- LT used to monitor a remarkable recurrent nova in M31
- Black Hole discovered orbiting a Spinning Star
- LT's GAIA tracking featured on the BBC's Northwest Tonight news show
- RINGO2 Used to Probe Early Evolution of Gamma Ray Bursts
- Comet chasing with the BBC
- 14A Call for Proposals
- LT spectra confirm the nature of the naked-eye brightness Nova Delphini 2013
- Liverpool Telescope celebrates 10 years at the forefront of Time Domain Astronomy
- Liverpool Telescope plans double-sized successor
In late 2013 another outburst of a rather unusual "recurrent nova (RN)" in the Andromeda galaxy, M31, was announced by the intermediate Palomar Transient Factory (iPTF). Novae are thought to be associated with binary systems which undergo a sudden brightening as material from an evolved secondary star falls (or "accretes") onto a compact primary star, usually a white dwarf. The accreting material ignites via nuclear fusion producing a sudden burst of radiation. Recurrent novae are - as the name suggests - objects which undergo multiple outbursts.
Like other RN, the object in M31, dubbed M31N 2008-12a, has been observed in outburst a number of times in the past. What makes this particular object interesting is its very short "recurrence timescale", i.e. the time between outbursts. M31N 2008-12a outbursts have been recorded almost annually since late 2008, when the object was first identified as a nova. Previously the most frequent RN was the Galactic system U Scorpii, which has a ~10 year inter-outburst time, making M31N 2008-12a all the more remarkable!
M31N 2008-12a is classed as a "very-fast" nova because it takes just four days for the brightness of the object to decline by two magnitudes. As such, our knowledge of its "lightcurve" (a graph showing how the object's brightness changes with time) is limited, even after five outbursts have been witnessed. Follow-up observations of the RN - something the LT does extremely well - were clearly needed.
Following the 2013 outburst, Dr Matt Darnley of the Astrophysics Research Institute here at Liverpool John Moores University formed a collaboration with Dr Martin Henze of the European Space Astronomy Centre in Spain. Their goal was to investigate ground-based optical plus space-based Swift X-ray and UV observations of the outburst, as well as Hubble Space Telescope (HST) infra-red, optical and UV observations of the "progenitor" system, i.e. the system before an outburst occurred. The collaboration also included LJMU's Steven Williams and Prof. Mike Bode.
A Liverpool Telescope IO:O image of the 2013 outburst, shown on the right, was used to precisely determine the position of the nova so that a search for a progenitor could be made. Archival HST observations - taken when the system was not in outburst - indicated the presence of a system coincident with the outburst position. This progenitor is consistent with a binary system known to contain an evolved secondary star (a sub-giant or red giant) and a luminous accretion disk. Such a bright disk indicates a high accretion rate, which is required for a system with such a short recurrence timescale.
An X-ray plus UV monitoring campaign undertaken with the Swift satellite soon after the 2013 outburst clearly detected a bright X-ray source only six days after the optical discovery. Such X-ray emission can only be detected when the nuclear burning on the surface of the white dwarf is viewed directly. The X-ray source persisted for two weeks before "turning-off", indicating the end of the nuclear burning phase. From these and other supporting observations Darnley et al. were able to identify the primary as a very high mass white dwarf.
Such a system - containing an evolved secondary star, a high mass white dwarf star, and a luminous accretion disk - coupled with a short recurrence time, is a prime candidate for a system that may one day become a "Type Ia supernova". SN Ia can be used to accurately measure the distances to very distant galaxies, and thereby map the expansion (and indeed the acceleration!) of the universe. As such our understanding of Type Ia supernova is of considerable importance. With its one-year outburst timescale, the team will be eagerly monitoring M31N 2008-12a with the LT and with other facilities over the next 12 months to see what happens next with this remarkable object.
A group of Spanish astronomers using the Liverpool and Mercator Telescopes at the Observatorio del Roque de los Muchachos have recently reported the discovery of a binary star system comprising a Be-type star and, remarkably, a black hole.
