I am a Postdoc in the Astronomy and Astrophysics group at the University of Warwick, where I work with Tom Marsh. My research focuses on AM CVns, a class of He-dominated cataclysmic variables which include the shortest period binaries known. I am particularly interested in characterising the evolutionary history of this class of binaries.

Research

AM CVn-type binaries are laboratories of extreme physics and the dominant source of gravitational waves at frequencies detectable by a space interferometer such as LISA, as well as potential sources of dwarf novae, classical novae, type 1a supernovae, and ".1a" supernovae. They consist of a central white dwarf accreting He-rich material from a donor, which may be either another white dwarf or a He-atmosphere star.

Because of their low space density only around 50 are known. In 2014 the first fully-eclipsing AM CVn was discovered, Gaia14aae, offering an unprecedented wealth of information on the structure and evolutionary history of these objects. My papers analysing this system came out in 2018 and 2019. I also led the discovery paper of a new AM CVn binary with a 16-minute orbital period, SDSS J1351-0659.

Across the last few years, the trend for AM CVn binaries seems to be that the donors are hotter and higher mass than predicted by models. This has evolutionary implications -- it seems to suggest that the predicted white dwarf donor systems are not seen, perhaps because they do not survive.

Outreach

I volunteer for the department's planetarium, which is used on visits to local schools. I have been a regular writer for Astrobites, who summarise astro-ph papers aimed at an undergraduate level.

Publications

First Author

• "Phase-Resolved Spectroscopy of Gaia14aae: Line Emission From Near the White Dwarf Surface" -- MNRAS (2019), 485, 1947 -- M. J. Green, T. R. Marsh, D. Steeghs, E. Breedt, T. Kupfer, P. Rodriguez-Gil, J. van Roestel, R. P. Ashley, L. Wang, E. Cukanovaite, S. Outmani

• "A 15.7-Minute AM CVn Binary Discovered in K2" -- MNRAS (2018), 477, 5646 -- M. J. Green, J. J. Hermes, T. R. Marsh, D. T. H. Steeghs, Keaton J. Bell, S. P. Littlefair, S. G. Parsons, E. Dennihy, J. T. Fuchs, J. S. Reding, B. C. Kaiser, R. P. Ashley, E. Breedt, V. S. Dhillon, N. P. Gentile Fusillo, P. Kerry, D. I. Sahman
• "High-Speed Photometry of Gaia14aae: An Eclipsing AM CVn That Challenges Formation Models" -- MNRAS (2018), 476, 1663, -- M. J. Green, T. R. Marsh, D. T. H. Steeghs, T. Kupfer, R. P. Ashley, S. Bloemen, E. Breedt, H. C. Campbell, A. Chakpor, C. M. Copperwheat, V. S. Dhillon, G. Hallinan, L. K. Hardy, J. J. Hermes, P. Kerry, S. P. Littlefair, J. Milburn, S. G. Parsons, N. Prasert, J. van Roestel, D. I. Sahman, N. Singh

