Teaching practical astronomy at a professional observatory

In 1988 Southampton University established a new Programme of Study, Physicswith- Astronomy and it was felt to be essential to provide the students with detailed practical experience in observational astronomy. The obvious difficulties of scheduling and successfully executing observational work from the UK led to the establishment of an annual Field Trip to the Observatario del Teide at Izana in Tenerife, Spain. The course allows 12 second-year astronomy students to visit the observatory in Tenerife every Easter vacation for one week

XMM-Newton observation of the highly magnetised accreting pulsar Swift J045106.8-694803: evidence of a hot thermal excess

Several persistent, low luminosity (LX ~ 1034 erg s-1), long spin period (P > 100 s) High Mass X-ray Binaries have been reported with blackbody components with temperatures > 1 keV. These hot thermal excesses have correspondingly small emitting regions (< 1 km2) and are attributed to the neutron star polar caps. We present a recent XMM-Newton target of opportunity observation of the newest member of this class, Swift J045106.8-694803. The period was determined to be 168.5 ± 0.2 s as of 17 July 2012 (MJD = 56125.0). At LX ~ 1036 erg s-1, Swift J045106.8-694803 is the brightest member of this new class, as well as the one with the shortest period. The spectral analysis reveals for the first time the presence of a blackbody with temperature kTBB = 1.8 +0.2-0.3 keV and radius RBB = 0.5 ± 0.2 km. The pulsed fraction decreases with increasing energy and the ratio between the hard (> 2 keV) and soft (< 2 keV) light curves is anticorrelated with the pulse profile. Simulations of the spectrum suggest that this is caused by the pulsations of the blackbody being ~ π out of phase with those of the power law component. Using a simple model for emission from hot spots on the neutron star surface, we fit the pulse profile of the blackbody component to obtain an indication of the geometry of the system

Multiwavelength observations of the Be/X-ray binary 4U1145-619

We report optical and infrared observations of the massive X-ray binary system 4U1145-619 (V801 Cen) which show that the circumstellar disc of the Be star component is in decline. Infrared J,H,K,L magnitudes of V801Cen have been monitored from 1993 March to 1996 April. H alpha spectra have been obtained throughout the same period. We find that both the infrared excess and the Balmer emission have been in decline throughout the period of observations. A 13 year optical and X-ray history of the source has been collated, revealing a possible correlation between the optical and X-ray activity. In addition, we have used u,v,b,y,beta indices, corrected for both circumstellar and interstellar effects, to calculate the physical parameters of the underlying B star.Comment: 8 pages postscript. Accepted by MNRA

Two populations of X-ray pulsars produced by two types of supernovae

Two types of supernova are thought to produce the overwhelming majority of neutron stars in the Universe. The first type, iron-core collapse supernovae, occurs when a high-mass star develops a degenerate iron core that exceeds the Chandrasekhar limit. The second type, electron-capture supernovae, is associated with the collapse of a lower-mass oxygen-neon-magnesium core as it loses pressure support owing to the sudden capture of electrons by neon and/or magnesium nuclei. It has hitherto been impossible to identify the two distinct families of neutron stars produced in these formation channels. Here we report that a large, well-known class of neutron-star-hosting X-ray pulsars is actually composed of two distinct sub-populations with different characteristic spin periods, orbital periods and orbital eccentricities. This class, the Be/X-ray binaries, contains neutron stars that accrete material from a more massive companion star. The two sub-populations are most probably associated with the two distinct types of neutron-star-forming supernovae, with electron-capture supernovae preferentially producing system with short spin period, short orbital periods and low eccentricity. Intriguingly, the split between the two sub-populations is clearest in the distribution of the logarithm of spin period, a result that had not been predicted and which still remains to be explaine

Anti-correlation between X-ray luminosity and pulsed fraction in the Small Magellanic Cloud pulsar SXP 1323

