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Gamma Ray Bursts Gamma Ray Bursts Maurizio Falanga The First Discoveries • Designed to detect nuclear test (in violaon of the Nuclear Test Ban Treaty, 1963) Vela 4 and 5 satellite pair were launched in 1963 and 1969. • The Gamma Ray Bursts (GRB) were discovered accidentally in 1967 by US military satellites in search of non authorized nuclear explosions. The discovery was announced by Klebesadel, Strong, and Olson (ApJ, 182, 85) in 1973. • The Vela 5 satellites detected a total of 73 gamma ray bursts similar to what they would expect3C273 from such explosions, but coming from space. • These bursts where short, from 0.01 to about 100 s, and had most of their energy carried by photons in the energy range between 150-750 keV . • They remained mysteries for more than 30 years. Follow-Up: Compton Gamma-Ray Observatory 1991-2000 BATSE was a high energy astrophysics experiment in orbit around Earth on NASA's Compton Gamma-Ray Observatory. With its 8 modules, it was able to see the whole sky, and detected about 1 GRB per day. Q$ !%'*$ ").$ 0*3+)3H02$ <0*+)0B(+.<I$ 'N,DW$ 2>.")>&$ *";$ 7$ <0*[=2+$ ,-.0)$ 0*$ =3$ 23)).>"[3=$ ;0+-$ 3()$ H3H(>"[3=*$ 3E$ B()*+*K$ *-3)+$ "=<$ L">"2[2$H>"=.K$"*$3=.$;3(><$.GH.2+$ >3=L$ !%'*K$ B(+$ .G2.H+$ E3)$ +-.0)$ 0E$ +-.*.$ !%'*$ ").$ E)3#$ L">"2[2$ <()"[3=K$ =3$ *0L=0\2"=+$ 3)0L0=I$$ <0].).=2.*$ ;.).$ E3(=<K$ <(.$ +3$ +-.$>"2U$3E$"<<0[3=">$<"+"I$ >3=L$ *-3)+$ 7$*.2$ D4.)(B.#(/".--8(&""'"'(B.#(#*,/+"($'"&2E+.2*&#$ Ø First observed in 1967 by U.S. Vela 3 Ø For decades, searches were made to and 4 satellites launched in idenfy counterparts in other spectral conjuncon with Nuclear Test Ban regimes without success Treaty Ø Breakthrough reached in 1997 with Ø Signature unlike a nuclear weapon, satellite BeppoSAX detected the burst but observaons were classied GRB 970228 Ø Connued observaons of bursts Ø X-ray camera detected fading X-ray connued, and solar and terrestrial emission and op[cal oBservaons origins ruled out found a fading opcal counterpart. Ø Observaons declassied in 1973 Deep imaging revealed a faint host galaxy at this locaon. Dimness of Ø Controversy concerning locaons of galaxy did not allow a redshic bursts: Milky Way or cosmological? measurement at the me. seled only aer launch in 1991 of the Compton Gamma Ray Observatory Ø A second GRB detected by BeppoSAX, containing the Burst and Transient GRB 970508, was idened in opcal Source Explorer (BATSE), which only 4 hours aer its discovery. showed isotropic, and therefore Redshi of z = 0.835 measured (D = 6 cosmological, distribuon billion lt. yr.) What was really needed was source idenficaons BeppoSax 1996-2002 (Italian-Dutch X-ray astronomy mission) Beppo-SAX made some further discoveries possible due to its good angular resoluon. While BATSE had about 4 degrees pixels, Beppo-SAX reached about 50" (i.e. 290 mes beer). It had on board, in addion to a GRB monitor, various X-ray detectors (lower 3 months later, GRB 970508 was detected energy than gamma). by Beppo-SAX