About the discovery of X-ray bursts35 years ago

John Heise’s After Dinner speech

X-ray burst workshop

Leiden 2010

SRON-Utrecht

many high-energy satellites in the period 1960-1975

UHURU 1971

Vela-5 1969

SAS-3 1975

ANS 1974

1960 1975

Mostly “scanning” satellites

• small fraction of time “on source”• but seeing large fraction of the sky• rare phenomenae better seen while

pointing

• ANS, the Astronomical Netherlands Satellitethe first X-ray pointing satellite

ANS, 1974-1976, the first 3-axis stabilized X-ray satellite

• for X-ray & UV

• with unfavorable orbit:

ANS

Instruments:

SRON-Utrecht SXX 0.2 – 0.25 keV

1-7 keV

Harvard+MIT HXX 2-25 keV

bragg-crystal spectr.

Groningen UV-telescope

SXX: John Heise

HXX: Gursky, Grindlay

bragg: Schnopper,

X-ray bursts discovered for the wrong reasonNGC 6624, a centrally condensed

globular cluster

errorbox

3U1820-30

In 1974 thought

(Bahcall) to contain a

Central Black Hole of

~100-1000 Msun

characteristics of

BHs were thought to be

● soft spectrum

● variability

1974 Rothschild

et al.

~millisec bursts

(for ~1 Msun)

so possibly

Expecting

~sec bursts

(for ~1000 Msun)

In 1974: 1 candidate Black Hole: Cyg X-1exhibiting millisec bursts

summer 1974

(after visit John Bahcall)

Heise planned

observations

for 3U1820-30 around

28 september 1974

swapping time with

the UV-experiment t

maximize exposure time

with window

ANS planning:visibility per source ~1 day/cos(lat)

Data analysis nov 1975

35 years ago

nov 1975 discovery of 2 X-ray Bursts in 3U 1820-30

ANS-data

NGC6624

3U1820-30

ANS data arrived in nov 1975

Data reduction with

Josh Grindlay, Harvard:

Grindlay & Heise, 1975

(IAU-circular)

Grindlay et al, 1976

10 s

dec 1975: energy explosions in spaceDutch press:

sensational discovery with “ANS”

“ANS”

Astronomical Netherlands Satellite

1974-1976

main concern in the beginning:background particle events?

• SXX and HXX different respons

to high-energy particles

• collimators were slightly offset

and ratio was consistent

with celestial source

NO:

others were less concernedabout the possibility of bg-events

COSMOS 428

1960 1975

Background events?

Hard “bursts” seen everywhere since 1971! But these were background

Kosmos 428 satellite,

IKI, Moscow

Babushkina

Kudryavtsev

Melioranskii

Walter Lewin 1977:

correlated with geoposition

(all near van Allen belts)

Thermonuclear explanationof X-ray bursts

● 1975, Hansen and van Horn

“Nuclear fusion in accreting neutron star envelopes”

● 1976, first mentioned in the context of X-ray bursts

by Laura Maraschi (Milaan)

● 1976, Woosley and Taam

Thermonuclear explosions on Neutron Stars

● 1976, Jean Swank

BB emission size consistent with NS

What about the Vela-5A/B short transients?

Including the

“Norma burster”

position accuracy

~6 degree

Walter Lewin in reviews:

ignored by definition

(Def. : X-ray bursts have

rise times ~1 sec, not seen

in Vela-bursts)

Other Fast Transients in X-rays

● Other satellites (Ariel V etc) discovered

fast Transients also at high galactic latitude

● What is the nature of these sources?

some may be Gamma Ray Bursts

some may be related with flare stars

● The study required the use of wide field

imaging in X-rays with long exposure times:

just sit and wait till a transient occurred within the FOV

Wide Field Cameras in X-rays

To localize new fast Transients and establish there nature

SRON-Utrecht invested in Coded Mask Camera’s

Wide Field Cameras in X-rays1980 5 WFCs?

new Dutch satellite TIXTE?

TIXTE:S/C concept

WFC’s

WFC’s

1982 4 WFCs?

new ESA satellite X80?

1981 COMIS/TTM om MIR-station

a pilot study with 1 WFC? YES! Launched 1987

1983 3 WFCs?

Dutch-Italian satellite

1985 2 WFCs!

Dutch-Italian SAX satellite

biggest succes:arcmin localization of GRBs

Cyg X-1Burst

40o

40o

sign

ifica

nce→

exposure 52 ksec 30 sec 48 ksec

3ox3o 3ox3o 3ox3o

GRB960720

GRB970228

WFC

GRB

WFC view on the Galactic Center

discovery of new neutron stars

SAXJ1808-36

WFC discovery of superbursts a new thermonuclear burning regime

4U1735-44 Cornelisse et al. 2001

KS1731-26

X-r

ay

inte

nsi

ty →

har

dn

ess

→

E~1039 ergs

E~1042 ergs

X-ray

Burst

Superburst

Rön

tgen

-inte

nsite

it→

time →

Xray-burst publications per year

1976 1985 1995 2005

Tod’s discovery of

burst oscillations

data Jean in ‘t Zand

Top of most cited papers

Wallace & Woosley (1981): 372 (TH, Explosive hydrogen burning)

Lewin et al. (1993): 284 (Space Science Review)

Strohmayer et al (1996): 283 (OBS, Discovery burst oscillations)

Grindlay et al. (1976) 198 (OBS, discovery paper)

Lewin et al. (1981): 181 (Space Science Review)

Woosley & Taam (1976): 174 (TH, 1st interpretation)Fujimoto et al. (1981): 165 (TH, Accretion regimes for bursting)

Chakrabarty et al. (2003): 164 (OBS, burst.osc. pulsar in J1808)

Schatz et al. (2001): 158 (TH, endpoint of rp process)

Ayasli et al. (1982): 152 (TH)

Kuulkers et al. (2003): 125 (OBS, PRE bursts in Globular clusters)

Swank et al. (1977): 116 (BB emission size consistent with NS)

Joss et al. (1977): 107 (TH)

Strohmayer et al. (2002): 104 (OBS, Superburst from 4U 1820-30)

most productive authors

nr as first author (Citation score)

Lewin: 41 (20)

van Paradijs: 21 (23)

Strohmayer: 34 (29)

Grindlay: 15 (26)

in 't Zand: 14 (23)

Kuulkers: 13 (19)

Taam: 13 (23)

Swank: 10 (17)

Hoffman: 10 (21)

Cumming: 11 (18)

Conclusion

X-ray burst astronomy

is a thriving field

with a promise to extract

fundamental NS-data