We report the evidence for the anti-correlation between pulsed fraction (PF) and luminosity of the X-ray pulsar SXP 1323, found for the first time in a luminosity range $10^{35}$--$10^{37}$ erg s$^{-1}$ from observations spanning 15 years. The phenomenon of a decrease in X-ray PF when the source flux increases has been observed in our pipeline analysis of other X-ray pulsars in the Small Magellanic Cloud (SMC). It is expected that the luminosity under a certain value decreases as the PF decreases due to the propeller effect. Above the propeller region, an anti-correlation between the PF and flux might occur either as a result of an increase in the un-pulsed component of the total emission or a decrease of the pulsed component. Additional modes of accretion may also be possible, such as spherical accretion and a change in emission geometry. At higher mass accretion rates, the accretion disk could also extend closer to the neutron star (NS) surface, where a reduced inner radius leads to hotter inner disk emission. These modes of plasma accretion may affect the change in the beam configuration to fan-beam dominant emission.Comment: It has been accepted for publication in Monthly Notices of the Royal Astronomical Society Letter

Confirmation of six Be X-ray binaries in the Small Magellanic Cloud

The X-ray binary population of the Small Magellanic Cloud (SMC) contains a large number of massive X-ray binaries, and the recent survey of the SMC by XMM–Newton has resulted in almost 50 more tentative high-mass X-ray binary (HMXB) candidates. Using probability parameters from Haberl and Sturm together with the optical spectra and timing in this work, we confirm six new massive X-ray binaries in the SMC. We also report two very probable binary periods of 36.4 d in XMM 1859 and of 72.2 d in XMM 2300. These Be X-ray binaries are likely part of the general SMC population, which rarely undergoes an X-ray outburst.This paper is based on ESO data from 079.D−0371 and 088.D−0352. The AAT observations have been supported by the OPTICON project (observing proposals 2011A/014 and 2012/A015), which is funded by the European Commission under the Seventh Framework Programme (FP7). VAM acknowledges financial support from the National Research Foundation of South Africa (Grant 93405) and the World Universities Network. RD, AM and IN from the University of Alicante acknowledge support from the Spanish Government Ministerio de Economía y Competitividad under grant AYA2015-68012-C2-2-P (MINECO/FEDER). ESB acknowledges support from a Claude Leon Foundation fellowship and from the Marie Curie Actions of the European Commission (FP7-COFUND). The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to AU

Advances in Understanding High-Mass X-ray Binaries with INTEGRAL and Future Directions

High mass X-ray binaries are among the brightest X-ray sources in the Milky Way, as well as in nearby Galaxies. Thanks to their highly variable emissions and complex phenomenology, they have attracted the interest of the high energy astrophysical community since the dawn of X-ray Astronomy. In more recent years, they have challenged our comprehension of physical processes in many more energy bands, ranging from the infrared to very high energies. In this review, we provide a broad but concise summary of the physical processes dominating the emission from high mass X-ray binaries across virtually the whole electromagnetic spectrum. These comprise the interaction of stellar winds with the high gravitational and magnetic fields of compact objects, the behaviour of matter under extreme magnetic and gravity conditions, and the perturbation of the massive star evolutionary processes by presence in a binary system. We highlight the role of the INTEGRAL mission in the discovery of many of the most interesting objects in the high mass X-ray binary class and its contribution in reviving the interest for these sources over the past two decades. We show how the INTEGRAL discoveries have not only contributed to significantly increase the number of high mass X-ray binaries known, thus advancing our understanding of the population as a whole, but also have opened new windows of investigation that stimulated the multi-wavelength approach nowadays common in most astrophysical research fields. We conclude the review by providing an overview of future facilities being planned from the X-ray to the very high energy domain that will hopefully help us in finding an answer to the many questions left open after more than 18 years of INTEGRAL scientific observations.The INTEGRALteams in the participating countries acknowledge the continuous support from their space agencies and funding organizations: the Italian Space Agency ASI (via different agreements including the latest one, 2019-35HH, and the ASIINAF agreement 2017-14-H.0), the French Centre national d’études spatiales (CNES), the Russian Foundation for Basic Research (KP, 19-02-00790), the Russian Science Foundation (ST, VD, AL; 19-12-00423), the Spanish State Research Agency (via different grants including ESP2017-85691-P, ESP2017-87676-C5-1-R and Unidad de Excelencia María de Maeztu – CAB MDM-2017-0737). IN is partially supported by the Spanish Government under grant PGC2018-093741-B-C21/C22 (MICIU/AEI/FEDER, UE). LD acknowledges grant 50 OG 1902