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Multi-messanger searches: past results and future programs G. Stratta on behalf LIGO Scientific Collaboration and Virgo Collaboration Università di Urbino,

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Presentation on theme: "Multi-messanger searches: past results and future programs G. Stratta on behalf LIGO Scientific Collaboration and Virgo Collaboration Università di Urbino,"— Presentation transcript:

1 Multi-messanger searches: past results and future programs G. Stratta on behalf LIGO Scientific Collaboration and Virgo Collaboration Università di Urbino, INFN-Firenze Recontres de Moriond March 21-28, 2015

2 In this talk I will briefly review the main properties of three classes of transient astrophysical sources that are well known in the EM spectrum These sources are expected to produce transient GW signals in the LIGO and Virgo frequency range, and possibly 1) Coalescence of NS and BH binary systems 2) core collapsing stars 3) flaring/bursting NSs Joint GW+EM and neutrino observations are expected to provide a wealth of information among which:  Improvement in the confidence in first GW detection  Useful priors in GW data analysis parameter space  Complement our knowledge on the physics of sources

3 ● Three best known astrophysical transient sources in the GW frequency domain of LIGO and Virgo ● Results from past MM searches ● Future observing scenario Outline

4 Best candidates for GW emission with well modeled waveform morphology Observational evidence associate these systems to the progenitor of Short Gamma Ray Bursts (SGRB) (e.g. Berger et al. 2014) Tburst = 0.1 sec (by def. <2 sec) EM spectrum = from keV to MeV (GeV for GRB and ) EM released Energy = erg Coalescence of NS-NS and BH-NS binaries Ackermann et al GRB keV > GeV Fermi/BGM Fermi/LAT

5 Afterglow emission = a non-thermal emission (synchrotron) that rapidly fade with time. Short GRB afterglows “Internal-external” shock model (e.g. Kobayashi et al. 1997, Sari & Piran 1998) afterglow 40% 80% 10% Fong 2014 (presentation in “Swift10years” Rome 2014) BH TeV-PeV ? ( see e.g. Waxman&Bahcal2000)

6 Core collapsing stars Core collapse of massive stars  SN II emission in the optical band after tens of days MeV neutrinos observed for SN1987A in LMC (50 kpc) Ott et al High angular momentum + low metallicity environment  Long Gamma Ray Bursts Burst duration: sec (by def. >2 sec) Energies: erg (assuming isotropical emission) Neutrinos expected Core collapsing stars  GW amplitude expected to be 2 order of magnitudes less than for binary systems + poorly known waveform morphology

7 Galactic magnetars are thought to originate the episodic bursts observed in the hard X-ray/soft- gamma ray range (30-40 keV, Ex<10 42 erg, duration of 0.1-1s, SGR) Very rare giant flares (3 over 30 years so far) of hundreds of seconds (Ex= erg) (see Mereghetti 2008 for a review) TeV-PeV neutrinos are expected during giant flares (e.g. Ioka et al. 2005) GW amplitude from these sources is highly uncertain, with possible estimates that goes from 2 down to less than 8 orders of magnitude than compact binary coalescence (e.g. Abadie et al. 2011, ApJ 734) Rotating neutron stars (magnetars) Example of an episodic burst Example of a giant flare

8 Short GRB distances and rate So far ~100 SGRB of which ~25 at known distance =0.5 = 3 Gpc z min = 0.12 = 560 Mpc Short GRB rate (e.g. Wanderman & Waxman 2014): R = [1-10]x10 -9 Mpc -3 yr -1 = 3x10 -9 Mpc -3 yr -1  R GRB (300* Mpc) = 0.08 yr -1  R GRB (600* Mpc) = 0.6 yr -1 (*Distance range for NS-NS (200 Mpc) and for NS-BH (400 Mpc) expected at final sensitivity, times 1.5 for face-on systems as are sGRB, e.g. Clark et al. 2014) NOTE: THESE ARE “ON-AXIS” Short GRBs! : 25 short GRB with measured z ~40 Mpc ~300 Mpc AdvLIGO/ aVirgo

9 We expect much more short GRBs considering also those that are not pointing towards us R true = R GRB / (1-cos  ) Jet opening angle could be measured only for a few short GRBs with: 1) known distance 2) multi-wavelength set of afterglow data  lack of statistics Ex: R true = R GRB x 10 assuming  =30 deg R true = R GRB x 300 assuming  =5 deg Short GRB jet opening angle Fong et al. 2013

