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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...

Young stars and their circumstellar disks in the Sigma Orionis cluster (2004)
Conference Proceeding
M. Oliveira, J., D. Jeffries, R., Th. van Loon, J., & J. Kenyon, M. (2004). Young stars and their circumstellar disks in the Sigma Orionis cluster. In Open Issues in Local Star Formation (55–62). https://doi.org/10.1007/1-4020-2600-5_6

The sigma Orionis cluster is a young association evolving under the disruptive influence of its massive O-star namesake. We are analysing this cluster as part of a program to characterise the influence of O-stars on the early stages of stellar evolut... Read More about Young stars and their circumstellar disks in the Sigma Orionis cluster.

The Li Overabundance of J37: Diffusion or Accretion? (2004)
Journal Article
F. Ashwell, J., Jeffries, R. D., Smalley, B., P. Deliyannis, C., Steinhauer, A., & R. King, J. (2004). The Li Overabundance of J37: Diffusion or Accretion?. Proceedings of the International Astronomical Union, 2004(IAUS224), https://doi.org/10.1017/S1743921305009385

In September 2002 the discovery of a super Li-rich F-dwarf (J37) in NGC 6633, an iron poor analogue of the better studied Hyades and Praecepe open clusters, was announced. This unique star was thought to be the smoking gun for the action of diffusion... Read More about The Li Overabundance of J37: Diffusion or Accretion?.

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.

The lithium depletion boundary and the age of NGC 2547 (2003)
Journal Article
Oliveira, J., Barrado y Navascues, D., Jeffries, R., Devey, C., Navascues, D., Naylor, T., …Totten, E. (2003). The lithium depletion boundary and the age of NGC 2547. Monthly Notices of the Royal Astronomical Society, 342(2), 651 -663. https://doi.org/10.1046/j.1365-8711.2003.06592.x

We present the results of a photometric and spectroscopic survey of cool M dwarf candidates in the young open cluster NGC 2547. Using the 2dF fiber spectrograph, we have searched for the luminosity at which lithium remains unburned in an attempt to c... Read More about The lithium depletion boundary and the age of NGC 2547.

No disks around low-mass stars and brown dwarfs in the young sigma Orionis cluster? (2002)
Journal Article
Oliveira, J., Jeffries, R., Kenyon, M., Thompson, S., & Naylor, T. (2002). No disks around low-mass stars and brown dwarfs in the young sigma Orionis cluster?. Astronomy & Astrophysics, https://doi.org/10.1051/0004-6361%3A20011778

We report on the analysis of 2MASS near-infrared data of a sample of low-mass stars and brown dwarfs in the sigma Orionis cluster. Youth and cluster membership have been spectroscopically confirmed using the Li I spectral line. We find little evidenc... Read More about No disks around low-mass stars and brown dwarfs in the young sigma Orionis cluster?.

Ages, distances, and the initial mass functions of stellar clusters (2000)
Journal Article
Jeffries, R. (2000). Ages, distances, and the initial mass functions of stellar clusters. arXiv,

We provide a review of the current status of several topics on the ages, distances, and mass functions of open clusters, with a particular emphasis on illuminating the areas of uncertainty. Hipparcos has obtained parallaxes for nearby open clusters t... Read More about Ages, distances, and the initial mass functions of stellar clusters.

Rotation, activity and lithium in NGC 6475 (1997)
Journal Article
James, D. J., & Jeffries, R. D. (1997). Rotation, activity and lithium in NGC 6475. Monthly Notices of the Royal Astronomical Society, 292(2), 252–272. https://doi.org/10.1093/mnras/292.2.252

Radial and rotational velocities, chromospheric activity and lithium abundances are presented for an X-ray-selected sample of stars in the young (220 Myr) open cluster NGC 6475. Low-mass members of the cluster have been identified on the basis of pho... Read More about Rotation, activity and lithium in NGC 6475.

On the initial-final mass relation and maximum mass of white dwarf progenitors (1997)
Journal Article
Jeffries, R. (1997). On the initial-final mass relation and maximum mass of white dwarf progenitors. Monthly Notices of the Royal Astronomical Society, 288(3), 585–588. https://doi.org/10.1093/mnras/288.3.585

The four white dwarfs (WDs) discovered in the young open cluster NGC 2516 are crucial in defining the shape of the initial-final mass relation (IFMR) and upper mass limit for WD progenitors (Mwd). The cluster metallicity has been recently determined... Read More about On the initial-final mass relation and maximum mass of white dwarf progenitors.

