The Progenitors of Short-Hard GRBs from an Extended Sample of Events

1. The Progenitors of Short-Hard GRBs from an Extended Sample of Events Avishay Gal-Yam Hubble Fellow CALTECH

2. Outline - Observational breakthrough 2005- An extended sample from the IPN- Population analysis – hosts- Final remarks

3. Short GRBs (SHBs) - Papers:Nakar, Gal-Yam, Piran & Fox 2005, ApJ Fox et al. 2005, ApJL, 050509bFox et al. 2005, Nature, Oct. 6, 050709Berger et al. 2005, Nature, Nov. issue, 050724Gal-Yam et al. 2006, ApJ, Submitted, astro-ph/0509891Nakar et al. 2006, ApJ, in press, astro-ph/0511254Also:Bloom et al. 2005Prochaska et al. 2005Tanvir et al. 2005…

4. People:E. Nakar (Caltech)T. Piran (HUJI), D. Fox (Penn State), E. Ofek (Caltech)(Extended) Caltech GRB group (Kulkarni, Frail, Berger, Cenko…)

5. The new SHB (Swift-HETE-Bursts) era • Arcmin -> arcsec localizations -> hosts • 4 relevant bursts, as of August 2005

6. Very faint GRB X-ray: T+62 s detects 11 photons(!) No optical, no radio. Very faint limits. Giant elliptical galaxy in a cluster. z=0.22 . Host? No SN GRB 050509B: Swift Detection Gehrels et al. 2005 T90=40 ms

7. HST Imaging: No Supernova 48 sources in XRT error circle Error radius = 9.3 arcsec 4 HST Epochs May 14 to June 10 Giant elliptical (Bloom et al 2005) L=1.5L* SFR<0.1 M yr-1 Fox et al. 2006

8. A Hard spike, 84 keV A Soft bump Roughly equal energy in each component SHB 050709: HETE Detection Villasenor et al. 2005 T90=70 ms

9. SHB 050709 - localization • X-ray afterglow • Optical afterglow • Secure association with a galaxy: late-type, z=0.16, moderate SFR (MW), lots of old stars (>1 GY) - Covino et al. 2005 • No SN

10. Hard spike/soft bump X-ray, optical, IR and radio afterglow detected Secure association with elliptical galaxy, z=0.26 No SN (Berger et al. 2006) Gal-Yam et al. 2005 GRB 050724: Swift Detection 15-150 keV 250 ms T90=3 s T90=40 ms 15-25 keV 100 s

11. SHB 050813: Swift Detection • Another Swift SHB • Deep imaging identifies a high-z cluster (Gladders et al. 2006) • Initial spectroscopy shows z=0.722 (Berger 2005, Prochaska et al. 2005) (but perhaps revised higher, z=1.8)

12. Recent Swift/HETE sample: • Low redshift • Most in early types • No SNe So: • Different from long GRBs • Similar to SNe Ia • Long lived progenitors • “A merger origin”?

13. Extended Sample from IPN • Goal: Search for luminosity over-density inside or around old, small, IPN error boxes (either single luminous galaxies or galaxy overdensities - clusters) • Sample: 4 small error boxes • Method: multicolor imaging (P60, LCO100), spectoscopy (P200) • Comparison with SDSS luminosity functions and galaxy densities.

14. SHB 790613 • Smallest IPN box (<1 arcmin2) • 4 reddish galaxies with similar colors – very high density (~1% prob.) • 6.5’ away from Abell 1892 (z=0.09), <1% chance association in our entire sample • Therefore assume: z=0.09 (nearest SHB), host likely early type, in cluster 26 years … !

