57,153 research outputs found
Is 4U 0114+65 an eclipsing HMXB?
We present the pulsation and spectral characteristics of the HMXB 4U 0114+65
during a \emph{Suzaku} observation covering the part of the orbit that included
the previously known low intensity emission of the source (dip) and the egress
from this state. This dip has been interpreted in previous works as an X-ray
eclipse. Notably, in this Suzaku observation, the count rate during and outside
the dip vary by a factor of only 2-4 at odds with the eclipses of other HMXBs,
where the intensity drops upto two orders of magnitude. The orbital intensity
profile of 4U 0114+65 is characterized by a narrow dip in the RXTE-ASM (2-12
\rm{keV}) light curve and a shallower one in the Swift-BAT (15-50 \rm{keV}),
which is different from eclipse ingress/egress behaviour of other HMXBs. The
time-resolved spectral analysis reveal moderate absorption column density
(N - 2-20 atoms ) and a relatively low
equivalent width ( 30 \rm{eV} \& 12 \rm{eV} of the iron K and
K lines respectively) as opposed to the typical X-ray spectra of HMXBs
during eclipse where the equivalent width is 1 \rm{keV}. Both XIS and
PIN data show clear pulsations during the dip, which we have further confirmed
using the entire archival data of the IBIS/ISGRI and JEM-X instruments onboard
\emph{INTEGRAL}. The results we presented question the previous interpretation
of the dip in the light curve of 4U 0114+65 as an X-ray eclipse. We thus
discuss alternative interpretations of the periodic dip in the light curve of
4U 0114+65.Comment: 16 pages, 7 figures, 1 table, Accepted in MNRA
Large igneous provinces and mass extinctions: an update
The temporal link between mass extinctions and large igneous provinces is well known. Here, we examine this link by focusing on the potential climatic effects of large igneous province eruptions during several extinction crises that show the best correlation with mass volcanism: the Frasnian-Famennian (Late Devonian), Capitanian (Middle Permian), end-Permian, end-Triassic, and Toarcian (Early Jurassic) extinctions. It is clear that there is no direct correlation between total volume of lava and extinction magnitude because there is always sufficient recovery time between individual eruptions to negate any cumulative effect of successive flood basalt eruptions. Instead, the environmental and climatic damage must be attributed to single-pulse gas effusions. It is notable that the best-constrained examples of death-by-volcanism record the main extinction pulse at the onset of (often explosive) volcanism (e.g., the Capitanian, end-Permian, and end-Triassic examples), suggesting that the rapid injection of vast quantities of volcanic gas (CO 2 and SO 2 ) is the trigger for a truly major biotic catastrophe. Warming and marine anoxia feature in many extinction scenarios, indicating that the ability of a large igneous province to induce these proximal killers (from CO 2 emissions and thermogenic greenhouse gases) is the single most important factor governing its lethality. Intriguingly, many voluminous large igneous province eruptions, especially those of the Cretaceous oceanic plateaus, are not associated with significant extinction losses. This suggests that the link between the two phenomena may be controlled by a range of factors, including continental configuration, the latitude, volume, rate, and duration of eruption, its style and setting (continental vs. oceanic), the preexisting climate state, and the resilience of the extant biota to change
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