10/21/03Prof. Lynn Cominsky1 Class web site: Office: Darwin 329A and NASA E/PO (707) Best way to reach me: Astronomy 305/Frontiers in Astronomy

10/21/03Prof. Lynn Cominsky2 Group 8

10/21/03Prof. Lynn Cominsky3 Stellar evolution made simple – a review Stars like the Sun go gentle into that good night More massive stars rage, rage against the dying of the light Puff! Bang! BANG!

10/21/03Prof. Lynn Cominsky4 Exploding Stars At the end of a star’s life, if it is large enough, it will end with a bang (and not a whimper!) At the end of a star’s life, if it is large enough, it will end with a bang (and not a whimper!) Supernova 1987A in Large Magellanic Cloud HST/WFPC2

10/21/03Prof. Lynn Cominsky5 Supernova Remnants Radioactive decay of chemical elements created by the supernova explosion Radioactive decay of chemical elements created by the supernova explosion Vela Region CGRO/Comptel

10/21/03Prof. Lynn Cominsky6 Neutron Stars: Dense cinders Mass: ~1.4 solar masses Radius: ~10 kilometers Density: g/cm 3 Magnetic field: gauss Spin rate: from 1000Hz to 0.08 Hz

10/21/03Prof. Lynn Cominsky7 Making a Neutron Star

10/21/03Prof. Lynn Cominsky8 Black holes Mass: > 3 to a few x 10 9 solar masses Defined: an object where the escape velocity Is greater than the speed of light V e = (2 G m / r) 1/2 Schwarzschild radius = 2 G m/c 2 R s = 3 km for the Sun

10/21/03Prof. Lynn Cominsky9 Accretion Powered by gravity, heated by friction Black holes, neutron stars and white dwarfs in binaries Accretion is 10% efficient 1 marshmallow = atomic bomb (about 10 kilotons)

10/21/03Prof. Lynn Cominsky10Accretion Matter transfers through inner Lagrange point from normal star onto compact companion Matter transfers through inner Lagrange point from normal star onto compact companion Swirls around in accretion disk Swirls around in accretion disk Blondin 1998 movie

10/21/03Prof. Lynn Cominsky11 Accretion movies Roche lobe overflow Roche lobe overflow 3D Simulations by John Blondin Stellar wind capture Stellar wind capture

10/21/03Prof. Lynn Cominsky12 Classifying Bursts In this activity, you will be given twenty cards showing different types of bursts In this activity, you will be given twenty cards showing different types of bursts Pay attention to the lightcurves, optical counterparts and other properties of the bursts given on the reverse of the cards Pay attention to the lightcurves, optical counterparts and other properties of the bursts given on the reverse of the cards How many different types of bursts are there? Sort the bursts into different classes How many different types of bursts are there? Sort the bursts into different classes Fill out the accompanying worksheet to explain the reasoning behind your classification scheme Fill out the accompanying worksheet to explain the reasoning behind your classification scheme

10/21/03Prof. Lynn Cominsky13 Aitoff Projection & Galactic Coordinates (1)

10/21/03Prof. Lynn Cominsky14 Aitoff Projection & Galactic Coordinates (2)

10/21/03Prof. Lynn Cominsky15 Answers (1) X-ray BurstersSoft Gamma- Ray Repeaters Gamma ray bursts

10/21/03Prof. Lynn Cominsky16 Answers (2) X = Gamma Ray Bursts = Soft Gamma Ray Repeaters = X-ray Bursters

10/21/03Prof. Lynn Cominsky17 Distributions If sources are located randomly in space, the distribution is called isotropic If sources are located randomly in space, the distribution is called isotropic If the sources are concentrated in a certain region or along the galactic plane, the distribution is anisotropic If the sources are concentrated in a certain region or along the galactic plane, the distribution is anisotropic

10/21/03Prof. Lynn Cominsky18 What makes Gamma-ray Bursts? X-ray Bursts X-ray Bursts Properties Properties Thermonuclear Flash Model Thermonuclear Flash Model Soft Gamma Repeaters Soft Gamma Repeaters Properties Properties Magnetar model Magnetar model Gamma-ray Bursts Gamma-ray Bursts Properties Properties Models Models Afterglows Afterglows Future Mission Studies Future Mission Studies

