Very massive stars and the Eddington Limit (2012)
Journal Article
(2012). Very massive stars and the Eddington Limit

We use contemporary evolutionary models for Very Massive Stars (VMS) to assess whether the Eddington limit constrains the upper stellar mass limit. We also consider the interplay between mass and age for the wind properties and spectral morphology of... Read More about Very massive stars and the Eddington Limit.

Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014) (2012)
Journal Article
(2012). Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014). Astronomy & Astrophysics, https://doi.org/10.1051/0004-6361/201117751

[abridged] Many topical astrophysical research areas, such as the properties of planet host stars, the nature of the progenitors of different types of supernovae and gamma ray bursts, and the evolution of galaxies, require complete and homogeneous se... Read More about Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014).

The helium abundance in the ejecta of U Scorpii (2012)
Journal Article
(2012). The helium abundance in the ejecta of U Scorpii. Monthly Notices of the Royal Astronomical Society, 3414 -3415. https://doi.org/10.1111/j.1365-2966.2011.19803.x

U Scorpii (U Sco) is a recurrent nova which has been observed in outburst on 10 occasions, most recently in 2010. We present near-infrared (near-IR) and optical spectroscopy of the 2010 outburst of U Sco. The reddening of U Sco is found to be E(B - V... Read More about The helium abundance in the ejecta of U Scorpii.

Debris discs in the 27 Myr old open cluster IC4665 (2011)
Journal Article
(2011). Debris discs in the 27 Myr old open cluster IC4665. Monthly Notices of the Royal Astronomical Society, 2186-2198. https://doi.org/10.1111/j.1365-2966.2010.17835.x

We present Spitzer IRAC and MIPS 24um imaging of members of the 27+/-5Myr old open cluster IC 4665. Models for the assembly of terrestrial planets through planetesimal collisions and mergers predict episodic dust debris discs at this epoch. We determ... Read More about Debris discs in the 27 Myr old open cluster IC4665.

The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit (2010)
Journal Article
Hirschi. (2010). The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit. Monthly Notices of the Royal Astronomical Society, 731 -751. https://doi.org/10.1111/j.1365-2966.2010.17167.x

Spectroscopic analyses of H-rich WN5-6 stars within the young star clusters NGC 3603 and R136 are presented, using archival HST & VLT spectroscopy, & high spatial resolution near-IR photometry. We derive high T* for the WN stars in NGC 3603 (T*~42+/-... Read More about The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit.

The low-mass Initial Mass Function in the young cluster NGC 6611 (2009)
Journal Article
Jeffries, M. Oliveira, J., D. Jeffries, R., & Th. van Loon, J. (2009). The low-mass Initial Mass Function in the young cluster NGC 6611. Monthly Notices of the Royal Astronomical Society, 1034-1050. https://doi.org/10.1111/j.1365-2966.2008.14140.x

NGC 6611 is the massive young cluster (2-3 Myr) that ionises the Eagle Nebula. We present very deep photometric observations of the central region of NGC 6611 obtained with the Hubble Space Telescope and the following filters: ACS/WFC F775W and F850L... Read More about The low-mass Initial Mass Function in the young cluster NGC 6611.

Nucleosynthesis simulations for a wide range of nuclear production sites from NuGrid (2008)
Preprint / Working Paper
Herwig, F., Fryer, C., Hirschi, R., Bennett, M., L. Fryer, C., Diehl, S., Hungerford, A., Magkotsios, G., Pignatari, M., Rockefeller, G., Timmes, F., X. Timmes, F., & Young, P. Nucleosynthesis simulations for a wide range of nuclear production sites from NuGrid

Simulations of nucleosynthesis in astrophysical environments are at the intersection of nuclear physics reaction rate research and astrophysical applications, for example in the area of galactic chemical evolution or near-field cosmology. Unfortunate... Read More about Nucleosynthesis simulations for a wide range of nuclear production sites from NuGrid.

