Jillian Bornak
|
| Research/Teaching Assistant |
| Entered: | 2005 |
| Office: | 112 Astronomy |
| Phone: | (575)646-6399 |
| Fax: | (575)646-1602 |
| |
| E-mail: | jbornak |
| (append "@nmsu.edu") |
| |
|
|
| B.A. | Syracuse University, | 2000 |
|
Research
I'm very interested in stellar astronomy, particularly in compact objects such
as white dwarfs, neutron stars, and black holes. The best place for me to
study these objects is in binary systems, where mass transfer and orbital
mechanics can tell us about their chemical composition and masses. I am thus
studying low-mass X-ray binaries (LMXBs), with Dr. Tom Harrison and Dr. Bernie
McNamara in the Stellar research group.
An infrared survey of low-mass X-ray binaries
My first project is 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 secondary stars
of such systems look like: they could be normal-looking or possibly
stripped stars. By studying the secondaries we will estimate the masses of
the primaries and constrain their radii, as well as observe behaviors of the
systems such as disc activity and jet activity (as well as looking for jets!).
This will help us to constrain the neutron star equation of state.
The peculiar source GX 17+2
My second project involves a peculiar LMXB. GX 17+2 is a faint and unusual
binary with a neutron star primary. Historically, it has often been confused
on the sky with NP Ser, a field star which lies almost directly in front of it; however, recent work of Callanan et al. (2002) has shown clearly that NP Ser is not the X-ray source.
GX 17+2 has only been observed twice
before in the infrared, once when it appeared to be quite bright (14th
magnitude at K) and once more when it was significantly fainter (18th
magnitude at K). The spectrum suggests that this system may actually have a
precessing infrared jet, which would make it the first neutron star system
known to have a jet.
GX 17+2 jumps four magnitudes from faint to bright, a tremendous change in
luminosity for a LMXB. This suggests the presence of a jet, versus some kind
of surface nova action. The source is very red, being clearly detected in K
and H but never J (even when bright). The Z diagram (X-ray color-color plot)
shows a horizontal branch (quiescent), a normal branch, and a flaring branch
--- but on one night of observation we took data showing the source on the
flaring and normal branches! The branches of a Z source are sacrosanct:
sources do not jump from branch to branch, they trace out the Z shape for
which the sources are named (granted, not all Z sources have every branch).
GX 17+2 is weird and interesting, which is why we want to study it further,
especially as compared with Sco X-1, a classic LMXB Z-source. Our first goal
is to determine GX 17+2's period. We intend to take spectra of it when it is
bright to look for cyclotron humps in the infrared. It will also be useful to
have a time-resolved light curve to determine the opening angle of the jet.
I am pleased to acknowledge support from a Consortium for Higher Education
(CHE) grant for women in the sciences.
Research and teaching page
Personal website
