vice.yields.ccsne.engines.E16.m4
================================

Type : ``list`` [elements of type ``float``]

The quantity :math:`M_4` at the time of core collapse for stars with
ZAMS masses given by the attribute ``masses``. :math:`M_4` is defined
as the normalized mass enclosed in a region defined by the
dimensionless energy per nucleon of :math:`s` = 4.

Ertl et al. (2016) [1]_ conclude that the quantities :math:`M_4` and
:math:`\mu_4` can predict whether or not a massive star will produce
a core collapse supernova based on the following criterion with only a
few exceptions (~1 - 2.5%):

.. math:: \mu_4 \leq a M_4 \mu_4 + b

where they report :math:`a` = 0.283 and :math:`b` = 0.043 as best fit
values. The values of :math:`a` and :math:`b` are controlled by the
attributes ``slope`` and ``intercept`` respectively.

.. note:: This attribute's values are adopted from Sukhbold et al.
	(2016) [2]_.

Example Code
------------
>>> from vice.yields.ccsne.engines import E16
>>> E16.m4
[1.357,
 1.36955,
 1.38349,
 ...,
 1.66232,
 1.81781,
 1.60252]

.. [1] Ertl et al. (2016), ApJ, 818, 124
.. [2] Sukhbold et al. (2016), ApJ, 821, 38