Jorge Casares of the Instituto de Astrofisica de Canarias (IAC) and La Laguna University (ULL) is lead author on a paper1, recently published in the science journal Nature, in which he and his colleagues present their exciting results.
Be-type stars are known to be fast rotators, and many find themselves to be one-half of an interacting binary system. However, their companions are usually neutron stars. This is the first time that the object orbiting the Be star has been identified as a black hole.
The newly-discovered system is located in the constellation Lacerta (the Lizard), at a distance of about 8,500 light years from the Earth. Known as MWC 656, the Be star rotates with an angular velocity of more than 1 million kilometres per hour. At this speed the star is close to being ripped apart by centrifugal forces, and is ejecting matter through an equatorial disk towards its mysterious companion. Casares' new spectroscopic observations indicate that this companion is a black hole.
A detailed analysis of the spectrum of MWC 656 suggests that its companion has a mass somewhere between 3.8 and 6.9 times that of the sun. Such an object is too massive to be a neutron star, and can only be a black hole. Matter is transferred from the Be star, though its equatorial disk, down onto the black hole via a second disk (an "accretion disk"). By analysing the emission from this second disk Casares and his team were able to measure the mass of the black hole.
In all likelihood, binary systems comprising Be-type stars and black holes are far more common than previously thought. Even so, it is notable that such a discovery was made using two relatively modest-sized telescopes, the 2.0 meter LT and the 1.2 meter Mercator telescope.
|Spectroscopic observations obtained with FRODOspec on the Liverpool Telescope showing the orbital evolution of emission lines from ionised Iron (Fe) and ionised Helium (He) atoms: (a) a sequence of spectra showing the change in line profile shape through one orbital phase; the vertical dashed line indicates the rest wavelength of each transition. (b) trailed intensity images of the same two emission lines plotted across two orbital cycles. See paper [ Nature | Astro-ph ] for further details.|
As part of the BBC's Stargazing Live 2014 series of events, the Liverpool Telescope featured recently on the Northwest Tonight news programme. LT staff and scientists from the Astrophysics Research Institute at Liverpool John Moores University explained how the telescope is being used to track the recently-launched GAIA satellite.
GAIA is a major ESA space telescope which aims at obtaining a 3-dimensional map of large chunks of the Milky Way. To do this, the position of the satellite must be known precisely. Telescopes like the LT are thus conducting nightly observations of the satellite, which will observe from a gravitationally stable point in space called 'L2'. At a distance of 1.5 million km from Earth, L2 lies on the axis that links the Earth to the Sun, and is in fact in the shadow of the Earth. GAIA will therefore orbit this point so that sunlight can be used to provide power to the satellite.
GAIA will measure the positions and velocities of about one billion stars - that's about 1% of all stars in the Milky Way. With these data astronomers should be able to probe the composition, formation and evolution of our Galaxy. GAIA should also reveal thousands of variable and transient phenomena, since it will re-observe large sections of sky every few days.
GAIA will observe the Milky Way for at least five years. Monitoring the position of GAIA is just one of many nightly duties conducted robotically by the LT. It is, however, arguably one of its most important.
A team led by Professors Carole Mundell and Iain Steele of Liverpool John Moores University (LJMU) is making great strides in understanding the enigmatic jets produced by massive stars in distant galaxies. These jets slam into gas and dust surrounding the system, producing a sudden burst of energy which, when directed towards the earth, is identified as a surge in gamma-ray emission. This surge is usually spotted first by NASA's SWIFT satellite, which immediately alerts astronomers on the ground who can then pursue rapid follow-up observations with other telescopes.
Gamma-Ray Bursts, as they have become known, are intrinsically the brightest sources of electromagnetic radiation in the night sky. Yet these burst are extremely short-lived, lasting in some cases less than minutes or even much less than a second. The initial burst is followed by a longer-lived though quickly fading afterglow. Rapid response to these events is therefore a necessity - and that's where the LT comes in.
