Liverpool Telescope 2
Chris Copperwheat
Liverpool Telescope group:
Iain Steele, Chris Davis, Rob Barnsley, Stuart Bates, Neil Clay, Steve
Fraser, Jon Marchant, Chris Mottram, Robert Smith, Mike Tomlinson
The Liverpool Telescope
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The Liverpool Telescope is a robotic
2m alt-az telescope currently in
operation on La Palma
Not 'remote controlled' – operated
autonomously without night-time
supervision
Software decides what and how to
observe and is responsible for safe
operation of telescope throughout
the night
Liverpool Telescope Instrumentation
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IO O: Main imaging camera: 10' FoV; 12 optical filters
FRODOspec: 12x12 0.82'' lenslet IFU
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R~2500/5500; 400 < λ < 940nm
RINGO3: Fast-readout tri-band polarimetry
RISE: Rapid readout (0.6sec) photometry; 10' FoV
IO THOR: High cadence photometry (~7ms); 2.25' FoV
Coming this year:
IO I: Infrared (Y, J, H) imager. 6x6' FoV
SPRAT: R~500 spectrograph
LT Science
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Flexible nature of LT observing modes makes it ideal for
time domain work
High-impact science
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36 citations/paper average (for papers > 3yr old)
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15 publications in Nature/Science (86 citations on average)
GRB Polarimetry
Polarisation evolution of GRB 120308A (Mundell et al., 2013)
Results indicate that GRBs contain magnetized baryonic jets with
large-scale uniform fields that can survive long after the initial explosion
(See also Mundell et al., 2007; Steele et al., 2009)
Eclipsing binaries
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CSS080502
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Eclipsing white dwarf – M dwarf binary. Porb ~3.59 hrs
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Eclipses timed to sub-second precision
Variations in orbital period due to magnetic variability or
circumbinary planets (e.g. Beuermann et al. 2010)
(Data from Bours et al.)
Long period binaries
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Subdwarf-B star with FGK-type MS companion
Orbital period (~months – years) measured via radial
velocity shifts
Example of the type of project which would be impossible
on a classically scheduled telescope
Liverpool Telescope 2
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The Liverpool Telescope is now a mature facility which is expected to
stay competitive until at least 2020
The next decades will see an increased emphasis worldwide on time
domain science, with many new facilities and missions coming on line
We aim to build a new 'Liverpool Telescope 2' facility designed to
capitalise on this exciting new era, to come into operation ~2020
LJMU has committed £200,000 to fund the feasibility and initial
design study for LT2. We are 15 months into that process and things
are proceeding well
No real preconceptions other than that LT2 will build on the existing
strengths of the LT
Operational strengths of the LT
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Low operational cost (robotic observing)
● 10.5 staff; £500k/year or £10k/paper
Rapid response to transient alerts (avg ~180s)
● Robotic telescope
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Design – telescope, enclosure, software
Instrumentation
● Diverse suite of instruments
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Quick instrument changes
Rapid deployment of new instruments to meet new
needs
LT2 key science objectives
Transient science
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Transients (of various types) a key research area at LJMU,
and in astronomy groups worldwide
An area of study well matched to robotic observing
Synoptic surveys such as PTF, Pan-STARRS, Skymapper
provide large numbers of transients detected at early times
Number of detections to increase significantly with next
generation of surveys (LSST)
For fast fading transients like GRBs, rapid response more
important than aperture
Next decades will see the discovery of exotic transients
across the EM spectrum
Early time spectra of SN2011fe
Light curve
(Fulton/LCOGT/PTF)
High velocity OI feature detected in
LT+Frodospec spectrum, 1.18 days
after explosion (Nugent et al. 2011)
LSST
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Sited at Cerro Pachón, Chile (Gemini South)
Engineering first light 2020, 10 yr survey begins 2022
8m primary mirror, 9.6 deg2 field of view
1000 visits to each patch of sky in 10 years.
