Research

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Research Interests

The main interests of this research group is to study massive stars in a variety of environments, and so overlaps with other Sheffield astrophysics research groups involving studies of core-collapse supernovae, star clusters and starbursts.

Joachim Bestenlehner (2017-2024) has been leading analyses of the massive star populations in the Milky Way and Magellanic Clouds, including VLT/MUSE integral-field observations of NGC2070 in the LMC. Thaer Alkousa started his PhD studies on ULLYSES/XshootU datasets in Oct 2022. Gemma Rate has previously studied Wolf-Rayet stars with ESA GAIA (PhD completed in Dec 2020), Katie Tehrani (PhD completed in Nov 2019) investigated Wolf-Rayet stars at X-ray and optical wavelengths with honorary researcher Andy Pollock. 

We are also involved in the WHT/WEAVE galactic plane Stellar, Circumstellar and Interstellar Physics (SCIP) survey (PI Drew). Bestenlehner is a member of the upcoming VISTA/4MOST spectroscopic survey of the Magellanic Clouds 1001MC (PI Cioni) and I am member of the science team for CASTOR (PI Cote) which is a proposed Canadian-led UV mission (imaging and spectroscopy). 

R136 star cluster

Ultraviolet HST/STIS spectroscopy of the young, rich star cluster R136 is available in ASCII format (figure 12 from MNRAS paper, erg/s/cm^2/Ang):

We have undertaken spectral analyses of these stars from HST/STIS optical and UV  spectroscopy (see paper). Former students/postdocs are still involved in our research projects, notably Dr Saida Caballero-Nieves (FIT) involving massive binaries and the R136 star cluster, plus Dr Joanne Pledger (nee Bibby) (UCLan) who is involved with studying Wolf-Rayet populations in nearby star forming galaxies.

Large and Small Magellanic Clouds

Template optical spectra of Wolf-Rayet and related stars from our 2023 study are available via zenodo. Template optical spectra from our previous 2006 study are also available in ASCII format, below, for completeness (though more recent templates are recommended instead).

Large Magellanic Cloud

Small Magellanic Cloud

In addition, high quality VLT/UVES optical spectroscopy of Magellanic Cloud OB stars has been obtained, which are complementary to recent VLT/Xshooter datasets of ULLYSES (HST/STIS+COS) targets. 

Galactic Wolf-Rayet catalogue

We host a Galactic Wolf-Rayet catalogue. Template optical spectra of Milky Way Wolf-Rayet stars are available on zenodo from our 2023 study based on GAIA DR3 parallaxes. Earlier templates were produced based on estimated distances – primarily from this article for completeness.

Nitrogen sequence

Carbon sequence

Current projects

VLT/Large Programme (P112-115): FLAMES monitoring of ~1000 massive stars in the SMC (PI: Tomer Shenar, 116.7hr)

VLT (P112): Weighing the most massive stars with VLT/ERIS (PI: Julia Bodensteiner, 14.75hr)

HST/Director: ULLYSES (Hubble UV Legacy Library of Young Stars as Essential Standards, 1000 orbits) plus XShootU (ULLYSES and XShooter massive stars collaboration).

HST/Cycle 28: GULP (Galaxy UV Legacy Project, PI: E. Sabbi, 88 orbits).

Chandra/Cycle 15: The Tarantula – Revealed by X-rays (T-ReX): A definitive Chandra investigation of 30 Doradus (PI: L. Townsley, 2Msec).

HST/Cycle 20+22: Proper motions of isolated massive stars near the Galactic Centre (GO 12915, PI: D. Lennon, 18+18 orbits).

HST/Cycle 19+20: A massive star census of the starburst cluster R136 (GO 12465+13052: PI: P. Crowther, 32+7 orbits).

Herschel/OT2: Oxygen abundances in carbon-type Wolf-Rayet stars from PACS scan spectroscopy (PI: P. Crowther, 7.7 hours).

HST/Cycle 19: Weighing the most luminous main-sequence star in the Galaxy (GO 12615: PI: O. Schnurr, 14 orbits).

HST/Cycle 19+21: Proper motions of massive stars in 30 Doradus (GO 12499: PI: D. Lennon, 15+15 orbits).

VLT/Large Programme: VLT/FLAMES Tarantula Survey (PI: Chris Evans)