Staff profile

Responsibilities within department

Current: Director of Education;

Previous: Health & Safety committee; Teaching Review committee; Admissions selector; L4 course director; General Problems paper committee chair; Assessment & Feedback Committee; Physics in Society module leader

Teaching activity

Current: L4 Radiative Processes in Astrophysics lecture course; L4 project supervisor.

Previous: L1 Phases of Matter lecture course; L1 Astrobiology lecture course; L1 Thermodynamics lecture course; L1 tutor; L2 tutor; L2 labs; L2 Physics in Society tutor; L3 General Problems class organiser; L3 Planetary Systems lecturer; L4 project moderator; Postgrad lectures on Black Holes.

• Ultraluminous X-ray sources
• The X-ray emission of nearby normal galaxies
• Starburst galaxies
• Low-luminosity active galactic nuclei

Journal Article

• Barra, F., Pinto, C., Middleton, M., Di Salvo, T., Walton, D. J., Gúrpide, A., & Roberts, T. P. (2024). Examining the nature of the ultraluminous X-ray source Holmberg II X-1. Astronomy & Astrophysics, 682, Article A94. https://doi.org/10.1051/0004-6361/202348471
• Bachetti, M., Middleton, M. J., Pinto, C., Gúrpide, A., Walton, D. J., Brightman, M., …Wolter, A. (2023). The high energy X-ray probe ( HEX-P ): studying extreme accretion with ultraluminous X-ray sources. Frontiers in Astronomy and Space Sciences, 10, Article 1289432. https://doi.org/10.3389/fspas.2023.1289432
• Roberts, T. P., Walton, D. J., Mackenzie, A. D. A., Heida, M., & Scaringi, S. (2023). Digging a little deeper: characterizing three new extreme ULX candidates. Monthly Notices of the Royal Astronomical Society, 525(3), 3330-3343. https://doi.org/10.1093/mnras/stad2367
• West, L., Garofali, K., Lehmer, B. D., Prestwich, A., Eufrasio, R., Luangtip, W., …Zezas, A. (2023). The Large Deficit of HMXB Emission from Luminous Infrared Galaxies: The Case of the Circumnuclear Starburst Ring in NGC 7552. Astrophysical Journal, 952(1), Article 22. https://doi.org/10.3847/1538-4357/acd9aa
• MacKenzie, A., Roberts, T., & Walton, D. (2023). The hyperluminous X‐ray source population. Astronomical Notes, 344(4), Article e230028. https://doi.org/10.1002/asna.20230028
• Fürst, F., Walton, D. J., Israel, G. L., Bachetti, M., Barret, D., Brightman, M., …Webb, N. (2023). Probing the nature of the low state in the extreme ultraluminous X-ray pulsar NGC 5907 ULX1. Astronomy & Astrophysics, 672, Article A140. https://doi.org/10.1051/0004-6361/202245048
• Barra, F., Pinto, C., Walton, D., Kosec, P., D’Aì, A., Di Salvo, T., …Roberts, T. (2022). Unveiling the disc structure in ultraluminous X-ray source NGC 55 ULX-1. Monthly Notices of the Royal Astronomical Society, 516(3), 3972-3983. https://doi.org/10.1093/mnras/stac2453
• Robba, A., Pinto, C., Pintore, F., Rodriguez, G., Ambrosi, E., Barra, F., …Walton, D. (2022). A transient ultraluminous X-ray source in NGC 55. Monthly Notices of the Royal Astronomical Society, 515(4), 4669-4674. https://doi.org/10.1093/mnras/stac2018
• Sathyaprakash, R., Roberts, T., Grisé, F., Kaaret, P., Ambrosi, E., Done, C., …Zampieri, L. (2022). A multi-wavelength view of distinct accretion regimes in the pulsating ultraluminous X-ray source NGC 1313 X-2. Monthly Notices of the Royal Astronomical Society, 511(4), 5346-5362. https://doi.org/10.1093/mnras/stac402
• Earnshaw, H. P., Brightman, M., Harrison, F. A., Heida, M., Jaodand, A., Middleton, M. J., …Walton, D. J. (2022). The variability behavior of NGC 925 ULX-3. Astrophysical Journal, 934(1), Article 42. https://doi.org/10.3847/1538-4357/ac79b0
• Walton, D., Mackenzie, A., Gully, H., Patel, N., Roberts, T., Earnshaw, H., & Mateos, S. (2022). A multimission catalogue of ultraluminous X-ray source candidates. Monthly Notices of the Royal Astronomical Society, 509(2), 1587-1604. https://doi.org/10.1093/mnras/stab3001
• Khan, N., Middleton, M., Wiktorowicz, G., Dauser, T., Roberts, T., & Wilms, J. (2022). The impact of precession on the observed population of ULXs. Monthly Notices of the Royal Astronomical Society, 509(2), 2493-2506. https://doi.org/10.1093/mnras/stab3049
• Alston, W., Pinto, C., Barret, D., D'Ai, A., Del Santo, M., Earnshaw, H., …Ambrosi, E. (2021). Quasi-periodic dipping in the ultraluminous X-ray source, NGC 247 ULX-1. Monthly Notices of the Royal Astronomical Society, 505(3), 3722-3729. https://doi.org/10.1093/mnras/stab1473
