530 research outputs found
The Local Environments of Core-Collapse SNe within Host Galaxies
We present constraints on core-collapse supernova progenitors through
observations of their environments within host galaxies. This is achieved
through 2 routes. Firstly, we investigate the spatial correlation of supernovae
with host galaxy star formation using pixel statistics. We find that the main
supernova types form a sequence of increasing association to star formation.
The most logical interpretation is that this implies an increasing progenitor
mass sequence going from the supernova type Ia arising from the lowest mass,
through the type II, type Ib, and the supernova type Ic arising from the
highest mass progenitors. We find the surprising result that the supernova type
IIn show a lower association to star formation than type IIPs, implying lower
mass progenitors. Secondly, we use host HII region spectroscopy to investigate
differences in environment metallicity between different core-collapse types.
We find that supernovae of types Ibc arise in slightly higher metallicity
environments than type II events. However, this difference is not significant,
implying that progenitor metallicity does not play a dominant role in deciding
supernova type.Comment: to appear in Proceedings of IAU 279 "Death of Massive Stars:
Supernovae and Gamma-ray Bursts
Door to door application of the international air law conventions; commercially convenient, but doctrinally dubious
International Air Cargo in Time of Crisis: Global Challenges and Modal Shift Provide Transformational Opportunity in Commerce and Law
The current pandemic has elevated the critical need for a dependable, resilient, air cargo supply chain to the forefront of commercial and legal discussion. Throughout its history, air cargo has evolved in parallel with other unimodal means of cargo transport into a global multimodal transport paradigm. The unimodal legal regimes governing individual modes of cargo transport have not kept pace with the growth and development of global cargo transport and its associated legal issues. The unimodal regimes do not adequately reflect the relational, commercial, and operational realities of the contemporary global multimodal supply chain. The authors identify key changes in air cargo and multimodal supply chain logistics and relationships, and discuss the resulting contemporary legal issues that have emerged and must be addressed. The authors advocate that a multimodal cargo transport regime is needed to reflect these current realities and to accommodate future multimodal evolution. At a minimum, update and integration of the Warsaw, Montreal, and CMR conventions is indicated. The authors emphasize the essential need for continued integration of new technologies and complete digitalization of the air cargo supply chain in order adequately to prepare for the global multimodal cargo transport paradigm of tomorrow
The Legacy of the Dinosaurs: Regulation of Planetary Defence and Near-Earth Objects at a Global Level
Type Ib/c Supernovae with and without Gamma-Ray Bursts
While the connection between Long Gamma-Ray Bursts (GRBs) and Type Ib/c
Supernovae (SNe Ib/c) from stripped stars has been well-established, one key
outstanding question is what conditions and factors lead to each kind of
explosion in massive stripped stars. One promising line of attack is to
investigate what sets apart SNe Ib/c with GRBs from those without GRBs. Here, I
briefly present two observational studies that probe the SN properties and the
environmental metallicities of SNe Ib/c (specifically broad-lined SNe Ic) with
and without GRBs. I present an analysis of expansion velocities based on
published spectra and on the homogeneous spectroscopic CfA data set of over 70
SNe of Types IIb, Ib, Ic and Ic-bl, which triples the world supply of
well-observed Stripped SNe. Moreover, I demonstrate that a meta-analysis of the
three published SN Ib/c metallicity data sets, when including only values at
the SN positions to probe natal oxygen abundances, indicates at very high
significance that indeed SNe Ic erupt from more metal-rich environments than
SNe Ib, while SNe Ic-bl with GRBs still prefer, on average, more metal-poor
sites than those without GRBs.Comment: 5 pages, 2 Figures. To appear in the Proceedings of IAU Symposium 279
"Death of Massive Stars: Supernovae and Gamma-ray Bursts". Contains updates
with respect to Modjaz et al (2011
A young stellar environment for the superluminous supernova PTF12dam
The progenitors of super luminous supernovae (SLSNe) are still a mystery.
Hydrogen-poor SLSN hosts are often highly star-forming dwarf galaxies and the
majority belongs to the class of extreme emission line galaxies hosting young
and highly star-forming stellar populations. Here we present a resolved
long-slit study of the host of the hydrogen-poor SLSN PTF12dam probing the kpc
environment of the SN site to determine the age of the progenitor. The galaxy
is a "tadpole" with uniform properties and the SN occurred in a star-forming
region in the head of the tadpole. The galaxy experienced a recent star-burst
superimposed on an underlying old stellar population. We measure a very young
stellar population at the SN site with an age of ~3 Myr and a metallicity of
12+log(O/H)=8.0 at the SN site but do not observe any WR features. The
progenitor of PTF12dam must have been a massive star of at least 60 M_solar and
one of the first stars exploding as a SN in this extremely young starburst.Comment: submitted to MNRAS letters. 5 pages, 3 figures, supplementary
material: 2 figures, 2 table
A metallicity study of 1987A-like supernova host galaxies
The origin of the blue supergiant (BSG) progenitor of Supernova (SN) 1987A
has long been debated, along with the role that its sub-solar metallicity
played. We now have a sample of 1987A-like SNe that arise from the core
collapse (CC) of BSGs. The metallicity of the explosion sites of the known BSG
SNe is investigated, as well as their association to star-forming regions. Both
indirect and direct metallicity measurements of 13 BSG SN host galaxies are
presented, and compared to those of other CC SN types. Indirect measurements
are based on the known luminosity-metallicity relation and on published
metallicity gradients of spiral galaxies. To provide direct estimates based on
strong line diagnostics, we obtained spectra of each BSG SN host both at the SN
explosion site and at the positions of other HII regions. Continuum-subtracted
Ha images allowed us to quantify the association between BSG SNe and
star-forming regions. BSG SNe explode either in low-luminosity galaxies or at
large distances from the nuclei of luminous hosts. Therefore, their indirectly
measured metallicities are typically lower than those of SNe IIP and Ibc. This
is confirmed by the direct estimates, which show slightly sub-solar values
(12+log(O/H)=8.3-8.4 dex), similar to that of the Large Magellanic Cloud (LMC),
where SN 1987A exploded. However, two SNe (1998A and 2004em) were found at near
solar metallicity. SNe IIb have a metallicity distribution similar to that of
BSG SNe. Finally, the association to star-forming regions is similar among BSG
SNe, SNe IIP and IIn. Our results suggest that LMC metal abundances play a role
in the formation of some 1987A-like SNe. This would naturally fit in a single
star scenario for the progenitors. However, the existence of two events at
nearly solar metallicity suggests that also other channels, e.g. binarity,
contribute to produce BSG SNe.Comment: 28 pages, 17 figures; accepted for publication (Astronomy and
Astrophysics); abstract abridged for arXiv submissio
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