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Stefan Hild ASR Group meting, November 2008

Squeezing the best astrophysics out of Advanced Virgo. Stefan Hild ASR Group meting, November 2008. Advanced Virgo. Virgo is currently the second largest gravitational wave detector in the world (3km).

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Stefan Hild ASR Group meting, November 2008

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  1. Squeezing the best astrophysics out of Advanced Virgo Stefan Hild ASR Group meting, November 2008

  2. Advanced Virgo • Virgo is currently the second largest gravitational wave detector in the world (3km). • Advanced Virgo is an upgrade with 10 times better sensitivity => allows us to scan 1000 times larger volume of the universe than current instruments. • Start of Construction in 2009, Design sensitivity in 2015(?) ASR group meeting, November 2008

  3. Topic for the next 10 minutes: How to optimise the Advanced Virgo sensitivity ? Birmingham contribution to Advanced Virgo • Optical design of the Advanced Virgo core interferometer. • A. Freise appointed: system manager for optical design and simulations. • Some examples of the topics we are working on: • Definition of the optical configuration • Optimisation of the sensitivity curve • System integrity and interfaces to all other subsystems of Advanced Virgo Advanced Virgo core interferometer ASR group meeting, November 2008

  4. Sources of Gravitational Waves we may see with Advanced Virgo Colliding black holes, inspiraling neutron stars, pulsars, supernovae, aftermath of the Big Bang … Problem: All these sources are expected to have different spectral content. => We have to find the optimal shape of the sensitivity to get maximal science out of Advanced Virgo. http://numrel.aei.mpg.de/Visualisations/ http://hubblesite.org/ ASR group meeting, November 2008

  5. Non-optimised senstivity curve Inspirals: Mid frequency Pulsars + Stochastic: Low frequency Supernovae: High frequency ASR group meeting, November 2008

  6. Limits of the optimization • Our optimisation is limited by Coating thermal noise and Gravity Gradient noise. • Quantum noise to be optimised! • We have three knobs available for this optimisation: 1) Optical power, 2) Signal recycling tuning, 3) Signal Recycling trans-mittance ASR group meeting, November 2008

  7. Optimization Parameter 1:Signal-Recycling (de)tuning • Frequency of pure optical resonance goes down with SR-tuning. • Frequency of opto-mechanical resonanced goes up with SR-tuning Advanced Virgo, Power = 125W, SR-transmittance = 4% Photon ra-diation pres-sure noise knob 1 Photon shot noise Opto-mechanical Resonance (Optical spring) Pure optical resonance ASR group meeting, November 2008

  8. Optimization Parameter 2:Signal-Recycling mirror transmittance • Resonances are less developed for larger SR transmittance. Advanced Virgo, Power = 125W, SR-tuning = 0.07 knob 2 ASR group meeting, November 2008

  9. Optimization Parameter 3:Laser-Input-Power • High frequency sensitivity improves with higher power (Shotnoise) • Low frequency sensitivity decreases with higher power (Radiation pressure noise) Advanced Virgo, SR-tuning=0.07, SR-transmittance = 4% knob 3 ASR group meeting, November 2008

  10. Figure of merit: Inspiral • Inspiral ranges for BHBH and NSNS coalesence: • Parameters usually used: • NS mass = 1.4 solar masses • BH mass = 10 solar masses • SNR = 8 • Averaged sky location Frequency of last stable orbit (BNS = 1570 Hz, BBH = 220 Hz) Symmetric mass ratio Spectral weighting = f-7/3 Total mass Detector sensitivity [1] Damour, Iyer and Sathyaprakash, Phys. Rev. D 62, 084036 (2000). [2] B. S. Sathyaprakash, “Two PN Chirps for injection into GEO”, GEO Internal Document ASR group meeting, November 2008

  11. Example: Optimizing 2 Parameters • Inspiral ranges for free SR-tuning and free SRM-transmittance, but fixed Input power NSNS-range BHBH-range ASR group meeting, November 2008

  12. Example: Optimizing 2 Parameters Parameters for maximum • Different source usually have their maxima at different operation points. • It is impossible to get the maximum for BNS AND BBH both at the same time ! Maximum NSNS-range Parameters for maximum Maximum BHBH-range ASR group meeting, November 2008

  13. Example: Optimizing 3 Parameterfor Inspiral range • Scanning 3 parameter at the same time: • SR-tuning • SR-trans • Input Power • Using a video to display 4th dimension. ASR group meeting, November 2008

  14. Optimal configurations Curves show the optimal sensitivity for a single source type. ASR group meeting, November 2008

  15. Which is the most promising source? Binary neutron star inspirals: Based on observations of existing binary stars Based on models of binary star formation and evolution Expected event rates seen by Advanced Virgo: ~1 to 10 events per year. Binary neutron star inspirals are chosen to be the primary target for Advanced Virgo and Advanced LIGO. Binary neutron star inspirals: Binary black hole inspirals: C.Kim, V.Kalogera and D.Lorimer: “Effect of PSRJ0737-3039 on the DNS Merger Rate and Implications for GW Detection”, astro-ph:0608280 http://it.arxiv.org/ abs/astro-ph/0608280. K.Belczynski, R.E.Taam, V.Kalogera, F.A.Rasio, T.Buli:, “On the rarity of double black hole binaries: consequences for gravitational-wave detection”, The Astrophysical Journal 662:1 (2007) 504-511. ASR group meeting, November 2008

  16. If we do a good job on making our Gravitational wave detectors more sensitive … … we have a chance to hear the symphony of the Universe soon !! http://hubblesite.org/ ASR group meeting, November 2008

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