Alan Garner

CIRCE: The Canarias InfraRed Camera Experiment for the Gran Telescopio Canarias

The Canarias InfraRed Camera Experiment (CIRCE) is a near-infrared (1-2.5 micron) imager, polarimeter and low-resolution spectrograph operating as a visitor instrument for the Gran Telescopio Canarias 10.4-meter telescope. It was designed and built largely by graduate students and postdocs, with help from the UF astronomy engineering group, and is funded by the University of Florida and the U.S. National Science Foundation. CIRCE is intended to help fill the gap in near-infrared capabilities prior to the arrival of EMIR to the GTC, and will also provide the following scientific capabilities to compliment EMIR after its arrival: high-resolution imaging, narrowband imaging, high-time-resolution photometry, imaging polarimetry, low resolution spectroscopy. In this paper, we review the design, fabrication, integration, lab testing, and on-sky performance results for CIRCE. These include a novel approach to the opto-mechanical design, fabrication, and alignment.

A precise measurement of the magnetic field in the corona of the black hole binary V404 Cygni

Conditions in a black hole outburst The binary system V404 Cygni consists of a red giant star orbiting a black hole. In 2015, a surge of accretion by the black hole caused the surrounding plasma to brighten suddenly for the first time since 1989, briefly becoming the brightest x-ray source in the sky. Dallilar et al. combined observations from radio, infrared, optical, and x-ray telescopes taken during the outburst. They compared how fast the flux decayed at each wavelength, which allowed them to constrain the size of the emitting region, determine that the plasma within it cooled through synchrotron radiation, and measure the magnetic field around the black hole. Science, this issue p. 1299 A black hole binary system contains plasma cooling by synchrotron radiation in a weaker-than-expected magnetic field. Observations of binary stars containing an accreting black hole or neutron star often show x-ray emission extending to high energies (>10 kilo–electron volts), which is ascribed to an accretion disk corona of energetic particles akin to those seen in the solar corona. Despite their ubiquity, the physical conditions in accretion disk coronae remain poorly constrained. Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 33.1 ± 0.9 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems.

First results and future plans for the Canarias Infrared Camera Experiment (CIRCE) for the Gran Telescopio Canarias

CIRCE is a near-infrared (1-2.5 micron) imager (including low-resolution spectroscopy and polarimetery) in operation as a visitor instrument on the Gran Telescopio Canarias 10.-4m tele scope. It was built largely by graduate students and postdocs, with help from the UF Astronomy engineering group, and is funded by the University of Florida and the U.S. National Science Foundation. CIRCE is helping to fill the gap in time between GTC first light and the arrival of EMIR, and will also provide the following scientific capabilities to compliment EMIR after its arrival: high-resolution imaging, narrowband imaging, high-time-resolution photometry, polarimetry, and low-resolution spectroscopy. There are already scientific results from CIRCE, some of which we will review. Additionally, we will go over the observing modes of CIRCE, including the two additional modes that were added during a service and upgrading run in March 2016.

Demonstration of high-performance cryogenic probe arms for deployable IFUs

We describe the design, development, and laboratory test results of cryogenic probe arms feeding deployable integral field units (IFUs) for the Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS) - a near-infrared multi-object echelle spectrograph for the 10.4-meter Gran Telescopio Canarias. MIRADAS selects targets using 20 positionable pickoff mirror optics on cryogenic probe arms, each feeding a 3.7x1.2-arcsec field of view to the spectrograph integral field units, while maintaining excellent diffraction-limited image quality. The probe arms are based on a concept developed for the ACES instrument for Gemini and IRMOS for TMT. We report on the detailed design and opto-mechanical testing of MIRADAS prototype probe arms, including positioning accuracy, repeatability, and reliability under fully cryogenic operation, and their performance for MIRADAS. We also discuss potential applications of this technology to future instruments.

Status and first results of the Canarias infrared camera experiment (CIRCE) for the Gran Telescopio Canarias

CIRCE is a near-infrared (1-2.5 micron) imager, polarimeter and low-resolution spectrograph intended as a visitor instrument for the Gran Telescopio Canarias 10.-4m telescope. It was built largely by graduate students and postdocs, with help from the UF astronomy engineering group, and is funded by the University of Florida and the U.S. National Science Foundation. CIRCE is intended to help fill the gap in time between GTC first light and the arrival of EMIR, and will also provide the following scientific capabilities to compliment EMIR after its arrival: high- resolution imaging, narrowband imaging, high-time-resolution photometry, imaging- and spectro- polarimetry, low-resolution spectroscopy. In this poster, we review the lab testing results for CIRCE from 2013 and describe the instrument status (currently in shipment to GTC).

Image quality tests on the Canarias InfraRed Camera Experiment (CIRCE)

In this paper we present the results of image quality tests performed on the optical system of the Canarias InfraRed Camera Experiment (CIRCE), a visitor-class near-IR imager, spectrograph, and polarimeter for the 10.4 meter Gran Telescopio Canarias (GTC). The CIRCE optical system is comprised of eight gold-coated aluminum alloy 6061 mirrors. We present surface roughness analysis of each individual component as well as optical quality of the whole system. We found all individual mirror surface roughness are within specifications except Fold mirrors 1 and 2. We plan to have these components re-cut and re-coated. We used a flat 0.2-arcseconds pinhole mask placed in the focal plane of the telescope to perform the optical quality tests of the system. The pinhole mask covers the entire field of view of the instrument. The resulting image quality allows seeing-limited performance down to seeing of 0.3 arcseconds FWHM. We also observed that our optical system produces a negative field curvature, which compensates the field curvature of the Ritchey-Chretien GTC design once the instrument is on the telescope.