Andrew H. Szentgyorgyi

Ground-based Transit Spectroscopy of the Hot-Jupiter WASP-19b in the Near-infrared

We present ground-based measurements of the transmission and emission spectra of the hot-Jupiter WASP-19b in nine spectroscopic channels from 1.25 to 2.35µm. The measurements are based on the combined analysis of time-series spectroscopy obtained during two complete transits and two complete secondary eclipses of the planet. The observations were performed with the MMIRS instrument on the MagellanII telescope using the technique of multi-object spectroscopy with wide slits. We compare the transmission and emission data to theoretical models to constrain the composition and thermal structure of the planet’s atmosphere. Our measured transmission spectrum exhibits a scatter that corresponds to 1.3 scale heights of the planet’s atmosphere, which is consistent with the size of spectral features predicted by theoretical models for a clear atmosphere. We detected the secondary eclipses of the planet at significances ranging from 2.2 to 14.4�. The secondary eclipse depths, and the significances of the detections increase towards longer wavelengths. Our measured emission spectrum is consistent with a 2250K effectively isothermal 1-D model for the planet’s dayside atmosphere. This model also matches previously published photometric measurements from the Spitzer Space Telescope and ground-based telescopes. These results demonstrate the important role that groundbased observations using multi-object spectroscopy can play in constraining the properties of exoplanet atmospheres, and they also emphasize the need for high-precision measurements based on observations of multiple transits and eclipses. Subject headings: planets and satellites: atmospheres — planets and satellites: individual: WASP-19b — techniques: photometric

[Ne V] Imaging of the Cygnus Loop

We present continuum-subtracted images of a 20 × 20 region of the eastern Cygnus Loop (NGC 6995) in the 3425 A forbidden line of Ne V. The images reveal bright linear filaments which are associated with, but not positionally coincident with, bright features seen in Hα, [O III], and other narrowband images. In some areas, the [Ne V] filaments define the edge of X-ray-emitting regions. The filaments exhibit a peak surface brightness of 1.2 × 10-4 photons cm-2 s-1 arcsec-2 at the top of the atmosphere in images with typical detection limits of ~10-5 photons cm-2 s-1 arcsec-2. We present arguments that these structures are produced by radiative shock waves and discuss implications for the shock velocities and the three-dimensional structure of this section of the Cygnus Loop. We place limits on the importance of thermal conduction-driven evaporation as a contribution to the mass of X-ray-emitting gas. Lack of evidence of [Ne V] emission resulting from thermal evaporation may have significance for supernova remnants and interstellar medium models that rely heavily on the importance of thermal evaporation.

The High-Excitation Planetary Nebula NGC 246: Optical and Near-Ultraviolet Observations and Two-dimensional Numerical Models

We have imaged the planetary nebula (PN) NGC 246 in the near-ultraviolet wavelengths [Ne V] 342.6 nm, the Bowen fluorescence line of O III at 344.4 nm, and a nearby line-free region centered on 338.6 nm, as well as H?, [O III] 500.7 nm, and [S II] 673.0 and 671.5 nm. Imaging in the 344.4 nm line is necessary to deconvolve contamination of the [Ne V] images by O III 342.9 nm. The emission from the shell and inner parts of the nebula is detected in [Ne V]. The radial profiles of the [Ne V] brightness decrease with radius from the exciting star, indicating that the bulk of the emission from this ion is due to the hard UV stellar radiation field, with a (probably) marginal contribution from collisional ionization in a shock between the PN shell and the interstellar medium (ISM). In contrast, the radial profiles of the emission in H?, [O III] 500.7 nm, and [S II] are flatter and peak at the location of the shell. The emission of [S II] probably traces the interaction of the PN with the ambient ISM. We also present two-dimensional numerical simulations for this PN-ISM interaction. The simulations consider the stellar motion with respect to the ambient ISM, with a velocity of 85 km s-1, and include the time evolution of the wind parameters and UV radiation field from the progenitor star.

