The Great Debate II: The Distance Scale To GRB

1. The Great Debate II:The Distance Scale To GRB • GDI • GDII • What is a GRB? • Characteristics of GRB • Galactic Scale • Cosmological Scale • Resolution? Conclusions and Asides

2. GDI • Debate over the scale of the universe • Objects in question were the “spiral nebulae” • 1920 in SNHM • Curtis (Island Universes) • Shapley (orbit MW) won Harvard position • Hubble studying the nature of SN • 1923 Hubble found CV in Andromeda and others • Left no room for doubt of distance scale • His observations changed our view forever

3. GDII • Aka Diamond Jubilee Debate • Distance Scale to GRBs (parallels) • 75th anniversary of GDI • Lamb (Galactic) • Paczynski (Cosmological) • Importance of GD's

4. “The Curtis-Shapley debate makes interesting reading even today. It is important not only as an historical document, but also as a glimpse into the reasoning process of eminent scientists engaged in a great controversy for which the evidence on both sides is fragmentary and partly faulty. This debate illustrates forcefully how tricky it is to pick one's way through the treacherous ground that characterizes research at the frontiers of science” Importance of GD's

5. What is a GRB?

6. Characteristics of GRB • Seemingly Isotropic • Energies range from tens of keV to tens of Gev • Most of the Bursts outshine all other GR sources combined! • Wide variety of time profiles (30ms-1000s) • Some Chaotic and Spiky • Some Simple with a single spike • Some Exhibit Both Characteristics

10. Characteristics of GRB • HE GRB are generally shorter with sharper spikes • Generally Asymmetric (Leading edge is shorter) • No observed optical counterpart • Very Difficult to classify • “Tip of the Iceberg” effect • Most of power at >50keV

12. Characteristics of GRB • Low Energies Display Inhomogeneity • High Energies Display homogeneity

14. Galactic Model (Lamb's side) • 2 independent sources of evidence demonstrate that NS have median velocities of about 600km/s • Offset of pulsar from SNR “the duck” • Greater understanding of an observational bias that affects determination of pulsar velocities. (factor of 2) • About half have speeds greater than 800km/s • Revolutionized understanding of NS distribution • Compare with galactic escape velocity, 500-600km/s

16. HCNS Model • Many NS have speeds great than escape • Forms a halo of NS around the galaxy

17. HVNS Model • Establishes that NS distribution forms a distant corona which may appear isotropic when viewed from the earth. • To avoid any anisotropies due to the the fact that we are not in the center, it is required that the radius of the NS sphere be greater and one sixth the distance to M31.

18. HVNS Model • Great, NS can account for Isotropy. Can they produce GRB's • Yes! • SGR • 3 known SGR in our galaxy, each associated with a SNR with severe offset like “the duck” • Energies and time durations overlap with those of garb's • Implies HVNS produce Burst-like behavior

19. HVNS Model • So, HVNS can produce Burst-like Behavior. Have they ever been observed to produce an event looks just like a GRB? • YES! • The Famous 1979 March 5th event. • SGR 0526-66, located in the LMC at 50 kpc • Associated with SNR N49, and has the severe offset that is the signature of a HVNS of about 1200km/s

21. HVNS Model • March 5th event spectrum was found to be indistinguishable from a GRB spectrum. • This Demonstrates that HVNS in our halo are capable of producing events which appear to be garb's • Whether the March 5th event was a true GRB or a unique event is debatable.

22. HVNS Model • Mechanism? • Unclear • Energy source • Ultra High B field • Stress-strain

23. HVNS Model (future) • Test for M31 anisotropy • Requires about 10-50 times the sensativity • Test for Anisotropies due to off center • Need Better Data!!

24. Conclusions