C: - Abbott2009p5729Astrophys_J

The Astrophysical Journal

, 701:L68–L74, 2009 August 20

doi:

10.1088/0004-637X/701/2/L68

STACKED SEARCH FOR GRAVITATIONAL WAVES FROM THE 2006 SGR 1900+14 STORM

B. P. Abbott

, R. Abbott

, R. Adhikari

,P.Ajith

, B. Allen

, G. Allen

,R.S.Amin

, S. B. Anderson

W. G. Anderson

,M.A.Arain

, M. Araya

, H. Armandula

, P. Armor

,Y.Aso

,S.Aston

, P. Aufmuth

, C. Aulbert

S. Babak

, P. Baker

, S. Ballmer

, C. Barker

, D. Barker

,B.Barr

, P. Barriga

, L. Barsotti

, M. A. Barton

I. Bartos

, R. Bassiri

, M. Bastarrika

, B. Behnke

, M. Benacquista

, J. Betzwieser

, P. T. Beyersdorf

I. A. Bilenko

, G. Billingsley

,R.Biswas

, E. Black

, J. K. Blackburn

, L. Blackburn

, D. Blair

, B. Bland

T. P. Bodiya

, L. Bogue

,R.Bork

, V. Boschi

,S.Bose

, P. R. Brady

, V. B. Braginsky

,J.E.Brau

, D. O. Bridges

M. Brinkmann

, A. F. Brooks

,D.A.Brown

, A. Brummit

, G. Brunet

, A. Bullington

, A. Buonanno

O. Burmeister

,R.L.Byer

, L. Cadonati

,J.B.Camp

, J. Cannizzo

,K.C.Cannon

,J.Cao

, L. Cardenas

S. Caride

, G. Castaldi

, S. Caudill

, M. Cavagli

, C. Cepeda

, T. Chalermsongsak

, E. Chalkley

, P. Charlton

S. Chatterji

, S. Chelkowski

, Y. Chen

, N. Christensen

, C. T. Y. Chung

, D. Clark

, J. Clark

, J. H. Clayton

T. Cokelaer

, C. N. Colacino

, R. Conte

, D. Cook

, T. R. C. Corbitt

, N. Cornish

, D. Coward

,D.C.Coyne

J. D. E. Creighton

, T. D. Creighton

,A.M.Cruise

, R. M. Culter

, A. Cumming

, L. Cunningham

,S.L.Danilishin

K. Danzmann

, B. Daudert

, G. Davies

,E.J.Daw

, D. DeBra

, J. Degallaix

, V. Dergachev

,S.Desai

R. DeSalvo

, S. Dhurandhar

,M.D

ıaz

, A. Dietz

, F. Donovan

, K. L. Dooley

, E. E. Doomes

, R. W. P. Drever

J. Dueck

,I.Duke

, J.-C. Dumas

,J.G.Dwyer

, C. Echols

, M. Edgar

,A.Effler

, P. Ehrens

,E.Espinoza

T. Etzel

, M. Evans

, T. Evans

, S. Fairhurst

, Y. Faltas

, Y. Fan

, D. Fazi

, H. Fehrmann

,L.S.Finn

, K. Flasch

S. Foley

, C. Forrest

, N. Fotopoulos

, A. Franzen

, M. Frede

, M. Frei

, Z. Frei

, A. Freise

, R. Frey

, T. Fricke

P. Fritschel

, V. V. Frolov

, M. Fyffe

, V. Galdi

, J. A. Garofoli

, I. Gholami

,J.A.Giaime

,S.Giampanis

K. D. Giardina

, K. Goda

, E. Goetz

, L. M. Goggin

,G.Gonz

alez

, M. L. Gorodetsky

, S. Goßler

, R. Gouaty

A. Grant

,S.Gras

, C. Gray

, M. Gray

, R. J. S. Greenhalgh

, A. M. Gretarsson

, F. Grimaldi

, R. Grosso

H. Grote

,S.Grunewald

, M. Guenther

, E. K. Gustafson

, R. Gustafson

, B. Hage

, J. M. Hallam

, D. Hammer

G. D. Hammond

,C.Hanna

,J.Hanson

,J.Harms

, G. M. Harry

, I. W. Harry

, E. D. Harstad

,K.Haughian

K. Hayama

, J. Heefner

,I.S.Heng

, A. Heptonstall

