We discussed two papers last week:
- Gustavo presented the paper (submitted on March): jet signatures in the spectra of accreting black holes
- Rodrigo presented the paper recently posted to arXiv (though we don’t know where/if they submitted it): Echoes from the Abyss: Evidence for Planck-scale structure at black hole horizons
Both papers are very interesting.
Gustavo’s paper shows promising places in the multiwavelength SEDs of stellar-mass black holes where we could find evidence of jet emission. They implemented grmonty radiative transfer on top of HARM GRMHD simulations, painting the simulation with different electron/ion temperatures for the jet and accretion flow. Curiously, they find no QPOs at all in the emission. This is related to Gustavo’s PhD thesis work.
Rodrigo’s paper shows very interesting search for evidence of fuzzballs or firewalls near the event horizons, by searching the LIGO waveforms for the three detections so far. These membranes — which are very close to the horizon, a Planck length away — should reflect back to infinity the GWs produced during the ringdown phase, though I am completely unfamiliar with the physics of such membranes. This should produced periodic, GW echoes which could teach us about the physics of these “apparent horizons”. They find a 2sigma hint that the echoes are present in the GW150914 event, about 0.3 seconds after the merger.
Two things I would like to see:
- They should show a Figure 4 with a broader range of time, such that we could judge how the average noise is compared to the maximum amplitude of the possible echo
- If these echoes are really there, then they should show up in the wavelet periodogram with a frequency of ~3 Hz (see the slides I prepared). I am sure that the LIGO Collaboration is searching for this right now.
I find it suspect the way they combined the waveforms of three GW signals of mergers with different masses and found a 2.9sigma evidence of echoes.