Excess barium in a K dwarf-white dwarf binary system. (1996)
Journal Article
Jeffries, R. D., & Smalley, B. (1996). Excess barium in a K dwarf-white dwarf binary system. Astronomy and Astrophysics, 315, L19-L22

We present spectroscopic evidence for an excess of the s-process element barium, in the rapidly rotating, K-dwarf component of the wide binary system 2REJ0357+283. The secondary star is a hot white dwarf (WD) and our result argues for a model where t... Read More about Excess barium in a K dwarf-white dwarf binary system..

2RE J0241-525: a nearby post-T Tauri visual binary system (1996)
Journal Article
Jeffries, R., Buckley, D., James, D., & Stauffer, J. (1996). 2RE J0241-525: a nearby post-T Tauri visual binary system. Monthly Notices of the Royal Astronomical Society, 281(3), 1001–1015. https://doi.org/10.1093/mnras/281.3.1001

We present high-spatial-resolution X-ray observations, photometry and spectroscopy of the two low-mass, active stars proposed as optical counterparts to the extreme ultraviolet source 2RE J0241 —525 (=EUVE J0241—530). It is confirmed that both stars,... Read More about 2RE J0241-525: a nearby post-T Tauri visual binary system.

The appearance of broad H$α$ in BL Lacertae (1996)
Journal Article
Corbett, E., Robinson, A., Axon, D., Hough, J., Jeffries, R., Thurston, M., & Young, S. (1996). The appearance of broad H$α$ in BL Lacertae. Monthly Notices of the Royal Astronomical Society, 281(3), 737–749. https://doi.org/10.1093/mnras/281.3.737

We present optical spectropolarimetry confirming Vermeulen et al.' recent discovery of a broad Ha emission line in BL Lacertae. This feature, which is present at about the same strength in spectra taken two days apart, is comparable in width (FWHM ≈... Read More about The appearance of broad H$α$ in BL Lacertae.

Wind-accretion induced rapid rotation and a new class of active star (1996)
Journal Article
Jeffries, R., & Stevens, I. (1996). Wind-accretion induced rapid rotation and a new class of active star. Monthly Notices of the Royal Astronomical Society, 279(1), 180–190. https://doi.org/10.1093/mnras/279.1.180

A physical model is presented to explain the occurrence of wide binary systems discovered at EUV wavelengths, such as 2RE J0044 + 093, which consist of a hot white dwarf and an ultra-rapidly rotating K-dwarf. It is difficult to explain the rapid rota... Read More about Wind-accretion induced rapid rotation and a new class of active star.

Are there any isolated old neutron stars in the ROSAT Wide Field Camera survey? (1996)
Journal Article
Manning, R., Jeffries, R., & Willmore, A. (1996). Are there any isolated old neutron stars in the ROSAT Wide Field Camera survey?. Monthly Notices of the Royal Astronomical Society, 278(2), https://doi.org/10.1093/mnras/278.2.577

We present the results of Monte Carlo simulations to predict the number of isolated old neutron stars (IONs) that are observed in the ROSAT Wide Field Camera (WFC) survey as a result of accretion-powered extreme ultraviolet (EUV) emission. Magnetic f... Read More about Are there any isolated old neutron stars in the ROSAT Wide Field Camera survey?.

Is 2RE J0357+283 the most coronally active star in the Galaxy? (1996)
Journal Article
Jeffries, R. D., Burleigh, M. R., & Robb, R. M. (1996). Is 2RE J0357+283 the most coronally active star in the Galaxy?. Astronomy and Astrophysics, 305,

The late-type stellar counterpart to the EUV source 2RE J0357+283 is found to be an ultra-fast rotating K2V star, with a rotation period of 8.76 hrs and vsini of 141+/-5km/s. If this were the only source of the EUV emission, then it would be the most... Read More about Is 2RE J0357+283 the most coronally active star in the Galaxy?.

New Extreme Ultraviolet-Selected Active Binaries from the ROSAT Wide Field Camera all Sky Survey (1995)
Journal Article
Jeffries, R., Bertram, D., & Spurgeon, B. (1995). New Extreme Ultraviolet-Selected Active Binaries from the ROSAT Wide Field Camera all Sky Survey. Monthly Notices of the Royal Astronomical Society, 276(2), 397–408. https://doi.org/10.1093/mnras/276.2.397

We present the results of radial velocity measurements for an EUV-selected sample of 11 new G- and K-type binary systems, discovered in a sample of 22 EUV sources from the ROSAT Wide Field Camera (WFC) all-sky survey. The physical status of each syst... Read More about New Extreme Ultraviolet-Selected Active Binaries from the ROSAT Wide Field Camera all Sky Survey.