The Supernova, the Black Hole and the Gamma Ray BurstPhil Plait, beaming proudlyJuly 17, 2002The First Burst•Vela satellite fleet launched to detect nuclear weapons test in late 60s•Multiple satellites flown:allowed crude position determination and could test for coincidence•In 1969, data from 1967 foundwhich showed a burst that wasclearly not a clandestine bombtest (plot on right)•16 bursts found between 1969 and 1972Compton Gamma Ray Observatory-BATSE (1991 –2000)•8 instruments on corners of spacecraft•NaI scintillators Flash ForwardOver time, it became clear that nothing was clear. •Some show the single rapid burst followed bya longer secondary burst•Some are relatively smooth, others spiky•Durations range from 30 milliseconds to 1000 secondsThe GRB GalleryThe Big Questions: What and WhereSparse data makes for guessing gamesClearly, dealing with high energy eventsBut, a clue eventually became apparent:GRBs are evenly spreadacross the whole sky!Near or Far?Isotropic distribution implications:Silly or not, the only way to be sure was to findthe afterglow.Very close: within a few parsecs of the SunVery far: huge, cosmological distancesSort of close: out in the halo of the Milky WayWhy no faint bursts?What could produce such a vast amount of energy?A comet hitting a neutron star fits the billBreakthrough!In 1997, BeppoSAX detects X-rays from a GRBafterglow for the first time, 8 hours after burstThe View From Hubble/STIS, 7 months laterOn a clear day, you really cansee forever990123 reached 9thmagnitudefor a few moments!First optical GRB afterglow detected simultaneouslyThe new problemSo: They really are far away! What can do that?HypernovaBinary neutron star mergerLack of very faint bursts implied they are not close by,eventually confirmed by redshiftsStellar evolution made simpleStars like the Sun go gentle into that good nightMore massive stars rage, rage against the dying of the lightPuff!Bang!Bang!A more complicated view…Disaster: creating a supernova•Massive star (>8 solar masses)•Fusion generates heat•Gravity inward balances pressure outward•Core fusion builds up “onion layers”•Iron builds up in core•Iron fusion robs core of electrons, heat•Collapse: Kaboom! Huge energies released:1053ergs, > Sun’s lifetime emission•Result: neutron star or black hole, expandingshell of radioactive matter which fadesover monthsNeutron Stars: Dense cindersMass: about 1.4 to 2.8 solar massesRadius: 5 kilometersDensity: 1014g/cm3 = atomic nucleusMagnetic field: 1012gauss (Earth = 1 gauss)Rotation rate: from 1000Hz to 0.08 HzPulsars are neutron starsRadio and gamma ray pulsesBlack holesMass: > 3 to a few x 109solar massesDefined: an object where the escape velocityIs greater than the speed of lightVe= (2 G m /r)1/2Schwarzschild radius = 2 G m/c2Rs= 3 km for the SunIf they’re black, how come they’re so bright?Accretion disks! Powered by gravity, heated by frictionAn object falling in can create about 10% of rest mass into energy1 marshmallow= atomic bomb(about 10 kilotons)So, a supernova creating a neutron star or black hole is a natural candidate for a GRB progenitorEnergetics problem is even better if energy is beamed! Don’t need as much energy, but do need more GRBsThe Supernova ConnectionGRB011121Afterglow faded like supernovaData showed presence of gas like a stellar windIndicates some sort of supernova and not a NS/NS mergerNot so fast, pardner!The data seem to indicate two kinds of GRBs•Those with burst durations less than 2 seconds•Those with burst durations morethan 2 secondsShort bursts tend to produce “harder” gamma rays, as predicted by the NS/NS merger modelLong bursts tend to produce “softer” gamma rays, as predicted by the hypernova merger modelClearly, more info is neededHow exactly does a supernova or NS/NS merger turn into a GRB?Good question. Wanna win the Rossi prize?What we know:•Gamma rays created in explosion through interaction of shock wave and charged particles•Matter accelerated from 99.99% to 99.99999%of speed of light•Beaming?•Huge energies available for tappingThe high view: getting a better lookHETE-2GLASTSwift