Far Ultraviolet Spectroscopic Explorer Spectroscopy of the XA Region in the Cygnus Loop Supernova Remnant

Spectra of the XA shock-cloud interaction region in the Cygnus Loop obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) are presented and analyzed. Several weak emission lines never before detected in the spectra of remnants are identified in a combined spectrum from four bright regions. The intensities of the silicon lines measured in this spectrum show that the 120-200 km s-1 shocks are present in the XA region and are effective at liberating silicon from grains. Differences among the spectra imply that the shocked gas has a complex ionization structure. The strongest lines in the spectra, and also the most uniformly distributed, are O VI λλ1032, 1038. Approximately 10% of the O VI emission from regions interior to the main shock interaction arises from coronal (million-degree) gas. Model calculations show that the shock at the boundary between the cloud and remnant has a velocity of about 180 km s-1 and has swept up a hydrogen column NH = 1.66 × 1018 cm-2, indicating that the blast wave encountered the cloud about 5000 years ago. The O VI line profiles imply that the boundary shock is dominated by a single broad component with an intrinsic velocity width parameter, b ≈ 48 km s-1, which is probably the result of bulk motions due to curvature of the shock front. Differences between the O VI velocity profiles of two regions separated by 20 on the sky suggest the presence of a concentrated region of dust, which absorbs emission from the shock on the far side of the cloud.

The optical design of the G-CLEF Spectrograph: the first light instrument for the GMT

for the GMT Sagi Ben-Ami, Jeffrey D. Crane, Ian Evans, Stuart McMcmuldroch, Mark Mueller, William Podgorski, Andrew Szentgyorgyi Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02140; UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 Abstract The GMT-Consortium Large Earth Finder (G-CLEF), one of the first light instruments for the Giant Magellan Telescope (GMT), is a fiber-fed, high-resolution echelle spectrograph. G-CLEF is expected to proceed towards fabrication in the coming months. In this paper, we present the current, pre-construction G-CLEF optical design, with an emphasis on the innovative features derived for the spectrograph fiber-feed, the implementation of a volume-phase holographic (VPH)based cross disperser with enhanced blue throughput and our novel solutions for a multi-colored exposure meter and a flat-fielding system.

Cross dispersion and an integral field unit for Hectochelle

We describe our plans to add cross-dispersion and an integral field unit to the Hectochelle spectrograph, a multiobject, fiber-fed echelle spectrograph for the converted MMT. Hectochelle was originally designed without cross-dispersion to be used in a single order or overlapping orders selected by interference filters. The addition of cross-dispersion allows us to trae off multiplex advantage for spectral coverage. Our cross-disperser uses an unusual segmented, zero-deviation prism that is very compact, allowing it to fit into the existing instrument without modification. The planned integral field unit can be used with either Hectochelle or the moderate-dispersion Hectospec bench spectrograph. Both spectrographs were originally designed to be fiber-fed with a robotic fiber positioner as a front end, so adding an integral field capability is a natural enhancement. The integral field unit will use smaller diameter fibers than the robotic fiber positioner (subtending 0.6 vs. 1.5), so that both spectrographs will achieve higher spectral resolution in integral field mode. With the integral field unit Hectochelle will reach a two pixel resolution, R approximately 70,000, and Hectospec will reach R approximately 2000 with its 270 line mm-1 grating.

Wide-field CCD imager for the 6.5-m MMT telescope

The conversion of the Multiple Mirror Telescope from six 1.8 m primary mirrors to a single 6.5 m primary will significantly increase its capability for imaging. The f/5 configuration will provide a corrected field of view for imaging that is flat and 30 arcminutes in diameter. The image quality in the absence of atmospheric seeing is 0.1 over the full field. We are currently designing a camera system to take advantage of this large field. The proposed direct imaging system will be located at the Cassegrain focus of the telescope, behind a three-element refractive corrector. We will use an array of 8 X 4 three-edge-buttable CCDs, each with 2048 X 4096 pixels and two output amplifiers. This will provide a field of view of 24 X 24. With a new packaging scheme we will reduce the gap along the readout edge to a few millimeters. The pixel size is 15 microns, or 0.09, well sampling the point-spread- function. In many applications it will be possible to bin the pixels, thus reducing the amount of data (500 Mb per read at full resolution). The back-illuminated CCDs will be thinned and anti- reflection coated to provide high quantum efficiency from 320 to 1000 nm. The camera system will be useful for many studies requiring both a large collecting area and large area coverage on the sky. Planned projects include redshift and photometric surveys of faint galaxies, searches for high-redshift quasars and searches for objects in the outer solar system.