Together with her team, Prof. Mundell has made use of a custom designed instrument, RINGO2, to measure and, importantly, monitor the polarisation of the optical emission from these events. RINGO2 was built by Prof. Steele and his small yet highly talented group of instrument builders at LJMU (indeed, RINGO2 has already been replaced by an upgraded "three beam" polarimeter, RINGO3, which is on the telescope and is currently being characterized).
As reported recently in the science journal Nature, the detection of highly polarized light from a Gamma Ray Burst detected in March 2012 (GRB 120308A), and the evolution of its afterglow with time, showed that GRBs contain large-scale, uniform magnetic fields that can survive long after the initial explosion.
Previous observations of optical afterglows from GRBs have detected polarizations of about 10 percent. However, these studies provided no information about how this value changed with time. As a result, they could not be used to test competing GRB jet models.
Remarkably, the LT managed to slew to and observe GRB 120308A within just four minutes of its discovery. Professor Mundell and her colleagues were able to report the initial detection of visible light with 28% polarization; within ten minutes the degree of polarization had decreased to 16%, although the polarization angle remained remarkably stable. Theoretical models predict the presence of strong and stable polarized emission if the jet possesses a structured magnetic field. Mundell's findings infer the existence of such a globally ordered magnetic field, and therefore support these models. Moreover, the observations suggest that these fantastic cosmic explosions are powered magnetically, like a solar flare, and not by radiation, like the big bang.
As well as providing new insight into the physical mechanisms of the most powerful and distant explosions in the Universe, the discovery of highly polarised light from this GRB afterglow may pave the way for future space missions. Conducting measurements similar to those described above - but in X-rays - could be of great value. This could, for examople, be accomplished by fitting a burst monitor and X-ray polarimeter to the recently approved ESA mission ATHENA+. Such a device could be the prime GRB facility for the coming decades.
Keen astronomers will no doubt have noticed that the Liverpool Telescope recently featured in an episode of the BBC's Sky at Night programme. The TV crew spent a few days at both the LT and the Isaac Newton Telescope, where images and spectroscopy of Comet C/2012 S1 ISON, the so-called "Comet of the Century", were obtained. Prof. Mike Bode and Dr Jon Marchant welcomed the TV crew and a group of amateurs and professional astronomers to the LT. Mike and Jon spent a long though fruitful night observing (a rarity for the LT, which of course is fully robotic and therefore usually operates without human intervention). The BBC team, meanwhile, went about their business, and managed to get some great footage of the observatory, including some wonderful time-lapse photography of the telescope in action.
The skies remained clear through most of the night. The telescope and instruments behaved flawlessly, and a considerable amount of data were obtained, on Comet ISON, but also on a couple of other comets which also featured in the show.
Streaming video of the episode itself can be found here: Sky at Night episodes
The Liverpool Telescope has now released its Call for Observing Proposals for semester 14A. The deadline for submission of proposals to the STFC Panel for the Allocation of Telescope Time (PATT) is Friday, 4th October, 2013 at 4pm GMT. The same deadline applies to the submission of proposals to the internal JMU TAG by JMU staff. Please see the Phase 1 page for further details.
At 2pm (UTC/GMT) on Wednesday 14th August 2013 the astronomer Koichi Itagaki, based in Yamagata, Japan, reported the discovery of a possible erupting nova in the constellation of Delphinus (the Dolphin). The report was of a "new" star at magnitude 6.3 (almost naked-eye brightness), whereas the previous day there was no object visible at this location (down to a limiting magnitude of 13th).
Following these reports, a team of astronomers at LJMU's Astrophysics Research Institute (Dr Matt Darnley, Prof Mike Bode and Dr Robert Smith) and a close collaborator at Keele University (Prof Nye Evans) requested spectroscopic observations of the system from the 2m robotic Liverpool Telescope. The immediate purpose of these observations was to confirm the classical nova nature of this object as early as possible to enable numerous follow-up programmes on other facilities to begin.
