[Okc-wp4] Reminder: First EO seminar tomorrow

[Smaranika Banerjee]

Dear all,

Reminder of the next EO seminar this week, the speaker is Avinash from Supernova group.

When: 13:15 on September 19th
Where: Usual room, A5:1003
Speaker: Avinash Singh

Title: Asphericities in explosion and multi-faceted neighborhood of the nearest SN of the decade, SN2023ixf
Abstract:
In this talk, I will present the multi-wavelength observations concerning photometry, spectroscopy, and polarimetry of the nearest SN of the decade, SN 2023ixf. I will primarily explore the significance of polarimetry and hydrodynamical modeling in understanding the complex nature of core-collapse supernovae. Polarization provides crucial insights into the geometry of the supernova ejecta and the circumstellar matter (CSM), revealing the dynamics at play during and after the explosion. Hydrodynamical modeling, on the other hand, enables us to simulate the physical conditions of the progenitor star and its environment, helping to reconstruct the mass-loss history and the explosion parameters.

Building on this framework, the polarimetric observations revealed three distinct peaks post-explosion. These peaks indicate a highly asymmetric dense CSM, an aspherical shock front, and/or clumpiness within the extended CSM, as well as asymmetry in the inner ejecta and He-core. The evolution of polarization in time exhibits two axes of asymmetry: one linked to the CSM and outer ejecta and the other to the inner ejecta/He-core, suggesting independent origins of asymmetry in the early and late evolution of SN2023ixf. Complementing these observations, hydrodynamical modeling suggested a two-zone CSM structure consisting of a dense inner region with a significant mass-loss rate and a more extended outer region with a lower mass-loss rate. Spectroscopic data further supported the presence of an aspherical shock front, evidenced by high-velocity broad absorption features in the Balmer lines. Together, these findings point to a red supergiant progenitor star with a mass of around 10 solar mass, having enhanced stages of mass loss closer to the explosion, offering new insights into the intricate dynamics and complex environments of hydrogen-rich supernovae.

Hope to see many of you there :)
See
Kind regards,
Smaranika (on behalf of the organisers)

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Dr. Smaranika Banerjee
Astronomy Department, Stockholm University
Email: smaranika.banerjee at astro.su.se<mailto:smaranika.banerjee at astro.su.se>
Old email: smaranikab at astr.tohoku.ac.jp<mailto:smaranikab at astr.tohoku.ac.jp>
Website: https://sites.google.com/view/smaranikabanerjee/welcome?authuser=0
Zoom: https://stockholmuniversity.zoom.us/j/3760189321
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________________________________
From: Okc-wp4-at-fysik.su.se <okc-wp4-at-fysik.su.se-bounces at lists.su.se> on behalf of Haakon Andresen via Okc-wp4-at-fysik.su.se <okc-wp4-at-fysik.su.se at lists.su.se>
Sent: Wednesday, September 4, 2024 5:00:10 PM
To: EO meeting email
Subject: [Okc-wp4] Reminder: First EO seminar tomorrow


Hi everyone,

just a short reminder of the first seminar of the semester.

- Haakon

When: 13:15 on September 5th
Where: The VLR room in the astro department (let me know if you need help finding it)
Speaker: Julian Westerweck Black hole spectroscopy and beyond no-hair
Black hole quasi-normal modes are proving a rich phenomenon in terms of their properties, data-analysis, and potential for discovery of new physics. I present work analysing gravitational-wave data both for the signal of black holes in GR and for several types of alternative quasi-normal modes, covering scalar/vector fields, horizonless objects, and r-modes.
Black hole spectroscopy directly probes the nature of a binary merger's final object by measuring the characteristic spectrum of gravitational-wave modes emitted as it settles down from its perturbed state. This facilitates (no-hair) tests of GR predictions, unexpectedly already using current data. I will discuss some recent advances in analysis methods helping to perform these tests and their results.
In contrast, the presence of additional post-merger signals could reveal more exotic objects or deviations from GR. Scalar- or vector-fields, if present, possess a distinct spectrum of modes, which may couple to and drive gravitational waves with their characteristic frequencies, making them detectable. In current work we aim to constrain their presence with available data and predict future prospects using third-generation instruments.
Exotic compact objects proposed as alternatives to black holes would show characteristic signatures in their post-merger emission. Horizonless compact objects emit at late times weak but long-lived modes following the initial unmodified signal. R-mode oscillations in compact objects consisting of fluid matter produce a similar signal. Employing methods adapted to these long-duration signals, we analyse data from the most promising detections, placing strict bounds on both the location of possible deviations from the Kerr geometry and the proposed fluid's properties.

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