The nature of very faint X-ray binaries; hints from light curves

Very faint X-ray binaries (VFXBs), defined as having peak luminosities Lx of 10^34-10^36 erg/s, have been uncovered in significant numbers, but remain poorly understood. We analyse three published outburst light curves of two transient VFXBs using the exponential and linear decay formalism of King and Ritter (1998). The decay timescales and brink luminosities suggest orbital periods of order 1 hour. We review various estimates of VFXB properties, and compare these with suggested explanations of the nature of VFXBs. We suggest that: 1) VFXB outbursts showing linear decays might be explained as partial drainings of the disc of "normal" X-ray transients, and many VFXB outbursts may belong to this category; 2) VFXB outbursts showing exponential decays are best explained by old, short-period systems involving mass transfer from a low-mass white dwarf or brown dwarf; 3) persistent (or quasi-persistent) VFXBs, which maintain an Lx of 10^34-10^35 erg/s for years, may be explained by magnetospheric choking of the accretion flow in a propeller effect, permitting a small portion of the flow to accrete onto the neutron star's surface. We thus predict that (quasi-)persistent VFXBs may also be transitional millisecond pulsars, turning on as millisecond radio pulsars when their Lx drops below 10^32 erg/s.Comment: 12 pages, 4 figures. MNRAS, in pres

A survey of growth performance, intestinal micro-flora and meat shelf-life in rainbow trout fed with Pistacia atlantica kurdica essential oil

In this study, the essential oil (EO) of Pistacia atlantica subsp. kurdica was added at the rate of 10 g/kg of daily diet of rainbow trout and its effect on gut microbiota (Enterobacteriaceae, Lactobacillus spp., total count), growth performance and antioxidant status of rainbow trout fillet was investigated. Sixty apparently healthy rainbow trout with an approximate weight of 150 g ±3.5 were randomly divided into treatment and control groups. Physical and chemical conditions of water were adjusted to optimal for fish farming and sampling was done after 3 months. The results showed that feed conversion ratio in the control group was significantly (p0.05) after 1 and 7 days cold storage (3°C). According to the obtained results, the EO of Pistacia atlantica kurdica at this dose is not advised for increasing the shelf life of meat and growth performance of fish

Short communication: A survey on growth performance, intestinal micro-flora and meat shelf-life in rainbow trout fed with Pistacia atlantica kurdica essential oil

Qualitative characteristics and nutritional value of fish can reduce by microbial growth and oxidative changes during storage (Rezaei et al., 2008). To prevent or delay such deteriorative changes and extend fish meat shelf life, several ways were recommended. The use of natural preservatives such as essential oils is one of the suggested solutions (Çoban, 2013). Essential oils (EOs) which are aromatic oily liquids of plant material consider in many aspects such as antioxidant, antibacterial, antiviral, antimycotic, antitoxigenic and antiparasitic properties (Burt, 2004; Miguel, 2010). EOs can also replace antibiotic growth promoters in aquatic and terrestrial animal feeds. Supplementation of animal’s diet with EOs can effect on growth performance, intestinal microbiota,non-specific immune response and antioxidant status of their products (Giannenas et al., 2012)

Two heterostigmatic mite species (Acari: Dolichocybidae, Podapolipidae) associated with Scarabaeus pius (Coleoptera: Scarabaeidae) from Iran

During a study on insect-associated heterostigmatic mites (Acari: Prostigmata) in southern Isfahan Province, Central Iran, two colonies of mites were found on Scarabaeus pius (Illiger, 1803) (Coleoptera: Scarabaeidae): Pavania lanceolata sp. n. Bahramian et Hajiqanbar (Dolichocybidae) that is easily discernible by some modified foliate setae on tarsi I–III; and Tarsopolipus massai Husband, 1989 (Podapolipidae) for which Scarabaeus pius is a new host recor

Evolution of the disc atmosphere in the X-ray binary MXB 1659-298, during its 2015-2017 outburst

