Nalin H. Samarasinha

Samarasinha continued his research on coma morphologies of comets (in collaboration with T. Farnham, B. Mueller, S. Larson and colleagues) and two papers are already published on comet Machholz (C/2004 Q2) and comet Hale-Bopp (C/1995 O1). Continuing future work will involve characterization of nucleus and coma properties of the Jupiter-family comet 73P/Schwassmann-Wachmann 3. Another paper which will critically analyze the image enhancement techniques used in coma morphological studies is in preparation (with S. Larson and E. Beshore).

Spin studies of comets using rotational lightcurves (in collaboration with B.Mueller) is progressing and the objects under study includes comets 9P/Tempel 1, 10P/Tempel 2, and 19P/Borrelly.

Samarasinha is continuing his study on the spin evolution of sub-km size asteroids due to YORP torques. A paper inspired by this work and addresses how rotation and spacecraft experiments which cause changes in the spin state could be used to determine the interior structures of comets and asteroids has been accepted for publication. Two papers on YORP torques and spin evolution of asteroids are planned to be submitted for publication during 2008.

Figure 1: A sequence of CN images depicting the evolution of the coma morphology during a rotation cycle in April 2005 for comet Machholz (C/2004 Q2). The relative rotational phase is shown in the upper left corner of each panel. These and other data were used by Samarasinha and colleagues (Farnham et al. 2007) to derive basic spin parameters for this comet.

Figure 2: This outburst of comet Hale-Bopp (C/1995 O1) observed by NICMOS/HST was modeled by Samarasinha and colleagues (McCarthy et al. 2007). In October 2007, a cometary outburst in comet 17P/Holmes that shares many similarities to this one caught the attention of both the astronomers as well as the general public.

Papers:

Farnham, T.L., Samarasinha, N.H., Mueller, B.E.A., Knight, M.M., 2007. Cyanogen Jets and the Rotation State of Comet Machholz (C/2004 Q2). Astron. J. 133, 2001-2007.

McCarthy, D. W., Stolovy, S.R., Campins, H., Larson, S., Samarasinha, N.H., Kern, S.D., 2007. Comet Hale Bopp in Outburst: Imaging the Dynamics of Icy Particles with HST/NICMOS. Icarus 189, 184-195.

Knight, M.M., Walsh, K.J., A'Hearn, M.F., Swaters, R.A., Zauderer, B.A., Samarasinha, N.H., Vazquez, R., Reitsema, H., 2007. Ground-based Visible and Near-IR observations of Comet 9P/Tempel 1 During the Deep Impact Encounter. Icarus 187, 199-207.

Samarasinha, N.H., 2007. Rotation and Activity of Comets. Advances. Space Res. 39, 421-427.

Abstracts:

Samarasinha, N.H., 2007. Spin Evolution of Sub-km Sized Asteroids Due to YORP Torques. B.A.A.S. 39, #50.08.

Mueller, B.E., Samarasinha, N.H., 2007. An Improved Rotation Period for Deep Space 1 Target, Comet 19P/Borrelly. B.A.A.S. 39, #36.02.

Samarasinha, N.H., 2007. Morphological Studies of Cometary Comae and Coma-Nucleus Connections. Workshop on Planetary Atmospheres, LPI Cont. # 1376, pp 101-102.