Dr. Abigail J. Frost

Dr. Abigail J. Frost

Astrophysicist studying massive stars and star formation

Talks and presentations

Massive stars from young to old - an investigation in the infrared

November 18, 2020

Seminar, University of Exeter Seminar Series, Virtual

Massive stars (>8Mdot) are important driving factors within our universe. Massive stars are the sole origin of the heavy elements within the Universe and their winds, outflows and supernovae enrich the interstellar medium and inhibit and trigger further stellar formation. On galactic scales, massive stars allow the inference of the mass of spatially unresolved galaxies and their SNe ejecta winds contribute to the galactic super-wind. Additionally, when a massive binary star system ends its life the gravitational wave events that occur can be felt across galaxies. In my talk I will discuss how I use infrared astronomy, and primarily interferometry, to study stars from young to old, describing how this regime can be used to study the dusty surrounding of forming massive stars to the evolved stellar multiple systems which are gravitational wave progenitors.

Unveiling substructures in disks around massive young stellar objects

October 12, 2020

Talk, ESO IR 2020, Virtual

Protostellar disks play key roles in the accretion process and formation of planetesimals for low-mass stars, and form various substructures, as different physical processes occur within them. Massive stars (M>8Mdot) form from the same clouds of dust and gas as low-mass stars and affect the both their own stellar environment and galaxies as a whole. Despite their importance, the formation of massive stars is poorly understood as they are deeply embedded, distant and rare, which introduces more observational challenges. While disks have recently been found around massive protostars massive disk evolution is yet to be constrained. In my talk, I will discuss our recent work which has, using a multi-scale analysis on a sample of massive young stellar objects (MYSOs), detected inner holes and gap-like substructures within the MYSO disks. I will also tie these geometrical traits to an independently determined evolutionary sequence and discuss what this means for disk evolution around MYSOs.

Investigating the origins of a single magnetic star within a binary system

July 13, 2020

Talk, MOBSTER-1 2020, Virtual

HD148937 is one of the three Galactic O-type sources belonging to the rare class of Of?p objects. These stars are characterised by recurrent spectral variations, the origin of which is found to be their strong magnetic fields. Originally thought to be a single star, long baseline near-IR interferometry with PIONIER has revealed HD148937 to be a binary system. In this presentation I will discuss our investigations into the source using a combination of multi-epoch GRAVITY and PIONIER data. These data reveal that the two components are of similar brightness but one star shows the BrG line in emission and the other in absorption, confirming that only one of the two stars is magnetic. Combining our data with existing spectroscopic measurements, a preliminary 3D orbit of the system can be obtained and subsequently absolute masses. We use these new constraints to discuss the evolutionary status of this unique object in the context of the origin of the magnetic star.

Unveiling the traits of MYSOs using a high-resolution, multi-scale analysis

September 01, 2019

Talk, StarformMapper Conference, York, UK

Young massive stars have the power to influence their surroundings from local to galactic scales. Despite this, their rarity and deeply embedded nature has limited our understanding of their formation. Work on single objects has given us valuable snapshots of the massive star formation process, but the fact remains that a lack of observational data prevents us from conclusively confirming its details. Combining various observational techniques can assist with this by providing a more complete view of MYSOs. My work fits 3D radiative transfer models to three different observables simultaneously to constrain the physical characteristics of MYSOs, tracing multiple scales through the combination of infrared interferometric data (~10mas resolution), imaging data (~100mas resolution) and SEDs. In this talk I will present the results obtained when applying this analysis to a sample of ~10 MYSOs. the largest sample analysed with such a dataset, and the resultant implications for massive star formation.

Unveiling the traits of MYSOs using a high-resolution, multi-scale analysis

June 01, 2019

Talk, From Stars to Planets II conference, Chalmers, Gothenburg, Sweden

Discs are a crucial component of the low-mass star formation process and many types of discs have been found around low-mass protostars. The transition disc [e.g. 1] is one such type and represents an evolutionary step from the young, accreting protoplanetary disc to the older debris disc when observed around low-mass stars. Massive protostars are deeply embedded and difficult to observe, and as such only a few cases of early-type Keplerian discs have been identified around O-type stars [2] [3] [4]. In this talk I will discuss our recent work [5] which infers the presence of the first observed transition disc around a massive young stellar object. By simultaneously fitting a 3D radiative transfer model to infrared interferometric data (MIDI, VLTI), a near-diffraction-limited image (VISIR, VLT) and a spectral energy distribution, we have constrained the geometry of an MYSO from ~10mas scales upwards. Our results show a that a disk is required to satisfy the interferometric data, that the inner circumstellar regions must cleared out to a radius three times the size of the dust sublimation radius, and that the MYSO is less dense than others of its class. These characteristics imply that this object may be one of the first observed examples of a transition disc phase around a massive young star, and a prime example to test theories of circumstellar disc dispersal and the end stages of accretion in massive protostars.

Unmasking massive forming stars using mid-IR observations and 3D radiative transfer modelling

July 01, 2018

Talk, Tracing the Flow: Galactic Environments and the Formation of Massive Stars, Windermere, UK

Young massive stars have huge influence, spanning from their own natal cradles to the galaxy as a whole. Despite their influence, the rarity of young massive stars combined with the fact that they are often deeply dust-embedded has limited our understanding of their formation. Work on single objects has given us valuable snapshots of the massive star formation process, but the fact remains that a lack of observational data prevents us from conclusively confirming the details. In order to truly understand the environments which are birthing these monsters, as many different observations and techniques must be combined and consolidated. My work fits 3D radiative transfer models to three different types of observational data simultaneously, thereby constraining the physical characteristics of the objects. I have interferometric data, images and SEDs for a sample of over 20 MYSOs and the overall goal is to search for trends between their features as the aforemention! ed analysis is performed on each individual object. My talk will briefly cover the topics of mid-infrared interferometry and imaging, my RT modelling, the work done on my sample so far and future work involving techniques such as sparse aperture masking.