NuGrid: Toward High Precision Double-Degenerate Merger Simulations with SPH in 3D (2008)
Presentation / Conference Contribution
(2008, July). NuGrid: Toward High Precision Double-Degenerate Merger Simulations with SPH in 3D. Presented at 10th Symposium on Nuclei in the Cosmos, Mackinac Island, Michigan, USA

We present preliminary results from recent high-resolution double-degenerate merger simulations with the Smooth Particle Hydrodynamics (SPH) technique. We put particular emphasis on verification and validation in our effort and show the importance of... Read More about NuGrid: Toward High Precision Double-Degenerate Merger Simulations with SPH in 3D.

Nucleosynthetic Yields from "Collapsars" (2008)
Presentation / Conference Contribution
(2008, July). Nucleosynthetic Yields from "Collapsars". Presented at 10th Symposium on Nuclei in the Cosmos, Mackinac Island, Michigan, USA

The "collapsar" engine for gamma-ray bursts invokes as its energy source the failure of a normal supernova and the formation of a black hole. Here we present the results of the first three-dimensional simulation of the collapse of a massive star down... Read More about Nucleosynthetic Yields from "Collapsars".

The impact of stellar rotation on the CNO abundance patterns in the Milky Way at low metallicities (2008)
Presentation / Conference Contribution
(2008, July). The impact of stellar rotation on the CNO abundance patterns in the Milky Way at low metallicities. Presented at 10th Symposium on Nuclei in the Cosmos, Mackinac Island, Michigan, USA

We investigate the effect of new stellar models, which take rotation into account, computed for very low metallicities on the chemical evolution of the earliest phases of the Milky Way. We check the impact of these new stellar yields on a model for t... Read More about The impact of stellar rotation on the CNO abundance patterns in the Milky Way at low metallicities.

Nucleosynthesis Calculations from Core-Collapse Supernovae (2008)
Presentation / Conference Contribution
(2008, July). Nucleosynthesis Calculations from Core-Collapse Supernovae. Presented at 10th Symposium on Nuclei in the Cosmos, Mackinac Island, Michigan, USA

We review some of the uncertainties in calculating nucleosynthetic yields, focusing on the explosion mechanism. Current yield calculations tend to either use a piston, energy injection, or enhancement of neutrino opacities to drive an explosion. We s... Read More about Nucleosynthesis Calculations from Core-Collapse Supernovae.

Complete nucleosynthesis calculations for low-mass stars from NuGrid (2008)
Presentation / Conference Contribution
(2008, July). Complete nucleosynthesis calculations for low-mass stars from NuGrid. Presented at 10th Symposium on Nuclei in the Cosmos, Mackinac Island, Michigan, USA

Many nucleosynthesis and mixing processes of low-mass stars as they evolve from the Main Sequence to the thermal-pulse Asymptotic Giant Branch phase (TP-AGB) are well understood (although of course important physics components, e.g. rotation, magneti... Read More about Complete nucleosynthesis calculations for low-mass stars from NuGrid.

A survey for low mass spectroscopic binary stars in the young clusters around sigma Orionis and lambda Orionis (2008)
Journal Article
(2008). A survey for low mass spectroscopic binary stars in the young clusters around sigma Orionis and lambda Orionis. Monthly Notices of the Royal Astronomical Society, 2210-2224. https://doi.org/10.1111/j.1365-2966.2008.13008.x

We have obtained multi-epoch, high-resolution spectroscopy of 218 candidate low-mass stars and brown dwarfs in the young clusters around sigma Ori and lambda Ori. We find that 196 targets are cluster members based on their radial velocity, the equiva... Read More about A survey for low mass spectroscopic binary stars in the young clusters around sigma Orionis and lambda Orionis.

Testing convection in stellar models using detached eclipsing binaries (2006)
Presentation / Conference
(2006, August). Testing convection in stellar models using detached eclipsing binaries. Presented at IAUS 239 (Convection in Astrophysics), Prague

The fundamental properties of detached eclipsing binary stars can be measured very accurately, which could make them important objects for constraining the treatment of convection in theoretical stellar models. However, only four or five pieces of in... Read More about Testing convection in stellar models using detached eclipsing binaries.

