Andrew Cumming

Research

Overview

A general theme of research in my group is ‘stellar astrophysics at the extremes’.

The dense leftovers of massive stars, neutron stars and white dwarfs are incredible laboratories for extreme matter physics ranging from the equation of state of super-nuclear density matter in neutron star cores to the condensed matter physics of the solid crust of neutron stars or cores of white dwarfs. They are also fascinating from the point of view of nuclear astrophysics, with neutron stars in particular involving nuclei from across the nuclear chart from the most proton-rich to the most neutron-rich nuclei. They are also important as endpoints of stellar evolution, and there are many puzzles about how the diverse types of compact objects that we see relate to each other and to their parent stars.

Studies of the ever-increasing number of exoplanets discovered orbiting stars in our Galaxy are telling us about planet formation and evolution and the physical processes at work in planet interiors. With the discovery of planets booming, this is a unique and exciting time to learn about planets and planetary systems. With their dense interiors, giant planets also offer a chance to study matter under extreme conditions.

Our research has the goal of using observations of these objects to learn about the fundamental physics processes at work in their formation and evolution.

Publications     Talks     Summer school lectures     Codes and models

Recent papers

Accreting neutron star winds
Compositionally-driven convection and white dwarf dynamos

  • A short intense dynamo at the onset of crystallization in white dwarfs, J.R. Fuentes, Matias Castro-Tapia, Andrew Cumming 2024, ApJ, in press arXiv

  • Fast and slow crystallization-driven convection in white dwarfs, Matias Castro Tapia, Andrew Cumming, J.R. Fuentes 2024, ApJ, in press arXiv

  • Heat transport and convective velocities in compositionally-driven convection in neutron star and white dwarf interiors, J.R. Fuentes, Andrew Cumming, Matias Castro-Tapia, and Evan H. Anders 2023, submitted to ApJ arXiv

Chemical separation on freezing in neutron stars and white dwarfs

  • Cooling delays from iron sedimentation and iron inner cores in white dwarfs, M.E. Caplan et al. 2021, ApJ 919, L12 arXiv

  • Neon Cluster Formation and Phase Separation during White Dwarf Cooling, M. E. Caplan, C. J. Horowitz, and A. Cumming 2020, ApJL 902, 44 arXiv

  • Polycrystalline crusts in accreting neutron stars, M. E. Caplan, A. Cumming, D. Berry, C. Horowitz, R. Mckinven 2018, ApJ 860, 148 arXiv

  • A Survey of Chemical Separation in Accreting Neutron Stars, R. Mckinven, A. Cumming, Z. Medin, Schatz, H. 2016, ApJ, 823, 117 arXiv

  • Time Dependent Compositionally Driven Convection in the Oceans of Accreting Neutron Stars, Z. Medin and A. Cumming 2015, ApJ, 802, 29 arXiv

  • A Signature of Chemical Separation in the Cooling Curves of Transiently Accreting Neutron Stars, Zach Medin and Andrew Cumming 2014, ApJ, 783, L3 arXiv

  • Direct MD simulation of liquid-solid phase equilibria for three-component plasma, Hughto, J., Horowitz, C. J., Schneider, A. S., Medin, Z., Cumming A., and Berry, D. K., 2012, PRE, 86, 066413 arXiv

  • Compositionally-driven convection in the oceans of accreting neutron stars, Zach Medin and A. Cumming, 2011, ApJ, 730, 97 arXiv

  • Crystallization of classical multicomponent plasmas, Zach Medin and A. Cumming, 2010, PRE, 81, 6107 arXiv

Magnetized hot jupiters
Neutron star cooling and interiors

  • Fast neutrino cooling in the accreting neutron star MXB 1659-29, Melissa Mendes, Farrukh J. Fattoyev, Andrew Cumming, and Charles Gale 2022, ApJ 938, 119 arXiv

  • Glitch Rises as a Test for Rapid Superfluid Coupling in Neutron Stars, Vanessa Graber, Andrew Cumming, and Nils Andersson 2018, ApJ 865, 23 arXiv

  • Rapid neutrino cooling in the neutron star MXB 1659-29, E. Brown, A. Cumming, F. Fattoyev, C. Horowitz, D. Page, S. Reddy 2018, PRL 120, 182701 arXiv

  • A lower limit on the heat capacity of the neutron star core, A. Cumming, E. Brown, F. Fattoyev, C. Horowitz, D. Page, S. Reddy 2017, PRC 95, 025806 arXiv