10/21/03Prof. Lynn Cominsky19 X-ray Bursts Thermonuclear flashes on Neutron Star surface – hydrogen or helium fusion Thermonuclear flashes on Neutron Star surface – hydrogen or helium fusion Accreting material burns in shells, unstable burning leads to thermonuclear runaway Accreting material burns in shells, unstable burning leads to thermonuclear runaway Bursts repeat every few hours to days Bursts repeat every few hours to days Bursts are never seen from black hole binaries (no surface for unstable nuclear burning) or from (almost all) pulsars (magnetic field quenches thermonuclear runaway) Bursts are never seen from black hole binaries (no surface for unstable nuclear burning) or from (almost all) pulsars (magnetic field quenches thermonuclear runaway)

10/21/03Prof. Lynn Cominsky20 X-ray Burst Sources Locations in Galactic Coordinates Locations in Galactic Coordinates burstersnon-burstersGlobular Clusters Most bursters are located in globular clusters or near the Galactic center They are therefore relatively older systems

10/21/03Prof. Lynn Cominsky21 X-ray Burst Source Properties Weaker magnetic dipole: B~10 8 G Weaker magnetic dipole: B~10 8 G NS spin period seen in bursts ~0.003 sec. NS spin period seen in bursts ~0.003 sec. Orbital periods : h from X-ray dips & eclipses and/or optical modulation Orbital periods : h from X-ray dips & eclipses and/or optical modulation > 15 well known bursting systems > 15 well known bursting systems Low mass companions Low mass companions L x = erg/s L x = erg/s Neutron Stars in binary systems Neutron Stars in binary systems

10/21/03Prof. Lynn Cominsky22 X-ray Emission X-ray emission from accretion can be modulated by magnetic fields, unstable burning and spin l Modulation due to spin of neutron star can sometimes be seen within the burst

10/21/03Prof. Lynn Cominsky23 Thermonuclear Flash Model movie

10/21/03Prof. Lynn Cominsky24 X-ray Burst Sources Burst spectra are thermal black-body Burst spectra are thermal black-body Cominsky PhD 1981 L(t) = 4  R 2  T(t) 4 Radius Expansion Temperature 22

10/21/03Prof. Lynn Cominsky25 Soft Gamma Repeaters There are four of these objects known to date There are four of these objects known to date One is in the LMC, the other 3 are in the Milky Way One is in the LMC, the other 3 are in the Milky Way LMC SGR

10/21/03Prof. Lynn Cominsky26 Making a magnetar

10/21/03Prof. Lynn Cominsky27 SGR Emission l Emission from accretion can be modulated by magnetic fields l Modulation due to spin of neutron star can be seen within the burst movie

10/21/03Prof. Lynn Cominsky28 Soft Gamma Repeater Properties Superstrong magnetic dipole: B~ G Superstrong magnetic dipole: B~ G NS spin period seen in bursts ~5-10 sec, shows evidence of rapid spin down NS spin period seen in bursts ~5-10 sec, shows evidence of rapid spin down No orbital periods – not in binaries! No orbital periods – not in binaries! 4 well studied systems + several other candidate systems 4 well studied systems + several other candidate systems Several SGRs are located in or near SNRs Several SGRs are located in or near SNRs Soft gamma ray bursts are from magnetic reconnection/flaring like giant solar flares Soft gamma ray bursts are from magnetic reconnection/flaring like giant solar flares L x = erg/s at peak of bursts L x = erg/s at peak of bursts Young Neutron Stars near SNRs Young Neutron Stars near SNRs

10/21/03Prof. Lynn Cominsky29 SGR Strong burst showing ~5 sec pulses Strong burst showing ~5 sec pulses Change in 5 s spin rate leads to measure of magnetic field Change in 5 s spin rate leads to measure of magnetic field Source is a magnetar! Source is a magnetar!

