Pro-Am astronomy

Meeting report Pro-Am astronomy A s the participants poured out at the end of the RAS Pro–Am meeting at the University of London Observatory, Mill Hill, on 16 September 2000, a typical remark was: “That was an excellent meeting. When is the next one?” The meeting was organized to help to develop closer collaborations between professional and amateur astronomers over a wide range of topics. Despite the fuel crisis, which made getting to the meeting difficult for many people, 40 or so keen astronomers came together for this extremely lively meeting. Nial Tanvir (University of Hertfordshire) stressed the importance of amateur observations in his research programme to understand Gamma-Ray Bursters (GRBs). He said that, although originally discovered in the 1960s by US military spacecraft monitoring the effectiveness of the nuclear test ban treaty, the astronomical world was not aware of GRBs until 1973. Because of the short duration of the bursts it has proved difficult to identify these objects with an optical counterpart and for more than 20 years opinions were divided as to whether the bursts originated in our own galaxy or were at cosmological distances. By the early 1990s the BATSE experiment on the Compton Gamma Ray Explorer satellite (CGRE) had discovered nearly 2000 objects from which it was clear that they were uniformly distributed on the sky and that there was no concentration of objects along the galactic plane. Nial told the audience that the first identification breakthrough came in 1997 when the Italian–Dutch satellite Beppo-Sax was able to pinpoint the source of gamma rays with sufficient accuracy for optical telescope to make February 2001 Vol 42 The meeting assembled in front of the University of London Observatory. rapid follow-up observations. The NASA HETE-2 satellite (successfully launched on 9 October) is expected to discover tens of new objects a year with positions accurate to a few arcminutes. Nial described how he is working with amateur astronomer Guy Hurst to establish a network of amateurs in the UK who can react rapidly to discovery announcements. Speed of reaction to the announcements is very important as bursts may last only from seconds to tens of minutes. Amateur astronomers are becoming equipped with increasingly sophisticated telescopes which can often be made to react more quickly than the professional telescopes. He also stressed that naked-eye observations may be extremely valuable and able to demonstrate the temporal behaviour of a burst better than more complex equipment. Supernovae Peter Meikle (Imperial College) then spoke on “Supernovae – observe early, observe often”. He said that although type Ia supernovae are increasingly being used by cosmologists as standard candles to explore the size and evolution of the universe, they were far from being well understood and could vary by a factor of between 2 and 4 in luminosity. Type Ia are intrinsically the brightest supernovae and therefore used to probe the cosmological distance scale. They are thought to result from a thermonuclear explosion of a white dwarf in a binary system as material from the companion spirals onto it. Both the mechanism which ignites the explosion and the nature of the progenitor stars are poorly understood and until some of the problems are resolved they are clearly of limited use as standard candles. Peter said that amateurs are playing a vital role in the study of supernovae; currently about fourfifths of known supernovae are discovered by amateurs. Many amateur astronomers are also well placed to make regular observations over a long period of time to follow the light curve and to take spectra. He asked all observers to keep their galaxy observations for some time to help in the study of pre-discovery observations. Mark Armstrong, an amateur astronomer from Rolvenden, Kent, described his supernova patrol programme which (at the date of the meeting) had led to his discovery of 13 of the 26 supernovae which have been discovered by UK amateurs since October 1996; nine of his discoveries have been in the past year. Mark has three telescopes in an observatory shed in his back garden, the largest of which is a Celestron 14 on a Paramount GT-1100. This and his 12 inch Meade LX200 are used in the supernova patrol. With one telescope he takes 30 s integrations and can observe as many as 90 galaxies an hour to a limiting magnitude of 19–19.5 in the zenith. He examines the images in real time on a computer screen indoors, comparing them with standard images of each galaxy. Follow-up observations of any suspect field are made as soon as possible. Mark has 7000 galaxies of all types on his program and says that he has now made about 86 000 patrols. Introducing another topic in which professional and amateur astronomers collaborate, Duncan Steel (University of Salford) described the essential contribution amateurs can make to the study of asteroids and comets. Although robotic telescopes are routinely discovering 1.31 The long history of close collaboration between amateur and professional in astronomy continued with an RAS discussion meeting held in September. Margaret Penston reports on the lively and enthusiastic discussion. Meeting report Above: The speakers, from left to right: Maurice Gavin, Peter Meikle, Bill Worraker, Denis Buczynski (front), Peter Wheatley, Andrew Elliott, Margaret Penston, Nial Tanvir, Mark Armstrong, Tim Naylor, Mark Cropper, Nick James. Duncan Steel, who also spoke, is not shown. Left: Mark Armstrong, Maurice Gavin and Nial Tanvir chat during a break in sessions. Dwarf novae Tim Naylor (University of Keele) described the current theories to explain the outbursts of dwarf novae. These are close binary systems where angular momentum loss is slowly forcing a main sequence star closer to its white dwarf companion. When a critical size (defined by the Roche lobe surface) becomes smaller than the normal star, matter pours from it into an accretion disk surrounding the white dwarf. Although normally quite faint, these disks can brighten by two orders of magnitude, a process thought to involve a dramatic change on the viscosity of the disk. Theories predict that this brightening may begin close to the outer edge of the disk (an “outside in” outburst) or close to the inner edge (“inside out”). Deciding which of these occurs in particular systems allows us to investigate the viscosity of dwarf nova disks, knowledge which we seek to apply to disks in AGN and star-forming regions. We can distinguish the outburst type using light curves of eclipsing dwarf novae, easily obtained with amateur telescopes. Bill Worraker described a co-ordinated effort by amateur astronomers to observe dwarf novae to look for eclipses. Amateurs often have the telescope time available to follow a variable for many hours and can quickly determine whether the star is an eclipsing system. He said that from the models one would expect about one in three systems to (...truncated)