Time Domain Astrophysics

The time-scales associated with stellar and galactic evolution are generally so vast that the Universe has been traditionally viewed as static. Of course, we have long known of short - human - timescale events, such as Solar System events, eclipsing binaries, and stellar explosions. But only within the past decade or so, with the advent of robotically controlled telescopes, and high cadence near-all sky monitoring the field of time-domain astronomy - the study of astronomical events on ever shorter time-scale - has literally exploded. With access to this new steam of data, our understanding of many phenomena has increased significant, but also, so have the number of unanswered questions. As the designers, builders, and operators of the 2m fully-robotic Liverpool Telescope, one of the leading time-domain facilities in the world, Astronomers at the Astrophysics Research Institute (ARI) of Liverpool John Moores University are uniquely placed at the forefront of this field. The time-domain work at the ARI is focussed on the Explosive Transients, particularly, Novae, Supernovae (SNe), and Gamma Ray Bursts (GRBs). In this module a number of world-leading astronomers in their respective areas will introduce the general field of time-domain astronomy, and focus on the observations and physics of explosive transients and other variables.

This module will be structured as follows: the first few lectures will cover the general background and history of time-domain astronomy, serving as an introduction to the course; we will then move on to explore the observing and data analysis techniques specific to the time-domain, and we will also introduce some of the past, present, and future facilities specialising in, or dedicated to, time-domain observations. The core section of the course will be focussed specifically on the three explosive transient phenomena that the ARI specialises in, Novae, both thermonuclear and core-collapse SNe, and GRBs. Here we will explore the fundamental physics of these systems and their sub-classes, their progenitor systems including their formation, the population statistics, and their wider importance to Astronomy as a whole; all the time linking these concepts to the research on-going in the ARI and further afield. This module will also introduce a range of other time-domain phenomena, such as: periodic and quasi-periodic variable stars, e.g. Cepheid and Mira variables, pulsars, and eclipsing binaries; all the time explaining the physical processes at play and the importance of each system. We will also explore more ‘exotic’ transient events, such as: tidal disruptions; luminous blue variables and luminous red nova; cataclysmic variables, e.g. dwarf novae, in general; the related X-ray transients; active galactic nuclei; and the potential gravitational wave sources. Finally, we will briefly explore one of the most exciting and faster moving fields related to the time-domain - extra Solar planets.

The majority of the content for this module will be delivered through a series of lectures, most delivered by a leading astronomer in that particular field. The lectures will also be supported by a number of extended tutorials and exercises, which will be used to explore the more involved concepts in the course, and some of the data analysis techniques related to the time-domain.

Here we provide a brief, but non-exhaustive, list of some of the concepts and phoneme covered in the course:

- Historical time-domain astronomy, how the field has developed
- 'Stella novae', proper motion, expansion parallax, early observations of pulsars
- Data analysis techniques, e.g., relative photometry, difference imaging, spectral line morphology evolution
- Time-domain facilities, past, present (e.g. Liverpool Telescope, Swift, PTF/iPTF, etc.), future (e.g. LT2, LSST, SKA, etc.)
- Classical and Recurrent Novae (CNe & RNe), formation, mass-loss and accretion, eruption mechanism and properties
- CN & RN observational properties and classifications, importance (e.g. link to SN Ia, C13, N15, O17, Li)
- General introduction to SNe, historical observations and development of classification scheme (e.g. Type I vs. II), nebular remnants, general importance
- Thermonuclear SNe (Ia), progenitor scenarios (single-degenerate vs. double-degenerate, C-O WD vs. O-Ne WD), explosion mechanisms
- SNIa observational properties (photometric and spectroscopic), standardisable candles and cosmic distance indicators
- Core colapse SNe (CCSNe), progenitors and environments, explosion mechanisms, remnants (neutron stars and black holes)
- CCSNe observational properties, ISM enrichment
- GRBs historic discovery, observational properties, proposed mechanisms - long vs. short time-scale events
- Variable stars, periodic and quasi-periodic systems, intrinsic and extrinsic variability, pulsating stars, eclipsing systems
- Cataclysmic variables, e.g. dwarf novae, X-ray binaries
- Exotic transients and exotic physics, e.g. tidal disruption events, AGN, gravitational waves (and optical counterparts), exotic and rare transients
- Extrasolar planets, discovery techniques, e.g. transits, radial velocity, astrometric, microlensing and selected population statistics update