A superburst from 4U 1254-690

We report the detection with the BeppoSAX Wide Field Cameras of a superburst from 4U 1254-690. The superburst is preceded by a normal type-I X-ray burst, has a decay time that is the longest of all eight superbursts detected so far and a peak luminosity that is the lowest. Like for the other seven superbursts, the origin is a well-known type-I X-ray burster with a persistent luminosity level close to one tenth of the Eddington limit. Based on WFC data of all persistently bright X-ray bursters, the average rate of superbursts is 0.51+/-0.25 per year per persistently bright X-ray burster. Some systems may have higher superburst rates. For all superbursters, we present evidence for a pure helium layer which is burnt in an unstable as well as a stable manner.Comment: Accepted by A&A Letter

New BeppoSAX-WFC results on superbursts

Presently seven superbursters have been identified representing 10% of the total Galactic X-ray burster population. Four superbursters were discovered with the Wide Field Cameras (WFCs) on BeppoSAX and three with the All-Sky Monitor and Proportional Counter Array on RXTE. We discuss the properties of superbursters as derived from WFC observations. There are two interesting conclusions. First, the average recurrence time of superbursts among X-ray bursters that are more luminous than 10% of the Eddington limit is 1.5 yr per object. Second, superbursters systematically have higher alpha values and shorter ordinary bursts than most bursters that have not exhibited superbursts, indicating a higher level of stable thermonuclear helium burning. Theory predicts hitherto undetected superbursts from the most luminous neutron stars. We investigate the prospects for finding these in GX~17+2.Comment: Submitted in January 2004 for the Proceedings of the meeting 'X-Ray Timing 2003: Rossi and Beyond', eds. P. Kaaret, F. K. Lamb, & J. H. Swank (Melville, NY: American Institute of Physics

The main problems of food allergic consumers concerning food labeling: an ethnographic study

It has been estimated that 58% of children and 12% of the adults in developed countries are affected by food allergy, with symptoms ranging from discomfort to fatality. At present, avoidance of problematic foods is the only effective treatment strategy. As of November 25 th , 2005 food manufacturers in the EU are obliged to list 12 potentially allergic ingredients in food. Although the label is still not always fully understood by the consumer, or they get confused by precautionary labelling practices. This paper aims to gain insights into the information preferences of food allergic consumers regarding existing food labelling and additional information delivery systems. The results of this study will facilitate the development of best practices in information provision regarding food safety in the area of food allergy. In particular the research will elicit preferences for new ICT approaches to information delivery which can be focused on the individual needs of consumers. We argue that improved information supply will contribute to the quality of life of food allergic people.Food allergy, consumers, food labelling, information needs, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety,

Superbursts at near-Eddington mass accretion rates

Models for superbursts from neutron stars involving carbon shell flashes predict that the mass accretion rate should be anywhere in excess of one tenth of the Eddington limit. Yet, superbursts have so far only been detected in systems for which the accretion rate is limited between 0.1 and 0.25 times that limit. The question arises whether this is a selection effect or an intrinsic property. Therefore, we have undertaken a systematic study of data from the BeppoSAX Wide Field Cameras on the luminous source GX 17+2, comprising 10 Msec of effective observing time on superbursts. GX 17+2 contains a neutron star with regular Type-I X-ray bursts and accretes matter within a few tens of percents of the Eddington limit. We find four hours-long flares which reasonably match superburst characteristics. Two show a sudden rise (i.e., faster than 10 s), and two show a smooth decay combined with spectral softening. The implied superburst recurrence time, carbon ignition column and quenching time for ordinary bursts are close to the predicted values. However, the flare decay time, fluence and the implied energy production of (2-4) x 10^17 erg/g are larger than expected from current theory.Comment: Accepted for publication in Astronomy & Astrophysic

On the Origin of the Absorption Features in SS433

We present high-resolution optical spectroscopy of the X-ray binary system SS433, obtained over a wide range of orbital phases. The spectra display numerous weak absorption features, and include the clearest example seen to date of those features, resembling a mid-A type supergiant spectrum, that have previously been associated with the mass donor star. However, the new data preclude the hypothesis that these features originate solely within the photosphere of the putative mass donor, indicating that there may be more than one region within the system producing an A supergiant-like spectrum, probably an accretion disc wind. Indeed, whilst we cannot confirm the possibility that the companion star is visible at certain phase combinations, it is possible that all supergiant-like features observed thus far are produced solely in a wind. We conclude that great care must be taken when interpreting the behaviour of these weak features.Comment: Accepted for publication in MNRAS, 8 pages, 6 figure

Deliverable 2: Report on the production of GIF by turbot, the effects on growth performance of turbot of local GIF production within RAS and the presence of GIF at commercial farm level

One of the working hypotheses of this project is that growth retardation of turbot cultured in recirculating aquaculture systems (RAS) is caused by the accumulation of growth inhibiting factors (GIF) produced by the turbot themselves in the culture water. Our first goal was to demonstrate the production of growth inhibiting factors by turbot following the methodology of Yurl and Perlmutter. A series of successive experiments was performed. Extracts from turbot culture water were tested for GIF presence in early life stage tests using eggs and larvae and small scale growth trials with juveniles. Our second goal was to demonstrate the transfer of GIF between tanks. Four experiments involving the integration of experimental tanks in a farm scale setting were performed. Our third goal was to demonstrate the presence of GIF at commercial farms. Two juvenile growth trials were performed

On the nature of two low M-dot X-ray bursters: 1RXS J170854.4-321857 and 1RXS J171824.2-402934

We carried out Chandra observations of two low-luminosity low-mass X-ray binaries, 1RXS J170854.4-321857 and 1RXS J171824.2-402934, for which previously single X-ray bursts had been detected with the Wide Field Cameras (WFCs) on board BeppoSAX. Both were detected in our Chandra observations in an actively accreting state three to eight years after the X-ray bursts, with 0.5-10 keV luminosities between 5x10^34 and 2x10^36 erg/s. The apparently persistent nature is remarkable for 1RXS J171824.2-402934 given its low luminosity of 0.001L_Edd. The persistence of both sources also distinguishes them from 5 other low-L bursters, which have also been seen during bursts with the WFCs but were not detected during Chandra observations above a luminosity of 10^33 erg/s. Those are probably transient rather than persistent sources.Comment: accepted for publication in Astronomy & Astrophysics, 7 pages, 5 figure