Документ взят из кэша поисковой машины. Адрес оригинального документа : http://zebu.uoregon.edu/~uochep/talks/talks02/G020045.pdf Дата изменения: Thu Sep 26 00:26:36 2002 Дата индексирования: Tue Oct 2 10:34:52 2012 Кодировка: Поисковые слова: massive stars

Searching for Gravitational Wave Bursts Using External Triggers From Gamma - ray Bursts ( GRBs )
R. Rahkola, Sz. MАrka, S. Mohanty, S. Mukherjee, V. Kalogera LSC Meeting, LLO, March 20, 2002
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Introduction to Gamma -ray Bursts
q

High- energy, short- duration electromagnetic radiation from extra galactic sources Favored models point to exploding fireball
ь ь ь
Involve large amounts of matter, ejected at relativistic speeds, producing a series of high - energy E/M shockwaves --o o o o initially gamma - rays (some redshift to lower-energy gamma - rays or X - rays, others are absorbed), then X - rays (red - shifted to optical wavelengths), visible light may burst before, during, or after finally radio wavelengths

http://online. itp. ucsb . edu/online/gamma_c99/ piran /oh/06.html

q

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GRBs and Gravitational Waves
q Gravitational Wave Bursts ( GWBs ) possibly emitted from

same source as GRBs
q Most probably GWBs emitted before GRBs q Estimates from GRB observations are 1054 erg/s luminous

energy (assuming isotropic GRB)
q How much GW energy can be expected from these

sources? Unknown, but could be very high...

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Motivation for a Statistics-based Search
q GRB astronomy is very active ь Relatively large number of events are detected (~O(1/day)) q Current sensitivity to GW bursts is low due to excess IFO noise ь Could be confused with noise bursts in interferometer channels ь However, even at LIGO I design sensitivity most bursts may be too far away q Expected GW would be broadband in frequency ь Bursts = short- duration ь The waveform probably varies from source type to source type q Uncertainty in time delay between the GW and GRB ь The delay probably varies from source type to source type

All lead to diminishing confidence for single events...
Using a statistical method would increase our confidence!
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GRB Events Observed During E7

Detector

Tr# 1 2 3 4 5 7 9 10 1885 1887 1888 1890 1891

Date Time(UTC) 12/28/01 12/29/01 12/30/01 12/31/01 12/30/01 1/12/02 1/13/02 1/14/02 1/5/02 1/8/02 1/8/02 1/10/02 1/13/02 23:19:15 10:23:20 8:48:23 3:34:40 15:03:29 18:52:02 13:37:13 2:51:02 12:46:01 8:20:37 8:27:26 10:20:43 2:04:12

GPS 693616768 693656613 693737316 693804893 693759822 694896735 694964246 695011875 694269973.9 694513250.5 694513659.4 694693256.1 694922665.3

Tr #1- 10 are courtesy of Kevin Hurley ( khurley@ssl. berkeley.edu)

q 13 triggers GRB received q 5 have directional info q It seems that most have IFO

coverage

BEPPOSAX GRBM KONUS WIND BEPPOSAX GRBM BEPPOSAX GRBM BEPPOSAX GRBM BEPPOSAX GRBM KONUS HETE GCN/HETE GCN/HETE GCN/HETE GCN/HETE GCN/HETE

ь We have to wait until the vetoes
are considered

q We are collecting updated info

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http://space.mit.edu/HETE/spacecraft.html
http://heasarc.gsfc. nasa. gov/docs/sax/gallery/inst.html

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http://heasarc.gsfc. nasa. gov/docs/ he asarc/missions/wind.html