10 At late times (days/weeks) the ejecta decelerates to non-relativistic regime and starts to laterally spread (e.g. Granot et al. 2002) “Off-axis GRB” are not detected in gamma-rays/X-rays. So far only one possible case: PTF11agg (Chenko et al. 2013). Main reason is the unknown trigger time RHD simulations show that off-axis afterglow emission is expected to peak days / tens of days after the trigger  important information for observational strategies in EM follow-up campaign Do short GRB emit off-axis? OFF-AXIS AFTERGLOW From RHD numerical simulations joined with radiative transfer code (e.g. VanEerten&McFa dyen 2010)

11 Coalescing NS-NS systems are expected to isotropically eject a small quantity of neutron rich matter. The radioactive decay of this matter produces optical/NIR transients with typical thermal spectrum (e.g. Metzger & Berger 2012) So far only one (possible) evidence for GRB B (Tanvir et al. 2013, Nature), because kilonova component is faint and typically dominated by the afterglow for on-axis GRBs Kilonova models predict a peak in the optical-NIR domain at >1 day after the trigger Do short GRB emit off-axis? KILONOVA

12 MULTI-MESSENGER SEARCHES

13 1)“External triggers” (e.g. from GRB, SN,…) drive GW data analysis providing trigger time and position in the sky 1)GW triggers above a certain threshold are released after tens of minutes to main observatories activating EM and neutrinos follow-up Next slides show the results from coincident searches during LIGO and Virgo science runs LIGOVirgo S5 November 2005 – August 2007 VSR1 May 2007 – October 2007 S6 June 2009 – October 2010 VSR2 July 2009 – January 2010 VSR3 August 2010 – October 2010 Two main methods Sensitivity at the last run was Dh*=40Mpc *Horizon distance for a NS-NS system

14 1)EM and/or “EXTERNAL TRIGGERS”  GW event search

15 196 long GRBs and 27 short GRBs have been detected with the high energy satellite network (IPN) during the LIGO-Virgo science run periods The GRB distance lower limits were computed assuming 2 different GW signal morphologies (i.e. exclusion distance, this depends also on detector sensitivity at each GRB time)  Obtained values are well below typical GRB distances (e.g. nearby SGRB is at 500 Mpc and long GRB at 40 Mpc) From EM to GW using GRBs Median ex. dist. 12 Mpc NS-NS 22 Mpc BH-NS 90% c.l. Median ex. dist. 4.9 Hz 13 Hz 90% c.l. CBC Waveform Face-on “Unmodeled” burst waveform Abadie et al. 2012, ApJ,760,12

16 Two interesting cases: ● short GRB IPN sky error box overlaps with Andromeda galaxy at 770 kpc (  Eiso~10 45 erg) Abbott et al. 2008, ApJ, 681, 1419 ● short GRB IPN sky error box overlaps with M81 at 3.6 Mpc (  Eiso=10 46 erg Abadie et al. 2012, ApJ, 755 NS-NS or NS-BH progenitor for these two short GRBs are excluded by the lack of GW detections  SGRs ? From EM to GW using GRBs

17 6 bursting magnetars were observed between November 2006 and June 2009 (S5,VSR1) From no GW detection  upper limits on the E GW Most stringent upper limits were obtained for SGR at d<1kpc (quoted lowest E GW upper limits and brightest burst E GW u.l.) and AXP1E with 2 bright burst E GW upper limits reached 1 order of magnitude below previous limits (for SGR ) From EM to GW using NSs 12 waveform types Abadie et al. 2011, Apj, 734, 35 SGR at d<1kpc AXP 1E With 2 bright bursts

18 Search for coincident signals from LIGO and Virgo and  detectors No significant coincident event Assuming E GW =0.01 Mc 2 and E =10 51 erg  R < Mpc -3 yr -1 This rate upper limit does not constraint current astrophysical models (Aartsen et al (Icecube), Adrian-Martinz et al (ANTARES))  see also next talk by Bruny Baret on ANTARES results From neutrino to GW Ando et al. (2014)

19 2) GW trigger  low latency all-sky searchs

20 ● GW detectors are non-imaging detectors with large and fragmented FOV ● Localization is based on triangulation method, thus it needs multiple detector network ● Localization uncertainty is driven by: o amplitude of the signal o time delay between detectors ● Localization strongly benefit of detector network with similar sensitivities and far apart one with the other (e.g. LIGO – Virgo – IndiaLIGO - KAGRA) GW event sky localization Example of GW skymap for trigger G Aasi et al ApJS 211,7