,M.Hewitson

,S.Hild

,E.Hirose

, D. Hoak

, K. A. Hodge

K. Holt

, D. J. Hosken

,J.Hough

, D. Hoyland

, B. Hughey

, S. H. Huttner

, D. R. Ingram

, T. Isogai

,M.Ito

A. Ivanov

,B.Johnson

,W.W.Johnson

,D.I.Jones

,G.Jones

,R.Jones

,L.Ju

, P. Kalmus

, V. Kalogera

S. Kandhasamy

,J.Kanner

, D. Kasprzyk

, E. Katsavounidis

, K. Kawabe

,S.Kawamura

, F. Kawazoe

W. Kells

, D. G. Keppel

, A. Khalaidovski

, F. Y. Khalili

,R.Khan

, E. Khazanov

,P.King

,J.S.Kissel

S. Klimenko

, K. Kokeyama

, V. Kondrashov

, R. Kopparapu

, S. Koranda

, D. Kozak

,B.Krishnan

, R. Kumar

P. Kwee

,P.K.Lam

, M. Landry

, B. Lantz

, A. Lazzarini

,H.Lei

,M.Lei

, N. Leindecker

, I. Leonor

,C.Li

H. Lin

,P.E.Lindquist

, T. B. Littenberg

, N. A. Lockerbie

, D. Lodhia

, M. Longo

, M. Lormand

,P.Lu

M. Lubinski

, A. Lucianetti

,H.L

uck

, B. Machenschalk

, M. MacInnis

, M. Mageswaran

, K. Mailand

I. Mandel

, V. Mandic

,S.M

arka

,Z.M

arka

, A. Markosyan

, J. Markowitz

, E. Maros

, I. W. Martin

R. M. Martin

,J.N.Marx

, K. Mason

, F. Matichard

, L. Matone

, R. A. Matzner

, N. Mavalvala

, R. McCarthy

D. E. McClelland

,S.C.McGuire

,M.McHugh

, G. McIntyre

, D. J. A. McKechan

, K. McKenzie

, M. Mehmet

A. Melatos

,A.C.Melissinos

,D.F.Men

endez

, G. Mendell

, R. A. Mercer

, S. Meshkov

,C.Messenger

M. S. Meyer

, J. Miller

, J. Minelli

,Y.Mino

, V. P. Mitrofanov

, G. Mitselmakher

, R. Mittleman

O. Miyakawa

,B.Moe

, S. D. Mohanty

, S. R. P. Mohapatra

, G. Moreno

, T. Morioka

, K. Mors

, K. Mossavi

C. MowLowry

, G. Mueller

,H.M

uller-Ebhardt

, D. Muhammad

, S. Mukherjee

, H. Mukhopadhyay

A. Mullavey

,J.Munch

, P. G. Murray

, E. Myers

, J. Myers

,T.Nash

, J. Nelson

, G. Newton

, A. Nishizawa

K. Numata

, J. O’Dell

, B. O’Reilly

, R. O’Shaughnessy

,E.Ochsner

,G.H.Ogin

, D. J. Ottaway

, R. S. Ottens

H. Overmier

,B.J.Owen

, Y. Pan

, C. Pankow

, M. A. Papa

, V. Parameshwaraiah

, P. Patel

, M. Pedraza

S. Penn

, A. Perreca

, V. Pierro

,I.M.Pinto

, M. Pitkin

, H. J. Pletsch

,M.V.Plissi

, F. Postiglione

M. Principe

, R. Prix

, L. Prokhorov

, O. Punken

, V. Quetschke

,F.J.Raab

, D. S. Rabeling

, H. Radkins

P. Raffai

, Z. Raics

,N.Rainer

, M. Rakhmanov

, V. Raymond

,C.M.Reed

, T. Reed

, H. Rehbein

,S.Reid

D. H. Reitze

,R.Riesen

, K. Riles

, B. Rivera

, P. Roberts

, N. A. Robertson

, C. Robinson

,E.L.Robinson

S. Roddy

,C.R

over

, J. Rollins

,J.D.Romano

,J.H.Romie

,S.Rowan

,A.R

udiger

,P.Russell

, K. Ryan

S. Sakata

, L. Sancho de la Jordana

, V. Sandberg

, V. Sannibale

, L. Santamar

ıa

, S. Saraf

, P. Sarin

B. S. Sathyaprakash

, S. Sato

, M. Satterthwaite

, P. R. Saulson