● Each visit 2 x 15 sec exposures
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Single visit depth r ~ 24.5
Total survey covers 20,000 deg2 in ugrizy
● Coadded depth r ~ 26.5
~ 1e6 transient alerts per night
● Alerts published 60 s after observation
Transient science in 2020+
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LSST (and the other synoptic surveys) will provide
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Large, unbiased and statistically complete samples
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Very early detections (many objects like SN2011fe). New parameter
space
CC SNe: progenitors (pre-explosion imaging), relative frequencies of
rare subtypes, unusual environments
Potentially new types of stellar explosions (combined with radio, high
energy, GW, neutrino detections)
Many photometric monitoring programmes running on the LT currently –
these data will be provided 'for free' by next gen synoptic surveys
Will not provide
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Spectroscopy (low R for classification, intermediate R for most science)
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Photometry optimised to the SN light curve: LSST 3-4 days between
visits (even longer for same filter)
High cadence observations at early time and over peak
Transient spectroscopy in 2020+
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Current synoptic surveys such as PTF provide large
numbers of transients detected at early times
Spectroscopic follow-up is the bottleneck
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The need for flexible spectroscopic follow-up will become
even more acute in the next decade
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Only ~10% of PTF detections get a spectral classification
LSST will issue ~1e6 alerts per night! Even accounting for
variable stars and NEOs, still 1000s of targets
Programmes like PESSTO are showing that large scale
optical follow-up of transients with 4m class telescopes
can be very productive.
A telescope dedicated primarily to transient spectroscopy
with the speed and flexibility of robotic operations would be
a powerful tool
Gamma-ray bursts
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A topic well matched to the LT's capabilities, so no
surprise it has been a productive area
GRB science 2020:
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High z bursts
Cosmological parameters, reionisation, star formation
history
● Requires 8m+ class facilities unless you catch afterglow
very early (seconds - minutes)
Low to intermediate z bursts
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GRB-supernova associations
Prompt phase – particle acceleration, radiation
processes, internal shocks
Short GRBs – nature of the binary merger components
Gamma-ray bursts
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With rapidly fading transients like GRB afterglows, slew time is
incredibly important – perhaps even more important than
aperture!
LT can get on target in 2-3 min – a facility which could better
this time with a larger aperture would provide a powerful
capability
Instrumentation
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Multiband imager, something along the lines of GROND,
optical-infrared for SED
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Spectroscopy requires extremely rapid response
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Afterglow polarimetry a specialisation of the current facility
In 2020+ where will the triggers come from?
SVOM
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Joint French/Chinese mission
Payload very similar to Swift
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Optical and X-ray telescopes for afterglow
Ground based component for quick localisation and
photometric redshifts
● Array of wide field cameras (a la SuperWASP)
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Wide field gamma ray detector – improved energy range and
sensitivity compared to Swift BAT
2x 1m robotic telescopes
Some political issues, but I hear
things are back on track...
Variability across the EM spectrum
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X-ray: LOFT is a ESA M3 candidate (launch ~2022)
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Wide Field Monitor: X-ray transient detections and triggers
Optical: Gaia final catalogue will be published in 2020
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1e9 stars with accurate positions and distances, limited
photometry and very limited spectroscopy
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Millions of variables and binaries. Statistically complete
samples, rare subclasses...
Radio: SKA full science operations 2020 (phase 1), 2024 (phase 2)
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Pulsars, RRATs, AXPs, SGRs, NS-NS binaries, synchrotron
emission from jets, coherent emission from flare stars, brown
dwarfs and hot Jupiters...
High energies: Cherenkov Telescope Array begins construction
~2018
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Northern site (Tenerife?): AGN, GRBs, clusters
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Southern site:Galactic centre, SNR, pulsars, SFR, XRBs
Astrophysical Neutrino Searches
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IceCube completed 2010 and
currently operational at the south
pole
Most sensitive to muon neutrinos
Vast majority of detections due to
atmospheric muons and neutrinos
from cosmic ray showers
Best sensitivity for northern
hemisphere (Earth serves as filter
for atmospheric muons)
Companion KM3NeT detector
planned for the north
Science: point sources of high
energy neutrinos, coincident
GRBs, galactic SNe, decay
products from WIMPs...
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Detection of 28
astrophysical neutrino
events reported in 2013
Science paper
Upgrades planned for
increased sensitivity
Capability for triggered EM
follow-up in place. No
coincident detections yet...
