Publications by Patrick Irwin


Jupiter's auroral-related stratospheric heating and chemistry II: Analysis of IRTF-TEXES spectra measured in December 2014

ICARUS 300 (2018) 305-326

JA Sinclair, GS Orton, TK Greathouse, LN Fletcher, JI Moses, V Hue, PGJ Irwin


Jupiter's North Equatorial Belt expansion and thermal wave activity ahead of Juno's arrival

GEOPHYSICAL RESEARCH LETTERS 44 (2017) 7140-7148

LN Fletcher, GS Orton, JA Sinclair, P Donnelly, H Melin, JH Rogers, TK Greathouse, Y Kasaba, T Fujiyoshi, TM Sato, J Fernandes, PGJ Irwin, RS Giles, AA Simon, MH Wong, M Vedovato


A precise optical transmission spectrum of the inflated exoplanet WASP-52b

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 470 (2017) 742-754

T Louden, PJ Wheatley, PGJ Irwin, J Kirk, I Skillen


Spatial variations in Titan's atmospheric temperature: ALMA and Cassini comparisons from 2012 to 2015

Icarus (2017)

AE Thelen, CA Nixon, NJ Chanover, EM Molter, MA Cordiner, RK Achterberg, J Serigano, PGJ Irwin, N Teanby, SB Charnley

© 2017 Elsevier Inc. Submillimeter emission lines of carbon monoxide (CO) in Titan's atmosphere provide excellent probes of atmospheric temperature due to the molecule's long chemical lifetime and stable, well constrained volume mixing ratio. Here we present the analysis of 4 datasets obtained with the Atacama Large Millimeter/Submillimeter Array (ALMA) in 2012, 2013, 2014, and 2015 that contain strong CO rotational transitions. Utilizing ALMA's high spatial resolution in the 2012, 2014, and 2015 observations, we extract spectra from 3 separate regions on Titan's disk using datasets with beam sizes ranging from 0.35 × 0.28'' to 0.39 × 0.34''. Temperature profiles retrieved by the NEMESIS radiative transfer code are compared to Cassini Composite Infrared Spectrometer (CIRS) and radio occultation science results from similar latitude regions. Disk-averaged temperature profiles stay relatively constant from year to year, while small seasonal variations in atmospheric temperature are present from 2012 to 2015 in the stratosphere and mesosphere (~100-500 km) of spatially resolved regions. We measure the stratopause (320 km) to increase in temperature by 5 K in northern latitudes from 2012 to 2015, while temperatures rise throughout the stratosphere at lower latitudes. We observe generally cooler temperatures in the lower stratosphere (~100 km) than those obtained through Cassini radio occultation measurements, with the notable exception of warming in the northern latitudes and the absence of previous instabilities; both of these results are indicators that Titan's lower atmosphere responds to seasonal effects, particularly at higher latitudes. While retrieved temperature profiles cover a range of latitudes in these observations, deviations from CIRS nadir maps and radio occultation measurements convolved with the ALMA beam-footprint are not found to be statistically significant, and discrepancies are often found to be less than 5 K throughout the atmosphere. ALMA's excellent sensitivity in the lower stratosphere (60-300 km) provides a highly complementary dataset to contemporary CIRS and radio science observations, including altitude regions where both of those measurement sets contain large uncertainties. The demonstrated utility of CO emission lines in the submillimeter as a tracer of Titan's atmospheric temperature lays the groundwork for future studies of other molecular species - particularly those that exhibit strong polar abundance enhancements or are pressure-broadened in the lower atmosphere, as temperature profiles are found to consistently vary with latitude in all three years by up to 15 K.


Ammonia in Jupiter's Troposphere From High-Resolution 5 μm Spectroscopy

Geophysical Research Letters (2017)

RS Giles, LN Fletcher, PGJ Irwin, GS Orton, JA Sinclair

© 2017. American Geophysical Union. All Rights Reserved. Jupiter's tropospheric ammonia (NH 3 ) abundance is studied using spatially resolved 5 μm observations from the cryogenic high-resolution infrared spectrograph (CRIRES) at the European Southern Observatory's Very Large Telescope. The high-resolving power (R = 96,000) allows the line shapes of three NH 3 absorption features to be resolved. We find that within the 1-4 bar pressure range, the NH 3 abundance decreases with altitude. The instrument slit was aligned north-south along Jupiter's central meridian, allowing us to search for latitudinal variability. There is considerable uncertainty in the large-scale latitudinal variability, as the increase in cloud opacity in zones compared to belts can mask absorption features. However, we do find evidence for a strong NH 3 enhancement at 4-6°N, consistent with a localized “ammonia plume“ on the southern edge of Jupiter's North Equatorial Belt.


