Liverpool Telescope 2: A new time domain facility for 2020+ - Chris Copperwheat Liverpool Telescope group: Iain Steele, Robert Barnsley, Stuart ...
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Liverpool Telescope 2:
A new time domain facility for 2020+
Chris Copperwheat
Liverpool Telescope group:
Iain Steele, Robert Barnsley, Stuart Bates, Neil Clay, Chris Davis,
Steve Fraser, Jon Marchant, Chris Mottram, Robert Smith, Mike Tomlinson
The Liverpool Telescope
● The Liverpool Telescope (LT) is a
robotic 2m alt-az telescope currently in
operation on La Palma
● Not 'remote controlled' – operated
autonomously without night-time
supervision
● Largest fully robotic telescope
dedicated to science
● Diverse suite of simultaneously
mounted instrumentation: opt/IR
imaging, medium resolution IFU
spectroscopy, fast tri-band polarimetry
etc.
Science with the LT
Early time polarization
measurements of GRBs,
demonstrating the presence of
magnetized baryonic jets with
large-scale uniform fields
(Mundell et al. 2013)
High velocity OI feature detected in
LT+Frodospec spectrum of
SN2011fe, 1.18 days after explosion
(Nugent et al. 2011)
Liverpool Telescope 2
● Planning for a successor 'Liverpool Telescope 2' facility, began
at the end of 2012
● Much of our focus to date has been establishing the scientific
rationale for the new telescope. Science white paper to be
published within the next 1-2 months
● Science motivations have also been used to produce a user
requirements document, which have informed some initial
optical design studies
● Site decision made
Motivation: transient science
● Synoptic surveys such as
PTF, Pan-STARRS,
Skymapper provide large
numbers of transients
detected at early times
● LSST will probe the 'faint
and fast' regime of this
transient phase plot
● ~1e6 alerts per night! After accounting for NEOs and variable stars,
still 1000s of targets for follow-up
● Pressing need for low to intermediate resolution spectroscopic
follow-up for classification and exploitation (a major bottleneck even
today)
Figure adapted from LSST science book and Rau et al (2009)
Motivation: GRBs and GWEM
● Fast fading afterglows means a fast slewing telescope can
potentially collect more photons than a slower telescope of much
larger aperture
● Plenty still to do in post-Swift era:
● High z bursts for cosmological parameters, reionisation, etc.
● Low to intermediate z bursts for GRB-supernova associations,
short GRB progenitors, particle acceleration, radiation
processes, internal shocks
● Triggers from French/Chinese SVOM mission?
● Gravitational wave counterparts
● aLIGO/aVirgo full sensitivity by ~2022
● NS/NS or NS/BH mergers
● Poor localisation, uncertain EM signature
http://www.svom.fr/
Other time domain facilities in 2020+
● Transiting exoplanets: NGTS (2014-2018), TESS (2017+) and
PLATO (2022+) all targeting bright stars to maximise follow-up
potential
● Gaia: final catalogue will be published in 2020
● Limited photometry and very limited spectroscopy. Millions of
variables and binaries. Statistically complete samples, rare
subclasses...
● SKA: full science operations 2020 (phase 1), 2024 (phase 2)
● Pulsars, RRATs, AXPs, SGRs, NS-NS binaries, synchrotron
emission from jets, coherent emission from flare stars, brown
dwarfs and hot Jupiters...
● Cherenkov Telescope Array: begins construction ~2018
● AGN, GRBs, pulsars, XRBs...
Liverpool Telescope 2
● A new, 4-metre class Ritchey–Chrétien telescope for rapid
follow-up of astrophysical transients
● To be co-located with the LT on La Palma
● First light ~2020 to capitalise on the next generation of synoptic
surveys, CTA, Advanced LIGO/Virgo, etc.
● Flexible, robotic observing with multiple instruments. Main
instrument will be a high-throughput, optical-infrared,
intermediate resolution (R < 10,000) spectrograph
● Extremely rapid reaction for fast-fading objects. On target and
taking data within ~30 seconds of receiving a trigger
Rapid Reaction with LT2
● Mechanical design more challenging
than optics. Minimise moment of
inertia for fast slewing
● Key issues are: weight of mirror,
materials for structure, choice of focal
stations for instruments...
● Our optical design studies advocate a
RC design with an f/1 – f/1.5 primary
and an f/6.5 – f/10 final focal ratio
● Faster primaries reduce primary
-secondary distance
● However longer final focal length
allows for a reduced secondary
mass which can more than
compensate for increased length
Segmented primary mirror?
● For fast slewing, the mass of the
primary mirror is important
● 4m thin meniscus primary has a mass
~5500kg
● 6 segment mirror, total mass 2700kg
● 18 segments, total mass 1400kg
● 36 segments, total mass 920kgSegmented primary mirror?
● As well as reducing the total mirror mass, more segments makes
operations much easier – handling, re-coating etc.
● However, segment alignment becomes a more complicated issue
● Steep rise in the polishing and
testing cost with number of
segments is due to the
increased number of family
groupsSegmented primary mirror?
● As well as reducing the total mirror mass, more segments makes
operations much easier – handling, re-coating etc.
● However, segment alignment becomes a more complicated issue
● Steep rise in the polishing and
testing cost with number of
segments is due to the
increased number of family
groupsAngular resolution
● To phase or not to phase? Factor ~100 difference in
alignment tolerances between simple co-alignment and
optical phase coherenceSite
● 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.
● Our preferred site is La Palma, and we are developing this option in
collaboration with the Instituto de Astrofisica de Canarias
● La Palma (29° N) still provides a lot
of scope for follow-up of Southern
hemisphere facilities (LSST)
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 < 1.5Future of LT1
● Two potential options:
1) For some of our optical layout
concepts, LT2 will fit inside the
existing enclosure. Upgrade LT1 to
LT2?
2) Replace LT1 instrument suite
with wide field, prime focus imager.
2x2 deg FoV, ugriz filters, low
resolution spectrograph fibre. Run
both telescopes as a combined
rapid reaction robotic facilityNext steps
● We are currently finalising the optical design. We are also now
beginning to look into the issues of mechanical design: mirror
support, mass balance, materials etc.
● An important priority for the next year will be to finalise our
first-light instrumental needs.
● Opt-IR intermediate resolution spectroscopy
● What else? High cadence photometry? Polarimetry
● Technologies for high time resolution. EMCCDs, CMOS,
Kinetic Induction Detectors...
● On 14 Nov 2014 there will be a discussion meeting at the RAS
on 'The future of time domain astronomy with the LT and LT2'
for all potential science users of the new telescopeSummary
● 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?
For more information:
Chris Copperwheat (c.m.copperwheat@ljmu.ac.uk)
LT2 website: http://telescope.livjm.ac.uk/lt2/Mirror support
● Early days, but mirror support system
based on Keck / E-ELT solution looks
feasible
● Whiffle tree support utilising a series
of flexural joints (+ warping harness?)
● Peak-to-valley print-through similar to
calculated values for E-ELTMotivation: GWEM counterparts
● ALIGO commissioning 2015 – full sensitivity 2022
● Key problems for detection of electromagnetic counterparts are
● Localisation (few sq. deg at best)
● Uncertain EM signature. For a NS-NS or NS-BH merger,
counterpart might consist of
● Short GRB – prompt emission and
afterglow, harder to detect off axis
● '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)You can also read