At 9:22pm (UTC) on 14th August, the FRODOSpec instrument on the LT obtained the first "professional" spectra of the system. These spectra contained strong neutral hydrogen Balmer series emission and absorption lines, with a characteristic "P Cygni" profile. Neutral Helium and singlely ionized Iron with similar P Cygni profiles were also visible. The P Cygni profile, named for the star in which they were first observed, is indicative of optically thick expanding gas. The LT spectra were used to measure this expansion velocity to be around 2000 km/s. These spectral characteristics strongly suggested that this object was indeed a classical nova in the early, optically thick, "fireball" stage.
These LT results were reported rapidly via the Astronomer's Telegram system and provided the first confirmation of the nature of this object - now referred to as Nova Delphini 2013 (Nova Del 2013).
The considerable brightness of the nova caused problems for many professional observatories, facilities that are designed to observe objects that are hundreds if not thousands of times fainter. As such, the observations of amateur astronomer networks, such as the American Association of Variable Star Observers (AAVSO), become invaluable. The AAVSO light-curve of Nova Del 2013 shows that the nova peaked at around magnitude 4.3 at approximately midday on 16th August. Since then the outburst has plateaued at around magnitude 4.8. This means that, in good conditions and with dark skies, Nova Del 2013 is still a naked-eye object. This is the first naked-eye nova since the eruption of KT Eridani in 2009, whose peak brightness was in fact overlooked until after discovery when previous observations of that part of the sky were searched, including those from the LT SkyCams.
The progenitor system of the Nova Del 2013 outburst appears to be the previously unremarkable star USNO-B1.0 1107-0509795 which, prior to the current outburst, had a magnitude of about 17th. During the outburst, the luminosity of this system has increased by over 12 magnitudes, or by a factor of ~100,000! The outburst of a classical nova in this system indicates that this star is in fact a close interacting binary system.
Extensive monitoring of the nova continues with the LT as the explosion evolves.
On 21st July, 2013, the Liverpool Telescope celebrated the 10th anniversary of Engineering First Light1 with a solid night of robotic operations. The skies were clear, the "seeing" (image sharpness) was fair, and the near-full moon rose majestically from the east at about 9pm, local time. Four different instruments ( IO:O, FRODOSpec, RINGO3 and RISE) were used to observe Exoplanets, T Tauri stars, Novae, Supernovae, Gamma Ray Bursts, and Blazars. In all, data for nine different research projects were obtained and some examples of these tenth anniversary observations are included below.
The story was quite different ten years ago. Back then, an optical eyepiece was installed and the commissioning team needed to look through the telescope by eye to confirm the optical alignment. That changed very rapidly and within a week the first instrument, RATCam, was installed on the telescope and Science First Light was achieved, on 26th July 2003 - ten years ago today. RATCam is still mounted on the telescope and continues to be used by a number of researchers (although it was not used on these 10th anniversary nights, in part because it is in the process of being decommissioned and will soon be removed from the telescope to make way for a next generation infra-red camera, IO:I). Team members spent much of late-2003/early-2004 on La Palma commissioning systems until routine, fully-automated and unsupervised operations of the telescope, enclosure and instruments commenced in late 2004.
Ten years ago, as now, the telescope served a diverse user community. Though the majority of the time is used by UK-based professional astronomers, several observers work in research institutes across Europe and around the World and 5% of the telescope time has always been made available to school children through the National Schools Observatory programme. Since 2003, almost 60,000 observations have been secured for students from schools throughout the UK. A broad range of science projects have been conducted on the LT over the past decade and highights from many of them may be found in the LT News Archive. A few of the projects started in 2003 are still running even now, delivering unprecedented long-term monitoring of interesting astrophysical systems.
