School of Physical, Environmental and Mathematical Sciences

Professor Warrick Lawson

Professor of Physics, Head of School
BSc, MSc, PhD Cant.

Telephone: +61 2 6268 8061
Fax: +61 2 6268 8786
Email: w.lawson@adfa.edu.au
Location: PEMS Sth, Room 137

---

My UNSW Research Gateway Profile

Astronomy and Astrophysics Research Group

Current Research

I am an Astrophysicist with significant expertise in star formation, young stellar populations, and stellar evolution. Research highlights include pioneering X-ray/optical/IR studies of young stellar systems, and the discovery of two of the nearest young star clusters to Earth and the subsequent study of their stellar populations. The eta Cha and epsilon Cha clusters (named after their brightest stars) are 5- to 8-million year old systems located 300-350 light years distance from Earth. The eta Cha cluster is remarkable for being the fourth nearest star cluster to Earth and the nearest star cluster discovered in over a century. No younger stellar population lies closer to Earth. Neither of these clusters would have been discovered without X-ray observations made from satellite observatories, since X-ray selection is the only efficient method for selectively identifying magnetically-active young stars from far more numerous foreground and background, and unrelated field stars. I have coordinated extensive observing campaigns to study these clusters and have published over 20 journal papers on these two groups, as well as more than 10 papers on other nearby star formation regions.

My research takes a deliberate multi-wavelength approach in order to study these objects across a wide regime of energies, and to investigate different physical processes. I utilise state-of-the-art astronomical facilities ranging from X-ray space observatories such Chandra, leading ground-based optical, infrared and radio telescopes, and infrared space observatories such as Spitzer and Herschel.

The central question underlying my research concerns the timescale for the evolution of young solar analogues including the timescales and conditions conducive to planet formation, with comparison to the contemporary Sun. I achieve this by studying stellar populations of different ages, particularly those less than 10 million years old where circumstellar, planet-forming disks remain prevalent. I probe science ranging from magnetic activity in young stars, to fundamental stellar properties such as mass, temperature, age and composition, and the frequency and properties of planet-forming circumstellar disks.

I enjoy considerable success at being awarded access to leading astronomical facilities, which is a highly competitive process and subject to rigorous peer and technical review.

Recent Achievements

• Lawson is a co-investigator of successful proposals in 2006 and 2007 to use to NASA’s Spitzer Space Telescope. The proposals are to investigate the influence of hot stars on the formation and evolution of protoplanetary disks (CI: Bouwman, Max Planck Institute for Astronomy, Heidelberg, Germany), and a joint Spitzer Space Telescope/Chandra X-ray Observatory study of star formation in the Carina Giant Molecular Cloud (CI: Townsley, Pennsylvania State University, State College, USA.
• Along with colleagues in Europe and the USA, Lawson completed a study of Spitzer Space Telescope observations of stars in the eta Chamaeleontis star cluster, which was co-discovered at UNSW@ADFAin 1998. The Spitzer study shows that the presence of protoplanetary disks in the cluster is related to whether stars are single (in which case disks are common) or binary (in which case disks are rare). A characteristic disk lifetime for single stars is estimated at ~ 9 million years, while for binary stars the lifetime is ~ 4 million years. The former timescale is consistent with core accretion models of planet formation; the latter may be too short. The results were published by Bouwman et al. 2006, Astrophysical Journal, 653, L57-60.
• Results of dynamical modeling of the eta Cha star cluster were published by Moraux, Lawson & Clarke (2007, Astronomy & Astrophysics, 473, 163–170). The cluster appears unusual compared to other young clusters of stars in having remained in a relatively compact configuration for ~ 10 million years while appearing to have lost most of its low mass objects. N-body modeling showed that a very dense initial state can reproduce the observed configuration in ~ 5% of realisations. Further modeling will investigate the impact of binary systems and residual gas in the young cluster, while observational programs will attempt to locate cluster members that may have escaped the cluster core region.

Research Collaborators

Mike Bessell, Australian National University, Australia
Jeroen Bouwman, Max Planck Institute for Astronomy, Heidelberg, Germany
Geoff Clayton, Louisiana State University, USA
Eric Feigelson, Pennsylvania State University, USA
Estelle Moraux, Observatoire de Grenoble, France
Simon Murphy, Australian National University, Australia
Veronica Roccatagliata, University of Munich, Germany
Aurora Sicilia-Aguilar, University of Madrid, Spain

 

PhD Opportunities and Scholarships

MPhil, MSc and PhD thesis topics studying properties of the stellar populations of some of the nearest star forming regions to Earth are available. These topics will make use of Australian and international ground-based optical, infrared and radio facilities, and archival space-based data from satellites such as NASAs Spitzer Space Telescope.