10/21/03Prof. Lynn Cominsky30 SGR burst affects Earth On the night of August 27, 1998 Earth's upper atmosphere was bathed briefly by an invisible burst of gamma- and X-ray radiation. This pulse - the most powerful to strike Earth from beyond the solar system ever detected - had a significant effect on Earth's upper atmosphere, report Stanford researchers. It is the first time that a significant change in Earth's environment has been traced to energy from a distant star. (from the NASA press release) On the night of August 27, 1998 Earth's upper atmosphere was bathed briefly by an invisible burst of gamma- and X-ray radiation. This pulse - the most powerful to strike Earth from beyond the solar system ever detected - had a significant effect on Earth's upper atmosphere, report Stanford researchers. It is the first time that a significant change in Earth's environment has been traced to energy from a distant star. (from the NASA press release)

10/21/03Prof. Lynn Cominsky31 Gamma Ray Burst Properties Unknown magnetic field Unknown magnetic field No repeatable periods seen in bursts No repeatable periods seen in bursts No orbital periods seen – not in binaries No orbital periods seen – not in binaries Thousands of bursts seen to date – no repetitions from same location Thousands of bursts seen to date – no repetitions from same location Isotropic distribution Isotropic distribution Afterglows have detectable redshifts which indicate GRBs are at cosmological distances (i.e., far outside our galaxy) Afterglows have detectable redshifts which indicate GRBs are at cosmological distances (i.e., far outside our galaxy) L  = erg/s at peak of bursts L  = erg/s at peak of bursts A cataclysmic event of unknown origin A cataclysmic event of unknown origin

10/21/03Prof. Lynn Cominsky32 The first Gamma-ray Burst Discovered in 1967 while looking for nuclear test explosions - a 30+ year old mystery! Discovered in 1967 while looking for nuclear test explosions - a 30+ year old mystery! Vela satellite

10/21/03Prof. Lynn Cominsky33 Compton Gamma Ray Observatory Eight instruments on corners of spacecraft NaI scintillators BATSE

10/21/03Prof. Lynn Cominsky34 CGRO/BATSE Gamma-ray Burst Sky Once a day, somewhere in the Universe Once a day, somewhere in the Universe

10/21/03Prof. Lynn Cominsky35 The GRB Gallery When you’ve seen one gamma-ray burst, you’ve seen…. one gamma-ray burst!!

10/21/03Prof. Lynn Cominsky36 Near or Far? Isotropic distribution implications: Silly or not, the only way to be sure was to find the afterglow. Very close: within a few parsecs of the Sun Very far: huge, cosmological distances Sort of close: out in the halo of the Milky Way Why no faint bursts? What could produce such a vast amount of energy? A comet hitting a neutron star fits the bill

10/21/03Prof. Lynn Cominsky37 Breakthrough! In 1997, BeppoSAX detects X-rays from a GRB afterglow for the first time, 8 hours after burst

10/21/03Prof. Lynn Cominsky38 The View From Hubble/STIS 7 months later

10/21/03Prof. Lynn Cominsky39 On a clear day, you really can see forever reached 9 th magnitude for a few moments! First optical GRB afterglow detected simultaneously

10/21/03Prof. Lynn Cominsky40 The Supernova Connection GRB Afterglow faded like supernova Data showed presence of gas like a stellar wind Indicates some sort of supernova and not a NS/NS merger

10/21/03Prof. Lynn Cominsky41 Hypernova A billion trillion times the power from the Sun A billion trillion times the power from the Sun The end of the life of a star that had 100 times the mass of our Sun movie

10/21/03Prof. Lynn Cominsky42 Iron lines in GRB Chandra observations show link to hypernova model when hot iron-filled gas is detected from GRB Chandra observations show link to hypernova model when hot iron-filled gas is detected from GRB Iron is a signature of a supernova, as it is made in the cores of stars, and released in supernova explosions

10/21/03Prof. Lynn Cominsky43 Catastrophic Mergers Death spiral of 2 neutron stars or black holes Death spiral of 2 neutron stars or black holes

10/21/03Prof. Lynn Cominsky44 Which model is right? The data seem to indicate two kinds of GRBs Those with burst durations less than 2 seconds Those with burst durations more than 2 seconds Short bursts have no detectable afterglows so far as predicted by the NS/NS merger model Long bursts are sometimes associated with supernovae, and all the afterglows seen so far as predicted by the hypernova merger model

10/21/03Prof. Lynn Cominsky45 Gamma-ray Bursts Either way you look at it – hypernova or merger model Either way you look at it – hypernova or merger model GRBs signal the birth of a black hole! GRBs signal the birth of a black hole!

