Institute of Astronomy

- Julia Sisk-Reynes


Office: Obs O14
Office Tel: (01223) 337531
More Info (Internal)



I am interested in astrophysical searches of light Axion-Like Particles (ALPs). I have recently investigated the projected sensitivity of next-generation X-ray missions (in particular, the Athena and the proposed AXIS and LEM observatories) to constraining these particles. In the near future, I plan to investigate how a three-dimensional approach for the cluster magnetic field can further help us probe their parameter space, amongst others.

Selected papers

First author 

Physics Beyond the Standard Model with Future X-ray Observatories: Projected Constraints on Very-Light Axion-Like Particles with Athena and AXIS (in press) -  J. Sisk-Reynés, Christopher S. Reynolds, Michael L. Parker, et al. (2022)

Evidence for a moderate spin from X-ray reflection of the high-mass supermassive black hole at the centre of the cluster-hosted quasar H1821+643 - J. Sisk-Reynés, Christopher S. Reynolds, James H. Matthews, et al. (2022)

New constraints on light Axion-Like Particles using Chandra Transmission Grating Spectroscopy of the powerful cluster-hosted quasar H1821+643 - J. Sisk-Reynés, James H. Matthews, Christopher S. Reynolds, et al. (2021)


How do Magnetic Field Models Affect Astrophysical Limits on Light Axion-like Particles? An X-ray Case Study with NGC 1275 - James H. Matthews, Christopher S. Reynolds, M.C. David Marsh, J. Sisk-Reynés, Payton E. Rodman (2022)


2020 - 2022. University of Cambridge - Undergraduate Supervisions: Astrophysical Fluid Dynamics (Part II, 3rd year) and Mathematics 1A (Natural Sciences, 1st year).

2019. University of Manchester - Particle physics summer research: On direct dark matter detection at the DarkSide-20k liquid Argon experiment (under D. Price and A. Szelc).

2018 - 2019: Teaching placements in the UK: Teach First Insight Programme (2019), Teach Physics Internship from the Ogden Trust (2018).  


2020 - present: Ph.D. in Astronomy, Institute of Astronomy (IoA), The University of Cambridge (under C. Reynolds).

2016 - 2020: MPhys (Hons) Physics, The University of Manchester.

Awards and Prizes

2022 - Murdin Prize (Institute of Astronomy): for the best paper produced by a current Ph.D. student for MNRAS 510, 1, pages 1264 - 1277. Shared.

2020 - Stellify Award (University of Manchester): for contributions and commitment as an undergraduate student in the areas of volunteering, leadership and ethical grand challenges.

Press releases

June 2022 - Chandra Shows Giant Black Hole Spins Slower Than Its Peers 

Talks and Scientific conferences

Upcoming talks

(TBC) Invited seminar on 'Constraining Beyond the Standard Model Physics with AXIS' by the AXIS probe-class mission.

Delivered talks about my research in about 10 scientific conferences (both at national and international level) and specialised group meetings since Spring 2022. Invited and contributed presentations include short (15 minutes) and long (60 minutes) overviews.

Highlighted talks at: 3rd Scientific Conference dedicated to the Athena X-ray Observatory (Barcelona, Spain); CfA High Energy Special Seminar; Chandra/HETG Special Seminar (MIT Kavli Institute); Line Emission Mapper (LEM) IGM Working Group meeting (online)NASA Goddard Fermi Group (all in-person).

Contributed talks at the following conferences: "Progress in Axion Theory and Experiment Workshop" (Durham, UK); the European Astronomical Society Annual Conference (Valencia, Spain); the XMM-Newton "Black Holes under the X-ray microscope" Workshop (ESAC, Madrid, Spain); "New Results in X-ray Astronomy Annual UK meeting" (Leicester, UK).

Diversity and Inclusion and Science Outreach 

Upcoming events 

(March 2023) 'Heavy Black Holes and Tiny Exotic Particles' talk for a total of 160 Year 6 students - Magdalene College, The University of Cambridge. Event organised by the Lindemann Trust.

(March 2023) International Women's Day at the IoA. I am actively involved in organising some of the activities planned for the day, including a discussion panel with Physics and Astronomy graduates that are currently holding positions in academia and in the industry.  

Page last updated: 25 January 2023 at 15:07