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Venue: The Linnean Society of London, Burlington House, Piccadilly, London, W1J 0BF, UK
A vital component in pushing for the detection of many small long-period exoplanets involves urgently establishing the necessary ground-based infrastructure. This means to go bigger, not in size, but in number of telescopes, giving us effectively more observing time. One setup, like the Terra Hunting Experiment with HARPS3, can only observe 40 stars over 10 years, yielding only a handful of small planets. More telescopes will allow to significantly expand it to a robust statistical sample.
Therefore, we aim to realise a network of telescopes, fitted with high-resolution, high-stability optical spectrographs around the world. Provisionally, this could include 6-10 telescopes of 2-4m class, outfitted with optical spectrographs of $>$100k resolution, stabilised to better than 50 cm/s over a decade. Its main science goal would be the characterisation of small long-period exoplanets through the RV method. However, such a network could easily be of use across the wider Astronomy and Solar Physics research areas, including the study of young stars, brown dwarfs, galaxy evolution etc.
The meeting has two main aims. (1) Explore the variety of science objectives possible with a spectrograph network and how the full UK Astronomy, UKSP, and MIST communities are best served from such a suite of telescopes and spectrographs. (2) Understand the hardware requirements and potential hurdles to building this network in a timely and cost-effective manner.
The meeting will be split between covering science in the morning session (2hr) and hardware in the afternoon session (2r) with a 1hr lunch break. It will be formatted as talks interspersed with discussion sessions (both in small and large groups).
Invited speakers include: (1) Dr Ernst De Mooij (Queen's University Belfast); (2) Dr Nicholas Walton (University of Cambridge); (3) Dr Clark Baker (University of Cambridge); (4) Prof Derryck Reid (Heriot Watt University).
Programme:
10:30 - Welcome + context: Dr Annelies Mortier & Dr Heather Cegla
10:50 - Dr Ernst de Mooij (invited): "Opportunities for Solar System science, exoplanet atmosphere characterisation, exo-rings and exo-moon searches using a network of high-resolution spectrographs"
11:10 - Dr Daniela Iglesias: "Gas detection with high-resolution spectroscopy: from exocomets to interstellar clouds"
11:30 - Small group discussion
12:30 - Lunch break (lunch is not provided)
13:30 - Prof Hugh Jones: "Developments towards a small stable high-resolution spectrograph"
13:50 - Dr Clark Baker (invited): "The concepts behind ‘High Resolution Stabilised Spectrographs’ and the application of these, in a replicable way, to small telescopes – HARVY."
14:10 - Prof Derryck Reid (invited): "Continuous Ultraviolet to Blue-Green Astrocomb"
14:30 - Big group discussion
15:30 - End
All abstracts
Dr Ernst de Mooij
‘Opportunities for Solar System science, exoplanet atmosphere characterisation, exo-rings and exo-moon searches using a network of high-resolution spectrographs’
Over the past ˜15 years, high-resolution spectroscopy has significantly improved our understanding of exoplanet atmospheres, going from simple detections of atoms and molecules, such as sodium, water, carbon-monoxide, to detailed retrievals of atmospheric composition, atmospheric structure and atmospheric dynamics. Here I will present some opportunities for pushing this science forward, and discuss how we can also take advantage of a network of high-resolution spectrographs to search for exo-rings and exo-moons and do Solar System science
Dr Daniela Iglesias
‘Gas detection with high-resolution spectroscopy: from exocomets to interstellar clouds’
Planets and stellar companions can be detected via RV technique using high-resolutions spectrographs. Exocomets cannot, due to their extremely low mass. However, exocomets sublimate as they approach the star, and their gaseous tails can be detected via optical high-resolution spectroscopy. When gas crosses the line of sight of a star it produces narrow absorption features in the stellar spectra, which can only be resolved in high resolution (R>~40000). Exocomets, however, are sporadic events; we cannot predict their transit. Therefore, constant monitoring is needed to find them. The same technique can be used to search for the presence of gas in debris discs and to identify and characterize clouds in the interstellar medium. In this talk, I will show you how all these gas detections are connected and several additional reasons why it would be extremely useful to have a network of high-resolution optical spectrographs around the world.
Prof Hugh Jones
‘Developments towards a small stable high-resolution spectrograph’
The EXOplanet high resolution SPECtrograph (EXOhSPEC) is a high-resolution spectrograph project which provides developments towards a small stable high-resolution spectrograph via a fibre feed. The aim of the project is to be able to build a prototype with a small footprint to significantly reduce the cost of high resolution spectrographs and to extend the reach of radial velocities to higher precisions. The spectrograph is based on catalogue components tested on the Sun and local stars. To date we have successfully demonstrated several promising developments including modal noise control with a galvanometer, individual pixel read-out, fibre tapering and active metrology.
Dr Clark Baker
‘The concepts behind ‘High Resolution Stabilised Spectrographs’ and the application of these, in a replicable way, to small telescopes – HARVY’
High-resolution, stabilised, echelle spectrographs play a key role in exoplanet science, from the discovery of the first exoplanet around a main-sequence star, to the study of planetary atmospheres, the characterisation of planetary systems and now, the forefront of the search for Earth-like planets. From an optics perspective, high-resolution echelle spectrographs are extremely constrained systems, with each top-level parameter impacting the design of the rest of the optical system. This talk will present an overview on the design of echelle spectrographs and some of the factors that impact their stability. We will discuss the application of these concepts to HARVY: A Highly-repeatable Autonomous extreme-precision Radial Velocity facilitY concept. The HARVY concept consists of four highly efficient (goal: ~30% throughput), compact (instrument footprint: ~0.6mX0.5mX0.15m), extreme precision (req: 20cm/s, goal: 5cm/s instrument stability) radial-velocity, echelle-spectrographs each efficiently coupled to their own off-the-shelf 1.5m telescope; with the aim to increase the accessibility of radial velocity facilities, easing the bottle-neck on exoplanet transit follow-up and enabling further large-scale intensive search for low-mass, long-period, ‘Earth-like’ planets around main-sequence stars.
Prof Derryck Reid
‘Continuous Ultraviolet to Blue-Green Astrocomb’
Astrocombs—lasers providing a broadband sequence of ultra-narrow, drift-free, regularly spaced optical frequencies on a multi-GHz grid—promise an atomically-traceable, versatile calibration scale, but their realization is challenging because of the need for ultra-broadband frequency conversion of mode-locked infrared lasers into the blue-green region. Here, we introduce a new concept achieving a broad, continuous spectrum by combining second-harmonic generation and sum-frequency-mixing in an aperiodically-poled MgO:PPLN waveguide to generate gap-free 390–520 nm light from a 1 GHz Ti:sapphire laser frequency comb. We lock a low-dispersion Fabry-Pérot etalon to extract a sub-comb of bandwidth from 392–472 nm with a spacing of 30 GHz, visualizing the thousands of resulting comb modes on a high resolution cross-dispersion spectrograph. Complementary experimental data and simulations are presented that demonstrate the effectiveness of the approach for eliminating the spectral gaps present in second-harmonic-only conversion, in which weaker fundamental frequencies are suppressed. Our concept establishes a practical new route to broadband UV-visible generation at GHz repetition rates. We also take the opportunity to introduce two other parallel activities at Heriot-Watt, one working towards lower cost and more compact astrocombs, and the other developing a new concept for obtaining the complete wavelength solution of a spectrograph using only an astrocomb source.
Organisers:
Annelies Mortier (Birmingham)
Heather Cegla (Warwick)
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