, R. Savage

, P. Savov

, M. Scanlan

R. Schilling

, R. Schnabel

, R. Schofield

, B. Schulz

,B.F.Schutz

, P. Schwinberg

, J. Scott

, S. M. Scott

A. C. Searle

, B. Sears

, F. Seifert

, D. Sellers

, A. S. Sengupta

, A. Sergeev

, B. Shapiro

,P.Shawhan

D. H. Shoemaker

, A. Sibley

, X. Siemens

,D.Sigg

,S.Sinha

,A.M.Sintes

, B. J. J. Slagmolen

, J. Slutsky

J. R. Smith

,M.R.Smith

,N.D.Smith

, K. Somiya

, B. Sorazu

, A. Stein

, L. C. Stein

, S. Steplewski

A. Stochino

, R. Stone

, K. A. Strain

, S. Strigin

, A. Stroeer

, A. L. Stuver

, T. Z. Summerscales

,K.-X.Sun

M. Sung

, P. J. Sutton

, G. P. Szokoly

, D. Talukder

,L.Tang

,D.B.Tanner

, S. P. Tarabrin

, J. R. Taylor

R. Taylor

, J. Thacker

,K.A.Thorne

,K.S.Thorne

,A.Th

uring

, K. V. Tokmakov

, C. Torres

, C. Torrie

L68

No. 2, 2009

STACKED SEARCH FOR GRAVITATIONAL WAVES FROM SGR 1900+14

L69

G. Traylor

, M. Trias

, D. Ugolini

,J.Ulmen

, K. Urbanek

, H. Vahlbruch

, M. Vallisneri

, C. van den Broeck

M. V. van der Sluys

, A. A. van Veggel

,S.Vass

,R.Vaulin

, A. Vecchio

, J. Veitch

, P. Veitch

, C. Veltkamp

A. Villar

, C. Vorvick

, S. P. Vyachanin

, S. J. Waldman

, L. Wallace

,R.L.Ward

, A. Weidner

, M. Weinert

A. J. Weinstein

,R.Weiss

,L.Wen

,S.Wen

, K. Wette

, J. T. Whelan

, S. E. Whitcomb

,B.F.Whiting

C. Wilkinson

, P. A. Willems

, H. R. Williams

, L. Williams

, B. Willke

, I. Wilmut

, L. Winkelmann

W. Winkler

,C.C.Wipf

,A.G.Wiseman

, G. Woan

, R. Wooley

, J. Worden

,W.Wu

, I. Yakushin

H. Yamamoto

,Z.Yan

,S.Yoshida

, M. Zanolin

, J. Zhang

, L. Zhang

, C. Zhao

, N. Zotov

, M. E. Zucker

H. zur M

uhlen

, and J. Zweizig

(The LIGO Scientific Collaboration

)

LIGO - California Institute of Technology, Pasadena, CA 91125, USA

Albert-Einstein-Institut, Max-Planck-Institut f

ur Gravitationsphysik, D-30167 Hannover, Germany

University of Wisconsin–Milwaukee, Milwaukee, WI 53201, USA

Stanford University, Stanford, CA 94305, USA

Louisiana State University, Baton Rouge, LA 70803, USA

University of Florida, Gainesville, FL 32611, USA

University of Birmingham, Birmingham B15 2TT, UK

Leibniz Universit

at Hannover, D-30167 Hannover, Germany

Albert-Einstein-Institut, Max-Planck-Institut f

ur Gravitationsphysik, D-14476 Golm, Germany

Montana State University, Bozeman, MT 59717, USA

LIGO - Hanford Observatory, Richland, WA 99352, USA

University of Glasgow, Glasgow G12 8QQ, UK

University of Western Australia, Crawley, WA 6009, Australia

LIGO - Massachusetts Institute of Technology, Cambridge, MA 02139, USA

Columbia University, New York, NY 10027, USA

The University of Texas at Brownsville and Texas Southmost College, Brownsville, TX 78520, USA