15. SHB 000607 • Small IPN box (5.6 arcmin2) • A single luminous galaxy (R=17.57) • Sb galaxy at z=0.14, ~1.4 L* in SDSS r,i • Chance association 2% for this error box, 7% for entire sample • Therefore assume: z=0.14, intermediate spiral host

16. Z=0.31 SHBs 001204, 021201 • SHB 001204: Small IPN box (6 arcmin2) • Several galaxies • Inconsistent redshifts (0.31, 0.39), insignificant overdensity • z>0.25 (1) • SHB 021201: insignificant overdensity • z>0.25 (1)

17. Extended SHB sample

18. Mannucci et al. 2005 Comparison with SNe Ia • SNe Ia occur in galaxies of all types • But most of them occur in late-type galaxies ! • The normalized SN rate in Irr galaxies is 20 times that in E galaxies • Comparison of the observed relative rates disfavors an identical distribution (P=7%) • It appears like SHBs come from older progenitors (several Gy) (also: Zheng & Ramirez-Ruiz 2006) Gal-Yam et al. 2006

19. E Belczynski et al. 2006 Soderberg et al. 2006 Do we rule out NS-NS mergers? • No. • Main limit is small numbers (both SHBs and observed NS-NS pairs) • But, you really need to stretch to fit the data • Observations disfavor DNS models • This is not changed by 050813 z>0.72 and 051221 (Soderberg et al. 2006)

20. Concluding remarks • Similar results from redshift distribution (Nakar, Gal-Yam & Fox 2006) • Recent SHBs useless for similar analysis due to sample incompleteness (~1/10 with data) and obvious strong selection effects (in favor of gas-rich systems) • Additional observational effort imperative for further progress • Possible high local rates of SHBs (See Nakar, Gal-Yam & Fox) mean the LIGO (I or II) may provide conclusive evidence for compact binary models

21. Thanks

22. The rate and progenitor lifetime of SHBs (Nakar, Gal-yam & Fox 2005) • Goals: • Using the extended sample to constrain the local rate and the progenitors lifetime of short GRBs. • Evaluate the compatibility of these results with the compact binary progenitor model. • Explore the implications for gravitational wave detection of these events with LIGO.

23. Method: Comparing the observed redshift and luminosity distributions to predictions of various models of intrinsic redshift and luminosity distributions. (this method is an extension of a method used by Piran 1992; Ando 2004; Guetta & Piran 2005,2006)

24. Consistency test Several bursts with known z Redshift distribution Cosmology + Detector Intrinsic Observed ~400 BATSE bursts with unknown z Luminosity function

25. If f(L) is a single power-law: Cosmology Observed Intrinsic Detector In the case of BATSE SHBS a single power-law fits the data very well:f(L)  L-2±0.1

26. Progenitor lifetime distribution Intrinsic redshift distribution Star formation rate = + Porciani & Madau 2001

27. Results

28. Progenitor lifetime ttypical > 4[1]Gyr (95% [99.9%] c.l.) or if f(t)  ththenh > -0.5[-1] (95% [99.5%] c.l.) *Similar results are obtained when we take z050813>0.72 **Similar results are obtained by Guetta & Piran 2006

29. Main uncertainties and limitations • Luminosity function– any “knee” shaped broken power-law results in similar constraints. A short lifetime may be consistent with an “ankle” shaped broken power-law (expected in case of two populations of SHBs). • Star-Formation History– the results are valid for any of the three Porciani & Madau (2001) SFH functions (all peak at z≈1.5). • Detector Thresholds– important only if the luminosity function is not a single power-law (only Swift SHbs can be used). The results are valid for a range of reasonable threshold functions of Swift. • Small sample– the results are only at a level of ~3s and might be affected by unaccounted selection effects or wrong measurements.