We report on the evolution of the X-ray emission of the accreting neutron star (NS) low mass X-ray binary (LMXB), MXB 1659-298, during its most recent outburst in 2015-2017. We detected 60 absorption lines during the soft state (of which 21 at more than 3 $\sigma$), that disappeared in the hard state (e.g., the Fe xxv and Fe xxvi lines). The absorbing plasma is at rest, likely part of the accretion disc atmosphere. The bulk of the absorption features can be reproduced by a high column density ($log(N_H/cm^{-2})\sim23.5$) of highly ionised ($log(\xi/erg~cm~s^{-1})\sim3.8$) plasma. Its disappearance during the hard state is likely the consequence of a thermal photo-ionisation instability. MXB 1659-298's continuum emission can be described by the sum of an absorbed disk black body and its Comptonised emission, plus a black body component. The observed spectral evolution with state is in line with that typically observed in atoll and stellar mass black hole LMXB. The presence of a relativistic Fe K$\alpha$ disk-line is required during the soft state. We also tentatively detect the Fe xxii doublet, whose ratio suggests an electron density of the absorber of $n_e>10^{13} cm^{-3}$, hence, the absorber is likely located at $<7\times10^4 r_g$ from the illuminating source, well inside the Compton and outer disc radii. MXB 1659-298 is the third well monitored atoll LMXB showcasing intense Fe xxv and Fe xxvi absorption during the soft state that disappears during the hard state.Comment: MNRAS in pres

Short communication: Effect of oral consumption of Aloe vera gel on intestinal microflora and liver tissue of rainbow trout

Rainbow trout as an important breeding fish has a special place in the food basket of human societies. Statistical survey shows that in the period between the years of 1995 to 2011, the number of trout breeding farms and the amount of salmon production in Iran have increased respectively by more than 23 and 70 times. ... In recent years, several studies have been conducted on adding the medicinal plants to the feed and using their beneficial effects in aquaculture, while the diversity of medicinal plants and their treatment effects require extensive research. A. vera plant belongs to Liliaceae family which in traditional medicine, various effects such as rejuvenating, antiinflammatory, antifungal and germicidal have been listed for it. Sixty percent of the dry matter of A. vera gel is polysaccharides and if they have prebiotic material specifications, they can affect intestinal bacteria populations. … The aim of this study is addition of A. vera gel in rainbow trout feed and investigate its effect on intestinal microbial flora population and liver tissues of fish

Cu/Ni/Au multilayers by electrochemistry: A crucial system in electronics - A critical review

International audienc

Limits on thermal variations in a dozen quiescent neutron stars over a decade

In quiescent low-mass X-ray binaries (qLMXBs) containing neutron stars, the origin of the thermal X-ray component may be either release of heat from the core of the neutron star, or continuing low-level accretion. In general, heat from the core should be stable on timescales $<10^4$ years, while continuing accretion may produce variations on a range of timescales. While some quiescent neutron stars (e.g. Cen X-4, Aql X-1) have shown variations in their thermal components on a range of timescales, several others, particularly those in globular clusters with no detectable nonthermal hard X-rays (fit with a powerlaw), have shown no measurable variations. Here, we constrain the spectral variations of 12 low mass X-ray binaries in 3 globular clusters over $\sim10$ years. We find no evidence of variations in 10 cases, with limits on temperature variations below 11% for the 7 qLMXBs without powerlaw components, and limits on variations below 20% for 3 other qLMXBs that do show non-thermal emission. However, in 2 qLMXBs showing powerlaw components in their spectra (NGC 6440 CX 1 & Terzan 5 CX 12) we find marginal evidence for a 10% decline in temperature, suggesting the presence of continuing low-level accretion. This work adds to the evidence that the thermal X-ray component in quiescent neutron stars without powerlaw components can be explained by heat deposited in the core during outbursts. Finally, we also investigate the correlation between hydrogen column density (N$_H$) and optical extinction (A$_V$) using our sample and current models of interstellar X-ray absorption, finding $N_H ({\rm cm}^{-2}) = (2.81\pm0.13)\times10^{21} A_V$.Comment: 16 pages, 5 figures, MNRAS, in pres