Supercritically accreting stellar mass black holes as ultraluminous X-ray sourcesстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:We derive the luminosity-temperature relation for the supercritically
accreting black holes (BHs) and compare it to the data on ultraluminous
X-ray sources (ULXs). At super-Eddington accretion rates, an outflow
forms within the spherization radius. We construct the accretion disc
model accounting for the advection and the outflow, and compute
characteristic disc temperatures. The bolometric luminosity exceeds the
Eddington luminosity L$_{Edd}$ by a logarithmic factor (where is
the accretion rate in Eddington units) and the wind kinetic luminosity
is close to L$_{Edd}$. The apparent luminosity for the face-on
observer is 2-7 times higher because of geometrical beaming. Such an
observer has a direct view of the inner hot accretion disc, which has a
peak temperature T$_{max}$ of a few keV in stellar mass BHs. The
emitted spectrum extends as a power law F$_{E}$ \~{} E$^{-1}$
down to the temperature at the spherization radius . We associate
T$_{max}$ with a few keV spectral components and T$_{sp}$
with the soft, 0.1-0.2 keV components observed in ULXs. An edge-on
observer sees only the soft emission from the extended envelope, with
the photosphere radius exceeding the spherization radius by orders of
magnitude. The dependence of the photosphere temperature on luminosity
is consistent with that observed in the super-Eddington accreting BHs SS
433 and V4641 Sgr. Strong outflows combined with the large intrinsic
X-ray luminosity of the central BH explain naturally the presence of the
photoionized nebulae around ULXs. An excellent agreement between the
model and the observational data strongly argues in favour of ULXs being
supercritically accreting, stellar mass BHs similar to SS 433, but
viewed close to the symmetric axis.