interactions between gravitational waves and photon astronomy periodic signals
Download
Skip this Video
Download Presentation
Interactions between gravitational waves and photon astronomy (periodic signals)

Loading in 2 Seconds...

play fullscreen
1 / 22

Interactions between gravitational waves and photon astronomy (periodic signals) - PowerPoint PPT Presentation


  • 102 Views
  • Uploaded on

Interactions between gravitational waves and photon astronomy (periodic signals). Ben Owen. Intro. We can look for things better if we know more about them from photon astronomy (we think of 4 NS populations )

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Interactions between gravitational waves and photon astronomy (periodic signals)' - buck


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
interactions between gravitational waves and photon astronomy periodic signals

Interactions between gravitational waves and photon astronomy(periodic signals)

Ben Owen

LSC-VIRGO / NS meeting

intro
Intro
  • We can look for things better if we know more about them from photon astronomy (we think of 4 NS populations)
  • Photon astronomy sets indirect upper limits on GW - milestones for sensitivities of our searches
  • GW emission mechanisms influence where we look
  • Our interpretation of our results depends on emission mechanisms and previous indirect upper limits
  • Some review in Abbott et al gr-qc/0605028

LSC-VIRGO / NS meeting

gw emission mechanisms
GW emission mechanisms
  • Non-accreting stars (indirect limits beatable now!)
    • Free precession (looks pretty weak, I’ll skip)
    • Elastically supported “mountains” - internal too
    • Magnetically supported mountains(Melatos talk)
  • Accreting stars (indirect limits beatable with advLIGO…?)
    • Accretion provides natural mountain building mechanism
    • R-mode oscillations build themselves (CFS instability)
    • More likely to radiate at indirect limits
  • All mechanisms: how high is max & how to drive it there?
    • Put strength in terms of ellipticity ~ quadrupole, propto h

LSC-VIRGO / NS meeting

elastic mountains
Elastic mountains
  • How big can they be? (Owen PRL 2005)
    • Depends on structure, shear modulus (increases with density)
  • Standard neutron star
    • Bildsten ApJL 1998, Ushomirsky et al MNRAS 2000
    • Thin crust, < 1/2 nuclear density:  < few10-7
  • Mixed phase star (quark/baryon or meson/baryon hybrid)
    • Glendenning PRD 1992 … Phys Rept 2001
    • Solid core up to 1/2 star, several nuclear density:  < 10-5
  • Quark star (ad hoc model or color superconductor)
    • Xu ApJL 2003 …, Mannarelli et al hep-ph/0702021
    • Whole star solid, high density:  < few10-4
  • Also Lin PRD 2007, Haskell et al arXiv:0708.2984

LSC-VIRGO / NS meeting

elastic mountains in accreting stars
Elastic mountains in accreting stars

Bildsten ApJL 1998, Ushomirsky et al MNRAS 2000

  • How to build high mountains?
  • Non-uniform accretion flow hot & cold spots on crust
  • Hot spot at fixed density  faster electron capture  layer of denser nuclei moves upward (non-barotropic EOS)
  • If GW balance accretion,  is determined by x-ray flux
  • Best (Sco X-1) is few10-7, same as predicted max for normal neutron star crust

LSC-VIRGO / NS meeting

r modes in accreting stars
R-modes in accreting stars
  • Complicated phenomenology (Stergioulas Living Review)
  • 2-stream instability (CFS)
  • Viscosity stabilizes modes
  • Accretion keeps star balanced at critical frequency … if strange particles are in core
  • Max perturbation v/v ~ 10-5 from coupling to other modes
  • GW frequency = 4/3 spin freq. minus few % (depends on EOS)

LSC-VIRGO / NS meeting

four types of neutron stars
Four types of neutron stars

(P>50ms is off our radar)

  • Known pulsars (e.g. Crab)
    • Position & frequency evolution known (including derivatives, timing noise, glitches, orbit)  Computationally inexpensive
  • Unseen neutron stars (e.g. ???)
    • Nothing known, search over position, frequency & its derivatives  Could use infinite computing power, must do sub-optimally
  • Accreting neutron stars (e.g. Sco X-1)
    • Position known, search over orbit & frequency (+ random walk)
    • Emission mechanisms  different indirect limits
  • Non-pulsing neutron stars (“directed searches” e.g. Cas A)
    • Position known, search over frequency & derivatives

LSC-VIRGO / NS meeting

indirect upper limits
Indirect upper limits
  • Assume quadrupole GW emission
  • Use predicted M, R, I (could be off by 2)
  • Assume energy conservation & all df/dt from GW
  • Known pulsars - “spin-down limit”
    • Best is Crab at 1.410-24
  • Non-pulsing NS - substitute age = f/(-4df/dt)
    • Best is Cas A at 1.210-24

LSC-VIRGO / NS meeting

indirect upper limits1
Indirect upper limits
  • Accreting stars - energy conservation violated
    • Assume accretion spin-up = GW spin-down (Wagoner ApJL 1984)
    • Infer accretion rate from x-ray flux
    • Best is Sco X-1 at 210-26
  • Unknown neutron stars - ???
    • Assume simple population model
    • Plug in supernova rate in galaxy
    • Most optimistic estimate is 410-24(Abbott et al gr-qc/0605028)

LSC-VIRGO / NS meeting

known pulsars
Known pulsars
  • What we’ve published:
    • Limits on 1 pulsar in S1: Abbott et al PRD 2004
    • Limits on 28 pulsars in S2: Abbott et al PRD 2005
    • Limits on 78 pulsars in S3 & S4: Abbott et al PRD 2007
    • Note Kramer & Lyne in “et al”: timing data was crucial!
    • Best limit was 310-25 for PSR J1603-7202
  • When it gets interesting:
    • Last year (S5) for the Crab!(Pitkin talk)

