A systematic analysis of the XMM-Newton background: III. Impact of the magnetospheric environment

A detailed characterization of the particle induced background is fundamental for many of the scientific objectives of the Athena X-ray telescope, thus an adequate knowledge of the background that will be encountered by Athena is desirable. Current X-ray telescopes have shown that the intensity of the particle induced background can be highly variable. Different regions of the magnetosphere can have very different environmental conditions, which can, in principle, differently affect the particle induced background detected by the instruments. We present results concerning the influence of the magnetospheric environment on the background detected by EPIC instrument onboard XMM-Newton through the estimate of the variation of the in-Field-of-View background excess along the XMM-Newton orbit. An important contribution to the XMM background, which may affect the Athena background as well, comes from soft proton flares. Along with the flaring component a low-intensity component is also present. We find that both show modest variations in the different magnetozones and that the soft proton component shows a strong trend with the distance from Earth.Comment: To appear in Experimental Astronomy. Presented at AHEAD Background Workshop, 28-30 November 2016. Rome, Ital

Linking gravitational waves and X-ray phenomena with joint LISA and Athena observations

The evolution of cosmic structures, the formation and growth of the first black holes and the connection to their baryonic environment are key unsolved problems in astrophysics. The X-ray Athena mission and the gravitational-wave Laser Interferometer Space Antenna (LISA) offer independent and complementary angles on these problems. We show that up to 10 black hole binaries in the mass range 10^5 - 10^8 Msun discovered by LISA at redshift <~ 3.5 could be detected by Athena in an exposure time up to 100 ks, if prompt X-ray emission of ~ 1% - 10% of the Eddington luminosity is present. Likewise, if any LISA-detected extreme mass ratio inspirals occur in accretion disks, Athena can detect associated electromagnetic emission out to redshift ~ 1. Finally, warned by LISA, Athena can point in advance and stare at stellar-mass binary black hole mergers at redshift <~ 0.1. These science opportunities emphasise the vast discovery space of simultaneous observations from the two observatories, which would be missed if they were operated in different epochs.Comment: Published in Nature Astronom

Predicting reading recovery selection and outcomes : is it possible? : a thesis presented in partial fulfilment of the requirements for the degree of Master of Education (Literacy) at Massey University, Manawatū, New Zealand

Purpose: Predictive early literacy assessments are useful to identify students who are at risk of reading difficulty. This study investigated the use of six early literacy assessments, administered when students first entered school (Time 1), and in the middle of their first year at school (Time 2), in order to predict which students would be selected for Reading Recovery and to identify the Reading Recovery (RR) outcomes for students who participated in the intervention. Method: Unpublished data from a longitudinal study (Early Literacy Project, Chapman, Arrow, Tunmer, & Braid, 2016) was analysed to find predictive links between assessment results and later reading outcomes, for a cohort of 300 5-year-old children in New Zealand primary schools. Results: It was not possible to predict which students would be selected for Reading Recovery due to the variations in RR selection processes. It was found that children who participated in RR were more likely to be referred on for further support the lower their phonological awareness scores were. It was also found that if a child scored 20 points or less, in a combination of Time 1 assessments (letter names, letter sounds and three measures of phonological awareness), they were likely to have a body of literacy abilities that meant they would be working at least a year below the National Standard by the end of their second year at school. Implications: The findings indicate that standardising the selection of students for RR may mean students with the lowest literacy attainment all get support. In addition, early literacy assessments, including measures of phonological awareness, should be administered early in a child’s schooling and those identified as being at risk of reading difficulty should receive literacy support without delay. Addressing students’ low levels of phonological awareness in the first year of schooling may lead to better outcomes for students who participate in RR. Keywords: phonological awareness, Reading Recovery, early literacy assessment, letter names, letter sounds, New Zealand, timing of assessment, vocabular

First Production and Detection of Cold Antihydrogen Atoms

The ATHENA experiment recently produced the first atoms of cold antihydrogen. This paper gives a brief review of how this was achieved.Comment: Invited talk at Int. Conf. on Low Energy Antiprotons 2003 (LEAP03), to be published in NIM

Production of antihydrogen at reduced magnetic field for anti-atom trapping

We have demonstrated production of antihydrogen in a 1$,$T solenoidal magnetic field. This field strength is significantly smaller than that used in the first generation experiments ATHENA (3$,$T) and ATRAP (5$,$T). The motivation for using a smaller magnetic field is to facilitate trapping of antihydrogen atoms in a neutral atom trap surrounding the production region. We report the results of measurements with the ALPHA (Antihydrogen Laser PHysics Apparatus) device, which can capture and cool antiprotons at 3$,$T, and then mix the antiprotons with positrons at 1$,$T. We infer antihydrogen production from the time structure of antiproton annihilations during mixing, using mixing with heated positrons as the null experiment, as demonstrated in ATHENA. Implications for antihydrogen trapping are discussed

The First Stars: A Low-Mass Formation Mode

We perform numerical simulations of the growth of a Population III stellar system under photodissociating feedback. We start from cosmological initial conditions at z = 100, self-consistently following the formation of a minihalo at z = 15 and the subsequent collapse of its central gas to high densities. The simulations resolve scales as small as ~ 1 AU, corresponding to gas densities of 10^16 cm^-3. Using sink particles to represent the growing protostars, we evolve the stellar system for the next 5000 years. We find that this emerging stellar group accretes at an unusually low rate compared with minihalos which form at earlier times (z = 20 - 30), or with lower baryonic angular momentum. The stars in this unusual system will likely reach masses ranging from < 1 M_sun to 5 M_sun by the end of their main-sequence lifetimes, placing them in the mass range for which stars will undergo an asymptotic giant branch (AGB) phase. Based upon the simulation, we predict the rare existence of Population III stars that have survived to the present day and have been enriched by mass overflow from a previous AGB companion.Comment: 19 pages, 17 figures, to apper in Ap