and ground-based spectrometers were able to mesure the opcal spectrum of the aerglow. This th On February 28 of 1997, Beppo-SAX saw allowed to measure the redshi of the a burst both with its Gamma Ray detector object: z~0.84. It was the confirmaon and X-ray. It observed the burst during a that GRBs were cosmologicals. few days and saw an aerglow in X: the X- However, this discovery posed a new ray image became dimmer on mescales problem. If GRBs were so distant, then of days. they had to be incredibly powerful: about 1051 to 1054 ergs, the light of a billion galaxies! '.HH3D"G$!%'$@8S77P$:<0*234.).<$;0+-$Z/69$ •! /0)*+$$+3$>32">0F.$"$!%'*$"=<$\)*+$$#(>[T;"4.>.=L+-$23(=+.)H")+*$ <.+.2+.<$$ $T$$$dT)"&$@8S???$ T! MH[2">V$@8S77P$ T! %"<03V$@8SQSP$$ MH[2">V$!%'$@8S77P$ MH[2">$*H.2+)(#$3E$+-.$-3*+$L">"G&$3E$!%'$@8S77P$3B+"0=.<$"+$+-.$J.2U$7,.>.*23H.I$ k)3#0=.=+$.#0**03=$>0=.*$3E$3G&L.=$"=<$=.3=$").$0=<02"+.<$"=<$*-3;$+-"+$+-.$L">"G&$0*$ >32"+.<$ "+$ "$ ).<*-0c$ 3E$ F$ e$ SIA@QI$ '>33#K$ 1_3)L34*U0K$ "=<$ J(>U")=0$ :7SS?9K$ NHOK$ QQ^K$ A8PI$D..$">*3$!6X$7P@K$`"&$5K$?@@@I$ From the red shi, z, a distance can be inferred [ cz ≈ dH(t0) from the Hubble-law] – billions of light years. Far, far outside our galaxy. From the distance and brightness an energy can be inferred: Ø 1050-54 erg in gamma rays alone This is 13 mes as much energy as the sun will radiate in its ten billion year lifeme, but emied in gamma-rays in less than a minute. It is 2000 mes as much as a really bright supernova radiates in several months. Distances to GRBs !%'$<()"[3=$0*$(*(">>&$p("=[\.<$"*$"*$,@SK$+-.$<()"[3=$<()0=L$;-02-$ Qq$+3$@Qq$3E$+-.$+3+">$r(.=2.$0*$<.+.2+.<$B&$+-.$+)0LL.)0=L$<.+.2+3)I$ `3*+$10*+"=+$!%'*$ F$m$7$o$?S$ $ F$e$PI7A$ +$e$A5S$`&)$ F$e$@I^$ +$e$^PS$`&)$ !%'$S@S^75$ WDM$ !%'$").$+-.$B.*+$2"=<0<"+.*$+3$ *+(<&$+-.$<..H$C=04.)*.K$0I.IK$$ &3(=L$C=04.)*.$ Gamma-Ray Burst Coordinates Network (GCN) Open/free communicaon to all the worldwide astronomers Automated system to rapidly distribute GRB posions to sites worldwide via web Reporng of observaons via GCN Circulars allows coordinaon of subsequent observaons Bimodal GRBs distribuons t(.*[3=V$D-3)+$"=<$>3=L$B()*+*$-"4.$<0].).=+$3)0L0=$a$$ ?I$10].).=+$<()"[3=$"=<$=(#B.)$3E$<.+.2+.<$!%'$ 7I$10].).=+$.=.)L&$<0*+)0B([3=$ D-3)+$!%'*$").$-")<.)$ u3=L$!%'*$").$*3c.)$ i%$:?SS$o$5SS$U.R9s:QS$o$?SS$U.R9$ ,0#.$>"L*V$k-3+3=*$"))04">$[#.$"+$<0].).=+$.=.)L&$B"=<*$ u"L$ ,0#.$W43>40=L$W=.)L&$ DH.2+)(#$ />(G$ ,&H02">$*H.2+)(#$E3)$"$!%`$0*$"$ B)3U.=$H3;.)T>";$ W=.)L&$ u3;$W=.)L&$'"=<$ u0L-+$6()4.$ %"+.$ i0L-$W=.)L&$'"=<$ ,-.$-")<$:i0L-9$W=.)L&$B"=<$ >."<*$+-.$*3c$:>3;9$3=.$ ,0#.$ %.>"[40*[2$WGH"=<0=L$D-.>>$ %$ !%'$ w$m?sx$ x$e$u3).=+F$E"2+3)K$=.")>&$+-.$*H..<$3E$>0L-+$$ v%$ $13HH>.)$/"2+3)$e$?s$:?T4s2$23*$w9x$9$ 5I$,-.$-")<$B"=<$>."<*$+-.$*3c$3=.$3=>&$E3)$>3=L$B()*+*$ ,;3$U0=<$,-0)<$-0=+V$ D-3)+$!%'*$*..#$+3$ -"4.$F.)3$>"L*$ u(#0=3*0+&$ ,0#.$>"L$ D-3)+$"=<$>3=L$!%'$"$(=0\.<$40.;$ Long GRB Progenitor u3=L$!%'$0*$"$i&H.)=34"V$W=<$H30=+$3E$"$4.)&$#"**04.$$y5STQS$ *3>")$#"**.