Research

The Environment of ULXs

We are currently measuring the flux within a 500 pc region around ULX sources (like those in M51 - left) with available OM data. We will compare these values with what is expected for HII regions. This will give us a quantitative measurement of the UV environment of ULX sources. In an AAS poster, I presented the result that some ULXs appear to have no association with star-forming regions. This challenges the assumption that ULXs and SFR are intimately connected.

X-raying the ISM

This project involves using the bright ULX sources as background sources on which X-ray absorption of the ISM can be seen.  We determined hydrogen column densities for the host galaxies and also abundances of oxygen (using the oxygen K-shell absorption edge at approximately 0.53 keV).
This work has been submitted to the ApJ. We include an abstract and a description of some of the results on the link forward.
Click here

Second Year Project

My second year project was a study of ultra-luminous X-ray sources in nearby galaxies.  Click on the link to see a gallery of optical images with the XMM-Newton X-ray contours overlaid.  Spectral properties (obtained through fits in XSPEC) have been added to the page.  In addition, UV images from the Optical Monitor of individual ULXs have been added.  A link to the paper, available on astro-ph, is included.


Click here

BAT AGNs

SWIFT's Burst Alert Telescope (BAT) is busy detecting hard X-ray sources (15-150 keV) while not studying gamma ray bursts. Currently there are about 150 BAT detected AGN. This number will continue to grow as BAT surveys the sky (increasing signal-to-noise).

The link includes RA, Dec, and redshifts for all of the BAT AGN. Also, spectral information from the XMM Newton satellite is available for some of the sources. Eventually, optical properties and SWIFT properties will also be added for all of the sources.
BAT sources
For details to remember for observing at the KPNO 2.1m, go here: http://www.astro.umd.edu/~lwinter/research/KPNO/kpno.html.

Villanova University

As an undergrad I worked on a few projects:

• Cataclysmic variable systems: I worked with Dr. Sion on modelling spectra of dwarf novae systems in quiesence. These are systems consisting of a white dwarf accreting matter from a low-mass companion.
• Sakurai's Object: this was a project for my undergrad research course. I worked with Dr. Guinan and Jess Castora, looking at photometry of this "born-again" asymptotic giant branch star.
• V404 Cygnus: For my Honor's senior thesis I worked with Dr. Sion looking at H-alpha spectroscopy of this low-mass X-ray binary system. The data was from the MMT, given to us by Mark Wagner.
• Summer REU at Haystack Observatory: I worked with Dr. Robert Phillips on VLBA data of the red giant R Cas. We were looking at the SiO masers at different frequencies and made a neat movie.

Publications

• Winter, L.M., Mushotzky, R.F., Tueller, J., & Markwardt, C. X-ray properties of an Unbiased Hard X-ray Detected Sample of AGN. 2008, ApJ, (accepted) astro-ph
  
• Winter, L.M., Mushotzky, R.F., & Reynolds, C.S. Abundance Determination of the ISM of Nearby Galaxies from High Signal-to-Noise XMM-Newton Observations of Ultraluminous X-ray Sources. 2007, ApJ, 655, 163 astro-ph
  
• Mizuno, T.; Miyawaki, R.; Ebisawa, K.; Kubota, A.; Miyamoto, M.; Winter, L.; Ueda, Y.; Isobe, N.; Dewangan, G.; Done, C.; Griffiths, R. E.; Haba, Y.; Kokubun, M.; Kotoku, J.; Makishima, K.; Matsushita, K.; Mushotzky, R. F.; Namiki, M.; Petre, R.; Takahashi, H.; Tamagawa, T.; & Terashima, Y. Suzaku Observation of Two Ultraluminous X-Ray Sources in NGC 1313. (accepted to PASJ) astro-ph/0610185
  
• Winter, L.M., Mushotzky, R., & Reynolds, C.S. XMM-Newton Archival Study of the ULX Population in Nearby Galaxies. ApJ, 649, 730 astro-ph/0512480
  
• Sion, E.M. Winter, L. Urban, J.A., Tovmassian, G.H., Zharikov, S., Gaensicke, B.T., Orio, M. Composite Accretion Disk and White Dwarf Photosphere Analyses of the FUSE and HST Observations of EY Cygni. 2004, AJ, 128, 1795 astro-ph/0407534
• Winter, L., Sion, E.M. Composite Accretion Disk and White Dwarf Model Analyses of the Quiescence of Dwarf Novae: EM Cygni, CZ Orionis, and WW Ceti. 2003, ApJ, 582, 352


• Winter, L.M. & Mushotzky, R.F. X-ray and Optical Properties of an Unbiased Sample of Local AGN . 2007, BAAS, 211:64.02D
• Winter, L.M. & Mushotzky, R.F. Early Results From Swift's BAT AGN Survey . 2007, BAAS, 210:02.25 <\li>
• Winter, L.M., Mushotzky, R.F., & Reynolds, C.S.  Bolstering the IMBH hypothesis: Evidence for "Low" and "High" State ULX Sources from XMM-Newton. 2005, AAS, 207:90.05 (oral talk)
  
• Winter, L., Mushotzky, R., & Reynolds, C. Oxygen and Iron Abundances in nearby Galaxies Using Ultraluminous X-ray Sources. 2005, poster presentation at ESA's The X-ray Universe 2005 , El Escorial, Spain astro-ph/0511493
  
• Winter, L.M., Mushotzky, R., & Reynolds, C. Investigating The Ultraviolet Environment of Ultraluminous X-ray sources. 2004, AAS, 205:76.01 (oral talk)
• Phillips, R.B., Boboltz, D.A., Winter, L.A., Straughn, A.H. New Approaches in SiO Maser Shell Tomography Analysis. 2003, 203:49.05
• Castora, J.E., Winter, L.M., Guinan, E.F. The Last Heartbeats of a Dying Star: Pulsation of the Post-Asymptotic Giant Branch Star- Sakurai's Object 2002, AAS, 201:117.10
• Winter, L.M., Phillips, R.B., Crowley, R.J. SiO masers: Three-Transition movie for a Red Giant. 2002, AAS, 201:115.10
• Winter, L.M., Sion, E.M. Multi-Component Synthetic Spectral Analyses of Three Peculiar Dwarf Novae. 2001, AAS, 199:62.01