• Pinto, C., Soria, R., Walton, D., D'Ai, A., Pintore, F., Kosec, P., …Fabian, A. (2021). XMM-Newton campaign on the ultraluminous X-ray source NGC 247 ULX-1: outflows. Monthly Notices of the Royal Astronomical Society, 505(4), 5058-5074. https://doi.org/10.1093/mnras/stab1648
• Robba, A., Pinto, C., Walton, D., Soria, R., Kosec, P., Pintore, F., …Fabian, A. (2021). Broadband X-ray spectral variability of the pulsing ULX NGC 1313 X-2. Astronomy & Astrophysics, 652, Article A118. https://doi.org/10.1051/0004-6361/202140884
• Fuerst, F., Walton, D., Heida, M., Bachetti, M., Pinto, C., Middleton, M., …Wilms, J. (2021). Long-term pulse period evolution of the ultra-luminous X-ray pulsar NGC 7793 P13. Astronomy & Astrophysics, 651, Article A75. https://doi.org/10.1051/0004-6361/202140625
• Walton, D., Heida, M., Bachetti, M., Fürst, F., Brightman, M., Earnshaw, H., …Stern, D. (2021). A new transient ultraluminous X-ray source in NGC 7090. Monthly Notices of the Royal Astronomical Society, 501(1), 1002-1012. https://doi.org/10.1093/mnras/staa3666
• D'a, ì. A., Pinto, C., Del Santo, M., Pintore, F., Soria, R., Robba, A., …Walton, D. (2021). The chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1. Monthly Notices of the Royal Astronomical Society, 507(4), 5567-5579. https://doi.org/10.1093/mnras/stab2427
• López, K., Heida, M., Jonker, P., Torres, M., Roberts, T., Walton, D., …Harrison, F. (2020). NIR Counterparts to ULXs (III): Completing the photometric survey and selected spectroscopic results*. Monthly Notices of the Royal Astronomical Society, 497(1), 917-932. https://doi.org/10.1093/mnras/staa1920
• Walton, D., Pinto, C., Nowak, M., Bachetti, M., Sathyaprakash, R., Kara, E., …Kosec, P. (2020). The unusual broad-band X-ray spectral variability of NGC 1313 X-1 seen with XMM–Newton, Chandra, and NuSTAR. Monthly Notices of the Royal Astronomical Society, 494(4), 6012-6029. https://doi.org/10.1093/mnras/staa1129
• Rodríguez Castillo, G., Israel, G., Belfiore, A., Bernardini, F., Esposito, P., Pintore, F., …Wolter, A. (2020). Discovery of a 2.8 s Pulsar in a 2 Day Orbit High-mass X-Ray Binary Powering the Ultraluminous X-Ray Source ULX-7 in M51. Astrophysical Journal, 895(1), Article 60. https://doi.org/10.3847/1538-4357/ab8a44
• Pinto, C., Walton, D., Kara, E., Parker, M., Soria, R., Kosec, P., …Barret, D. (2020). XMM–Newton campaign on ultraluminous X-ray source NGC 1313 X-1: wind versus state variability. Monthly Notices of the Royal Astronomical Society, 492(4), 4646-4665. https://doi.org/10.1093/mnras/staa118
• Earnshaw, H. P., Heida, M., Brightman, M., Fürst, F., Harrison, F. A., Jaodand, A., …Walton, D. J. (2020). The (re)appearance of NGC 925 ULX-3, a new transient ULX. Astrophysical Journal, 891(2), Article 153. https://doi.org/10.3847/1538-4357/ab77b8
• Kara, E., Pinto, C., Walton, D., Alston, W., Bachetti, M., Barret, D., …Webb, N. (2020). Discovery of a soft X-ray lag in the Ultraluminous X-ray Source NGC 1313 X-1. Monthly Notices of the Royal Astronomical Society, 491(4), 5172-5178. https://doi.org/10.1093/mnras/stz3318
• Pinto, C., Mehdipour, M., Walton, D., Middleton, M., Roberts, T., Fabian, A., …Ness, J. -. (2020). Thermal stability of winds driven by radiation pressure in super-Eddington accretion discs. Monthly Notices of the Royal Astronomical Society, 491(4), 5702-5716. https://doi.org/10.1093/mnras/stz3392
• Pintore, F., Marelli, M., Salvaterra, R., Israel, G., Rodríguez Castillo, G., Esposito, P., …Middleton, M. (2020). The Ultraluminous X-ray sources population of the galaxy NGC 7456. Astrophysical Journal, 890(2), Article 166. https://doi.org/10.3847/1538-4357/ab6ffd
• Song, X., Walton, D., Lansbury, G., Evans, P., Fabian, A., Earnshaw, H., & Roberts, T. (2020). The Hunt for Pulsating Ultraluminous X-ray Sources. Monthly Notices of the Royal Astronomical Society, 491(1), 1260-1277. https://doi.org/10.1093/mnras/stz3036
• Middleton, M., Fragile, P., Ingram, A., & Roberts, T. (2019). The Lense-Thirring timing-accretion plane for ULXs. Monthly Notices of the Royal Astronomical Society, 489(1), 282-296. https://doi.org/10.1093/mnras/stz2005
• Anderson, G., Miller-Jones, J., Middleton, M., Soria, R., Swartz, D., Urquhart, R., …Roberts, T. (2019). Discovery of a radio transient in M81. Monthly Notices of the Royal Astronomical Society, 489(1), 1181-1196. https://doi.org/10.1093/mnras/stz1303