D/H Ratios on Saturn and Jupiter from Cassini CIRS

ASTRONOMICAL JOURNAL 154 (2017) ARTN 178

JDR Pierel, CA Nixon, E Lellouch, LN Fletcher, GL Bjoraker, RK Achterberg, B Bezard, BE Hesman, PGJ Irwin, FM Flasar


Latitudinal variability in Jupiter ' s tropospheric disequilibrium species: GeH4, AsH3 and PH3

ICARUS 289 (2017) 254-269

RS Giles, LN Fletcher, PGJ Irwin


HST/WFC3 observations of Uranus' 2014 storm clouds and comparison with VLT/SINFONI and IRTF/Spex observations

ICARUS 288 (2017) 99-119

PGJ Irwin, MH Wong, AA Simon, GS Orton, D Toledo


Mapping Vinyl Cyanide and Other Nitriles in Titan's Atmosphere Using ALMA

ASTRONOMICAL JOURNAL 154 (2017) ARTN 206

JC-Y Lai, MA Cordiner, CA Nixon, RK Achterberg, EM Molter, NA Teanby, MY Palmer, SB Chamley, JE Lindberg, Z Kisiel, MJ Mumma, PGJ Irwin


Jupiter's para-H-2 distribution from SOFIA/FORCAST and Voyager/IRIS 17-37 mu m spectroscopy

ICARUS 286 (2017) 223-240

LN Fletcher, I de Pater, WT Reach, M Wong, GS Orton, PGJ Irwin, RD Gehrz


The PanCam Instrument for the ExoMars Rover

ASTROBIOLOGY 17 (2017) 511-541

AJ Coates, R Jaumann, AD Griffiths, CE Leff, N Schmitz, J-L Josset, G Paar, M Gunn, E Hauber, CR Cousins, RE Cross, P Grindrod, JC Bridges, M Balme, S Gupta, IA Crawford, P Irwin, R Stabbins, D Tirsch, JL Vago, T Theodorou, M Caballo-Perucha, GR Osinski, P Team


Jupiter's auroral-related stratospheric heating and chemistry I: Analysis of Voyager-IRIS and Cassini-CIRS spectra

ICARUS 292 (2017) 182-207

JA Sinclair, GS Orton, TK Greathouse, LN Fletcher, JI Moses, V Hue, PGJ Irwin


Moist convection and the 2010-2011 revival of Jupiter's South Equatorial Belt

ICARUS 286 (2017) 94-117

LN Fletcher, GS Orton, JH Rogers, RS Giles, AV Payne, PGJ Irwin, M Vedovato


Independent evolution of stratospheric temperatures in Jupiter's northern and southern auroral regions from 2014 to 2016

GEOPHYSICAL RESEARCH LETTERS 44 (2017) 5345-5354

JA Sinclair, GS Orton, TK Greathouse, LN Fletcher, C Tao, GR Gladstone, A Adriani, W Dunn, JI Moses, V Hue, PGJ Irwin, H Melin, RS Giles


ALMA detection and astrobiological potential of vinyl cyanide on Titan.

Science advances 3 (2017) e1700022-

MY Palmer, MA Cordiner, CA Nixon, SB Charnley, NA Teanby, Z Kisiel, PGJ Irwin, MJ Mumma

Recent simulations have indicated that vinyl cyanide is the best candidate molecule for the formation of cell membranes/vesicle structures in Titan's hydrocarbon-rich lakes and seas. Although the existence of vinyl cyanide (C2H3CN) on Titan was previously inferred using Cassini mass spectrometry, a definitive detection has been lacking until now. We report the first spectroscopic detection of vinyl cyanide in Titan's atmosphere, obtained using archival data from the Atacama Large Millimeter/submillimeter Array (ALMA), collected from February to May 2014. We detect the three strongest rotational lines of C2H3CN in the frequency range of 230 to 232 GHz, each with >4σ confidence. Radiative transfer modeling suggests that most of the C2H3CN emission originates at altitudes of ≳200 km, in agreement with recent photochemical models. The vertical column densities implied by our best-fitting models lie in the range of 3.7 × 1013 to 1.4 × 1014 cm-2. The corresponding production rate of vinyl cyanide and its saturation mole fraction imply the availability of sufficient dissolved material to form ~107 cell membranes/cm3 in Titan's sea Ligeia Mare.


A CONSISTENT RETRIEVAL ANALYSIS OF 10 HOT JUPITERS OBSERVED IN TRANSMISSION

ASTROPHYSICAL JOURNAL 834 (2017) ARTN 50

JK Barstow, S Aigrain, PGJ Irwin, DK Sing


Rayleigh scattering in the transmission spectrum of HAT-P-18b

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 468 (2017) 3907-3916

J Kirk, PJ Wheatley, T Louden, AP Doyle, I Skillen, J McCormac, PGJ Irwin, R Karjalainen


Detection of H-3(+) auroral emission in Jupiter's 5-micron window

ASTRONOMY & ASTROPHYSICS 589 (2016) ARTN A67

RS Giles, LN Fletcher, PGJ Irwin, H Melin, TS Stallard


Telling twins apart: exo-Earths and Venuses with transit spectroscopy

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 458 (2016) 2657-2666

JK Barstow, S Aigrain, PGJ Irwin, S Kendrew, LN Fletcher


ISOTOPIC RATIOS OF CARBON AND OXYGEN IN TITAN'S CO USING ALMA

ASTROPHYSICAL JOURNAL LETTERS 821 (2016) ARTN L8

J Serigano, CA Nixon, MA Cordiner, PGJ Irwin, NA Teanby, SB Charnley, JE Lindberg

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