Contact: Prof. Warrick Lawson
Email: w.lawson@adfa.edu.au

Recent Publications

Journal - refereed

2011

1. Clayton, G.C., Sugarman, B., Stanford, S.A., Whitney, B., Honor, J., Babler, B., Barlow, M.J., Gordon, K.J., Andrews, J.E., Geballe, T.R., Bond, H.E., De Marco, O., Lawson, W.A., Sibthorpe, B., Olofsson, G., Polehampton, E., Gomez, H.L., Matsuura, M., Hargrave, P.C., Ivison, R.J., Weeson, R., Leeks, S.J., Swinyard, B.M., Lim, T.L., 2011, The Circumstellar Environment of R Coronae Borealis Stars: White Dwarf Merger or Final-Helium-Shell Flash, The Astrophysical Journal, 743(1), 44-53, doi: 10.1088/0004-637X/743/1/44
2. Bullock, E., Szkody, P., Mukadam, A.S., Borges, B.W., Fraga, L., G?nsicke, B.T., Harrison, T.E., Henden, A., Holtzman, J., Howell, S.B., Lawson, W.A., Levine, S., Plotkin, R.M., Seibert, M., Templeton, M., Teske, J., Vrba, F.J., 2011, GALEX and optical observations of GW Librae during the long decline from superoutburst, The Astronomical Journal, 141(3),84-94, doi: 10.1088/0004-6256/141/3/84..
3. Clayton, G.C., De Marco, O., Whitney, B.A., Babler, B., Gallagher, J.S., Nordhaus, J., Speck, A.K., Wolff, M.J., Freeman, W.R., Camp, K.A., Lawson, W.A., Roman-Duval, J., Misselt, K.A., Meade, M., Sonneborn, G., Matsuura, M. & Meixner, M., 2011, The dust properties of two Hot R Coronae Borealis Stars and a Wolf-Rayet Central Star of a Planetary Nebula: In search of a possible link, Astronomical Journal, 142, 54-1 - 54-8, doi: 10.1088/0004-6256/142/2/54.
4. Lawson, W.A. & Crause, L.A., 2011, Rotational variability in pre-main sequence stars: TWA 6 in 2008, Information Bulletin on Variable Stars, 5989, 1-4.
5. Murphy, S.J., Lawson, W.A., Bessell, M.S., & Bayliss, D.D.R., 2011, Episodic disc accretion in the halo of the 'old' pre-main-sequence cluster η Chamaeleontis, Monthly Notices of the Royal Astronomical Society: Letters ,411(1), L51-L55, doi:10.1111/j.1745-3933.2010.00992.x.
6. Roccatagliata, V., Bouwman, J., Henning, T., Gennaro, M., Feigelson, E.D., Kim, J.S., Sicilia-Aquilar, A. & Lawson, W.A., 2011, Disk evolution in OB associations: Deep Spitzer/IRAC observations of IC 1795, The Astrophysical Journal, 733(2), 113-1 - 113-20, doi: 10.1088/0004-637X/733/2/113.

2010

3. Bouwman, J., Lawson, W.A., Juhasz, A., Dominik, C., Feigelson, E. D, Henning, Th., Tielens, A.G.G.M., Waters, L.B.F.M., 2010, The protoplanetary disk around the M4 star RECX 5: witnessing the influence of planet formation?, The Astrophysical Journal Letters, 723(2), L243 - L247, doi:10.1088/2041-8205/723/2/L243.
4. Murphy, S.J., Lawson, W.A., & Bessell, M.S. 2010, First detection of a low-mass halo around the young open cluster Chamaeleontis, Monthly Notices of the Royal Astronomical Society: Letters, 406(1), L50 - L54, doi:10.1111/j.1745-3933.2010.00879.x.