• López, K., Jonker, P., Heida, M., Torres, M., Roberts, T., Walton, D., …Harrison, F. (2019). Discovery and analysis of a ULX nebula in NGC 3521★. Monthly Notices of the Royal Astronomical Society, 489(1), 1249-1264. https://doi.org/10.1093/mnras/stz2127
• Sathyaprakash, R., Roberts, T., & Siwek, M. (2019). Observational limits on the X-ray emission from the bubble nebula surrounding Ho IX X-1. Monthly Notices of the Royal Astronomical Society, 488(4), 4614-4622. https://doi.org/10.1093/mnras/stz2022
• Sathyaprakash, R., Roberts, T., Walton, D., Fuerst, F., Bachetti, M., Pinto, C., …Soria, R. (2019). The discovery of weak coherent pulsations in the ultraluminous X-ray source NGC 1313 X-2. Monthly Notices of the Royal Astronomical Society, 488(1), L35-L40. https://doi.org/10.1093/mnrasl/slz086
• Earnshaw, H., Roberts, T., Middleton, M., Walton, D., & Mateos, S. (2019). A new, clean catalogue of extragalactic non-nuclear X-ray sources in nearby galaxies. Monthly Notices of the Royal Astronomical Society, 483(4), 5554-5573. https://doi.org/10.1093/mnras/sty3403
• Brightman, M., Baloković, M., Koss, M., Alexander, D., Annuar, A., Earnshaw, H., …Zezas, A. (2018). A long hard-X-ray look at the dual active galactic nuclei of M51 with NuSTAR. Astrophysical Journal, 867(2), Article 110. https://doi.org/10.3847/1538-4357/aae1ae
• Earnshaw, H., Roberts, T., & Sathyaprakash, R. (2018). Searching for propeller-phase ULXs in the XMM-Newton Serendipitous Source Catalogue. Monthly Notices of the Royal Astronomical Society, 476(3), 4272-4277. https://doi.org/10.1093/mnras/sty501
• Middleton, M., Fragile, P., Bachetti, M., Brightman, M., Jiang, Y., Ho, W., …Gehrels, N. (2018). Lense-Thirring precession in ULXs as a possible means to constrain the neutron star equation-of-state. Monthly Notices of the Royal Astronomical Society, 475(1), 154-166. https://doi.org/10.1093/mnras/stx2986
• Kaaret, P., Feng, H., & Roberts, T. P. (2017). Ultraluminous X-Ray Sources. Annual Review of Astronomy and Astrophysics, 55(1), 303-341. https://doi.org/10.1146/annurev-astro-091916-055259
• Siwek, M., Sadowski, A., Narayan, R., Roberts, T., & Soria, R. (2017). Optical and X-ray luminosity of expanding nebulae around ultraluminous X-ray sources. Monthly Notices of the Royal Astronomical Society, 470(1), 361-371. https://doi.org/10.1093/mnras/stx1185
• López, K., Heida, M., Jonker, P., Torres, M., Roberts, T., Walton, D., …Harrison, F. (2017). A Systematic Search for Near-Infrared Counterparts of Nearby Ultraluminous X-ray sources (II). Monthly Notices of the Royal Astronomical Society, 469(1), 671-682. https://doi.org/10.1093/mnras/stx857
• Pinto, C., Alston, W., Soria, R., Middleton, M., Walton, D., Sutton, A., …Roberts, T. (2017). From ultraluminous X-ray sources to ultraluminous supersoft sources: NGC 55 ULX, the missing link. Monthly Notices of the Royal Astronomical Society, 468(3), 2865-2883. https://doi.org/10.1093/mnras/stx641
• Earnshaw, H., & Roberts, T. (2017). Soft Extragalactic X-Ray Binaries at the Eddington Threshold. Monthly Notices of the Royal Astronomical Society, 467(3), 2690-2705. https://doi.org/10.1093/mnras/stx308
• Sutton, A., Swartz, D., Roberts, T., Middleton, M., Soria, R., & Done, C. (2017). Crossing the Eddington Limit: Examining Disk Spectra at High Accretion Rates. Astrophysical Journal, 836(1), Article 48. https://doi.org/10.3847/1538-4357/836/1/48
• Dudik, R., Berghea, C., Roberts, T., Grise, F., Singh, A., Pagano, R., & Winter, L. (2016). SPITZER IRAC observations of IR excess in Holmberg IX X-1: A circumbinary disk or a variable jet?. Astrophysical Journal, 831(1), Article 88. https://doi.org/10.3847/0004-637x/831/1/88
• Luangtip, W., Roberts, T., & Done, C. (2016). The X-ray spectral evolution of the ultraluminous X-ray source Holmberg IX X-1. Monthly Notices of the Royal Astronomical Society, 460(4), 4417-4432. https://doi.org/10.1093/mnras/stw1282
• Walton, D., Fürst, F., Bachetti, M., Barret, D., Brightman, M., Fabian, A., …Webb, N. (2016). A 78 Day X-Ray Period Detected from NGC 5907 ULX1 by Swift. Astrophysical Journal Letters, 827(1), Article L13. https://doi.org/10.3847/2041-8205/827/1/l13
• Pintore, F., Zampieri, L., Sutton, A., Roberts, T., Middleton, M., & Gladstone, J. (2016). The ultraluminous X-ray source NGC 5643 ULX1: a large stellar mass black hole accreting at super-Eddington rates?. Monthly Notices of the Royal Astronomical Society, 459(1), 455-466. https://doi.org/10.1093/mnras/stw669
