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Jillian Bornak

Research/Teaching Assistant
Entered: 2005
Office: 101 Astronomy
Phone: (575)646-4438
Fax: (575)646-1602
 
E-mail: jbornak
(append "@nmsu.edu")
 
Photo
M.S.New Mexico State University,2010
B.A. Syracuse University, 2000

Research

I'm interested in the behavior of binary systems with compact objects such as white dwarfs, neutron stars, and black holes. In particular, I have studied the formation of dust in classical nova ejecta and the behavior of jets in low-mass X-ray binaries. I am an observer and have collected optical and IR data from various telescopes at Apache Point Observatory, Kitt Peak National Observatory, Mauna Kea, and Cerro Tololo Inter-American Observatory.

Dust Production in Classical Novae
My dissertation project involves the study dust formation in classical novae. A classical nova is thought to occur in a binary system consisting of a white dwarf accreting from a low mass main sequence star via Roche Lobe overflow. The accreted material builds up as a layer on the surface of the white dwarf until the base temperature increases to the point where a CNO-dominated thermonuclear runaway occurs. This shell burning continues at Edddington luminosity for the white dwarf. Material is ejected at speeds from a few hundred to a thousand km/s. The shell starts as an optically thick fireball and expands and cools to be optically thin. Novae are classified by the speed at which they decrease in brightness. Classical novae are thought to recur every 10,000 years or so.

Some novae evidence a drop in optical/UV light with a corresponding increase in IR emission, indicating dust production. It seems that fast novae do not, on average, produce dust, while slow novae can evidence optically thick or thin dust emission or none at all. However, a unified model of dust production does not exist to explain these difference scenarios.

My dissertation is based on OIR photometry and optical spectroscopy of the slow Nova Cen 1991. Initial results indicate Nova Cen produced dust but also has simultaneous contamination by optical light, indicating less than uniform ejecta. Evidence exists for clumpy ejecta in images and line profile modling of novae. I model the geometry of the dust in Nova Cen using the advanced Monte Carlo radiative transfer dust emission code DIRTY

The Jets of GX 17+2
I have also studied the peculiar low-mass X-ray binary GX 17+2. X-ray binaries were the first X-ray sources detected, for they are among the brightest objects in the X-ray sky, and consist of a compact object accreting matter from a donor star. The accretion disk is the brightest component of the system, with a temperature of millions of degrees, and dominates the X-ray emission. The secondary star may contribute to the optical-infrared emission. Evidence suggests these systems may also launch a compact, self-absorbed, collimated jet of relativistic material. Synchrotron radiation from this jet would be most visible in the radio, IR, and possibly >20 keV X-rays.

GX 17+2 is one of eight Z sources, so-called for the shape they trace out in an X-ray color-color diagram. It is a strong X-ray source, indicating continuous (and presume near-Eddington) accretion onto its neutron star primary. Identification of GX 17+2 in the infrared has been problematic. Callanan et al. (2002) had the the fortunate timing to observe GX 17+2 with Keck on two nights, one in which the source was IR bright and one IR faint, an impressive difference of about 4 magnitudes in the K band. This activity had never been seen in this source nor in any of the other Z sources. Intrigued by this unusual behavior, we studied this source over the course of three years, accumulating the largest dataset of time-resolved IR light curves of this source. We have detected 5 IR brightening events and determined them to be periodic. Futher, the light curves are not uniform in character. A possible explanation for this behavior is that the IR radiation is synchrotron in nature from a compact jet. The periodic activity could be explained as a precessing jet (either from a precessing disk or from the influence of a third body), which is the model for SS 433.

An Infrared Survey of LMXBs
My first project was an infrared survey of LMXBs with neutron star primaries. Similar programs have been conducted previously for white dwarf systems, but never for neutron star systems. We will create the first infrared catalog of neutron star binary counterpart stars, as no one seems to have many infrared magnitudes for neutron star systems. We don't know what the non-evolved stars of such systems look like: they could be normal main sequence or giants, or they could be stripped stars. By studying the secondaries we will estimate the masses of the neutron star and possibly constrain their radii. This will help us to constrain the neutron star equation of state. Additionally, we might observe behaviors of the systems such as disc and jet activity.

I am pleased to acknowledge support from the New Mexico State University Higher Education Department (HED) graduate scholarship for women in the sciences, a graduate assistantship award, and the New Mexico Space Grant.

CV

Publications

Additional Spitzer IRS Spectroscopy of Three Intermediate Polars: The Detection of a Mid-Infrared Synchrotron Flare from V1223 Sagittarii
Harrison, T. E.; Bornak, J.; Rupen, M., Howell; S. B.; 2010, ApJ 710, 325-331

A Possible Period for the K-band Brightening Episodes of GX 17+2
Bornak, J.; McNamara B. J.; Harrison, T. E.; Rupen, M. P.; Bandyopadhyay, R. M.; Wachter, S.; 2009, ApJ Letters 701, L110-L113

Infrared Photometry and Spectroscopy of VY Aqr and EI Psc: Two Short-Period Cataclysmic Variables With Curious Secondary Stars
Harrison, T. E.; Bornak, J.; Howell, S. B.; Mason, E.; Szkody, P.; McGurk, R., 2009, ApJ 137, 4061-4071

Meetings

219th AAS, 2012 January 8-12
Talk: Classical Novae Blow Smoke Rings: A DIRTY Approach to Modeling Dust Formation
Jillian Bornak, Tom Harrison, Karl Gordon

Evolution of Compact Binaries (ESO), 2011 March 6-11
DIRTY Novae: Modeling dust formation in classical novae
Jillian Bornak, Tom Harrison, Karl Gordon

25th New Mexico Symposium, 2010 January 15
Talk: Dust to Dust: Grain Formation & Evolution in Classical Novae
Jillian Bornak, Tom Harrison, Karl Gordon

215th AAS, 2010 January 3-7
Poster: Dust in the Wind: Grain Formation and Evolution in Two Classical Novae
Jillian Bornak, Tom Harrison, Karl Gordon

214th AAS, 2009 June 7-11
Poster: Synchrotron Emission from Cataclysmic Variables
Tom Harrison, Jillian Bornak, Steve Howell, Michael Rupen

Wild Stars in the Old West II, 2009 March 15-19
Poster: Synchrotron "Jets" in Unexpected Places: GX 17+2 and V1223 Sgr
Jillian Bornak, Tom Harrison, Bernie McNamara

24th New Mexico Symposium, 2008 October 24
Talk: A Possible Period for the K-band Brightening Episodes of GX 17+2
Jillian Bornak, Tom Harrison, Bernie McNamara, Michael Rupen

211th AAS, 2008 January 7-11
Poster Are There Any Other Old Novae Like V1500 Cyg?
Joni Johnson, Tom Harrison, Joe Wellhouse, Jillian Bornak, Ryan Campbell, J. E. Lyke, S. B. Howell, P. Szkody, & F. Cordova

A Population Explosion: The Nature and Evolution of X-ray Binaries in Diverse Environments, 2007 October 28 - November 2
Poster: Multiwavelength Observations of the Highely-Reddened Z source GX 17+2
Jillian Bornak, Tom Harrison, Bernie McNamara, & Michael Rupen

23rd New Mexico Symposium, 2007 October 19
Poster: Multiwavelength Observations of the Highely-Reddened Z source GX 17+2
Jillian Bornak, Tom Harrison, Bernie McNamara, & Michael Rupen

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