San Jose State University, San Jose, CA 95192, USA

Moscow State University, Moscow 119992, Russia

LIGO - Livingston Observatory, Livingston, LA 70754, USA

Washington State University, Pullman, WA 99164, USA

University of Oregon, Eugene, OR 97403, USA

Syracuse University, Syracuse, NY 13244, USA

Rutherford Appleton Laboratory, HSIC, Chilton, Didcot, Oxon OX11 0QX, UK

University of Maryland, College Park, MD 20742, USA

University of Massachusetts, Amherst, MA 01003, USA

NASA

Goddard Space Flight Center, Greenbelt, MD 20771, USA

University of Michigan, Ann Arbor, MI 48109, USA

University of Sannio at Benevento, I-82100 Benevento, Italy

The University of Mississippi, University, MS 38677, USA

Charles Sturt University, Wagga Wagga, NSW 2678, Australia

Caltech-CaRT, Pasadena, CA 91125, USA

Carleton College, Northfield, MN 55057, USA

The University of Melbourne, Parkville, VIC 3010, Australia

Cardiff University, Cardiff CF24 3AA, UK

otv

os University, ELTE 1053 Budapest, Hungary

University of Salerno, 84084 Fisciano (Salerno), Italy

The University of Sheffield, Sheffield S10 2TN, UK

The Pennsylvania State University, University Park, PA 16802, USA

Inter-University Centre for Astronomy and Astrophysics, Pune 411007, India

Southern University and A&M College, Baton Rouge, LA 70813, USA

California Institute of Technology, Pasadena, CA 91125, USA

University of Rochester, Rochester, NY 14627, USA

The University of Texas at Austin, TX 78712, USA

Australian National University, Canberra 0200, Australia

Embry-Riddle Aeronautical University, Prescott, AZ 86301, USA

University of Minnesota, Minneapolis, MN 55455, USA

University of Adelaide, Adelaide, SA 5005, Australia

University of Southampton, Southampton SO17 1BJ, UK

Northwestern University, Evanston, IL 60208, USA

National Astronomical Observatory of Japan, Tokyo 181-8588, Japan

Institute of Applied Physics, Nizhny Novgorod 603950, Russia

University of Strathclyde, Glasgow G1 1XQ, UK

Loyola University, New Orleans, LA 70118, USA

Hobart and William Smith Colleges, Geneva, NY 14456, USA

Louisiana Tech University, Ruston, LA 71272, USA

Andrews University, Berrien Springs, MI 49104, USA

Universitat de les Illes Balears, E-07122 Palma de Mallorca, Spain

Sonoma State University, Rohnert Park, CA 94928, USA

Trinity University, San Antonio, TX 78212, USA

Rochester Institute of Technology, Rochester, NY 14623, USA

Southeastern Louisiana University, Hammond, LA 70402, USA

Received 2009 May 19; accepted 2009 July 17; published 2009 July 30

L70

ABBOTT ET AL.

Vol. 701

ABSTRACT

We present the results of a LIGO search for short-duration gravitational waves (GWs) associated with the

2006 March 29 SGR 1900+14 storm. A new search method is used, “stacking” the GW data around the times

of individual soft-gamma bursts in the storm to enhance sensitivity for models in which multiple bursts are

accompanied by GW emission. We assume that variation in the time difference between burst electromagnetic

emission and potential burst GW emission is small relative to the GW signal duration, and we time-align GW

excess power time–frequency tilings containing individual burst triggers to their corresponding electromagnetic

emissions. We use two GW emission models in our search: a fluence-weighted model and a flat (unweighted)

model for the most electromagnetically energetic bursts. We find no evidence of GWs associated with either

model. Model-dependent GW strain, isotropic GW emission energy

, and

≡

upper limits

are estimated using a variety of assumed waveforms. The stacking method allows us to set the most stringent

model-dependent limits on transient GW strain published to date. We find

upper limit estimates (at

a nominal distance of 10 kpc) of between 2

erg and 6

erg depending on the waveform

type. These limits are an order of magnitude lower than upper limits published previously for this storm

and overlap with the range of electromagnetic energies emitted in soft gamma repeater (SGR) giant flares.