• Heida, M., Jonker, P., Torres, M., Roberts, T., Walton, D., Moon, D., …Harrison, F. (2016). Keck/MOSFIRE spectroscopy of five ULX counterparts. Monthly Notices of the Royal Astronomical Society, 459(1), 771-778. https://doi.org/10.1093/mnras/stw695
• Roberts, T., Middleton, M., Sutton, A., Mezcua, M., Walton, D., & Heil, L. (2016). ULX behaviour: The ultraluminous state, winds and interesting anomalies. Astronomical Notes, 377(4-5), 534-540. https://doi.org/10.1002/asna.201612343
• Earnshaw, H. M., Roberts, T. P., Heil, L. M., Mezcua, M., Walton, D. J., Done, C., …Sutton, A. D. (2016). A variable ULX and possible IMBH candidate in M51a. Monthly Notices of the Royal Astronomical Society, 456(4), 3840-3854. https://doi.org/10.1093/mnras/stv2945
• Middleton, M. J., Walton, D. J., Fabian, A., Roberts, T. P., Heil, L., Pinto, C., …Sutton, A. (2015). Diagnosing the accretion flow in ultraluminous X-ray sources using soft X-ray atomic features. Monthly Notices of the Royal Astronomical Society, 454(3), 3134-3142. https://doi.org/10.1093/mnras/stv2214
• Sutton, A., Roberts, T., & Middleton, M. (2015). X-ray spectral residuals in NGC 5408 X-1: diffuse emission from star formation, or the signature of a super-Eddington wind?. Astrophysical Journal, 814(1), Article 73. https://doi.org/10.1088/0004-637x/814/1/73
• Heida, M., Torres, M., Jonker, P., Servillat, M., Repetto, S., Roberts, T., …Harrison, F. (2015). Discovery of a red supergiant counterpart to RX J004722.4-252051, a ULX in NGC 253. Monthly Notices of the Royal Astronomical Society, 453(4), 3510-3518. https://doi.org/10.1093/mnras/stv1853
• Hernández-García, L., Vaughan, S., Roberts, T., & Middleton, M. (2015). X-ray time lags and non-linear variability in the ultraluminous X-ray sources NGC 5408 X-1 and NGC 6946 X-1. Monthly Notices of the Royal Astronomical Society, 453(3), 2877-2884. https://doi.org/10.1093/mnras/stv1830
• Prestwich, A., Jackson, F., Kaaret, P., Brorby, M., Roberts, T., Saar, S., & Yukita, M. (2015). Ultra-luminous X-Ray Sources in HARO II and the Role of X-Ray Binaries in Feedback in Lyα Emitting Galaxies. Astrophysical Journal, 812(2), Article 166. https://doi.org/10.1088/0004-637x/812/2/166
• Sutton, A., Roberts, T., Gladstone, J., & Walton, D. (2015). The hyperluminous X-ray source candidate in IC 4320: another HLX bites the dust. Monthly Notices of the Royal Astronomical Society, 450(1), 787-793. https://doi.org/10.1093/mnras/stv505
• Mezcua, M., Roberts, T., Lobanov, A., & Sutton, A. (2015). The powerful jet of an off-nuclear intermediate-mass black hole in the spiral galaxy NGC 2276. Monthly Notices of the Royal Astronomical Society, 448(2), 1893-1899. https://doi.org/10.1093/mnras/stv143
• Middleton, M., Heil, L., Pintore, F., Walton, D., & Roberts, T. (2015). A spectral-timing model for ULXs in the supercritical regime. Monthly Notices of the Royal Astronomical Society, 447(4), 3243-3263. https://doi.org/10.1093/mnras/stu2644
• Walton, D., Harrison, F., Bachetti, M., Barret, D., Boggs, S., Christensen, F., …Zhang, W. (2015). NuSTAR and XMM-Newton observations of the extreme ultraluminous X-ray source NGC 5907 ULX1 : a vanishing act. Astrophysical Journal, 799(2), Article 122. https://doi.org/10.1088/0004-637x/799/2/122
• Luangtip, W., Roberts, T., Mineo, S., Lehmer, B., Alexander, D., Jackson, F., …Fischer, J. (2015). A deficit of ultraluminous X-ray sources in luminous infrared galaxies. Monthly Notices of the Royal Astronomical Society, 446(1), 470-492. https://doi.org/10.1093/mnras/stu2086
• Sutton, A. D., Done, C., & Roberts, T. P. (2014). Irradiated, colour-temperature-corrected accretion discs in ultraluminous X-ray sources. Monthly Notices of the Royal Astronomical Society, 444(3), 2415-2427. https://doi.org/10.1093/mnras/stu1597
• Heida, M., Jonker, P., Torres, M., Kool, E., Servillat, M., Roberts, T., …Harrison, F. (2014). Near-infrared counterparts of ultraluminous X-ray sources. Monthly Notices of the Royal Astronomical Society, 442(2), 1054-1067. https://doi.org/10.1093/mnras/stu928
• Middleton, M., Walton, D., Roberts, T., & Heil, L. (2014). Broad absorption features in wind-dominated ultraluminous X-ray sources?. Monthly Notices of the Royal Astronomical Society, 438(1), L51-L55. https://doi.org/10.1093/mnrasl/slt157
• Mezcua, M., Roberts, T., Sutton, A., & Lobanov, A. (2013). Radio observations of extreme ULXs : revealing the most powerful ULX radio nebula ever or the jet of an intermediate-mass black hole?. Monthly Notices of the Royal Astronomical Society, 436(4), 3128-3134. https://doi.org/10.1093/mnras/stt1794
