Dark matter at Chelsea

The Royal Horticultural Society’s annual Chelsea Flower Show in May is the top of the tree for garden enthusiasts – a huge and prestigious show where professional garden designers show off their skills and thousands of keen amateurs visit to admire their work. The National Schools’ Observatory’s “Dark Matter” garden not only won a gold medal this year, but also triumphed in the Fresh Garden section. We featured in almost all national newspapers and were on TV virtually every day of the show, reaching 163 million viewers worldwide according to the RHS. The garden’s raison d’être was to bring today’s ideas about the universe to a different, but very receptive, audience

A Luminous Red Nova in M31 and its Progenitor System

We present observations of M31LRN 2015 (MASTER OT J004207.99+405501.1), discovered in M31 in January 2015, and identified as a rare and enigmatic luminous red nova (LRN). Spectroscopic and photometric observations obtained by the Liverpool Telescope showed the LRN becoming extremely red as it faded from its M(V) = -9.4 +/- 0.2 peak. Early spectra showed strong Halpha emission that weakened over time as a number of absorption features appeared, including Na I D and Ba II. At later times strong TiO absorption bands were also seen. A search of archival Hubble Space Telescope data revealed a luminous red source to be the likely progenitor system, with pre-outburst Halpha emission also detected in ground-based data. The outburst of M31LRN 2015 shows many similarities, both spectroscopically and photometrically, with that of V838 Mon, the best studied LRN. We finally discuss the possible progenitor scenarios

On the Progenitors of Local Group Novae. II. The Red Giant Nova Rate of M31

In our preceding paper, Liverpool Telescope data of M31 novae in eruption were used to facilitate a search for their progenitor systems within archival Hubble Space Telescope (HST) data, with the aim of detecting systems with red giant secondaries (RG-novae) or luminous accretion disks. From an input catalog of 38 spectroscopically confirmed novae with archival quiescent observations, likely progenitors were recovered for eleven systems. Here we present the results of the subsequent statistical analysis of the original survey, including possible biases associated with the survey and the M31 nova population in general. As part of this analysis we examine the distribution of optical decline times (t(2)) of M31 novae, how the likely bulge and disk nova distributions compare, and how the M31 t(2) distribution compares to that of the Milky Way. Using a detailed Monte Carlo simulation, we determine that 30 (+13/-10) percent of all M31 nova eruptions can be attributed to RG-nova systems, and at the 99 percent confidence level, >10 percent of all M31 novae are RG-novae. This is the first estimate of a RG-nova rate of an entire galaxy. Our results also imply that RG-novae in M31 are more likely to be associated with the M31 disk population than the bulge, indeed the results are consistent with all RG-novae residing in the disk. If this result is confirmed in other galaxies, it suggests any Type Ia supernovae that originate from RG-nova systems are more likely to be associated with younger populations, and may be rare in old stellar populations, such as early-type galaxies

A compact, variable radio nebula around P Cygni

We present high spatial resolution images, at a wavelength of 6 cm, of the luminous blue variable star P Cygni. The images fully resolve the core of the stellar wind, and show that it is very clumpy. Two images were taken, separated in time by approximately a month, during which the structure in the wind has changed radically. The total flux observed has also changed significantly. We show that the clump sizes and electron densities are consistent with the radio variability being due to recombination of the ionized gas within the clumps, after key cooling lines become optically thin, causing the free-free emission to disappear. This is the first time that resolved radio images of a hot star wind have been obtained. It also represents important confirmation of a previous observation that thermal free-free wind emission can vary rapidly in a hot stellar wind

A DETAILED PHOTOMETRIC AND SPECTROSCOPIC STUDY OF THE 2011 OUTBURST OF THE RECURRENT NOVA T Pyxidis FROM 0.8 TO 250 DAYS AFTER DISCOVERY

We investigated the optical light curve of T Pyx during its 2011 outburst through compiling a database of Solar Mass Ejection Imager (SMEI) and AAVSO observations. The SMEI light curve, providing unprecedented detail covering t=1.5-49 days post-discovery, was divided into four phases based on the idealised nova optical light curve; the initial rise (1.5-3.3 days), the pre-maximum halt (3.3-13.3 days), the final rise (14.7-27.9 days), and the early decline (27.9 days - -). The SMEI light curve contains a strongly detected period of 1.44_0.05 days during the pre-maximum halt phase. These oscillations resemble those found in recent TNR models arising from instabilities in the expanding envelope. No spectral variations that mirror the light curve periodicity were found however. The marked dip at t_22-24 days just before light curve maximum at t=27.9 days may represent the same (shorter duration) phenomenon seen in other novae observed by SMEI and present in some model light curves. The spectra from the 2m Liverpool Telescope and SMARTS 1.5m telescope were obtained from t=0.8-80.7 and 155.1-249.9 days, covering the major phases of development. The nova was observed very early in its rise where a distinct high velocity ejection phase was evident with derived Vej_4000 km