Gravitational wave counterparts
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ALIGO commissioning 2015 – full sensitivity 2022
Key problems for detection of electromagnetic
counterparts are
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Localisation (hopeless in 2015, extremely difficult in 2022!)
Nature of counterpart is unclear, but potentially faint and
fast-fading
From 'Commissioning and Observing Scenarios for the Advanced LIGO and Advanced Virgo
Gravitational-Wave Observatories by The LIGO Scientific Collaboration and the Virgo Collaboration (2012)'
GW electromagnetic counterparts
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For an NS-NS or NS-BH merger,
counterpart might consist of
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sGRB - prompt emission and
afterglow, harder to detect further
off axis
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'kilonova' - SN like, isotropic
component powered by
radioactive decay of heavy
elements synthesised in ejecta
(GRB130603B, Tanvir et al. 2013)
Non-thermal radio afterglow. Long
time delay
Metzger and Berger (2012)
Exoplanet science
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Plenty to do, for example:
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Hot Jupiters – migration or
scattering?
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Planetary formation and evolution:
Planets of same radius have
vastly different masses
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Atmospheres
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Rings, moons, binary planets
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Smaller objects (Neptunes, super
Earths)
Stellar systems rather than
individual objects
Multi-planet systems from RV
surveys (Lovis and Fischer, 2010)
Future exoplanet facilities
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Kepler host stars typically 14.5 > mV > 13.5
New facilities will concentrate on brighter (mV ~ 8 - 13) stars to
maximise follow-up potential
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Millions of stars surveyed, tens of thousands of transiting
planets
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Neptunes / super-Earths / Earths
NGTS (2014-2018) under
construction at Paranal
TESS approved by NASA for a
2017 launch
PLATO potential ESA M3 mission
(~2022) decision this year
From http://www.ngtransits.org/
Exoplanet instrumentation
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Transit photometry – simultaneous multiband imager
High resolution spectroscopy – HARPS type instrument
Secondary eclipses. As far infrared as possible
Transmission spectroscopy (transit depth as a function of
wavelength). Stable, high throughput
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Water, biomarkers
Transmission spectroscopy with FORS
(Bean et al. 2010)
Is there a role for LT2 in the 2020 exoplanet landscape?
LT2 site and telescope design
Site
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Northern and southern sites both viable for our science: synoptic
transient surveys in both hemispheres, targets from space facilities,
GW detections over whole sky, etc.
Some important infrastructure will be in the south, but LSST for
example will cover the sky up to +15 in dec, so northern telescopes
will still have a significant follow-up role.
At this stage our preferred site is La Palma, and we are developing
this option in collaboration with the IAC
From La Palma:
Dec -30°, 1.5h TOT at airmass < 2.0
Dec -20°, 4h TOT at airmass < 2.0
1h TOT at airmass < 1.5
Dec -10°, 6.5h TOT at airmass < 2.0
4h TOT at airmass < 1.5
GW localisation
2016 – 2017 (BNS at 80Mpc)
2017 – 2018 (BNS at 80Mpc)
2019+ (BNS at 160Mpc)
2022+ (BNS at 160Mpc)
From 'Commissioning and Observing Scenarios for the Advanced LIGO and Advanced Virgo
Gravitational-Wave Observatories by The LIGO Scientific Collaboration and the Virgo Collaboration (2012)'
LT2 user requirements
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Liverpool Telescope 2 will be a robotic telescope designed for extremely rapid
follow-up of transients detected by other facilities
Fast slewing: aiming to be taking data within 30 seconds of alert
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Includes blind pointing, mirror settling and mechanical movement of enclosure
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Excellent open loop tracking performance (image elongation no greater than
0.2'' in ten minutes) so we don't have to be slowed down by autoguider
Important for fast-fading transients, but also reduced overhead for efficient
monitoring of large numbers of targets
The most pressing follow-up need will be for intermediate resolution (R<10,000)
spectroscopy
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Main instrument will be an opt/IR spectrograph, down to at least 2 micron
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Does not include acquisition of target onto IFU/slit
Focal stations for simultaneous mounting of at least 4 other instruments
Aperture of 4 metres will put us at the bright end for LSST follow-up, but still 100s
of targets per night!
