[Okc-wp4] EO meeting on Thursday 17th of May

[Francesco Taddia]

Hi all,

during our next EO meeting (13:00-14:00, May 17th, 5th floor KTH meeting room),
we will have Mattia Bulla talking about polarisation in macronovae. Here title and abstract:


Title: The origin of polarization in macronovae and the case of AT 2017gfo

Abstract: The gravitational wave event GW 170817 was due to the coalescence of two neutron stars and produced a transient electromagnetic source, labelled AT 2017gfo, that was target of a massive observational campaign. Together with photometric and spectroscopic observations, polarimetric measurements were also obtained. These data showed that the polarization detected from AT 2017gfo was consistent with being induced by dust in our Galaxy, thus suggesting that the intrinsic emission was at most weakly polarized (P < 0.4-0.5%). Polarimetry can be a powerful diagnostics of the geometry and emission processes of unresolved sources. In my talk, I will discuss a detailed analysis of the expected polarization from a macronova by means of 3D Monte Carlo radiative transfer simulations assuming a range of possible configurations, wavelengths, epochs and viewing angles. The main result is that the maximum polarization degree is relatively small (P < 1 %) at early times (1-2 days after the merger) and no polarization is expected at later times. Low polarization levels are expected at any epoch in the blue part of the spectrum and in the near-infrared with the best chances for a positive detection in the R-band. A clear dependence on the viewing angle allows us to derive independent constrains for the case of AT 2017gfo, which are fully consistent with estimates based on gravitational wave analysis.

cheers

/Francesco
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