21 From GW to EM follow-up 8 GW triggers Time Pipeline FAR 15 Telescopes slide from M. Branchesi’s talk Aasi et al. 2012

22 No detection  Rate upper limits Rate < 1 event / [Volume * Time] Time = 3 months Volume = within Dh=40/80/90 Mpc for NS- NS, NS-BH and BH-BH Astrophysically predicted rates are ~1 order of magnitude below the inferred upper limits (dashed-black lines showing the “realistic” estimates)  No strong constraints on current astrophysical models Past results from all sky search Abadie et al PhR D85h2002

23 FUTURE PROGRAMS

24 Expected detections Aasi et al arxiv: Second generation of GW detectors will start taking data by September 2015 (Advanced LIGO) and by 2016 (AdvLIGO+aVirgo) but they will reach design sensitivity on 2019+

25 Expected detections

26 Method 1): External triggers: Swift+Fermi up to 2020 (but likely more), SVOM (e.g. Schanne et al. 2010) (+2021) will provide time and position of candidate GW events. Triggers from neutrino detections will be provided by Icecube and KM3neT in their final configurations (e.g. Ando et al. 2014) Method 2): Follow-up campaigns of GW triggers by Advanced LIGO and aVirgo will be performed by more than 150 observatories from 19 countries who signed the LIGO and Virgo Collaboration MoU (more than 10 times the MoU partners of the last science run), covering the the entire EM spectrum from radio to gamma-rays Observing scenario https://gw- astronomy.org/wiki/LV_EM/Public ParticipatingGroups

27 KAGRA is expected to start by and India LIGO by >3 GW detector network  significant improvements in sky localization down to few degrees localization ellipses (e.g. Fairhurst 2012, Aasi et al arxiv ) Observing scenario Fairhurst 2012, Aasi et al Face on BNS at 160 Mpc 90% localization ellipses

28 Multi-messenger search is very important to 1) increase the confidence of the first GW detection, 2) to constrain GW data analysis parameter space and 3) to gain insights on the physics of the source Best known candidates of GW+EM and possibly neutrinos: coalescing binary systems of compact objects (Short GRBs) core collapsing rotating stars (SNe, Long GRBs) magnetars burst/flares (SGRs, Giant bursts) Past results from MM searches show no significant coincident events and obtained upper limits on the energetics in GW and source rate density did not provided strong contraints on astrophysical models By probed distances are expected to contain significant number of GW sources localized in few degrees areas in the sky and the >150 MoU partners will ensure EM and neutrino monitoring. Summary

29 Thank you!

30 Extra slides

31 HF Gravitational Wave detectors

32 ● A powerful way to reduce the large sky areas to survey with telescopes, is to focus on regions containing galaxies that more likely hosts a CBC ● Skymap pixels containing galaxies have combined probability defined as: (Nuttal & Sutton 2011) Galaxy “weighting” method Abadie et al A&A 541 galaxy distance (only for “bursts”) likelyhood from GW data galaxy lum

33 A SGRB jet opening angle of a few degrees is consistent with the realistic NS-NS rate density Realistic NS-BH rate densities are consistent with larger jet opening angle RshortGRB = f*Rcbc (1-cos(theta)) f=fraction of CBC that produce GRB theta = jet opening angle Rate densities NS-NS NS-BH GRB Realistic NS-NS rate density Abadie10 Clark et al. 2014

34 Aasi et al Mpc many upper limits are well below the expected flux!

35 LISA will be sensitive to 0.1 down to Hz → merger of MBH, Extreme Mass Ratio Inspirals of stellar scale compact objects into MBH, galactic close orbiting binary systems, etc.

36 Short GRB “kilonova” emission

37 OBSERVATIONS: So far only on-axis GRBs are observed. To observe the kilonova component, a very faint afterglow is required:...1 case (GRB130603B at z=0.356), 1 data point!! Short GRB “kilonova” emission Tanvir et al. 2014, Nature, 500, 547 Metzger & Berger 2012 On-axis GRBs have bright afterglow that dominates over the kilonova emission

38 On-axis short GRBs (i.e. detected in gamma-rays) are rare and are detected typically too far for GW detectors Off-axis short GRBs are times more frequent and a few to tens per year are expected within the GW horizon distances Two possible emission mechansims are expected to produce an optical/NIR transient from an off-axis short GRB, with a delay of the order of days from the burst: the non-thermal afterglow from laterally spreading jet, and the thermal kilonova. Short GRBs and GW signals


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