• Sutton, A., Roberts, T., & Middleton, M. (2013). The ultraluminous state revisited : fractional variability and spectral shape as diagnostics of super-Eddington accretion. Monthly Notices of the Royal Astronomical Society, 435(2), 1758-1775. https://doi.org/10.1093/mnras/stt1419
• Sutton, A., Roberts, T., Gladstone, J., Farrell, S., Reilly, E., Goad, M., & Gehrels, N. (2013). A bright ultraluminous X-ray source in NGC 5907. Monthly Notices of the Royal Astronomical Society, 434(2), 1702-1712. https://doi.org/10.1093/mnras/stt1133
• Walton, D., Miller, J., Harrison, F., Fabian, A., Roberts, T., Middleton, M., & Reis, R. (2013). X-Ray Outflows and Super-Eddington Accretion in the Ultraluminous X-Ray Source Holmberg IX X-1. Astrophysical Journal Letters, 773(1), Article L9. https://doi.org/10.1088/2041-8205/773/1/l9
• Heida, M., Jonker, P., Torres, M., Roberts, T., Miniutti, G., Fabian, A., & Ratti, E. (2013). VLT/FORS2 observations of four high-luminosity ULX candidates. Monthly Notices of the Royal Astronomical Society, 433(1), 681-687. https://doi.org/10.1093/mnras/stt756
• Prestwich, A., Tsantaki, M., Zezas, A., Jackson, F., Roberts, T., Foltz, R., …Kalogera, V. (2013). Ultra-luminous X-ray sources in the most metal poor galaxies. Astrophysical Journal, 769(2), Article 92. https://doi.org/10.1088/0004-637x/769/2/92
• Gladstone, J., Copperwheat, C., Heinke, C., Roberts, T., Cartwright, T., Levan, A., & Goad, M. (2013). Optical Counterparts of the Nearest Ultraluminous X-Ray Sources. Astrophysical Journal Supplement, 206(2), Article 14. https://doi.org/10.1088/0067-0049/206/2/14
• Nebot Gómez-Morán, A., Motch, C., Barcons, X., Carrera, F., Ceballos, M., Cropper, M., …Webb, N. (2013). The XMM-Newton SSC survey of the Galactic plane. Astronomy & Astrophysics, 553, Article A12. https://doi.org/10.1051/0004-6361/201220308
• Middleton, M. J., Miller-Jones, J. C., Markoff, S., Fender, R., Henze, M., Hurley-Walker, N., …Grainge, K. (2013). Bright radio emission from an ultraluminous stellar-mass microquasar in M 31. Nature, 493(7431), 187-190. https://doi.org/10.1038/nature11697
• Roberts, T., Fabbiano, G., Luo, B., Kim, D., Strader, J., Middleton, M., …Zezas, A. (2012). A variable ultraluminous X-ray source in a globular cluster in NGC 4649. Astrophysical Journal, 760(2), Article 135. https://doi.org/10.1088/0004-637x/760/2/135
• Jonker, P., Heida, M., Torres, M., Miller-Jones, J., Fabian, A., Ratti, E., …Roberts, T. (2012). The Nature of the Bright ULX X-2 in NGC 3921: A Chandra Position and HST Candidate Counterpart. Astrophysical Journal, 758(1), Article 28. https://doi.org/10.1088/0004-637x/758/1/28
• Gruyters, P., Exter, K., Roberts, T., & Rappaport, S. (2012). A VLT VIMOS IFU study of the ionisation nebula surrounding the supersoft X-ray source CAL 83. Astronomy & Astrophysics, 544, Article A86. https://doi.org/10.1051/0004-6361/201219051
• Sutton, A. D., Roberts, T. P., Walton, D. J., Gladstone, J. C., & Scott, A. E. (2012). The most extreme ultraluminous X-ray sources: evidence for intermediate-mass black holes?. Monthly Notices of the Royal Astronomical Society, 423(2), 1154-1177. https://doi.org/10.1111/j.1365-2966.2012.20944.x
• Jackson, F., Roberts, T., Alexander, D., Gelbord, J., Goulding, A., Ward, M., …Watson, M. (2012). On the nature of high X-ray luminosities in Sloan Digital Sky Survey galaxies. Monthly Notices of the Royal Astronomical Society, 422(1), 2-13. https://doi.org/10.1111/j.1365-2966.2011.20164.x
• Middleton, M., Sutton, A., Roberts, T., Jackson, F., & Done, C. (2012). The missing link: a low mass X-ray binary in M31 seen as an ultraluminous X-ray source. Monthly Notices of the Royal Astronomical Society, 420(4), 2969-2977. https://doi.org/10.1111/j.1365-2966.2011.20145.x
• Prestwich, A., Galache, J., Linden, T., Kalogera, V., Zezas, A., Roberts, T., …Trinchieri, G. (2012). Chandra observations of the collisional ring galaxy NGC 922. Astrophysical Journal, 747(2), Article 150. https://doi.org/10.1088/0004-637x/747/2/150
• Rasmussen, J., Bai, X., Mulchaey, J. S., van Gorkom, J., Jeltema, T. E., Zabludoff, A. I., …Roberts, T. P. (2012). Hot and cold galactic gas in the NGC 2563 galaxy group. Astrophysical Journal, 747(1), Article 31. https://doi.org/10.1088/0004-637x/747/1/31
