also have to be addressed to some degree.
Teviet Creighton (UWM) will report on the search parameter space gridding activity; Maria
Alessandra Papa (GEO/AEI) will report on the Hough transform detection code and other compo-
nents.
3 SCHEDULE AND DELIVERABLES
We expect task 2.1.1 (local line catalogs) to be substantially ready by the end of the scheduled
early summer (June `01) LIGO engineering run, and will test prototypes of code developed under
tasks 2.1.2 (Doppler/AM removal), 2.1.4 (test signal injection), 2.2.1 (short transform search),
and 2.2.2 (radio pulsar search) on "unofficial" data sets obtained from this run. This will leave
some time for iteration of codes and data flow before the actual "Upper Limit" data run in Sep-
tember. We also expect to have the parameter space gridding and basic Hough transform engine
components of the 2.2.3 (semi-coherent wide area search) completed by this time; the spindown
parameter search function, method for bridging data gaps, and criteria for selecting or rejecting
individual subtransforms in the global analysis of 2.2.3 will probably not be ready until about the
time of the September run.
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LIGO-T010019-A
We will report progress on each task in Section 2 at the Summer 2001 LIGO Science Collabo-
ration meeting. Active interventions in the Fall Engineering Run (e.g., signal injection & calibra-
tion) will be coordinated in advance with the acting Commissioning Directors at each detector
site. A technical report detailing the methods and results of each analysis task or group of tasks
will be submitted to the Collaboration, and the related publications prepared for submission, in
the January 2002 time frame (assuming the currently envisioned detector schedule is realized).
4 PERIODIC UPPER LIMIT GROUP MEMBERSHIP
(For updated list, see http://www.lsc-group.phys.uwm.edu/pulgroup/ )
member institution email
Alan Wiseman University of Wisconsin agw@gravity.phys.uwm.edu
Stuart Anderson LIGO Lab, Caltech anderson_s@ligo.caltech.edu
Bob Coldwell University of Florida coldwell@phys.ufl.edu
Curt Cutler GEO, AEI Potstdam cutler@aei-potsdam.mpg.de
Dave Chin University of Michigan dwchin@umich.edu
Sam Finn Penn State University finn@phys.psu.edu
Graham Woan GEO, Glasgow University graham@astro.gla.ac.uk
Dick Gustafson University of Michigan gustafso@umich.edu
Harry Ward GEO, Glasgow University h.ward@physics.gla.ac.uk
Jim Hough GEO, Glasgow University j.hough@physics.gla.ac.uk
Keith Riles University of Michigan kriles@umich.edu
Soumya Mohanty GEO, AEI Potstdam mohanty@aei-potsdam.mpg.de
Maria Alessandra Papa GEO, AEI Potstdam papa@aei-potsdam.mpg.de
Patrick Brady University of Wisconsin patrick@gravity.phys.uwm.edu
Ron Drever Caltech rdrever@caltech.edu
Rejean Dupuis GEO, Glasgow University rejean@astro.gla.ac.uk
Bernard Schutz GEO, AEI Potstdam schutz@aei-potsdam.mpg.de
Alicia Sintes-Olives GEO, AEI Potstdam sintes@aei-potsdam.mpg.de
Soma Mukherjee GEO, AEI Potstdam soma@aei-potsdam.mpg.de
Steven Berukoff GEO, AEI Potstdam steveb@aei-potsdam.mpg.de
Teviet Creighten University of Wisconsin teviet@gravity.phys.uwm.edu
Alberto Vecchio GEO, AEI Potstdam vecchio@aei-potsdam.mpg.de
Mike Zucker LIGO Lab, MIT zucker_m@ligo.mit.edu
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