Signal-to-noise models
Telescope slew models
Telescope Design
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We have commissioned some preliminary
optical design studies based on our user
requirements
Key challenges are mechanical, in order
to meet fast slewing requirement
One possible option for reducing weight
is a segmented primary
A short distance from Liverpool, Technium
OpTIC in North Wales are currently
developing large optics fabrication
methods for the ELT mirror segments and
can fabricate segments up to ~2m in size
Location of focal stations another
important issue. Everything on Nasmyth
platforms?
A new role for the LT?
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If LT2 will be colocated on La Palma with the existing LT, one
exciting possibility is to combine both telescopes into a single
facility
Replace existing LT instrument suite with prime focus wide field
imager – 2x2 deg FoV
Use the LT to discover our own transients and time variable
sources, which are then fed to LT2 for spectroscopic follow-up
A new PTF type facility, with the benefits of modern telescopes
and the rapid reaction capability of robotic operations
Also maintain (increase?) commitment to Schools Observatory
Novel instrumentation
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EM (electron multiplying) CCDs are seeing increasing use
at various observatories
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Effectively zero read noise
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Spectroscopic format chips imminent
CMOS detectors
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Very fast. QE historically a problem, things now improving
MKIDS: Microwave Kinetic Inductance Detectors
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Surface impedance of superconductor changed by incident
photon through kinetic inductance effect
Photon counting with spectral information
Largish arrays now possible, although energy resolution still
poor (R~10-15)
As you go to larger arrays the key challenges are
computational and cooling
Summary
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We intend to build a new 4m class telescope to come into
operation at the beginning of the next decade
Our preferred site is the ORM on La Palma
Telescope will be fully robotic with all the versatility that
entails
Time domain science with a focus on transients
Very rapid response for fast-fading objects
Intermediate resolution spectroscopy, but provision for a
diverse instrument suite
Future of LT? We would hope to keep it operational.
Replace instrument suite with prime focus wide field (2x2
deg) camera?
LT2 website: http://telescope.livjm.ac.uk/lt2/
Cherenkov Telescope Array (CTA)
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Array consists of three types of telescope – combined energy
range 10s of GeV – 100 TeV
5 – 10 improvement in sensitivity over HESS, MAGIC, VERITAS
Construction begins ~2018
Sites not yet determined
Northern site: focus on extragalactic astronomy
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AGN, GRBs, clusters
Southern site: focus on Galactic sources
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Galactic centre, SNR, pulsars, SFR, XRBs
http://www.cta-observatory.org/
X-ray transients with LOFT
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RXTE successor
Potential ESA M3 mission (decision this year)
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High-time resolution X-ray mission for compact
objects, bright AGN
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Launch date would be ~ 2022
Simultaneous optical/X-ray: TDEs, echo outbursts in XRBs
Transient detections from Wide Field Monitor
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Much larger effective area than RXTE ASM
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2 - 50 keV energy range
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Observes 50% of available sky
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Point source location accuracy (10σ) ~ 1'
Gaia
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Launch October, operational lifetime of 5 years, final
catalogue published 2020
So no LT2 overlap with the Gaia alerts programme,
although LT will participate
1e9 stars with accurate positions and distances,
limited photometry and very limited spectroscopy
Huge numbers of
variable stars and
binaries for
spectroscopic
follow-up! - statistically
complete samples, rare
subclasses...
Radio transients
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SKA Phase 1 full science operations 2020
SKA Phase 2 full science operations 2024
Transient science:
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Pulsars
Exotic related objects: RRATs, AXPs, SGRs
● Strong-field tests of gravity with pulsar – BH binaries
NS-NS / NS-BH binaries. Mergers.
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Synchrotron emission in jets from Cvs, XRBs, SNe and GRBs
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Coherent emission from flare stars, brown dwarfs, hot Jupiters
Characteristics of radio transient sky currently quite unclear –
SKA pathfinders will be very useful (LOFAR follow-up with LT)
GW optical counterpart models
Metzger and Berger (2012)