BelGrav weekly meeting "Talk" format
https://cern.zoom.us/j/8354516554?pwd=N3lSOWdhczdLcnNUSkZLRVNMeDFkQT09
virtual - zoom
News and announcements: link to slides
Archisman:
- VSC meeting last week:
- deputy spokesperson was appointed (Viola Sordini)
- EGO/Virgo organization is something new and it is being appointed at teh moment. There will be 3 members of Virgo, out of which 1 has to be external to the EGO countries (Italy, France and Netherlands).
- New virgo group: Virgo-Brazil → still undecided
Alex: The Virgo-Brazil group seems to be very versatile. They are also trying to get into ET. Concern: the Brazilian air force seems to be involved.
Archisman: they would be the first non-EU members
Archisman: reminders!!
- Keep VMD updated → to avoid extra charges or removal from the author list
- Keep ETMD updated (same as Virgo but for ET)
Max: please, add description about your groups here: Belgrav Projects
Archisman: next meeting on 3rd of July!
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Presentation by Stavros Venikoudis: impact of correlated magnetic noise on anisotropic stochast searches
- Link to slides
- Sources: Schumann resonances, superposition of individual lightning strikes, …
- Coupling mechanisms: coupling with permanent magnets of actuators/suspension systems and
- In our analysis we need to assume or data is given by:
- To determine the correlated magnetic noise we used data from magnetometer at LIGO and Virgo sites. There’re 2 perpendicular magnetometers outside each site.
- We consider two coupling functions:
- Inside to GW channel (coupling from inside the detector) → obtained from environmental noise injections
- LIGO: injection before and after O3
- Virgo: weekly injections during O3 from which an average value was obtained
- Inside to GW channel (coupling from inside the detector) → obtained from environmental noise injections
Via this formula:
If this was not possible, an upper limit was obtained.
- Outside to inside (effect of the building structure in the magnetic measurements)
- Obtained by using magnetic fields generated by lightning strokes near L1
- The two coupling functions are finally multiplied.
- The effect of the magnetic correlation on all sky all frequency anisotropic searches is subleading:
The highest effect is around 20Hz.
At 27.3Hz we find the 4th Schumann resonance peak
- Broadband analysis results: subleading effect
- Isotropic magnetic budget for O3 agrees with the results by Kamiel (orange line):
However, there’re small disagreements at high frequencies.
- We repeated the same for all baselines
Archisman: why are there peaks in the Omega_GW plot? Are these structures well known?
Stavros: the broadband structure between 20-60Hz are due to Schumann resonances. At higher freqs. We have the effect from lightning strikes.
Federico: More details can be found in this work by Kamiel et al. : https://arxiv.org/abs/2209.00284
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