Follow-up of GW counterparts with Liverpool Telescope and Liverpool Telescope 2

Follow-up of GW counterparts with
Liverpool Telescope and 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
       ●   The Liverpool Telescope is a robotic 2m
           alt-az telescope currently in operation on
           La Palma
       ●   Operated as a UK national facility in
           return for operational support from STFC
       ●   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
       ●   Flexible nature of LT observing modes
           makes it ideal for time domain work

Liverpool Telescope Instrumentation
●   IO O: Main imaging camera: 10' FoV; 12 optical filters
●   FRODOspec: 12x12 0.82'' lenslet IFU.
     ● 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 up:
●   IO I: Infrared (Y, J, H) imager. 6X6' FOV
●   SPRAT: R~500 spectrograph

Liverpool Telescope and ToOs
●   Rapid response: typical time to target from receipt of alert
    is ~180s
    ●   Robotic operation, telescope design and clamshell enclosure
●   Software: GCN socket and RTML based override systems
●   VOEvent triggered follow-up in the process of being added
●   GRB pipeline software (Guidorzi et al., 2006) detects new
    transients in data and prompts subsequent observations
    according to their properties
●   However, FoV of instruments (10'
    or less) small compared to the
    direct GW localisation
    ●   Tiling
    ●   Targeting most likely host galaxy
    ●   Triggered by wider field facilities

Sky Cameras
●   Simultaneous wide field observations with normal LT data taking
●   Andor cameras, unfiltered, 1024x1024 px

●   SkyCamA
    ●   4.5mm fisheye lens
    ●   All sky coverage down to 6th magnitude
●   SkyCamT
    ●   Parallel points with telescope
    ●   35mm lens, 20 sq deg FoV, 74''/px
    ●   R = 12 in 10 secs
●   SkyCamZ
    ●   Parallel points with telescope
    ●   Orion Optics AG8 telescope, 1 sq deg FoV, 3''/px
    ●   R = 18 in 10 secs

Liverpool Telescope 2

●   The Liverpool Telescope is now a mature facility which is
    expected to stay competitive until at least 2020
●   LJMU has committed £200,000 to fund a 2-year feasibility study
    for a successor 'Liverpool Telescope 2' facility, to come into
    operation ~2020. We are approaching the half-way stage of that
    process

●   LT2 will be a 4-metre class robotic facility dedicated to time
    domain science
●   Our preferred site is the ORM, La Palma
●   The core science programme will be the follow-up of transients
    discovered by ground based synoptic surveys and future space
    missions (SVOM, LOFT...)
●   The primary instrument will be an intermediate resolution
    spectrograph

Liverpool Telescope 2
●   LT2 will be designed to beat the response time of LT, for
    the rapid follow-up of fast fading transients like GRB
    afterglows and GW counterparts
●   We aim for an average target acquisition time of 30 secs
    ●   This includes the blind pointing, mirror settling time and any
        mechanical movement of the enclosure
●   Excellent open-loop tracking performance
    ●   Image elongation no greater than 0.2'' in ten minutes
●   Optimal image quality at times of median seeing (~0.8'')
●   FoV at least 15'' diameter
●   Wavelength range at least 350nm to 2.0 micron
●   Telescope focal ratio between f/4 and f/10
●   Focal stations for five instruments

Telescope slew models

Instrumentation
●   Primary LT2 instrument will be a spectrograph
    ●   Slit or IFU? Maximise throughput
    ●   Intermediate resolution (R < 10,000)
    ●   Optical/infrared
●   Instrumental diversity (and quick changes) a key strength of the LT
    ●   High cadence imager, polarimetry...
●   Novel detector technologies in order to properly exploit the rapid reaction
    capability of the telescope
    ●   EM (electron multiplying) CCDs now fairly commonplace. Spectroscopic
        format chips imminent
    ●   CMOS detectors. Very fast. QE historically a problem, things now improving
    ●   MKIDS: Microwave Kinetic Inductance Detectors
         ●   Photon counting with spectral information
         ●   Largish arrays now possible, although energy resolution still poor (R~10-
             15). Key challenges are computational and cooling

The LT in the next decade
●   We would intend the LT to stay in operation beyond 2020
●   Probably a much larger fraction (~50%) of LT time will be used
    for the National Schools Observatory
●   Likely future of the LT in the next decade is as a low cost, low
    maintenance, single instrument facility
●   Repurposing LT to provide a prime focus, wide field (2x2')
    imaging capability is one option we are discussing

●   Combination of wide field imaging on LT and narrow field
    spectroscopy on LT2 would be ideal for GW follow-up

Summary
●   LT rapid reaction makes it ideal for the follow-up of transients
    like GW EM counterparts
●   For direct triggering, FoV of LT is an issue – triggering from a
    wide field facility (GOTO) a better strategy
●   We intend to build a new 4m class telescope on La Palma to
    come into operation at the beginning of the next decade
    ●   Telescope will be fully robotic with all the versatility that entails
    ●   Time domain science with a focus on transients
    ●   Extremely rapid response for fast-fading transients
    ●   Spectroscopy, but the aim is a diverse instrument suite
●   Supplement LT2 spectroscopy with a wide field imager on LT?

              LT2 website: http://telescope.livjm.ac.uk/lt2/