13 research outputs found
Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets
The spins of ten stellar black holes have been measured using the
continuum-fitting method. These black holes are located in two distinct classes
of X-ray binary systems, one that is persistently X-ray bright and another that
is transient. Both the persistent and transient black holes remain for long
periods in a state where their spectra are dominated by a thermal accretion
disk component. The spin of a black hole of known mass and distance can be
measured by fitting this thermal continuum spectrum to the thin-disk model of
Novikov and Thorne; the key fit parameter is the radius of the inner edge of
the black hole's accretion disk. Strong observational and theoretical evidence
links the inner-disk radius to the radius of the innermost stable circular
orbit, which is trivially related to the dimensionless spin parameter a_* of
the black hole (|a_*| < 1). The ten spins that have so far been measured by
this continuum-fitting method range widely from a_* \approx 0 to a_* > 0.95.
The robustness of the method is demonstrated by the dozens or hundreds of
independent and consistent measurements of spin that have been obtained for
several black holes, and through careful consideration of many sources of
systematic error. Among the results discussed is a dichotomy between the
transient and persistent black holes; the latter have higher spins and larger
masses. Also discussed is recently discovered evidence in the transient sources
for a correlation between the power of ballistic jets and black hole spin.Comment: 30 pages. Accepted for publication in Space Science Reviews. Also to
appear in hard cover in the Space Sciences Series of ISSI "The Physics of
Accretion onto Black Holes" (Springer Publisher). Changes to Sections 5.2,
6.1 and 7.4. Section 7.4 responds to Russell et al. 2013 (MNRAS, 431, 405)
who find no evidence for a correlation between the power of ballistic jets
and black hole spi
Two new species ofAphelinidae [Hym.:Chalcidoidea] parasitic onAcaudaleyrodes rhachipora [Hom.: Aleyrodidae] from India
The tetramerous Aphelinidae (Hymenoptera) of Girault from Australia, with a key to the world genera
Application of the smoothed point interpolation methods in computational geomechanics: A comparative study
A revision of the genera Dirphys Howard and Encarsiella Hayat (Hymenoptera: Aphelinidae)
Additions to the Indian Aphelinidae (Hymenoptera: Chalcidoidea) – III: the genus Encarsia
Growth efficiency and temperature in scallops: A comparative analysis of species adapted to different temperatures
1. Data were collected on metabolic activity and growth in pectinid bivalves from published studies. The resulting database comprised three types of data sets: (i) synoptic data (13 populations, 7 species), where both individual growth performance and metabolism are known, (ii) 'metabolism only' data (82 populations, 13 species), and (iii) 'growth only' data (198 populations, 26 species).
2. In pectinid bivalves belonging to different species and living under different environmental conditions metabolic activity (standard metabolic rate, SMRAvg, Q10 = 2·97) is more closely related to temperature than individual growth (overall growth performance, OGP index P, Q10 = 1·12).
3. The synthesis of the two corresponding Arrhenius equations shows that the relationship between the SMRAvg-to-OGP ratio and temperature follows the Arrhenius model, too, with Q10 = 2·26.
4. SMRAvg-to-OGP is an inverse proxy for growth efficiency, hence growth efficiency decreases with rising temperature across a wide range of pectinid populations and species. Thus, there is strong empirical evidence that elevated temperature constrains growth efficiency in scallops and that adaptation does not fully compensate for this effect