Optical Supernovae and Detected Events During the Period of E7
q 31 records are noted q Details will be collected q Positions are WELL KNOWN q Time info is questionable...
SN 2002C 2002al 2002ak 2002aj 2002ai 2002ah 2002ag 2002af 2002ae 2002ad 2002ac 2002ab 2002aa 2002Z 2002Y 2002X 2002W 2002V 2002U 2002T 2002S 2002R 2002Q 2002P 2002O 2002N 2002M 2002L 2002K 2002B 2002A Galaxy IC3376 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A UGC3804 Date 1/14/2002 1/11/2002 1/11/2002 1/11/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/9/2002 1/7/2002 1/1/2002 Mag. 16.7 23.6 22.6 23.1 23.4 24.4 24.2 24.1 23.6 23.2 23.8 22.5 24.3 24.2 24.2 23.7 24 23.7 22.8 23.8 23.1 24.1 24.2 23.8 23.7 23.2 23.4 23.8 24 20.5 17.4 Circular IAUC-7793 IAUC-7804 IAUC-7804 IAUC-7804 IAUC-7802 IAUC-7802 IAUC-7802 IAUC-7802 IAUC-7802 IAUC-7802 IAUC-7802 IAUC-7802 IAUC-7802 IAUC-7802 IAUC-7802 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7801 IAUC-7791 IAUC-7786 R.A. 12 27 10 50 10 49 10 48 10 54 10 53 10 53 10 52 10 50 10 50 7 49 7 48 7 48 8 49 8 48 8 48 8 47 4 39 4 39 4 38 4 37 2 29 2 29 2 29 2 28 2 27 2 27 2 26 2 26 5 40 7 22 52.66 21.71 4.32 56.56 21.27 19.5 12.71 29.89 51.02 12.19 39.61 55.7 45.28 32.97 50.21 30.54 54.42 53.55 42.9 53.87 37.05 27.19 22.19 5.17 22.17 51.91 13.14 55.69 50.48 46.06 36.14 Decl. 27 0 -4 15 -5 55 -5 32 57 27 57 0 57 0 57 39 57 9 57 31 10 19 10 6 10 18 44 3 44 13 44 15 44 13 -1 13 -1 46 -1 34 -1 32 0 51 0 20 0 47 0 49 0 28 0 44 0 21 0 43 -71 51 71 35 6.1 5.9 33.7 14.1 58.2 36.6 25.9 44 4.6 11.6 8.2 6.3 0.8 27.6 3 35.3 42.9 33.5 4.2 26.6 36.9 38.9 25.8 20.1 46.5 53.6 41.2 37.8 30.1 15.1 41.5 Type Discoverer(s) II ? ? ? ? ? ? ? ? ? ? Ia ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Ia IIn LOTOSS Deep Lens Survey Deep Lens Survey Deep Lens Survey High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam High-Z SupernovSearchTeam SuperMacMicrolenSurvey Beijing SupernovSurvey

1990

Data courtesy of

http://cfa- www. harvard. edu /iau /lists/Supernovae.html and http://cfa- www. harvard. edu /iau / cbat.html .

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A Statistical Approach
(based on method proposed by Finn, Mohanty, and Romano, gr- qc/9903101)

q Make two types of cross- correlated time series for two

interferometers
ь "on-source": cross-correlated during times containing possible GW ь "off-source": cross-correlated during (related) times which likely do not
contain GW signals

ь Takes out uncorrelated noise while GW signal remains q Repeat for many GRBs ь Increases signal-to-noise q Compare the two distributions of cross -correlations ь Check if there is a statistical difference due to the GRB trigger
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Implementation: Overview
Search might be computationally intensive during particular event times (though rare) and statistical summary must be prepared (optimally) based on several weeks worth of GRB data

It is very natural to break up the search into LDAS and nonLDAS parts

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Implementation: LDAS
(

Э

­ what's been done so far)

Э Э Э

q (pre-LDAS) Obtain GRB timestamps t

when available

GRB

and source directions,
GRB

q Grab data from both interferometers around t

q Pick a likely time segment, length tw, for GWB to occur (e.g.

between 1- 5sec before GRB) "on-source"

q Pick a number of (randomly selected) segments, length tw, during

times when GWB is unlikely to occur (i.e. after GRB) "offsource" (but still reflects the "local" noise of the IFO signal)

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Implementation: LDAS (cont'd.)
(

Э

­ what's been done so far)

q For "on-source" segment, make use of expected time delay

between interferometers due to direction of GRB source

Э

q Compute and store cross-correlations (x

source" and "off-source" segment

on

and x off) for each "on-

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Implementation: non-LDAS
(

Э

­ what's been done so far)

q [Veto cross-correlations of suspect data, due to e.g. non-

stationarity or bad data quality]
q Determine the sample means X and sample variances

2 of "on-

source" (Xon) and "off-source" (Xoff) distributions
q Use Student's t-test to determine how well Xon and Xoff coincide:

t= 2 =

X

on

-X
on

off

N on N off N on + N off
2 off

(N

2 - 1) on + ( N off - 1) N on + N off - 2

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Foreseen Challenges
q Dealing w/ error - bars or missing information of source

direction
q Choice of t
GWB

and t

w

q How much non -stationarity is acceptable? q Sensitivity studies q Using data from more than two interferometers q Validation & verification of results

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LDAS Factors to Consider
q Getting data out of LDAS which can be used by non- LDAS

part
ь Currently writing to file using multi_burst table format ь Write ~20 entries/day to multi_burst table? ь Non-LDAS part can use Event Tool to read entries q Line removal ь Implemented in datacondAPI yet? q Testing on coincident data ь Non-coincident data doesn't reflect possibly correlated noise ь Will start testing when coincident playground data is available

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Summary / Short-term Outlook
q Making good progress! ь DSO has progressed since inception at E6 ь Work is underway to deal with error-bars, non-stationarity q Will calibrate sensitivity experimentally by "searching" for

bursts at simulated (random) GRB times (maybe late April)
q Will test sensitivity by injecting short, broadband bursts into

coincident (playground?) data (maybe May)

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