Co-Author

• "The evolutionary status of Cataclysmic Variables: Eclipse modelling of 15 systems" -- MNRAS (2019) -- M. McAllister, S. P. Littlefair, S. G. Parsons, V. S. Dhillon, T. R. Marsh, B. T. Gaensicke, E. Breedt, C. Copperwheat, M. J. Green, C. Knigge, D. I. Sahman, M. J. Dyer, P. Kerry, R. P. Ashley, P. Irawati, S. Rattanasoon
• "The physical properties of AM CVn stars: new insights from Gaia DR2" -- A&A (2018), 620, A141 -- G. Ramsay, M. J. Green, T. R. Marsh, T. Kupfer, E. Breedt, V. Korol, P.J. Groot, C. Knigge, G. Nelemans, D. Steeghs, P. Woudt, A. Aungwerojwit
• "The scatter of the M dwarf mass–radius relationship" -- MNRAS (2018) -- SG Parsons, Boris T Gänsicke, TR Marsh, RP Ashley, E Breedt, M R Burleigh, CM Copperwheat, VS Dhillon, MJ Green, JJ Hermes, P Irawati, P Kerry, SP Littlefair, A Rebassa-Mansergas, DI Sahman, M R Schreiber, M Zorotovic
• "A Refined Search for Pulsations in White Dwarf Companions to Millisecond Pulsars" -- MNRAS (2018) -- Mukremin Kilic, J. J. Hermes, A. H. Corsico, Alekzander Kosakowski, Warren R. Brown, John Antoniadis, Leila M. Calcaferro, A. Gianninas, Leandro G. Althaus, M. J. Green
• "The OmegaWhite survey for short-period variable stars - V. Discovery of an ultracompact hot subdwarf binary with a compact companion in a 44 minute orbit" -- ApJ (2017) -- T. Kupfer, G. Ramsay, J. van Roestel, J. Brooks, S. A. Macfarlane, R. Toma, P. J. Groot, P. A. Woudt, L. Bildsten, T. R. Marsh, M. J. Green, E. Breedt, D. Kilkenny, J. Freudenthal, S. Geier, U. Heber, S. Bagnulo, N. Blagorodnova, D. A. H. Buckley, V. S. Dhillon, S. R. Kulkarni, R. Lunnan, T. A. Prince
• "A search for optical bursts from the repeating fast radio burst FRB 121102" -- MNRAS (2017) -- Liam K Hardy, Vik S Dhillon, Laura G Spitler, Stuart P Littlefair, Richard P Ashley, Annalisa De Cia, Matthew J Green, Phrudth Jaroenjittichai, Evan F Keane, Paul Kerry, Michael Kramer, Daniele Malesani, Tom R Marsh, Steven G Parsons, Andrea Possenti, Somsawat Rattanasoon, David I Sahman
• "Testing the white dwarf mass-radius relationship with eclipsing binaries" -- MNRAS (2017) -- S. G. Parsons, B. T. Gänsicke, T. R. Marsh, R. P. Ashley, M. C. P. Bours, E. Breedt, M. R. Burleigh, C. M. Copperwheat, V. S. Dhillon, M. Green, L. K. Hardy, J. J. Hermes, P. Irawati, P. Kerry, S. P. Littlefair, M. J. McAllister, S. Rattanasoon, A. Rebassa-Mansergas, D. I. Sahman, M. R. Schreiber
• "Two white dwarfs in ultrashort binaries with detached, eclipsing, likely substellar companions detected by K2" -- MNRAS (2017) -- S. G. Parsons, J. J. Hermes, T. R. Marsh, B. T. Gänsicke, P.-E. Tremblay, S. P. Littlefair, D. I. Sahman, R. P. Ashley, M. Green, S. Rattanasoon, V. S. Dhillon, M. R. Burleigh, S. L. Casewell, D. A. H. Buckley, I. P. Braker, P. Irawati, E. Dennihy, P. Rodríguez-Gil, D. E. Winget, K. I. Winget, K. J. Bell, M. Kilic
• "Optical timing observations of Swift J1753.5-0127 during its Feb 2017 rejuvenation" -- ATel #10118 -- P. Gandhi (Southampton), V. S. Dhillon (Sheffield), T. R. Marsh, M. Green, R. P. Ashley (Warwick), D. Altamirano, A. Beri (Southampton), A. W. Shaw (Alberta), J. A. Tomsick (Berkeley)
• "Using large spectroscopic surveys to test the double degenerate model for Type Ia supernovae" -- MNRAS (2017), 468, 2910 -- Breedt, E.; Steeghs, D.; Marsh, T. R.; Gentile Fusillo, N. P.; Tremblay, P.-E.; Green, M.; De Pasquale, S.; Hermes, J. J.; Gänsicke, B. T.; Parsons, S. G.; Bours, M. C. P.; Longa-Peña, P.; Rebassa-Mansergas, A.
• "PTF1 J082340.04+081936.5: A Hot Subdwarf B Star with a Low-mass White Dwarf Companion in an 87-minute Orbit" -- ApJ (2017), 835, 131 -- Kupfer, Thomas; van Roestel, Jan; Brooks, Jared; Geier, Stephan; Marsh, Tom R.; Groot, Paul J.; Bloemen, Steven; Prince, Thomas A.; Bellm, Eric; Heber, Ulrich; Bildsten, Lars; Miller, Adam A.; Dyer, Martin J.; Dhillon, Vik S.; Green, Matthew; Irawati, Puji; Laher, Russ; Littlefair, Stuart P.; Shupe, David L.; Steidel, Charles C.; Rattansoon, Somsawat; Pettini, Max.