2003 REU Students' AAS Abstracts

AAS 203rd Meeting, January 2004
[5.07] A Survey of Classical and Weak-line T Tauri Stars in the Young Cluster NGC 2264
S. E. Dahm, T. Simon (U. of Hawaii), E. David (Xavier U.)

We present initial results from an Ha and X-ray emission survey of the young cluster NGC 2264 in the Mon OB1 association. Approximately 450 emission Ha stars were identified in a 25' × 40' field roughly centered between the O7V multiple star S Mon and the Cone Nebula. The Ha emission survey was carried out using the wide-field grism spectrograph on the University of Hawaii 2.2 meter telescope and the Gemini Multi-Object Spectrograph (GMOS). The XMM-EPIC observations of the cluster are discussed in detail in the accompanying poster by David et al. (2004). Additionally, we obtained optical (BVRCIC) and near infrared (JHK) photometry for selected fields in NGC 2264 to supplement published data from previous investigations and to ensure coverage for the majority of detected emission Ha stars and X-ray sources. Optical color-magnitude diagrams are presented and used to derive ages and masses from theoretical isochrones and evolutionary tracks for the candidate pre-main sequence stars. We analyze the X-ray luminosity functions of classical and weak-line T Tauri stars in NGC 2264 and seek correlations among LHa, LX, spectral type and theoretical age. Finally, the distribution and density of emission Ha stars in the cluster are discussed and compared with those found in other star forming regions including IC 348, IC 5146 and NGC 2362. This research was supported in part by the NASA XMM-Newton Guest Observer program and the NASA Graduate Student Research Program.

AAS 203rd Meeting, January 2004
[5.05] XMM Observations of the Star Forming Region NGC 2264
E. David (Xavier U.), T. Simon, S. E. Dahm (U. of Hawaii), B. M. Patten (Harvard-Smithsonian CfA)

X-ray images of the heavily-populated, young, star-forming region NGC 2264 were obtained with the XMM-Newton European Photon Imaging Cameras (EPIC). The region was observed in two 30' fields of view; the southern field contains the Cone Nebula, while the northern field is centered near the bright O star, SMon. In all, 320 X-ray sources were detected above a 3 s detection level of L_x = 3 × 10²⁹ ergs s^-1 . The large majority of the sources have optical counterparts from earlier surveys of the pre-main sequence population of the cluster. A dozen sources have no identified optical counterpart and therefore are possible candidates for very young, deeply embedded protostars. We describe our procedures for extracting source count rates and pulse-height spectra, light curves, and X-ray luminosities. More detailed analysis of these results and a comparison with ground-based optical and infrared data appears in the accompanying poster by Dahm et al. (2004). This research was supported in part by the NASA XMM Guest Observer program and by the NSF Research Experience for Undergraduate Program.

AAS 203rd Meeting, January 2004
[7.05] A Comparison Between Observations and Simulations of Polarization in Star Forming Regions
A.K. Hernandez (U.Colorado), J.P. Williams (IfA, U.Hawaii), E.G. Zweibel (U.Wisconsin)

Previous research has hinted that magnetic fields play a key role in the formation of cores in star forming molecular clouds. However, the extent of that role is not fully understood. Here, we compare polarization data of observed cores with clumps formed in a simulated model of turbulent molecular clouds. Through an investigation of the polarized angle dispersion of both sets of data, it was found that the simulations were accurate in representing cores formed with either a low turbulence or within a relatively strong magnetic field. Also, through investigation of data's polarized flux, the observed sources are found to have formed in fields that are more ordered than those modeled in the simulations. This finding is also supported by the calculated magnetic field strengths of the observed cores via the Chandrasekhar-Fermi method. This research will aid in understanding the conditions of star formation within turbulent molecular clouds. This work was funded by the National Science Foundation's Research Experience for Undergraduates program.

AAS 203rd Meeting, January 2004
[18.03] Time-Evolution of a White Light Flare: Observations in Optical, Microwave, Soft X-Ray, Ha
E. Lee (Harvard Univ.), J. Li (IfA, Univ. of Hawaii)

Since Richard Carrington's 1859 discovery of White Light Flares (WLFs), only fifty other WLFs have been observed. While the predicted frequency was 15.5 (± 4.5) per year for solar cycle 20, the lack of sensitive instruments makes WLFs extremely rare. Past observations suggest that WLFs do not accompany all high-energy events, and that some specific initial conditions and mechanisms produce WLFs. To analyze this claim, we found a WLF by combing through a list of X class events. This X5.6 flare occurred at AR 9415 on April 6th, 2001 (UT 19:14) and was accompanied by a halo CME. After confirming this event to be a WLF using Imaging Vector Magnetograph data, we found microwave, EUV, optical, soft X-ray, and magnetogram data. Our data suggests that this WLF erupted through the same mechanisms as the standard flare models, but was more energetic. This work was funded by the National Science Foundation's Research Experience for Undergraduates program.

AAS 203rd Meeting, January 2004
[17.06] Extra-Solar Planet Search Using Two 0.1-meter Diameter Telescopes
Y.R. Torres (Institute for Astronomy, University of Hawaii)

The research project my mentor, Dr. Jim Heasley, and I worked on this summer involved a search for extra-solar planets. My research was supported by the National Science Foundation. The search was conducted using a drift scanning method with two 0.1-meter diameter telescopes. By using these small telescopes, we were capable of attaining over 2 million stars per night and over 30 million stars for data analysis. The telescopes are mounted on Haleakala, Maui at an altitude of 10,000 feet. Our main interest was to detect subtle decreases in the intensity of the measured stars. Sixteen nights of observations were used for our data analysis which covered a range in right ascension from 40 degrees to 200 degrees. For this particular data set, a Stellar Photometry Software package, written by Janes & Heasley (1993), produced information for each star such as the raw instrumental magnitudes, ID numbers, (x,y) coordinates, and an estimated error for each reported magnitude. In order to flag down these transits and detect time history of any measured object, it was in our best interest to establish a database. The database is useful to us in such a way that large numbers of stars can be stored and examined, we are allowed flexibility in examining the data in a number of ways, and incorporating additional observations as they become available will be much more simplified. The observing program on Haleakala is set to operate for a three year period. This work was funded by the National Science Foundation's Research Experience for Undergraduates program.