It seems appropriate that the 10th anniversary of First Light coincides almost to the day with the launch of a new project, Liverpool Telescope 2. A complement to the LT, LT2 will make full use of the changing face of astrophysics, as time domain studies move progressively to the forefront of modern astronomy, driven by the launch of the GAIA satellite later this year, and the completion of ambitious ground-based observatories like the Low Frequency Radio Array (LOFAR), the Square Kilometer Array (SKA), and the Large Synoptic Survey Telescope (LSST) over the next decade.
In the meantime, the LT continues to work at the cutting edge of robotic astronomy, reacting to triggers from telescopes around the world and in space and monitoring transients, outbursts, and variables, in many cases immediately after they are discovered.
1First Light marks the point when the first images are obtained through the newly-constructed telescope.
360° panorama of the LT and environs, taken while standing on the south-west corner of the open enclosure. Credit: R. Smith
Planning is underway for a successor to the world's largest fully robotic telescope. The Liverpool Telescope (LT) is a 2-metre optical telescope located on La Palma that has been in operation since 2004. It has become a leading astronomical facility through its ability to react quickly to observe newly discovered or transient events in the universe, such as the cataclysmic explosions known as Gamma Ray Bursts (GRBs). It has also been used by more than 2000 schools as part of a thriving outreach programme. Now, the scientific community is being consulted on the facilit's successor, LT2. Dr Chris Copperwheat will present the current status of the project and invite feedback from the community at the National Astronomy Meeting in St Andrews on Tuesday 2 July.
Plans for the new telescope are being developed by the Astrophysics Research Institute of Liverpool John Moores University (LJMU), which owns and operates the LT. Already, some criteria have been identified: LT2 will be a 4m-class facility and the preferred location is La Palma.
"We've been having productive talks with the Instituto de Astrofisica de Canarias and hope to work in partnership with them to realise the project. La Palma is of course one of the best observing sites in the world, and there are obvious logistical benefits to siting LT2 at the same observatory as LT. There are potential science benefits as well - we'll be exploring the possibilities of using the two telescopes together to provide an enhanced capability. La Palma is a northern site but there is still good overlap with the southern sky," said Copperwheat.
Like the current telescope, LT2 will be fully robotic and will be able to make rapid and flexible observations to follow up on discoveries made by other observatories. This application is becoming increasingly important due to current and upcoming large-scale surveys of the night sky: from around 2020, the new US-built Large Synoptic Survey Telescope (LSST) will begin a 10 year mission in which the entire southern sky is photographed every few nights.
"These surveys will discover large numbers of exotic and rare supernova subtypes, and will also be discovering them at an extremely early point in their evolution. Currently, only a small fraction of transients get any follow-up analysis, and this problem will get even worse in the LSST era. This is where we envisage LT2 coming in to its own," said Copperwheat.
LT2 will be designed so that the telescope can slew extremely rapidly and get onto a new target very soon after receiving a 'trigger' from another facility. This is vital in order to catch the light from transient objects that fade extremely rapidly, like GRB afterglows. The aim is for LT2 to be able to detect the target and make follow-up observations in just a few tens of seconds.
"As well as GRB afterglows, there may be rapidly fading transients from more exotic sources. A new gravitational wave detector, Advanced LIGO, should be operational by 2014. One exciting possibility is that LT2 could make follow-up optical observations of merging neutron stars or black hole binaries that are initially detected through gravitational waves. There will be a lot of competition to detect these and the reaction speed of LT2 might give us an advantage," said Copperwheat.
Whilst transient science will be LT2's core mission, the telescope will also be used for observations of binary systems and variable stars detected by the European Space Agency's Gaia mission, which is due for launch later this year, as well as exoplanets discovered by the next generation of space and ground based missions.
The LJMU team is currently developing an outline of user requirements that they will use to commission a preliminary design for LT2 in the next few months. A white paper on the science case is also planned for the autumn.
"We want very much to engage with the community and would be keen to hear any views on the project at this stage. As we move on we'll be looking to establish more partnerships with groups and institutions in the UK and beyond," said Copperwheat.
For further information, visit the LT2 website
For older news items, see the News Archive