22,164 research outputs found
Reproductive biology of blue marlin (Makaira nigricans) in the western Pacific Ocean
The reproductive biology
of blue marlin (Makaira nigricans)
was assessed from 1001 fish (ranging
from 121 to 275 cm in eye-to-fork
length; EFL) caught by Taiwanese
offshore longliners in the western
Pacific Ocean from September 2000
to December 2001 and from 843 gonad
samples from these fish, The overall
sex ratio of the catch was approximately
1:1 dur ing the sampling
period, but blue marlin are sexually
dimorphic; females are larger than
males. Reproductive activity (assessed
by histology), a gonadosomatic index,
and the distribution of oocyte diameters,
indicated that spawning occurred
predominantly from May to September.
The estimated sizes-at-maturity
(EFL50) were 179.76 ±1.01 cm (mean
±standard error) for females and 130
±1 cm EFL for males. Blue marlin are
multiple spawners and oocytes develop
asynchronously. The proportion of
mature females with ovaries containing
postovulatory follicles (0.41) and
hydrated oocytes (0.34) indicated that
the blue marlin spawned once every
2–3 days on average. Batch fecundity
(BF) for 26 females with the
most advanced oocytes (≥1000 μm),
but without postovulatory follicles,
ranged from 2.11 to 13.50 million
eggs (6.94 ± 0.54 million eggs). The
relationships between batch fecundity
(BF, in millions of eggs) and
EFL and round weight (RW, kg) were
BF = 3.29 × 10 –12 EFL5.31 (r2 = 0.70)
and BF = 1.59 × 10–3 RW 1.73 (r2= 0.67),
respectively. The parameters estimated
in this study are key information
for stock assessments of blue
marlin in the western Pacific Ocean
and will contribute to the conservation
and sustainable yield o
The hot Jupiter period-mass distribution as a signature of in situ formation
More than two decades after the widespread detection of Jovian-class planets
on short-period orbits around other stars, their dynamical origins remain
imperfectly understood. In the traditional narrative, these highly irradiated
giant planets, like Jupiter and Saturn, are envisioned to have formed at large
stello-centric distances and to have subsequently undergone large-scale orbital
decay. Conversely, more recent models propose that a large fraction of hot
Jupiters could have formed via rapid gas accretion in their current orbital
neighborhood. In this study, we examine the period-mass distribution of
close-in giant planets, and demonstrate that the inner boundary of this
population conforms to the expectations of the in-situ formation scenario.
Specifically, we show that if conglomeration unfolds close to the disk's inner
edge, the semi-major axis - mass relation of the emergent planets should follow
a power law - a trend clearly reflected in the data. We
further discuss corrections to this relationship due to tidal decay of
planetary orbits. Although our findings do not discount orbital migration as an
active physical process, they suggest that the characteristic range of orbital
migration experienced by giant planets is limited.Comment: 5 pages, 1 figure, accepted in ApJ
Accretion disk wind in the AGN broad-line region: Spectroscopically resolved line profile variations in Mrk110
Detailed line profile variability studies of the narrow line Seyfert 1 galaxy
Mrk110 are presented. We obtained the spectra in a variability campaign carried
out with the 9.2m Hobby-Eberly Telescope at McDonald Observatory. The
integrated Balmer and Helium (HeI,II) emission lines are delayed by 3 to 33
light days to the optical continuum variations respectively. The outer wings of
the line profiles respond much faster to continuum variations than the central
regions. The comparison of the observed profile variations with model
calculations of different velocity fields indicates an accretion disk structure
of the broad line emitting region in Mrk110. Comparing the velocity-delay maps
of the different emission lines among each other a clear radial stratification
in the BLR can be recognized. Furthermore, delays of the red line wings are
slightly shorter than those of the blue wings. This indicates an accretion disk
wind in the BLR of Mrk110. We determine a central black hole mass of M =
. Because of the poorly known inclination angle of
the accretion disk this is a lower limit only.Comment: 12 pages, 11 figures, Astron & Astrophys, in pres
The Massive Disk Around OH 231.8+4.2
We have obtained 11.7 micron and 17.9 micron images at the Keck I telescope
of the circumstellar dust emission from OH 231.8+4.2, an evolved mass-losing
red giant with a well studied bipolar outflow. We detect both a central
unresolved point source and extended emission which is aligned with the bipolar
outflow seen on larger scales. We find that the unresolved central source can
be explained by an opaque, flared disk with an outer radius near 300 AU and an
outer temperature of about 130 K. One possible model to explain this flaring is
that the material in the disk is orbiting the central star and not simply
undergoing a radial expansion.Comment: ApJ, in pres
- …