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Black Hole

Lensing of space time around a black hole. At Oxford we study black holes observationally and theoretically on all size and time scales - it is some of our core work.

Credit: ALAIN RIAZUELO, IAP/UPMC/CNRS. CLICK HERE TO VIEW MORE IMAGES.

Michael Cretignier

Postdoctoral Research Assistant

Sub department

  • Astrophysics
  • About
  • Publications

Measuring the Sun’s radial velocity variability due to supergranulation over a magnetic cycle.

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025) staf1168

Authors:

Niamh K O’Sullivan, Suzanne Aigrain, Michael Cretignier, Ben Lakeland, Baptiste Klein, Xavier Dumusque, Nadège Meunier, Sophia Sulis, Megan Bedell, Annelies Mortier, Andrew Collier Cameron, Heather M Cegla

Abstract:

Abstract In recent years supergranulation has emerged as one of the biggest challenges for the detection of Earth-twins in radial velocity planet searches. We used eight years of Sun-as-a-star radial velocity observations from HARPS-N to measure the quiet-Sun’s granulation and supergranulation properties of most of its 11-year activity cycle, after correcting for the effects of magnetically active regions using two independent methods. In both cases, we observe a clear, order of magnitude variation in the time-scale of the supergranulation component, which is largest at activity minimum and is strongly anti-correlated with the relative Sunspot number. We also explored a range of observational strategies which could be employed to characterise supergranulation in stars other than the Sun, showing that a comparatively long observing campaign of at least 23 nights is required, but that up to 10 stars can be monitored simultaneously in the process. We conclude by discussing plausible explanations for the ”supergranulation” cycle.
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In-depth characterization of the Kepler-10 three-planet system with HARPS-N radial velocities and Kepler transit timing variations

Astronomy & Astrophysics EDP Sciences 696 (2025) a233

Authors:

AS Bonomo, L Borsato, VM Rajpaul, L Zeng, M Damasso, NC Hara, M Cretignier, A Leleu, N Unger, X Dumusque, F Lienhard, A Mortier, L Naponiello, L Malavolta, A Sozzetti, DW Latham, K Rice, R Bongiolatti, L Buchhave, AC Cameron, AF Fiorenzano, A Ghedina, RD Haywood, G Lacedelli, A Massa, F Pepe, E Poretti, S Udry
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TESS and HARPS-N unveil two planets transiting TOI-1453

Astronomy & Astrophysics EDP Sciences 696 (2025) a86

Authors:

M Stalport, A Mortier, M Cretignier, JA Egger, L Malavolta, DW Latham, KA Collins, CN Watkins, F Murgas, LA Buchhave, M López-Morales, S Udry, SN Quinn, AM Silva, G Andreuzzi, D Baker, W Boschin, DR Ciardi, M Damasso, L Di Fabrizio, X Dumusque, A Fukui, R Haywood, SB Howell, JM Jenkins, A Leleu, P Lewin, J Lillo-Box, AF Martínez Fiorenzano, N Narita, M Pedani, M Pinamonti, E Poretti, RP Schwarz, S Seager, A Sozzetti, EB Ting, A Vanderburg, JN Winn, C Ziegler
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Precise and efficient modeling of stellar-activity-affected solar spectra using SOAP-GPU

Astronomy & Astrophysics EDP Sciences 693 (2025) a262

Authors:

Yinan Zhao, Xavier Dumusque, Michael Cretignier, Khaled Al Moulla, Momo Ellwarth, Ansgar Reiners, Alessandro Sozzetti
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Revisiting the multi-planetary system of the nearby star HD 20794

Astronomy & Astrophysics EDP Sciences 693 (2025) a297

Authors:

N Nari, X Dumusque, NC Hara, A Suárez Mascareño, M Cretignier, JI González Hernández, AK Stefanov, VM Passegger, R Rebolo, F Pepe, NC Santos, S Cristiani, JP Faria, P Figueira, A Sozzetti, MR Zapatero Osorio, V Adibekyan, Y Alibert, C Allende Prieto, F Bouchy, S Benatti, A Castro-González, V D’Odorico, M Damasso, JB Delisle, P Di Marcantonio, D Ehrenreich, R Génova-Santos, MJ Hobson, B Lavie, J Lillo-Box, G Lo Curto, C Lovis, CJAP Martins, A Mehner, G Micela, P Molaro, C Mordasini, N Nunes, E Palle, SP Quanz, D Ségransan, AM Silva, SG Sousa, S Udry, N Unger, J Venturini
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