LSC-VIRGO / NS meeting

known pulsars1
Known pulsars

Crab, IL = 710-4

J1952+3252, IL = 110-4

95% confidence threshold

by end of S5

J0537-6910, IL = 910-5

LSC-VIRGO / NS meeting

known pulsars2
Known pulsars
  • What we’ve published:
    • Limits on 1 pulsar in S1: Abbott et al PRD 2004
    • Limits on 28 pulsars in S2: Abbott et al PRD 2005
    • Limits on 78 pulsars in S3 & S4: Abbott et al PRD 2007
    • Note Kramer & Lyne in “et al”: timing data was crucial!
    • Best limit was 310-25 for PSR J1603-7202
  • When it’s interesting:
    • Last year (S5) for the Crab!(Pitkin talk)
  • Where we’re going:
    • Now 97 of 160+ pulsars in our band … but want more! Timing!
    • Further down the road: SKA would provide us with many more

LSC-VIRGO / NS meeting

unseen neutron stars
Unseen neutron stars
  • What we’ve published:
    • S210 hours coherent search (Abbott et al gr-qc/0605028)
    • S2few weeks semi-coherent search (Abbott et al 2005)
    • S4few weeks semi-coherent searches (Abbott et al arXiv:0708.3818)
    • Best strain upper limit is 210-24 (sky & polarization combo)
  • When it’s interesting:
    • Already comparable to supernova limit, though that’s fuzzy

LSC-VIRGO / NS meeting

unseen neutron stars1
Unseen neutron stars

LSC-VIRGO / NS meeting

unseen neutron stars2
Unseen neutron stars
  • What we’ve published:
    • S210 hours coherent search (Abbott et al gr-qc/0605028)
    • S2few weeks semi-coherent search (Abbott et al 2005)
    • S4few weeks semi-coherent searches (Abbott et al arXiv:0708.3818)
    • Best strain upper limit is 210-24 (sky & polarization combo)
  • When it’s interesting:
    • Already comparable to supernova limit, though that’s fuzzy
  • Where we’re going:

LSC-VIRGO / NS meeting

directed searches
Directed searches
  • What we’re doing:
    • Cas A (youngest known neutron star?) ~10 days S5
    • Galactic center (innermost parsec, good place for unknowns)
  • When it’s interesting:
    • Cas A and any ~100yr old star in center have hIL ~ 110-24
    • Doable with present sensitivity!
    • Anything detectable now would require solid quark matter

LSC-VIRGO / NS meeting

directed searches1
Directed searches

IL = 10-4

IL = 10-5

LSC-VIRGO / NS meeting

directed searches2
Directed searches
  • What we’re doing:
    • Cas A (youngest known neutron star?) ~10 days S5
    • Galactic center (innermost parsec, good place for unknowns)
  • When it’s interesting:
    • Cas A and any ~100yr old star in center have hIL ~ 110-24
    • Doable with present sensitivity!
    • Anything detectable now would require solid quark matter
  • How photon astronomers can help:
    • Narrow positions on suspected neutron stars (e.g. HESSChandra): arcminute is OK, arcsecond is better
    • Find more young isolated neutron stars, small PWNe and SNRs

LSC-VIRGO / NS meeting

accreting neutron stars in lmxbs
Accreting neutron stars in LMXBs
  • What we’ve published (Sco X-1):
    • S26 hours coherent integration (Abbott et algr-qc/0605028)
    • S420 days incoherent “radiometer” (Abbott et al astro-ph/0703234)
    • Best strain upper limit is 310-24 at 200Hz
  • When it’s interesting:
    • 100 lower than that (Watts talk)
    • What kills our sensitivity? Not knowing frequency (orbit too)
  • What we’re doing:
    • Trying to come up with better methods (Krishnan talk)
    • Other sources? (Chakrabarty talk, Galloway talk)

LSC-VIRGO / NS meeting

observational interactions
Observational interactions
  • Timing data for known pulsars
    • Jodrell Bank, several others have agreed to more timing
    • RXTE: J0537-6910 (Marshall et al)
  • Timing data for LMXBs
    • Keeping RXTE alive would be a good thing…
    • Make friends in India: AstroSat?
  • New discoveries (& proposed discoveries)
    • When you hunt new PSR/CCO/etc, think of indirect GW limits
  • Old discoveries
    • Several NS positions poorly known (ROSAT/XMM), firming up with Chandra or Hubble would help our searches

LSC-VIRGO / NS meeting

theory ish interactions
Theory(-ish) interactions
  • Interpretation of upper limits
    • Beating indirect limits on h is more exciting
    • How fuzzy are indirect limits? Distances, braking indices…
    • Can’t rule out equations of state (stars could just be flat) unless we know mountain building, so what builds mountains?
  • Interpretation of detections (let’s hope!)
    • Frequency confirms emission mechanism (LMXBs)
    • R-mode signal means strange particles in core
    • High ellipticity means funny equation of state
    • Somewhat high  means EOS or high internal B field: what max?

LSC-VIRGO / NS meeting

slide22
Wrap
  • Starting to get interesting sooner than we thought
  • More interesting faster w/help from photon astronomy
  • Lots of theory stuff to think about too, even if we don’t see anything until advanced LIGO
  • Download [email protected]!

LSC-VIRGO / NS meeting

ad