• Middleton, M., Cackett, E., Shaw, C., Ramsay, G., Roberts, T., & Wheatley, P. (2012). Identifying a new intermediate polar using XMM-Newton and INTEGRAL. Monthly Notices of the Royal Astronomical Society, 419(1), 336-341. https://doi.org/10.1111/j.1365-2966.2011.19696.x
• Middleton, M., Sutton, A., & Roberts, T. (2011). X-ray spectral evolution in the ultraluminous X-ray source M33 X-8. Monthly Notices of the Royal Astronomical Society, 417(1), 464-471. https://doi.org/10.1111/j.1365-2966.2011.19285.x
• Walton, D., Roberts, T., Mateos, S., & Heard, V. (2011). 2XMM ultraluminous X-ray source candidates in nearby galaxies. Monthly Notices of the Royal Astronomical Society, 416(3), 1844-1861. https://doi.org/10.1111/j.1365-2966.2011.19154.x
• Walton, D., Gladstone, J., Roberts, T., Fabian, A., Caballero-Garcia, M., Done, C., & Middleton, M. (2011). Comparing spectral models for ultraluminous X-ray sources with NGC 4517 ULX1. Monthly Notices of the Royal Astronomical Society, 414(2), 1011-1022. https://doi.org/10.1111/j.1365-2966.2011.18397.x
• Jenkins, L., Brandt, W., Colbert, E., Koribalski, B., Kuntz, K., Levan, A., …Zezas, A. (2011). Investigating the Nuclear Activity of Barred Spiral Galaxies: The Case of NGC 1672. Astrophysical Journal, 734(1), Article 33. https://doi.org/10.1088/0004-637x/734/1/33
• Roberts, T., Gladstone, J., Goulding, A., Swinbank, A., Ward, M., Goad, M., & Levan, A. (2011). (No) dynamical constraints on the mass of the black hole in two ULXs. Astronomical Notes, 332(4), 398-401. https://doi.org/10.1002/asna.201011508
• Middleton, M., Roberts, T., Done, C., & Jackson, F. (2011). Does NGC 5408 X-1 really contain an intermediate-mass black hole?. Astronomical Notes, 332, 388-391. https://doi.org/10.1002/asna.201011506
• Walton, D., Gladstone, J., Roberts, T., & Fabian, A. (2011). A large catalogue of ultraluminous X-ray source candidates in nearby galaxies. Astronomical Notes, 332(4), 354-357. https://doi.org/10.1002/asna.201011498
• Gladstone, J., Roberts, T., & Done, C. (2011). Unlocking the nature of ultraluminous X-ray sources using their X-ray spectra. Astronomical Notes, 332(4), 345-348. https://doi.org/10.1002/asna.201011496
• Sutton, A., Roberts, T., & Walton, D. (2011). Key results from an XMM-Newton and Chandra study of a new sample of extreme ULXs from the 2XMM catalogue. Astronomical Notes, 332(4), 362-366. https://doi.org/10.1002/asna.201011500
• Russell, D., Yang, Y., Gladstone, J., Wiersema, K., & Roberts, T. (2011). New observations of ULX supershells, and their implications. Astronomical Notes, 332(4), 371-374. https://doi.org/10.1002/asna.201011502
• Middleton, M., Roberts, T., Done, C., & Jackson, F. (2011). Challenging times: a re-analysis of NGC 5408 X-1. Monthly Notices of the Royal Astronomical Society, 411(1), 644-652. https://doi.org/10.1111/j.1365-2966.2010.17712.x
• Richings, A., Fabbiano, G., Wang, J., & Roberts, T. (2010). The Hot Interstellar Medium of the Interacting Galaxy NGC 4490. Astrophysical Journal, 723(2), 1375-1392. https://doi.org/10.1088/0004-637x/723/2/1375
• Lehmer, B., Alexander, D., Bauer, F., Brandt, W., Goulding, A., Jenkins, L., …Roberts, T. (2010). A Chandra Perspective on Galaxy-wide X-ray Binary Emission and its Correlation with Star Formation Rate and Stellar Mass: New Results from Luminous Infrared Galaxies. Astrophysical Journal, 724(1), 559-571. https://doi.org/10.1088/0004-637x/724/1/559
• Vierdayanti, K., Done, C., Roberts, T., & Mineshige, S. (2010). X-ray spectral variability in the ultraluminous X-ray source Holmberg IX X-1. Monthly Notices of the Royal Astronomical Society, 403(3), 1206-1212. https://doi.org/10.1111/j.1365-2966.2009.16210.x
• Irwin, J., Brink, T., Bregman, J., & Roberts, T. (2010). Evidence for a Stellar Disruption by an Intermediate-mass Black Hole in an Extragalactic Globular Cluster. Astrophysical Journal Letters, 712(1), L1-L4. https://doi.org/10.1088/2041-8205/712/1/l1
• Zampieri, L., & Roberts, T. (2009). Low-metallicity natal environments and black hole masses in Ultraluminous X-ray Sources. Monthly Notices of the Royal Astronomical Society, 400(2), 677-686. https://doi.org/10.1111/j.1365-2966.2009.15509.x
• Gladstone, J., Roberts, T., & Done, C. (2009). The ultraluminous state. Monthly Notices of the Royal Astronomical Society, 397(4), 1836-1851. https://doi.org/10.1111/j.1365-2966.2009.15123.x