10/21/03Prof. Lynn Cominsky46 Gamma-ray Bursts Or maybe the death of life on Earth? Or maybe the death of life on Earth? No, gamma- ray bursts did not kill the dinosaurs!

10/21/03Prof. Lynn Cominsky47 How to study Gamma rays? Absorbed by the Earth’s atmosphere Absorbed by the Earth’s atmosphere Use rockets, balloons or satellites Use rockets, balloons or satellites Can’t image or focus gamma rays Can’t image or focus gamma rays Special detectors: crystals, silicon-strips Special detectors: crystals, silicon-strips GLAST balloon test

10/21/03Prof. Lynn Cominsky48 HETE-2 Launched on 10/9/2000 Launched on 10/9/2000 Operational and finding about 2 bursts per month Operational and finding about 2 bursts per month

10/21/03Prof. Lynn Cominsky49 Swift Mission Burst Alert Telescope (BAT) Burst Alert Telescope (BAT) Ultraviolet/Optical Telescope (UVOT) Ultraviolet/Optical Telescope (UVOT) X-ray Telescope (XRT) X-ray Telescope (XRT) To be launched in 2004

10/21/03Prof. Lynn Cominsky50 Swift Mission Will study GRBs with “swift” response Will study GRBs with “swift” response Survey of “hard” X-ray sky Survey of “hard” X-ray sky To be launched in 2003 To be launched in 2003 Nominal 3-year lifetime Nominal 3-year lifetime Will see ~150 GRBs per year Will see ~150 GRBs per year

10/21/03Prof. Lynn Cominsky51 Gamma-ray Large Area Space Telescope GLAST Burst Monitor (GBM) Large Area Telescope (LAT)

10/21/03Prof. Lynn Cominsky52 GLAST Mission First space-based collaboration between astrophysics and particle physics communities First space-based collaboration between astrophysics and particle physics communities Launch expected in 2006 Launch expected in 2006 Expected duration 5-10 years Expected duration 5-10 years Over 3000 gamma-ray sources will be seen Over 3000 gamma-ray sources will be seen

10/21/03Prof. Lynn Cominsky53 GLAST Burst Monitor (GBM) PI Charles Meegan (NASA/MSFC) PI Charles Meegan (NASA/MSFC) US-German secondary instrument US-German secondary instrument 12 Sodium Iodide scintillators 12 Sodium Iodide scintillators Few keV to 1 MeV Few keV to 1 MeV Burst triggers and locations Burst triggers and locations 2 bismuth germanate detectors 2 bismuth germanate detectors 150 keV to 30 MeV 150 keV to 30 MeV Overlap with LAT Overlap with LAT

10/21/03Prof. Lynn Cominsky54 Large Area Telescope (LAT) PI Peter Michelson (Stanford) PI Peter Michelson (Stanford) International Collaboration: USA NASA and DoE, France, Italy, Japan, Sweden International Collaboration: USA NASA and DoE, France, Italy, Japan, Sweden LAT is a 4 x 4 array of towers Each tower is a pair conversion telescope with calorimeter

10/21/03Prof. Lynn Cominsky55 Pair Conversion Telescope

10/21/03Prof. Lynn Cominsky56 LAT Schematic Tiled Anticoincidence Shield Tiled Anticoincidence Shield Silicon strip detectors interleaved with Tungsten converter Silicon strip detectors interleaved with Tungsten converter Cesium Iodide hodoscopic calorimeter Cesium Iodide hodoscopic calorimeter

10/21/03Prof. Lynn Cominsky57 GLAST video A public outreach product from the GLAST Education and Public Outreach group A public outreach product from the GLAST Education and Public Outreach group

10/21/03Prof. Lynn Cominsky58 Web Resources : GLAST E/PO web site GLAST E/PO web site Swift E/PO web site Swift E/PO web site Imagine the Universe! Imagine the Universe! Science at NASA’s Marshall Space Flight Center Science at NASA’s Marshall Space Flight Center John Blondin’s accretion simulations John Blondin’s accretion simulations

10/21/03Prof. Lynn Cominsky59 Web Resources Robert Duncan’s magnetar page Chandra observatory Jochen Greiner’s Gamma-ray bursts and SGR Summaries HETE-2 mission Compton Gamma Ray Observatory