The lithium depletion boundary in NGC 2547 as a test of pre-main-sequence evolutionary models (2005)
Journal Article
Jeffries, R. D., & Oliveira, J. M. (2005). The lithium depletion boundary in NGC 2547 as a test of pre-main-sequence evolutionary models. Monthly Notices of the Royal Astronomical Society, 358(1), 13 -29. https://doi.org/10.1111/j.1365-2966.2005.08820.x

Intermediate resolution spectroscopy from the ESO Very Large Telescope is analysed for 63 photometrically selected low-mass (0.08-0.30 Msun) candidates of the open cluster NGC 2547. We have confirmed membership for most of these stars using radial ve... Read More about The lithium depletion boundary in NGC 2547 as a test of pre-main-sequence evolutionary models.

Circumstellar discs around solar-mass stars in NGC 6611 (2005)
Journal Article
Oliveira, J., Jeffries, R., Th. van Loon, J., Littlefair, S., & Naylor, T. (2005). Circumstellar discs around solar-mass stars in NGC 6611. Monthly Notices of the Royal Astronomical Society: Letters, 358(1), L21-L24. https://doi.org/10.1111/j.1745-3933.2005.00020.x

We have performed IZJHKL' observations in NGC 6611, the young cluster that ionises the Eagle Nebula. We have discovered a rich pre-main sequence concentrated around the O-stars in the cluster. As measured by their L'-band excesses, at least 58% +/- 5... Read More about Circumstellar discs around solar-mass stars in NGC 6611.

Membership, binarity and accretion among very low-mass stars and brown dwarfs of the s Orionis cluster (2005)
Journal Article
Kenyon, M., Jeffries, R., Naylor, T., Oliveira, J., & Maxted, P. (2005). Membership, binarity and accretion among very low-mass stars and brown dwarfs of the s Orionis cluster. Monthly Notices of the Royal Astronomical Society, 356(1), 89 -106. https://doi.org/10.1111/j.1365-2966.2004.08455.x

Intermediate resolution (R=7000) spectroscopy is presented for 76 photometrically selected very low mass (0.04<M<0.3M_{sun}) candidate members of the Sigma Orionis cluster. More than two thirds appear to be genuine cluster members on the basis of Li...

Some updates on the role of magnetic fields in cataclysmic variables (2004)
Journal Article
Hellier, C. (2004). Some updates on the role of magnetic fields in cataclysmic variables

In this review talk I cover some recent developments in understanding the role that magnetic fields play in cataclysmic variables. I discuss the recent DNO--QPO unification models; the disk--magnetosphere boundary; some issues concerning the soft bla... Read More about Some updates on the role of magnetic fields in cataclysmic variables.

An L'-band survey for circumstellar discs around low-mass stars in the young σ Orionis cluster (2004)
Journal Article
Jeffries, R., Oliveira, J., & Van Loon, J. (2004). An L'-band survey for circumstellar discs around low-mass stars in the young σ Orionis cluster. Monthly Notices of the Royal Astronomical Society, 347(4), 1327 -1336. https://doi.org/10.1111/j.1365-2966.2004.07315.x

We present new K- and L'-band imaging of a representative sample of members of the young 3-5 Myr old sigma Orionis cluster. We identified objects with (K-L') excess by analysing colour-colour diagrams and comparing the observations with empirical mai... Read More about An L'-band survey for circumstellar discs around low-mass stars in the young σ Orionis cluster.

Cool stars in NGC 2547 and pre-main-sequence lithium depletion (2003)
Journal Article
Jeffries, R., Oliveira, J., Barrado y Navascués, D., & Stauffer, J. (2003). Cool stars in NGC 2547 and pre-main-sequence lithium depletion. Monthly Notices of the Royal Astronomical Society, 343(4), 1271-1284. https://doi.org/10.1046/j.1365-8711.2003.06768.x

We present the results of a spectroscopic survey of X-ray selected, low-mass candidate members of the young open cluster NGC 2547. Using a combination of photometry, spectroscopic indices and radial velocities we refine our candidate list and then us... Read More about Cool stars in NGC 2547 and pre-main-sequence lithium depletion.