• Heil, L., Vaughan, S., & Roberts, T. (2009). A Systematic Study of Variability in a Sample of Ultraluminous X-ray Sources. Monthly Notices of the Royal Astronomical Society, 397(2), 1061-1072. https://doi.org/10.1111/j.1365-2966.2009.15068.x
• Gladstone, J., & Roberts, T. (2009). The ultraluminous X-ray source population of NGC 4485/4490. Monthly Notices of the Royal Astronomical Society, 397(1), 124-134. https://doi.org/10.1111/j.1365-2966.2009.14937.x
• Berghea, C., Weaver, K., Colbert, E., & Roberts, T. (2008). Testing the Paradigm that Ultra-Luminous X-ray Sources as a Class Represent Accreting Intermediate-Mass Black Holes. Astrophysical Journal, 687(1), 471-487. https://doi.org/10.1086/591722
• Roberts, T., Levan, A., & Goad, M. (2008). New Hubble Space Telescope imaging of the counterparts to six ultraluminous X-ray sources. Monthly Notices of the Royal Astronomical Society, 387(1), 73-78. https://doi.org/10.1111/j.1365-2966.2008.13293.x
• Barcons, X., Carrera, F., Ceballos, M., Page, M., Bussons-Gordo, J., Corral, A., …Ziaeepour, H. (2007). The XMM-Newton serendipitous survey. IV. Optical identification of the XMM-Newton medium sensitivity survey (XMS). Astronomy & Astrophysics, 476(3), 1191-1203. https://doi.org/10.1051/0004-6361%3A20077606
• Prestwich, A., Kilgard, R., Crowther, P., Carpano, S., Pollock, A., Zezas, A., …Ward, M. (2007). The Orbital Period of the Wolf-Rayet Binary IC 10 X-1: Dynamic Evidence that the Compact Object Is a Black Hole. Astrophysical Journal Letters, 669(1), L21-L24. https://doi.org/10.1086/523755
• Roberts, T. (2007). X-ray observations of ultraluminous X-ray sources. Astrophysics and Space Science, 311(1-3), 203-212. https://doi.org/10.1007/s10509-007-9547-z
• Warwick, R., Jenkins, L., Read, A., Roberts, T., & Owen, R. (2007). An XMM-Newton view of M101 - III. Diffuse X-ray emission. Monthly Notices of the Royal Astronomical Society, 376(4), 1611-1620. https://doi.org/10.1111/j.1365-2966.2007.11571.x
• Vazquez, G., Hornschemeier, A., Colbert, E., Roberts, T., Ward, M., & Malhotra, S. (2007). Constraints on accretion in ultraluminous X-ray sources from Spitzer IRS observations of NGC 4485/4490: Infrared diagnostic diagrams. Astrophysical Journal Letters, 658(1), L21-L24. https://doi.org/10.1086/513423
• Roberts, T., Kilgard, R., Warwick, R., Goad, M., & Ward, M. (2006). Chandra monitoring observations of the ultraluminous X-ray source NGC 5204 X-1. Monthly Notices of the Royal Astronomical Society, 371(4), 1877-1890. https://doi.org/10.1111/j.1365-2966.2006.10821.x
• Stobbart, A., Roberts, T., & Warwick, R. (2006). The X-ray properties of the dwarf Magellanic-type galaxy NGC 55. Monthly Notices of the Royal Astronomical Society, 370(1), 25-42
• Stobbart, A., Roberts, T., & Wilms, J. (2006). XMM-Newton observations of the brightest ultraluminous X-ray sources. Monthly Notices of the Royal Astronomical Society, 368(1), 397-413. https://doi.org/10.1111/j.1365-2966.2006.10112.x
• Goad, M., Roberts, T., Reeves, J., & Uttley, P. (2006). A deep XMM-Newton observation of the ultraluminous X-ray source Holmberg II X-1: the case against a 1000-M-circle dot black hole. Monthly Notices of the Royal Astronomical Society, 365(1), 191-198
• Krauss, M., Kilgard, R., Garcia, M., Roberts, T., & Prestwich, A. (2005). M74 X-1 (CXOU J013651.1+154547): An extremely variable ultraluminous X-ray source. Astrophysical Journal, 630(1), 228-237
• Watson, M., Roberts, T., Akiyama, M., & Ueda, Y. (2005). Discovery of multiple ultra-luminous X-ray sources in the galaxy KUG 0214-057. Astronomy & Astrophysics, 437(3), 899-904
• Roberts, T., Warwick, R., Ward, M., Goad, M., & Jenkins, L. (2005). XMM-Newton EPIC observations of the ultraluminous X-ray source NGC 5204 X-1. Monthly Notices of the Royal Astronomical Society, 357(4), 1363-1369
• Jenkins, L., Roberts, T., Warwick, R., Kilgard, R., & Ward, M. (2005). An XMM-Newton view of M101 - II. Global X-ray source properties. Monthly Notices of the Royal Astronomical Society, 357(2), 401-419. https://doi.org/10.1111/j.1365-2966.2005.08645.x
• Jenkins, L., Roberts, T., Ward, M., & Zezas, A. (2005). XMM-Newton observations of the interacting galaxy pairs NGC 7771/0 and NGC 2342/1. Monthly Notices of the Royal Astronomical Society, 357(1), 109-123
• Jenkins, L., Roberts, T., Ward, M., & Zezas, A. (2004). XMM-Newton observations of the starburst merger galaxies NGC 3256 and NGC 3310. Monthly Notices of the Royal Astronomical Society, 352(4), 1335-1346