Key words:

gamma rays: bursts – gravitational waves – pulsars: individual (SGR 1900+14) – stars: neutron

1. INTRODUCTION

Soft gamma repeaters (SGRs) sporadically emit brief

(

∼

1 s) intense bursts of soft gamma-rays. Three of the five

known SGRs have produced rare “giant flare” events with initial

bright, short (

∼

2 s) pulses with peak electromagnetic (EM)

luminosities between 10

and 10

erg s

−

, placing them among

the most EM luminous events in the universe. According to the

“magnetar” model SGRs are galactic neutron stars with extreme

magnetic fields

∼

G (Duncan & Thompson

1992

). Bursts

may result from the interaction of the star’s magnetic field with

its solid crust, leading to crustal deformations and occasional

catastrophic cracking (Thompson & Duncan

1995

; Schwartz

et al.

2005

; Horowitz & Kadau

2009

) with subsequent excita-

tion of nonradial neutron star

-modes (Andersson & Kokkotas

1998

; de Freitas Pacheco

1998

; Ioka

2001

) and the emission

of GWs (de Freitas Pacheco

1998

; Ioka

2001

;Horvath

2005

;

Owen

2005

). For reviews, see Mereghetti (

2008

) and Woods &

Thompson (

2004

Occasionally, SGRs produce many soft gamma bursts in a

brief period of time; such intense emissions are referred to as

“storms.” We present a search for short-duration GW signals

(

0.3 s) associated with

multiple

bursts in the 2006 March 29

SGR 1900+14 storm (Israel et al.

2008

) using data collected

by the Laser Interferometer Gravitational Wave Observatory

(LIGO; Abbott et al.

2009b

). The storm light curve, obtained

from the Burst Alert Telescope (BAT) aboard the

Swift

satellite

(Barthelmy et al.

2005

), is shown in Figure

. It consists of

more than 40 bursts in

∼

30 s, including common SGR bursts

and some intermediate flares with durations

5 s. The total

fluence for the storm event was estimated by the Konus-Wind

team to be (1–2)

−

erg cm

−

in the (20–200) keV range

(Golenetskii et al.

2006

), implying an isotropic EM energy

(1–2)

erg at a nominal distance to SGR 1900+14

of 10 kpc (source location and distance is discussed in Kaplan

et al.

2002

). At the time of the storm both of the 4 km LIGO

detectors (located at Hanford, WA and Livingston, LA) were

taking science quality data.

We attempt to improve sensitivity to multiple weak GW burst

signals associated with the storm’s multiple EM bursts by adding

http://www.ligo.org

together GW signal power over multiple bursts. In doing so we

assume particular GW emission models, which we describe in

the next section. Figure

illustrates the stacking procedure using

the four most energetic bursts in the storm.

2. METHODS

The analysis is performed by the Stack-a-flare pipeline

(Kalmus et al.

2009

), which extends the method used in a

recent LIGO search for transient GW associated with individual

SGR bursts (Abbott et al.

2008a

) and relies on an excess

power detection statistic (Anderson et al.

2001

). To “stack”

bursts in the storm, we first generate

excess power time–

frequency tilings. These are two-dimensional matrices in time

and frequency produced by combining the two detectors’ data

streams so as to provide sensitivity to correlated signals, as

described in Kalmus et al. (

2007

). Each tiling element gives

an excess power estimate in the GW detector data stream in a

small period of time

δt

and a small range of frequency

δf

.The

time range of each tiling is chosen to be centered on the time of

one of the target EM bursts in the storm. We then align these

tilings along the time dimension so that times of the target EM

bursts coincide, and perform a weighted addition.

Stacking significantly improves sensitivity to GW emission

under a given model. However, improving detection probability

depends upon stacking according to GW emission models that

correctly describe nature. The storm light curve motivated

two stacking models: a flat-weighted model with an energy

cutoff, which includes the 11 most energetic EM bursts with

unity weighting factors; and an EM-fluence-weighted model

comprised of the 18 most energetic EM bursts. In the flat model,

we assume that a fixed amount of GW energy is released in each

burst independently of its EM energy, provided the EM energy is

above a threshold. The threshold choice is motivated by a clear

separation in EM fluence of the 11 most energetic bursts from

out of the total of

∼

40 bursts in the storm observed by BAT.

A histogram of EM fluence of bursts (in terms of BAT counts)

illustrating this separation is shown in Kalmus et al. (

2009

). In

the EM-fluence-weighted model, we make the hypothesis that

≡

is constant from burst to burst, i.e.,

always proportional to

. Including the 18 most energetic

bursts accounts for 95% of the total EM fluence of the more