*$*+")*$ GRB 041006 R (mag) Expected from GRB alone Expected from SN alone Days aer October 6.5126 MH[2">$>0L-+$2()4.$E3)$<0].).=+$DX$ +&H.*$ !%'$ @PS^7Q$ ;"*$ E3>>3;.<$ ;0+-0=$"$<"&$B&$DX$?@@PB;$ :+&H.$fB9$"+$+-.$*"#.$>32"[3=K$ H)340<0=L$+-.$)*+$2>(.*$"B3(+$ H)3L.=0+3)*I$ $ 'N,DW$.=<.<$0=$7SSS$"=<$;"*$ E3>>3;.<$B&$iW,WT7$E)3#$ 7SSST7SSP$ $ D;0c$>"(=2-.<$0=$7SS^$"=<$*[>>$ 3H.)"[=Lz$+-0*$">*3$23=+"0=*$ dT)"&$"=<$3H[2">$+.>.*23H.*$E3)$ DX$?@@PB;$ )"H0<$<.H>3&#.=+$+3$*.")2-$E3)$ 23(=+.)H")+*I$ $ /.)#0$!"##"T)"&$u")L.$N)."$ ,.>.*23H.$:!uND,9$>"(=2-.<$ 0=$7SSP$"=<$=3;$<.+.2+*$ *.4.)">$?SS$!%'$H.)$&.")$ 1")U$!%'*$ !%'*$N*$k)3B.*$3E$6-.#02">$W43>([3=$ Energecs of a GRBs The energy output of GRB 080319B, if spherically radiated, is > 1054 erg. This exceeds any reasonable source during such a short mescale, so the radiaon is likely highly beamed. A black hole forms at the center of the GRB source. It is rapidly rotang and almost certainly has a large magnec field. It creates a fireball of relavisc electrons, positrons and photons which expands and collides with stellar material and creates gamma rays which emerge from the star in beams ahead of the blast wave. This illustraon shows the most common type Addional emissions, or aerglow, are of gamma-ray burst, thought to occur when a created by collisions of the shock (and a massive star collapses, forms a black hole, and reverse shock) with intervening maer. blasts parcle jets outward at nearly the We can see both the jet and the aerglow speed of light. Credit: NASA/GSFC if the beam is directed towards us. '."#0=L$3E$"$!%'$ ,-.$ <.L)..$ 3E$ B."#0=L$ 2"=$ B.$ .*[#"+.<$ B&$ 3B*.)40=L$ Y_.+$ B)."U*Y$ 0=$ +-.$ "c.)L>3;$ >0L-+$ 2()4.*K$ "$ [#.$ "c.)$ ;-02-$ +-.$ "c.)L>3;$ E"<.*$ )"H0<>&$ "*$ +-.$ _.+$ *>3;*$ <3;=I$ MB*.)4"[3=*$*(LL.*+$_.+$"=L>.*$E)3#$7$+3$7S$<.L)..*I$,-.$_.+$"22.>.)"+.*$"$+-0=$*-.>>K$ ;-02-$<.2.>.)"+.*$"*$0+$.GH"=<*$0=$"$[#.$ 7 7 T?s7 %{$0*$+-.$*-.>>$)"<0(*K${S$e$:?$o$4 s2 9 $0*$+-.$).>"[40+&$H")"#.+.)K$=$0*$+-.$<.=*0+&$"=<$ W$0*$+-.$+3+">$.=.)L&I$ $ ,-.$_.+$B)."U$[#.$+_B$2"=$+-.=$B.$23==.2+.<$+3$+-.$).>"[40+&$H")"#.+.)$ N$).>"[40*[2$_.+$-"*$"=$3H.=0=L$3)$B."#0=L$"=L>.$w$m?sxI$ Ø Flashes of gamma rays associated with energec explosions in distant galaxies. GRBs occur in galaxies. Ø Isotropic distribuon shows they are at cosmological distances. Ø Observed frequency is about 1 per day; actual rate due to beaming is much greater. Ø Bursts last from milliseconds to tens of seconds and show great variety. Ejecta moves at relavisc speed Ø Believed to be most luminous electromagnec events since the Big Bang. Ø Observed fluxes are hundreds of mes brighter than supernovae, although seem to be highly beamed, so that total luminosity is comparable to that of a supernova. Ø Oen followed by an aerglow in longer wavelengths up to radio, in some cases resembling the light curve from a supernova. Ø Almost every long GRB has been associated with a galaxy with rapid star formaon, and some long GRBs are linked to supernovae.
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