Precision thermal control of the GMT-Consortium Large Earth Finder (G-CLEF)

The GMT-Consortium Large Earth Finder (G-CLEF) will be part of the first generation instrumentation suite for the Giant Magellan Telescope (GMT). G-CLEF will be a general purpose optical passband echelle spectrograph with a precision radial velocity (PRV) capability of 10 cm/sec, a requirement necessary for the detection of Earth analogues. The instrument will be particularly sensitive to thermal effects and the necessary stability cannot be achieved through the use of low CTE materials alone. It is the combination of low CTE materials and exquisite thermal control which will enable the instrument to achieve its precision requirements. G-CLEF will complete its Critical Design phase in mid-2018. In this paper, we discuss the precision thermal control systems which enable milli-Kelvin-level stability of the spectrograph and its red and blue focal planes. The measurement electronics and thermal control strategies used in the spectrograph are described. Of particular importance is the development of a continuous LN2 flow cryo-cooler system used to maintain the focal planes at stable cryogenic operational temperatures. This system has been validated with a prototyping effort completed during the instrument’s design phase. We also review G-CLEF’s insulated enclosure which simultaneously maintains the spectrograph a stable temperature and limits the maximum thermal leakage into the telescope dome. This work has been supported by the GMTO Corporation, a non-profit organization operated on behalf of an international consortium of universities and institutions: Arizona State University, Astronomy Australia Ltd, the Australian National University, the Carnegie Institution for Science, Harvard University, the Korea Astronomy and Space Science Institute, the São Paulo Research Foundation, the Smithsonian Institution, the University of Texas at Austin, Texas AM University, the University of Arizona, and the University of Chicago.

The opto-mechanical design of the GMT-Consortium Large Earth Finder (G-CLEF)

The GMT-Consortium Large Earth Finder (G-CLEF) will be part of the first generation instrumentation suite for the Giant Magellan Telescope (GMT). G-CLEF is a general purpose echelle spectrograph operating in the optical passband with precision radial velocity (PRV) capability. The measurement precision goal of G-CLEF is 10 cm/sec; necessary for the detection of Earth analogues. This goal imposes challenging stability requirements on the optical mounts and spectrograph support structures especially when considering the instrument’s operational environment. G-CLEF’s accuracy will be influenced by changes in temperature and ambient air pressure, vibration, and micro gravity-vector variations caused by normal telescope motions. For these reasons we have chosen to enclose G-CLEF’s spectrograph in a wellinsulated, vibration-isolated vacuum chamber in a gravity invariant location on GMT’s azimuth platform. Additional design constraints posed by the GMT telescope include; a limited space envelope, a thermal leakage ceiling, and a maximum weight allowance. Other factors, such as manufacturability, serviceability, available technology, and budget are also significant design drivers. G-CLEF will complete its Critical Design phase in mid-2018. In this paper, we discuss the design of GCLEF’s optical mounts and support structures including the choice of a low-CTE carbon-fiber optical bench. We discuss the vacuum chamber and vacuum systems. We discuss the design of G-CLEF’s insulated enclosure and thermal control systems which simultaneously maintain the spectrograph at milli-Kelvin level stability and limit thermal leakage into the telescope dome. Also discussed are micro gravity-vector variations caused by normal telescope slewing, their uncorrected influence on image motion, and how they are dealt with in the design. We discuss G-CLEF’s front-end assembly and fiber-feed system as well as other interface, integration and servicing challenges presented by the telescope, enclosure, and neighboring instrumentation. This work has been supported by the GMTO Corporation, a non-profit organization operated on behalf of an international consortium of universities and institutions: Arizona State University, Astronomy Australia Ltd, the Australian National University, the Carnegie Institution for Science, Harvard University, the Korea Astronomy and Space Science Institute, the São Paulo Research Foundation, the Smithsonian Institution, the University of Texas at Austin, Texas AM University, the University of Arizona, and the University of Chicago.

Detailed design of the G-CLEF flexure control camera subsystem

The GMT-Consortium Large Earth Finder (G-CLEF) is one of the first instrument for the Giant Magellan Telescope (GMT). The G-CLEF is a fiber fed, optical band echelle spectrograph that is capable of extremely precise radial velocity measurement. The G-CLEF Flexure Control Camera (FCC) is included as a part in the G-CLEF Front End Assembly (GCFEA), which monitors the field images focused on a fiber mirror to control the flexure and the focus errors within the GCFEA. The five optical components constituting the FCC are aligned on a common optical bench. The order of the optical train is: a collimator, neutral density filters, a focus analyzer, a reimaging camera barrel, and a detector module. The collimator receives the beam reflected by the fiber mirror and consists of a triplet lens. The neutral density filters are located just after the collimator to make it possible a broad range star brightness as a target or a guide. The tent prism focus analyzer is positioned at a pupil produced by the collimator and is used to measure a focus offset. The reimaging camera barrel includes two pairs of doublet lenses to focus the beam onto the CCD focal plane. The detector module is composed of a linear translator and a field de-rotator. In this article, we present the optical and mechanical detailed designs of the G-CLEF FCC.