Publications by Joanna Barstow


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

Monthly Notices of the Royal Astronomical Society Oxford University Press 458 (2016) 2657-2666

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

The planned launch of the James Webb Space Telescope (JWST) in 2018 will herald a new era of exoplanet spectroscopy. JWST will be the first telescope sensitive enough to potentially characterize terrestrial planets from their transmission spectra. In this work, we explore the possibility that terrestrial planets with Venus-type and Earth-type atmospheres could be distinguished from each other using spectra obtained by JWST. If we find a terrestrial planet close to the liquid water habitable zone of an M5 star within a distance of 10 parsec, it would be possible to detect atmospheric ozone if present in large enough quantities, which would enable an oxygen-rich atmosphere to be identified. However, the cloudiness of a Venus-type atmosphere would inhibit our ability to draw firm conclusions about the atmospheric composition, making any result ambiguous. Observing small, temperate planets with JWST requires significant investment of resources, with single targets requiring of the order of 100 transits to achieve sufficient signal to noise. The possibility of detecting a crucial feature such as the ozone signature would need to be carefully weighed against the likelihood of clouds obscuring gas absorption in the spectrum.


Probing Saturn's tropospheric cloud with Cassini/VIMS

Icarus Elsevier 271 (2016) 400-417

J Eberhardt, P Irwin, L Fletcher, C Merlet, R Giles, J Barstow

In its decade of operation the Cassini mission has allowed us to look deep into Saturn’s atmosphere and investigate the processes occurring below its enshrouding haze. We use Visual and Infrared Mapping Spectrometer (VIMS) 4.6—5.2 µm data from early in the mission to investigate the location and properties of Saturn’s cloud structure between 0.6 and 5 bars. We average nightside spectra from 2006 over latitude circles and model the spectral limb darkening using the NEMESIS radiative transfer and retrieval tool. We present our best-fit deep cloud model for latitudes −40◦ < λ < 50◦ , along with retrieved abundances for NH3, PH3 and AsH3. We find an increase in NH3 abundance at the equator, a cloud base at ∼2.3 bar and no evidence for cloud particles with strong absorption features in the 4.6—5.2 µm wavelength range, all of which are consistent with previous work. Non-scattering cloud models assuming a composition of either NH3 or NH4SH, with a scattering haze overlying, fit limb darkening curves and spectra at all latitudes well; the retrieved optical depth for the tropospheric haze is decreased in the northern (winter) hemisphere, implying that the haze has a photochemical origin. Our ability to test this hypothesis by examining spectra at different seasons is restricted by the varying geometry of VIMS observations over the life of the mission, and the appearance of the Saturn storm towards the end of 2010.


Exoplanet atmospheres with EChO: spectral retrievals using EChOSim

EXPERIMENTAL ASTRONOMY 40 (2015) 545-561

JK Barstow, NE Bowles, S Aigrain, LN Fletcher, PGJ Irwin, R Varley, E Pascale


Evidence for an external origin of heavy elements in hot DA white dwarfs

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 440 (2014) 1607-1625

MA Barstow, JK Barstow, SL Casewell, JB Holberg, I Hubeny


CONSTRAINING THE ATMOSPHERIC COMPOSITION OF THE DAY-NIGHT TERMINATORS OF HD 189733b: ATMOSPHERIC RETRIEVAL WITH AEROSOLS

ASTROPHYSICAL JOURNAL 789 (2014) ARTN 14

J-M Lee, PGJ Irwin, LN Fletcher, K Heng, JK Barstow


The transit spectra of Earth and Jupiter

ICARUS 242 (2014) 172-187

PGJ Irwin, JK Barstow, NE Bowles, LN Fletcher, S Aigrain, J-M Lee


CLOUDS ON THE HOT JUPITER HD189733b: CONSTRAINTS FROM THE REFLECTION SPECTRUM

ASTROPHYSICAL JOURNAL 786 (2014) ARTN 154

JK Barstow, S Aigrain, PGJ Irwin, T Hackler, LN Fletcher, JM Lee, NP Gibson


From spectra to atmospheres: Solving the underconstrained retrieval problem for exoplanets

