  The XXIXth IAU General Assembly in Honolulu adopted IAU 2015 Resolution B2 on
recommended zero points for the absolute and apparent bolometric magnitude
scales. The resolution was proposed by the IAU Inter-Division A-G Working Group
on Nominal Units for Stellar and Planetary Astronomy after consulting with a
broad spectrum of researchers from the astronomical community. Resolution B2
resolves the long-standing absence of an internationally-adopted zero point for
the absolute and apparent bolometric magnitude scales. Resolution B2 defines
the zero point of the absolute bolometric magnitude scale such that a radiation
source with $M_{\rm Bol}$ = 0 has luminosity L$_{\circ}$ = 3.0128e28 W. The
zero point of the apparent bolometric magnitude scale ($m_{\rm Bol}$ = 0)
corresponds to irradiance $f_{\circ}$ = 2.518021002e-8 W/m$^2$. The zero points
were chosen so that the nominal solar luminosity (3.828e26 W) adopted by IAU
2015 Resolution B3 corresponds approximately to $M_{\rm Bol}$(Sun) = 4.74, the
value most commonly adopted in recent literature. The nominal total solar
irradiance (1361 W/m$^2$) adopted in IAU 2015 Resolution B3 corresponds
approximately to apparent bolometric magnitude $m_{\rm bol}$(Sun) = -26.832.
Implicit in the IAU 2015 Resolution B2 definition of the apparent bolometric
magnitude scale is an exact definition for the parsec (648000/$\pi$ au) based
on the IAU 2012 Resolution B2 definition of the astronomical unit.