2009

5. Hussain, G. A. J. , Collier Cameron, A., Jardine, M. M., Dunstone, N. J., Ramirez Velez, J., Stempels, H. C., Donati, J.-F., Semel, M., Aulanier, G., Harries, T., Bouvier, J., Dougados, C., Ferreira, J., Carter, Brad D., Lawson, W. A., 2009, Surface magnetic fields on two accreting T Tauri stars: CV Cha and CR Cha, Monthly Notices of the Royal Astronomical Society, 398(1), 189-200, doi:10.1111/j.1365-2966.2009.14881.x.
6. Meeus, G., Juhasz, A., Henning, Th., Bouwman, J., Chen, C., Lawson, W.A., Apai, D., Pascucci, I., Sicilia-Aguilar, A., 2009, MBM 12: young protoplanetary discs at high galactic latitude, Astronomy & Astrophysics, 497(2), 379-392.
7. Lawson, W.A., Crause, L.A., 2009, Rotational and candidate-eclipsing-binary light curves for pre-main-sequence stars in the Chamaeleon I star-forming cloud, Publications of the Astronomical Society of Australia, 26(1), 31-36, doi:10.1071/AS08018.
8. Lawson, W.A., Lyo, A.R., & Bessell, M.S. 2009, The age rank of the nearest pre-main-sequence groups, Monthly Notices of the Royal Astronomical Society,400, L29 - L33, doi:10.1111/j.1745-3933.2009.00755.x.
9. Revnivtsev, M.G., Kniazev, A.Y., Sazonov, S.Y., Burenin, R.A., Tekola, A., Buckley, D.A.H., Pretorius, M.L., Menzies, J., Lawson, W.A., 2009, Optical identification of the source IGR J08390-4833 from the INTEGRAL all-sky survey, Astronomy Letters, 35(1), 33-38, doi:10.1134/S1063773709010046.
10. Sicilia-Aguilar, A., Bouwman, J., Juhasz, A., Henning, T., Roccatagliata, V., Lawson, W.A., Acke, B., Feigelson, E.D., Tielens, A.G.G.M., Decin, L., Meeus, G., 2009, The long-lived disks in the η Chamaeleontis cluster, The Astrophysical Journal, 701(2), 1188-1203, doi:10.1088/0004-637X/701/2/1188.
11. Skelly, M.B., Unruh, Y.C., Barnes, J.R., Lawson, W.A., Donati, J.F., Collier Cameron, A., 2009, Doppler images and chromospheric variability of TWA 17, Monthly Notices of the Royal Astronomical Society , 399, 1829-1838, doi:10.1111/j.1365-2966.2009.15411.x.

2008

12. Lyo, A-R., Lawson, W.A., Bessell, M.S.,  2008, Spectrophotometric properties of pre-main-sequence stars: the epsilon Chamaeleontis cluster, Monthly Notices of the Royal Astronomical Society, 389(3), 1461-1469.
13. Getman, K. V., Feigelson, E. D., Lawson, W. A., Broos, P. S. & Garmire, G. P., 2008, The stellar population and origin of the mysterious high-latitude star forming cloud CG 12, Astrophysical Journal, 673(1), 331-353.
14. Skelly, M. B., Unruh, Y. C., Collier Cameron, A., Barnes, J. R., Donati, J.-F., Lawson, W. A., Carter, B. D., 2008, Doppler images and chromospheric variability of TWA 6, Monthly Notices of the Royal Astronomical Society, 385(2), 708-715.

2007

15. Crause, L. A., Lawson, W. A. & Henden, A., 2007, Pulsation-decline relationships in R Coronae Borealis stars, Monthly Notices of the Royal Astronomical Society, 375(1), 301-306.
16. Moraux, E., Lawson, W. A. & Clarke, C. L., 2007, η Chamaeleontis: Abnormal initial mass function or dynamical evolution?, Astronomy & Astrophysics, 473(1), 163-170.
17. Smith, R. G., Lawson, W. A. & Wright, C. M., 2007, A Herbig-Haro object associated with GGD30 and its exciting source, Monthly Notices of the Royal Astronomical Society, 375(1), 257-260.

2006

18. Bouwman, J., Lawson, W. A., Dominik, C., Feigelson, E. D., Henning, T., Tielens, A. G. & Waters, L. B., 2006, Binarity as a key factor in protoplanetary disk evolution: SPITZER disk census of the η Camaeleontis cluster, The Astrophysical Journal, 653(1), L57-L60.
19. Feigelson, E. D., Lawson, W. A., Stark, M., Townsley, L. & Garmire, G. P., 2006, 51 Eridani and GJ 3305: A 10-15 Myr old binary star system at 30 Parsecs, Astronomical Journal, 131(3), 1730-1739.
20. Lyo, A. R., Song, I., Lawson, W. A., Bessell, M. S. & Zuckerman, B., 2006, A deep photometric survey of the η Chamaeleontis cluster down to the brown dwarf - planet boundary, Monthly Notices of the Royal Astronomical Society, 368(3), 1451-1455.

Recent Grants

External Grants

W.A. Lawson, Australian Academy of Science Academic Exchange Program, 2008: $6,700.
W. A. Lawson, Australia France Cooperation Fund in Astronomy, ARC Linkage, 2006: $1,800, 2007: $1,800.

UNSW Grants

W. A. Lawson, Angular momentum and planet-forming disk evolution in young stars: The epsilon Cha group, Special Research Grants, 2008: $7,420.
W. A. Lawson, What stellar properties most influence planet formation, Faculty Research Grants, 2007: $12,000.
W. A. Lawson, Unraveling nearby star clusters with the Spitzer Space Telescope, UNSW@ADFA Faculty Research Grant, 2006: $15,760.
W. A. Lawson, Rotation periods of stars in the beta Pic moving group, UNSW@ADFA Special Research Grant, 2006: $1,086.

Service

Chair of Scientific Organising Committee, member of Local Organising Committee, Annual Scientific Meeting of the Astronomical Society of Australia held in July 2006 at UNSW@ADFA.