2 research outputs found
Restless quiescence: thermonuclear flashes between transient X-ray outbursts
For thermonuclear flashes to occur on neutron-star surfaces, fuel must have
been accreted from a donor star. However, sometimes flashes are seen from
transient binary systems when they are thought to be in their quiescent phase,
during which no accretion, or relatively little, is expected to occur. We
investigate the accretion luminosity during several such flashes, including the
first-ever and brightest detected flash from Cen X-4 in 1969. We infer from
observations and theory that immediately prior to these flashes the accretion
rate must have been between about 0.001 and 0.01 times the equivalent of the
Eddington limit, which is roughly 2 orders of magnitude less than the peak
accretion rates seen in these transients during an X-ray outburst and 3-4
orders of magnitude more than the lowest measured values in quiescence.
Furthermore, three such flashes, including the one from Cen X-4, occurred
within 2 to 7 days followed by an X-ray outburst. A long-term episode of
enhanced, but low-level, accretion is predicted near the end of the quiescent
phase by the disk-instability model, and may thus have provided the right
conditions for these flashes to occur. We discuss the possibility of whether
these flashes acted as triggers of the outbursts, signifying a dramatic
increase in the accretion rate. Although it is difficult to rule out, we find
it unlikely that the irradiance by these flashes is sufficient to change the
state of the accretion disk in such a dramatic way.Comment: 9 pages, 3 figures, accepted for publication in A&A; referee comments
included plus improved text; results unchange
Genetic analysis of typical wet-type age-related macular degeneration and polypoidal choroidal vasculopathy in Japanese population
Age-related macular degeneration (AMD) is a common cause of blindness in the elderly. Caucasian patients are predominantly affected by the dry form of AMD, whereas Japanese patients have predominantly the wet form of AMD and/or polypoidal choroidal vasculopathy (PCV). Although genetic association in the 10q26 (ARMS2/HTRA1) region has been established in many ethnic groups for dry-type AMD, typical wet-type AMD, and PCV, the contribution of the 1q32 (CFH) region seem to differ among these groups. Here we show a single nucleotide polymorphism (SNP) in the ARMS2/HTRA1 locus is associated in the whole genome for Japanese typical wet-type AMD (rs10490924: \documentclass[12pt]{minimal}
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\begin{document}\end{document}, OR = 4.16) and PCV (rs10490924: \documentclass[12pt]{minimal}
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\begin{document}\end{document}, OR = 2.72) followed by CFH (rs800292: \documentclass[12pt]{minimal}
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\begin{document}\end{document}, OR = 2.08; \documentclass[12pt]{minimal}
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\begin{document}\end{document}, OR = 2.00), which differs from previous studies in Caucasian populations. Moreover, a SNP (rs2241394) in complement component C3 gene showed significant association with PCV (\documentclass[12pt]{minimal}
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\begin{document}\end{document}, OR = 3.47). We conclude that dry-type AMD, typical wet-type AMD, and PCV have both common and distinct genetic risks that become apparent when comparing Japanese versus Caucasian populations