  • Late time cooling of neutron star transients and the physics of the inner crust, A. Deibel, A. Cumming, E. Brown, S. Reddy 2017, ApJ 839, 95 arXiv

  • Disordered nuclear pasta, magnetic field decay, and crust cooling in neutron stars, C. J. Horowitz, D. K. Berry, C. M. Briggs, M. E. Caplan, A. Cumming, and A.S. Schneider 2015, PRL, 114, 031102 arXiv

Penetrative convection and layer formation

  • Rotation reduces convective entrainment in Jupiter and other gas giants, J. R. Fuentes, Evan H. Anders, Andrew Cumming, and Bradley W. Hindman 2023, ApJL, 950, L4 arXiv

  • Layer formation in a stably-stratified fluid cooled from above. Towards an analog for Jupiter and other gas giants, Rafael Fuentes, Andrew Cumming, and Evan Anders 2022, PR Fluids, 7, 124501 arXiv

  • Shear flows and their suppression at large aspect ratio. Two-dimensional simulations of a growing convection zone, Rafael Fuentes and Andrew Cumming 2021, PR Fluids, 6, 074502 arXiv

  • Penetration of a cooling convective layer into a stably-stratified composition gradient: entrainment at low Prandtl number, Rafael Fuentes and Andrew Cumming 2020, PR Fluids, 5, 124501 arXiv

Evolution of gas giant exoplanets
Neutron star magnetic field evolution

  • Hall drift and the braking indices of young pulsars, Konstantinos N. Gourgouliatos, and A. Cumming 2015, MNRAS, 446, 1121 arXiv

  • A Hall Attractor in Axisymmetric Magnetic Fields, Kostas Gourgouliatos and Andrew Cumming, 2014, PRL, 112, 171101 arXiv

  • Hall Effect in Neutron Star Crusts: Evolution, Endpoint, and Dependence on Initial Conditions, Kostas Gourgouliatos and Andrew Cumming, 2014, MNRAS, 438, 1618 arXiv

  • Hall Equilibria with Toroidal and Poloidal Fields: Application to Neutron Stars, K. N. Gourgouliatos, A. Cumming, A. Reisenegger, C. Armaza, M. Lyutikov, J. A. Valdivia, 2013, MNRAS, 434, 2480 arXiv

Type I X-ray bursts and nuclear burning on neutron stars

  • A Bayesian approach to matching thermonuclear X-ray burst observations with models, A. Goodwin et al. 2019, MNRAS, 490, 2228 arXiv

  • Mixed H/He bursts in SAX J1748.9-2021 during the spectral change of its 2015 outburst, Zhaosheng Li et al. 2018, A&A 620, A114 arXiv

  • Flux decay during thermonuclear X-ray bursts analysed using dynamic powerlaw index method, J. Kuuttila et al. 2017, A&A, 604, 77 arXiv

  • The link between coherent burst oscillations, burst spectral evolution and accretion state in 4U 1728-34, G. Zhang, M. Mendez, M. Zamfir, and A. Cumming 2016, MNRAS, 455, 2004

  • The Thermal Stability of Helium Burning on Accreting Neutron Stars, M. Zamfir, A. Cumming, and C. Niquette 2014, MNRAS, 445, 3278 arXiv

  • The cooling rate of neutron stars after thermonuclear shell flashes, in ‘t Zand, J. J. M., Cumming, A., Triemstra, T. L., Mateijsen, R.A.D.A., Bagnoli, T. 2014, A&A, 562, 16 arXiv

  • A superburst candidate in EXO 1745-248 as a challenge to thermonuclear ignition models, Altamirano, D. et al., 2012, MNRAS, 426, 927 arXiv

  • Constraints on neutron star mass and radius in GS 1826-24 from sub-Eddington X-ray bursts, Michael Zamfir, A. Cumming, and D. K. Galloway, 2012, ApJ, 749, 69 arXiv

  • Millihertz quasi-periodic oscillations and thermonuclear bursts from Terzan 5: A showcase of burning regimes, M. Linares, D. Altamirano, D. Chakrabarty, A. Cumming, L. Keek, 2012, ApJ, 748, 82 arXiv

  • What ignites on the neutron star of 4U 0614+091?, E. Kuulkers et al., 2010, A&A, 514, 65 arXiv

Superbursts

  • Urca cooling pairs in the neutron star ocean and their effect on superbursts, A. Deibel, Z. Meisel, H. Schatz, E. F. Brown, A. Cumming, 2016, ApJ 831, 13 arXiv

  • The imprint of carbon combustion on a superburst from the accreting neutron star 4U 1636-536, L. Keek et al. 2015, MNRAS, 454, 3559 arXiv

