IO:I, a near-infrared camera for the Liverpool Telescope

Abstract

IO:I is a new instrument that has recently been commissioned for the Liverpool Telescope, extending current imaging capabilities beyond the optical and into the near infrared. Cost has been minimised by use of a previously decommissioned instrument's cryostat as the base for a prototype and retrofitting it with Teledyne's 1.7µm cutoff Hawaii-2RG HgCdTe detector, SIDECAR ASIC controller and JADE2 interface card. In this paper, the mechanical, electronic and cryogenic aspects of the cryostat retrofitting process will be reviewed together with a description of the software/hardware setup. This is followed by a discussion of the results derived from characterisation tests, including measurements of read noise, conversion gain, full well depth and linearity. The paper closes with a brief overview of the autonomous data reduction process and the presentation of results from photometric testing conducted on on-sky, pipeline processed data.• Active Galactic Nuclei (AGN). Investigations into the variability of the various classes of AGN will allow us to probe the central engines of these objects, helping to discriminate between competing models.• Other areas of both time-domain (e.g. pixel microlensing, variability surveys) and non timedomain (e.g. metallicity gradients in galaxies and followup up X-ray cluster surveys) astronomy, proposals for which have already been solicited and undertaken. Instrument OverviewIO:I is positioned at the Cassegrain focus of the telescope where, without additional powered optics, the plate scale delivered at the focal plane is 97µm/ ′′ (2m diameter mirror, f/10 beam focal ratio). With a pixel pitch of 18µm, the total FOV of the 2048x2048 pixel detector is 6.27 ′ x6.27 ′ . The quantum efficiency of the detector is over 50% between 0.8 and 1.72 µm (peak 86% at 1.5µm), although the usable range within this window is limited by atmospheric transmission (see Figure 1). The detector itself is a HgCdTe Hawaii-2RG (H2RG) and is controlled via the SIDECAR ASIC controller and JADE2 interface card, all provided by Teledyne. Connected to the cryostat are two closed-cycle cooling units (IGC Polycold Cryotigers), each charged with PT13 gas, providing a total cooling capacity of 10W at a minimum temperature of 80K. Inside the cryostat are two corresponding cold heads. One of these cold heads is connected to the detector/SIDECAR mounting block. The other is attached to the floor of the radiation shield housing, shifting the bulk of the 300K blackbody radiative load incident from the warm cryostat chassis onto this thermal path. By thermally isolating the two paths, the majority of the cooling capacity provided by a single Cryotiger is available to cool the detector and SIDECAR only.Both J and H single filters have been procured, although the instrument has no filter wheel to allow robotic selection between the two. Following the requirements outlined by science proposals already received for this instrument, the H band filter has been preferred over the J. Changing between these various configurations is...

M31N 2008-12a—THE REMARKABLE RECURRENT NOVA IN M31: PANCHROMATIC OBSERVATIONS OF THE 2015 ERUPTION

“…For the 2015 eruption, we also employed the newly commissioned IO:I NIR imager (Barnsley et al 2016), a Teledyne2, 048 2, 048 Hawaii-2RG HgCdTe array providing a ¢´¢ 6.27 6.27 field of view. The IO:I instrument provides a fixed H-band filter, and each observation comprised of 9 60 s exposures using a 9 pointing (3 × 3) dither pattern with a 14 ″ spacing between each pointing.…”

“…The IO:I instrument provides a fixed H-band filter, and each observation comprised of 9 60 s exposures using a 9 pointing (3 × 3) dither pattern with a 14 ″ spacing between each pointing. The IO:I data were reduced by a pipeline running at the telescope; this included bias subtraction, correlated double sampling, non-linearity correction, flat fielding, sky subtraction, registration, and alignment (see Barnsley et al 2016 for details). Photometry was performed on the reduced data as described above for IO: O. Photometric calibration was carried out using sources in 2MASS (Skrutskie et al 2006; see Table 10).…”

AT 2019abn: multi-wavelength observations over the first 200 days

“…We obtained multi-colour follow-up using the IO:O (Smith & Steele 2017) and IO:I (Barnsley et al 2016) imagers on the 2 m Liverpool Telescope (LT; Steele et al 2004). We used SDSS u r i z and Bessel BV filters in IO:O and H-band imaging with IO:I.…”

The Weakening Outburst of the Young Eruptive Star V582 Aur

“…A. Acosta-Pulido). For this observation we used the IO:I camera built on a 2048x2048 HAWAII 2RG chip (Barnsley et al 2016). We obtained images at 9 dither positions, with 5.8 s exposure time each, and applied aperture photometry.…”