Proceedings of the International Astronomical Union 8 (2013) 275-276

JK Barstow, S Aigrain, PGJ Irwin, N Bowles, LN Fletcher, JM Lee

Spectroscopic observations of transiting exoplanets have provided the first indications of their atmospheric structure and composition. Optimal estimation retrievals have been successfully applied to solar system planets to determine the temperature, composition and aerosol properties of their atmospheres, and have recently been applied to exoplanets. We show the effectiveness of the technique when combined with simulated observations from the proposed space telescope EChO, and also discuss the difficulty of constraining a complex system with sparse data and large uncertainties, using the super-Earth GJ 1214b as an example. Copyright © 2013, International Astronomical Union.


Constraining the atmosphere of GJ 1214b using an optimal estimation technique

\mnras 434 (2013) 2616-2628-2616-2628

JK Barstow, S Aigrain, PGJ Irwin, LN Fletcher, J-M Lee


The Deep Blue Color of HD\nbsp189733b: Albedo Measurements with Hubble Space Telescope/Space Telescope Imaging Spectrograph at Visible Wavelengths

\apjl 772 (2013) L16-L16

TM Evans, F Pont, DK Sing, S Aigrain, JK Barstow, J-M Désert, N Gibson, K Heng, HA Knutson, A Lecavelier des Etangs


On the potential of the EChO mission to characterize gas giant atmospheres

MNRAS 430 (2013) 1188-1207-1188-1207

JK Barstow, S Aigrain, PGJ Irwin, N Bowles, LN Fletcher, J-M Lee


A Gemini ground-based transmission spectrum of WASP-29b: a featureless spectrum from 515 to 720 nm

Monthly Notices of the Royal Astronomical Society 428 (2013) 3680-3692-3680-3692

NP Gibson, S Aigrain, JK Barstow, TM Evans, LN Fletcher, PGJ Irwin


The optical transmission spectrum of the hot Jupiter HAT-P-32b: clouds explain the absence of broad spectral features?

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 436 (2013) 2974-2988

NP Gibson, S Aigrain, JK Barstow, TM Evans, LN Fletcher, PGJ Irwin


Models of the global cloud structure on Venus derived from Venus Express observations

Icarus (2011)

JK Barstow, CCC Tsang, CF Wilson, PGJ Irwin, FW Taylor, K McGouldrick, P Drossart, G Piccioni, S Tellmann


Correlations between cloud thickness and sub-cloud water abundance on Venus

GEOPHYSICAL RESEARCH LETTERS 37 (2010) ARTN L02202

CCC Tsang, CF Wilson, JK Barstow, PGJ Irwin, FW Taylor, K McGouldrick, G Piccioni, P Drossart, H Svedhem


O VI in the Local Interstellar Medium

\apj 723 (2010) 1762-1786-1762-1786

MA Barstow, DD Boyce, BY Welsh, R Lallement, JK Barstow, AE Forbes, S Preval


A Large-Scale Survey of White Dwarf Composition from the FUSE Archive

American Institute of Physics Conference Series 1273 (2010) 97-100-97-100

MA Barstow, SL Casewell, JK Barstow, BY Welsh, OHW Siegmund


Venus Cloud Properties from Venus Express VIRTIS Observations

AAS/Division for Planetary Sciences Meeting Abstracts #42 42 (2010) 994-994
Part of a series from Bulletin of the American Astronomical Society

J Barstow, FW Taylor, CCC Tsang, CF Wilson, PGJ Irwin, P Drossart, G Piccioni


Determining vertical cloud structure on Venus using near-infrared spectroscopy

European Planetary Science Congress 2009 (2009) 249-249

JK Barstow, FW Taylor, CCC Tsang, CF Wilson, PGJ Irwin, P Drossart, G Piccioni


Minor Species in the Deep Atmosphere of Venus: Dynamical Tracers seen by Venus Express

AAS/Division for Planetary Sciences Meeting Abstracts #41 41 (2009) #60.07-#60.07
Part of a series from AAS/Division for Planetary Sciences Meeting Abstracts

C Tsang, CF Wilson, JK Barstow, B Bezard, PGJ Irwin, FW Taylor, G Piccioni, P Drossart, K McGouldrick, SB Calcutt

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