Spectroscopic and Photometric Development of T Pyxidis (2011) from 0.8 to 250 Days After Discovery

We investigated the optical light curve of T Pyx during its 2011 outburst through compiling a database of SMEI and AAVSO observations. The SMEI light curve, providing unprecedented detail with high cadence data during t=1.5-49 days post-discovery, was divided into four phases based on the idealised nova optical light curve; the initial rise, the pre-maximum halt (or the 'plateau'), the final rise, and the early decline. Variation in the SMEI light curve reveals a strongly detected period of 1.44\pm0.04 days before the visual maximum. The spectra from the LT and SMARTS telescopes were investigated during t=0.8-80.7 and 155.1-249.9 days. The nova was observed very early in its rise and a distinct high velocity ejection phase was evident. A marked drop and then gradual increase in derived ejection velocities were present. Here we propose two different stages of mass loss, a short-lived phase occurring immediately after outburst followed by a more steadily evolving and higher mass loss phase. The overall spectral development follows that typical of a Classical Nova and comparison to the photometric behaviour reveals consistencies with the simple evolving pseudo-photosphere model of the nova outburst. The optical spectra are also compared to X-ray and radio light curves. Weak [Fe X] 6375A emission was marginally detected before the rise in X-ray emission. The middle of the plateau in the X-ray light curve is coincident with the appearance of high ionization species detected in optical spectra and the peak of the high frequency radio flux

Shaping of nova remnants by binary motion

We present the results of 2.5D hydrodynamic calculations of the effects of the underlying binary system on shaping the ejecta in a classical nova outburst. In the model, the outburst takes place in the form of a wind with secularly increasing velocity. This wind flows past a binary companion, which experiences a frictional drag force and transfers energy and angular momentum from its orbit into the expanding envelope. We find that many of the features seen in classical novaremnants can be reproduced, including polar blobs, polar rings and shells with tropical and equatorial bands. The features seen in the shells correlate with speed class in the observed manner — fast novae produce spherical shells, whereas slower novae produce banded shells and polar blobs. The effects of radiative cooling andthe Rayleigh-Taylor instability on the shells are discussed. It is found that, as observations appear to indicate, the shells of fast novae should comprise a few, large clumps, whereas the shells of slower novae will be clumped on scales which are small compared to the shell radius

Liverpool Telescope 2: a new robotic facility for time domain astronomy in 2020

The robotic 2m Liverpool Telescope, based on the Canary island of La Palma, has a diverse instrument suite and a strong track record in time domain science, with highlights including early time photometry and spectra of supernovae, measurements of the polarization of gamma-ray burst afterglows, and high cadence light curves of transiting extrasolar planets. In the next decade the time domain will become an increasingly prominent part of the astronomical agenda with new facilities such as LSST, SKA, CTA and Gaia, and promised detections of astrophysical gravitational wave and neutrino sources opening new windows on the transient universe. To capitalise on this exciting new era we intend to build Liverpool Telescope 2: a new robotic facility on La Palma dedicated to time domain science. The next generation of survey facilities will discover large numbers of new transient sources, but there will be a pressing need for follow-up observations for scientific exploitation, in particular spectroscopic follow-up. Liverpool Telescope 2 will have a 4-metre aperture, enabling optical/infrared spectroscopy of faint objects. Robotic telescopes are capable of rapid reaction to unpredictable phenomena, and for fast-fading transients like gamma-ray burst afterglows. This rapid reaction enables observations which would be impossible on less agile telescopes of much larger aperture. We intend Liverpool Telescope 2 to have a world-leading response time, with the aim that we will be taking data with a few tens of seconds of receipt of a trigger from a ground- or space-based transient detection facility. We outline here our scientific goals and present the results of our preliminary optical design studies. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

GRB optical and IR rapid follow-up with the 2 m Liverpool Robotic Telescope

The Liverpool Telescope, owned and operated by Liverpool John Moores University and situated at Roque de los Muchachos, La Palma, is the first 2-m, fully instrumented robotic telescope. We plan to use the LT in conjunction with Gamma Ray Observatories (HETE-2, INTEGRAL, Swift) to study GRB physics. A special over-ride mode will enable observations commencing less than a minute after the GRB alert, including optical and near infrared imaging and spectroscopy. These observations, together with systematic monitoring of the burst through the afterglow, will help to unravel the nature of prompt optical flashes, short bursts, optically dark bursts, redshift distribution, GRB - supernova connection and other questions related to the GRB phenomenon. In particular, the combination of aperture, instrumentation and rapid automated response makes the Liverpool Telescope excellently suited to the investigation of optically dark bursts and currently optically unstudied short bursts