• Stobbart, A., Roberts, T., & Warwick, R. (2004). A dipping black hole X-ray binary candidate in NGC 55. Monthly Notices of the Royal Astronomical Society, 351(3), 1063-1070
• Roberts, T., Warwick, R., Ward, M., & Goad, M. (2004). Chandra observations of five ultraluminous X-ray sources in nearby galaxies (vol 349, pg 1193, 2004). Monthly Notices of the Royal Astronomical Society, 350(4), 1536-1536. https://doi.org/10.1111/j.1365-2966.2004.07891.x
• Jenkins, L., Roberts, T., Warwick, R., Kilgard, R., & Ward, M. (2004). An XMM-Newton view of M101 - I. The luminous X-ray source population. Monthly Notices of the Royal Astronomical Society, 349(2), 404-424. https://doi.org/10.1111/j.1365-2966.2004.07546.x
• Roberts, T., Warwick, R., Ward, M., & Goad, M. (2004). Chandra observations of five ultraluminous X-ray sources in nearby galaxies. Monthly Notices of the Royal Astronomical Society, 349(4), 1193-1210. https://doi.org/10.1111/j.1365-2966.2004.07626.x
• Roberts, T., Goad, M., Ward, M., & Warwick, R. (2003). The unusual supernova remnant surrounding the ultraluminous X-ray source IC 342 X-1. Monthly Notices of the Royal Astronomical Society, 342(3), 709-714. https://doi.org/10.1046/j.1365-8711.2003.06593.x
• Roberts, T., & Colbert, E. (2003). Chandra reveals a black hole X-ray binary within the ultraluminous supernova remnant MF 16. Monthly Notices of the Royal Astronomical Society, 341(4), L49-L54
• Roberts, T., Warwick, R., Ward, M., & Murray, S. (2002). A Chandra observation of the interacting pair of galaxies NGC 4485/4490. Monthly Notices of the Royal Astronomical Society, 337(2), 677-692. https://doi.org/10.1046/j.1365-8711.2002.05950.x
• Goad, M., Roberts, T., Knigge, C., & Lira, P. (2002). The optical counterpart of the ultraluminous X-ray source NGC 5204 X-1. Monthly Notices of the Royal Astronomical Society, 335(3), L67-L70
• Barcons, X., Carrera, F., Watson, M., McMahon, R., Aschenbach, B., Freyberg, M., …Worrall, D. (2002). The XMM-Newton serendipitous survey - II. First results from the AXIS high galactic latitude medium sensitivity survey. Astronomy & Astrophysics, 382(2), 522-536. https://doi.org/10.1051/0004-6361%3A20011615
• Schurch, N., Roberts, T., & Warwick, R. (2002). High-resolution X-ray imaging and spectroscopy of the core of NGC 4945 with XMM-Newton and Chandra. Monthly Notices of the Royal Astronomical Society, 335, 241-246
• Roberts, T., Goad, M., Ward, M., Warwick, R., O'Brien, P., Lira, P., & Hands, A. (2001). The identification of an optical counterpart to the super-Eddington X-ray source NGC 5204 X-1. Monthly Notices of the Royal Astronomical Society, 325(2), L7-L11. https://doi.org/10.1046/j.1365-8711.2001.04659.x
• Roberts, T., Schurch, N., & Warwick, R. (2001). Do LINER 2 galaxies harbour low-luminosity active galactic nuclei?. Monthly Notices of the Royal Astronomical Society, 324(3), 737-746
• Pietsch, W., Roberts, T., Sako, M., Freyberg, M., Read, A., Borozdin, K., …Ward, M. (2001). XMM-Newton observations of NGC 253: Resolving the emission components in the disk and nuclear area. Astronomy & Astrophysics, 365(1), L174-L180. https://doi.org/10.1051/0004-6361%3A20000068
• Watson, M., Augueres, J., Ballet, J., Barcons, X., Barret, D., Boer, M., …Worrall, D. (2001). The XMM-Newton serendipitous survey I. The role of XMM-Newton Survey Science Centre. Astronomy & Astrophysics, 365(1), L51-L59
• Hopwood, M., Evans, A., Roberts, T., Burleigh, M., Odenkirchen, M., Beardmore, A., …Eyres, S. (2000). A possible detection of diffuse extended X-ray emission in the environment of the globular cluster NGC 6779. Monthly Notices of the Royal Astronomical Society, 316(1), L5-L8
• Roberts, T., & Warwick, R. (2000). A ROSAT High Resolution Imager survey of bright nearby galaxies. Monthly Notices of the Royal Astronomical Society, 315(1), 98-114
• Roberts, T., Warwick, R., & Ohashi, T. (1999). The X-ray properties of the nearby LINER galaxy NGC 4736. Monthly Notices of the Royal Astronomical Society, 304(1), 52-60
• Warwick, R., & Roberts, T. (1998). The extragalactic X-ray background at 0.25 keV. Astronomical Notes, 319(1-2), 59-62
• Roberts, T., & Warwick, R. (1998). Nuclear X-ray sources in nearby galaxies. Astronomical Notes, 319(1-2), 34-34
• Barber, C., Roberts, T., & Warwick, R. (1996). Shadowing of the 0.25-keV extragalactic X-ray background by the disc of NGC 55. Monthly Notices of the Royal Astronomical Society, 282(1), 157-166