August 2 Wed 14:30-15:30 ALMA-J seminar
Zoom / ALMA building #102 (hybrid)
August 2 Wed 15:30-16:30 NAOJ Science Colloquium
Zoom / Large Seminar Room (hybrid)
詳細は下記からご覧ください。
=============== August 2 Wed===============
Campus: Mitaka
Seminar: ALMA-J seminar
Regularly Scheduled/Sporadic: Every Wednesday
Date and time: August 2, 2023 (Wed), 14:30-15:30
Place: ALMA building #102 / Zoom (hybrid)
Speaker: Keiichi Maeda
Affiliation: Kyoto University
Title: Millimeter view on supernovae: uncovering the nature of massive star evolution toward their demise
Abstract:
Thanks to recent inflating opportunities in transient surveys and rapid follow-up observations, a new, surprising picture has emerged on the nature of massive starts in their final phase; through observations of core-collapse supernovae (CCSNe) in the optical window, dense circumstellar matter confined in the vicinity of the progenitor, reflecting the stellar activity, has been inferred around massive stars just before their demise – the massive stars are much more dynamic in the last few years than widely accepted previously. To further constraining the nature of the CSM and thus the evolution of massive stars in the final centuries to even months toward the explosion, radio synchrotron emission, especially in the higher frequency, can provide unique and unbiased diagnostics. In this talk, I will present some results from our rapid follow-up observation of nearby CCSNe with the ALMA, starting within ~5 days since the explosion; this is a new window that has become possible thanks to the great point-source sensitivity provided by the ALMA. I will especially focus on the following topics; sub-year timescale activity just before the explosion that changes the classical view of the single massive star evolution, and a case showing a rapid change in the mass-loss rate ~1,000 years before the explosion that confirms an important role of binarity in shaping the massive star evolution.
Facilitator: Bunyo Hatsukade, Kouichiro Nakanishi
=============== August 2 Wed==============
Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2023 Aug. 2, 15:30-16:30
Place：Zoom / the large seminar room (hybrid)
Speaker：Kousuke Ishihara
Affiliation：NAOJ (D2)
Title：Observational study of the fragmentation process in nearby
star-forming regions
Abstract：
Star formation is the process of forming protostars from diffuse
interstellar clouds by gravitational contraction, and it is known from
both observation and theory that hierarchical structures called clumps,
filaments, and cores are formed in this process. The collapse and
fragmentation of those structures is thought to contribute to the
determination of the spatial distribution and initial mass of stars. The
most fundamental mechanism controlling the fragmentation is the balance
between the self-gravity and the thermal pressure that supports the
structure against it (Jeans instability). Furthermore, non-thermal
pressures such as turbulence, and magnetic fields are thought to have an
inhibitory effect on fission. But the mechanism is not clear.
In this presentation, I introduce the results of the analysis applied
to 15 nearby regions of the Herschel Gould Belt Survey. Especially,
closer regions (d<200 pc) such as CoronaAustralis, Lupus, and Polaris
areas show distributions below the jeans parameter and cannot be
explained by the jeans fragmentation.
Speaker：Shunsuke Sasaki
Affiliation：NAOJ (D2)
Title：Phenomenological turbulent effects of core-collapse supernovae
Abstract：
It is not yet known how massive the star can explode as core collapse
supernova (CCSN), how much explosive energy, neutrinos and other
quantities will be observed when it explodes. Researches into
simulations of CCSN mechanism have succeeded in showing that such
explosions are possible even in three-dimensional (3D) simulations. It
was also revealed that turbulence associated with neutrino heating plays
an important role in the explosion. This has led to an active discussion
on the relationship between the quantity of progenitor before the
explosion and the physical quantity of CCSNe, which is called progenitor
dependence. In recent years, the development of phenomenological
one-dimensional simulations (1D+) introducing turbulence effects has
become an urgent issue in order to investigate the progenitor dependence
more realistically. We developed 1D+ and we got the result that our 1D+
can mimic the shock evolution in 3D. In this tolk, I will explain our
1D+ and preliminary results about progenitor dependence.
Facilitator
-Name：Meizhi Liu
-Comment: English