30. Observed Local Rate (and robust lower limit) -BATSE observed rate was  170 yr-1 -At least ¼ of these bursts are at D < 1Gpc Similar result is obtained by Guetta & Piran 2006

31. Total Local rate We consdider heref(L)  L-2with a lower cutoff Lmin fb– beaming correction (30-50 Fox et al. 2005 ???) Lmin– The current observation are insensitive to Lmin < 1049 erg/sec. Evidence for population of SHBs within ~100Mpc (Tanvir et al. 2005) suggests Lmin < 1047 erg/sec

32. Local rate – upper limit SHB progenitors are (almost certainly) the end products of core-collapse supernovae (SNe). The rate of core-collapse SNe at z~0.7 is 5×105 Gpc-3 yr-1(Dahlen et al. 2004), therefore:

33. Observed NS-NS systems in our galaxy Based on three systems, Kalogera et al. (2004) find: in our galaxy And when extrapolating to the local universe: This rate is dominated by the NS-NS system with theshortest lifetime – t~100 Myr(the double pulsar PSR J0737-3039). Excluding this system the rateis lower by a factor 6-7 (Kalogera et al. 2004).

34. SHBs and NS-NS mergers NS-NS (Kalogera et al. 2004): 200<RNS-NS< 3000 Gpc-3 yr-1 Dominated by binaries that merge within ~100 Myr SHBs (Nakar et al. 2005): 10<RSHB< 5·105Gpc-3 yr-1 Dominated by old progenitors>4 Gyr For the two to be compatible there should be ahidden population of old long-lived NS-NS systems. Can it be a result of selection effects? Maybe, but we cannot think of an obvious one. Caveat: small number statistics

35. Detection of SHB increases LIGO range by a factor of 1.5-2.5 (Kochanek & Piran 1993): • Timing information (~1.5) • Beaming perpendicular to the orbital plane (~1.5) • Localization information

36. LIGO-I: Probability for simultaneous detection Swift detects and localizes ~10 SHBs yr-1. If Lmin~1047 erg/s and f(L)L-2then ~3% of these SHBs are at D<100 Mpc and ~1% at D<50 Mpc R(merger+SHB) ~ 0.1 yr-1 • Notes: • This result depends weakly on beaming • In this scenario RSHB ~ 1000 fb Gpc-3yr-1 • Comparison with Swift and IPN non-localized bursts may significantly increase this rate

37. Thanks!

38. Single power-law fit to f(L) Maximum likelihood:f(L)  L-2±0.1 c2/d.o.f  1 a good fit The extended sample (8 SHB) can be used

39. SHBs Galaxies at D<100Mpc SHBs (E-Sbc galaxies) SHBs At least 5% of BATSE SHBs are at D<100Mpc Long GRBs Tanvir et al. 2005 Our model predicts that 3% of the SHBs are at D<100Mpc if Lmin 1047 erg/s

40. Broken power-law fit to f(L) For each f(t), a1 and a2 we fit L* to BATSE dN/dP Only Swift bursts can be used (unknown detector response for the rest). However we can carry a comparison with the two-dimensional L-z distribution

41. ttypical > 3Gyr or h>-0.5

42. Probability for blind search detection LIGO-I: Taking a speculative but reasonable SHB rate of 104 Gpc-3 yr-1 predicts a detection rate of: R(NS-NS) ~ 0.3 yr-1 R(BH*-NS) ~ 3 yr-1 LIGO-II: The SHB rate lower limit of 10Gpc-3 yr-1 implies: R(NS-NS)≥ 1 yr-1 R(BH*-NS)≥ 10 yr-1 *MBH ~ 10M

43. GRB missions *my rough estimate

44. LIGO-II: Probability for simultaneous detection • This year 3 bursts detected at D < 1Gpc • GLAST is expected to detect several SHBs at • D<500Mpc every year • LIGO-II range for simultaneous detection is • ~700 Mpc (NS-NS) and ~1.3 Gpc (BH-NS) Simultaneous operation of LIGO-II and an efficient SHB detector could yield at least several simultaneous detections each year. Non-detection will exclude the compact merger progenitor model

45. Offset 39 ± 13 kpc 3.5 ± 1.3 kpc 2.4 ± 0.9 kpc Prochaska et al., 2005