  • Carbon synthesis in steady state hydrogen and helium burning on accreting neutron stars, Jeremy Stevens, E. F. Brown, A. Cumming, R. Cyburt, H. Schatz, 2014, ApJ, 791, 106 arXiv

Crust cooling and shallow heating in accreting neutron stars

  • The effect of diffusive nuclear burning in neutron star envelopes on cooling in accreting systems, Marcella Wijngaarden et al. 2020, MNRAS, 493, 4936 arXiv

  • Consistent accretion-induced heating of the neutron-star crust in MXB 1659-29 during two different outbursts, A. S. Parikh et al. 2019, A&A 624, A84 arXiv

  • Deep Crustal Heating by Neutrinos from the Surface of Accreting Neutron Stars, F. Fattoyev et al. 2018, PRC 98, 5801 arXiv

  • Different accretion heating of the neutron star crust during multiple outbursts in MAXI J0556-332, A. S. Parikh et al. 2017, ApJL 851, L28 arXiv

  • The thermal state of KS 1731-260 after 14.5 years in quiescence, R. Merritt et al. 2016, ApJ 833, L1 arXiv

  • A strong shallow heat source in the accreting neutron star MAXI J0556-332, A. Diebel, A. Cumming, E. Brown, and D. Page 2015, ApJL, 809, L31 arXiv

  • Neutron star crust cooling in the Terzan 5 X-ray transient Swift J174805.3-244637, N. Degenaar et al. 2015, MNRAS, 451, 2071 arXiv

  • A Change in the Quiescent X-ray Spectrum of the Neutron Star Low Mass X-ray Binary MXB 1659-29, Cackett, E. M., Brown, E. F., Cumming, A., Degenaar, N., Fridriksson, J. K., Homan, J., Miller, J. M., and Wijnands, R., 2013, ApJ, 774, 131 arXiv

  • Continued Cooling of the Crust in the Neutron Star Low-mass X-ray Binary KS 1731-260, E. Cackett et al., 2010, ApJ, 722, L137 arXiv

  • Mapping crustal heating with the cooling lightcurves of quasi-persistent transients, E.F. Brown, and A. Cumming, 2009, ApJ, 698, 1020 arXiv

Magnetar outbursts

  • Flux relaxation after two outbursts of the magnetar SGR 1627-41 and possible hard X-ray emission, Hongjun An, A. Cumming, and V. Kaspi 2018, ApJ 859, 16 arXiv

  • The long-term post-outburst spin down and flux relaxation of the magnetar Swift J1822.3-1606, Paul Scholz, Vicky Kaspi, and Andrew Cumming, 2014, ApJ, 786, 62 arXiv

  • Spectral and Timing Properties of the Magnetar CXOU J164710.2-455216, An, H., Kaspi, V., Archibald, R., Cumming, A., 2013, ApJ, 763, 82 arXiv

  • Post-outburst X-ray Flux and Timing Evolution of Swift J1822.3-1606, Scholz, P., Ng, C.-Y., Livingstone, M. A., Kaspi, V. M., Cumming, A., and Archibald, R., 2012, ApJ, 761, 66 arXiv

  • Chandra observations of SGR 1627-41 near quiescence, An, H., Kaspi, V., Tomsick, J., Cumming, A., Bodaghee, A., Gotthelf, E., and Rahoui, F. 2012, ApJ, 757, 68 arXiv

Exoplanet statistics and planet formation

  • The effect of late giant collisions on the atmospheres of protoplanets and the formation of cold sub-Saturns, Mohamad Ali-Dib, Andrew Cumming, and Doug Lin 2022, MNRAS 509, 1413 arXiv

  • The Imprint of the Protoplanetary Disk in the Accretion of Super-Earth Envelopes, Mohamad Ali-Dib, Andrew Cumming, and Doug Lin 2020, MNRAS, 494, 2440 arXiv

  • Predictions of Planet Detections with NIR Radial Velocities in the Up-coming Spirou Legacy Survey, Cloutier, R. et al. 2018, AJ 155, 93 arXiv

  • The California-Kepler Survey V. Peas in a Pod: Planets in a Kepler Multi-planet System are Similar in Size and Regularly Spaced, L. Weiss et al. 2018, AJ 155, 48 arXiv

  • Shedding Light on the Eccentricity Valley: Gap Heating and Eccentricity Excitation of Giant Planets in Protoplanetary Disks, David Tsang, Neal J. Turner, and Andrew Cumming, 2014, ApJ, 782, 113 arXiv

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