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Exploring the Experiences of Dis/abled STEM Graduate Students
It is essential to include all individuals who can contribute to research, education, and society, especially those from diverse backgrounds and abilities. Yet dis/abled graduate students have been ignored in institutional policies, departmental practices, instruction, advising, and research. Responding to this gap in knowledge, I explore the experiences of seven Science, Technology, Engineering, and Mathematics (STEM) graduate students with less apparent dis/abilities. The study included two sequential phases of data collection through virtual interviews and qualitative analysis of the participant responses. I chose to highlight three topics in my dissertation: alienation, the culture of productivity, and interpersonal relationships. This dissertation explores the participants’ Stories (spelled with a capital S) and the impacts of these phenomena on their professional advancement, social relationships, well-being, health, and academics. It also offers opportunities to broaden awareness; challenge bias and violence; honor student agency; emancipate learners and educators from systems of oppression; support the supporters; and share resources and opportunities.</p
The accretion flow in the discless intermediate polar V2400 Ophiuchi
RXTE observations confirm that the X-ray lightcurve of V2400 Oph is pulsed at
the beat cycle, as expected in a discless intermediate polar. There are no
X-ray modulations at the orbital or spin cycles, but optical line profiles vary
with all three cycles. We construct a model for line-profile variations in a
discless accretor, based on the idea that the accretion stream flips from one
magnetic pole to the other, and show that this accounts for the observed
behaviour over the spin and beat cycles. The minimal variability over the
orbital cycle implies that 1) V2400 Oph is at an inclination of only ~10 deg,
and 2) much of the accretion flow is not in a coherent stream, but is circling
the white dwarf, possibly as a ring of denser, diamagnetic blobs. We discuss
the light this sheds on disc formation in intermediate polars.Comment: 10 pages, 12 figures, To appear in MNRAS, includes low-res figures to
reduce siz
1SXPS: A deep Swift X-ray Telescope point source catalog with light curves and spectra
We present the 1SXPS (Swift-XRT Point Source) catalog of 151,524 X-ray
point-sources detected by the Swift-XRT in 8 years of operation. The catalog
covers 1905 square degrees distributed approximately uniformly on the sky. We
analyze the data in two ways. First we consider all observations individually,
for which we have a typical sensitivity of ~3e-13 erg/cm2/s (0.3--10 keV). Then
we co-add all data covering the same location on the sky: these images have a
typical sensitivity of ~9e-14 erg/cm2/s (0.3--10 keV). Our sky coverage is
nearly 2.5 times that of 3XMM-DR4, although the catalog is a factor of ~1.5
less sensitive. The median position error is 5.5" (90% confidence), including
systematics. Our source detection method improves on that used in previous XRT
catalogs and we report >68,000 new X-ray sources. The goals and observing
strategy of the Swift satellite allow us to probe source variability on
multiple timescales, and we find ~30,000 variable objects in our catalog. For
every source we give positions, fluxes, time series (in four energy bands and
two hardness ratios), estimates of the spectral properties, spectra and
spectral fits for the brightest sources, and variability probabilities in
multiple energy bands and timescales.Comment: 27 pages, 19 figures; accepted for publication in ApJS. The
accompanying website, http://www.swift.ac.uk/1SXPS is live; the Vizier entry
should be available shortl
GRB 050713A: High Energy Observations of the GRB Prompt and Afterglow Emission
Swift discovered GRB 050713A and slewed promptly to begin observing with its
narrow field instruments 72.6 seconds after the burst onset, while the prompt
gamma-ray emission was still detectable in the BAT. Simultaneous emission from
two flares is detected in the BAT and XRT. This burst marks just the second
time that the BAT and XRT have simultaneously detected emission from a burst
and the first time that both instruments have produced a well sampled,
simultaneous dataset covering multiple X-ray flares. The temporal rise and
decay parameters of the flares are consistent with the internal shock
mechanism. In addition to the Swift coverage of GRB 050713A, we report on the
Konus-Wind (K-W) detection of the prompt emission in the energy range 18-1150
keV, an upper limiting GeV measurement of the prompt emission made by the MAGIC
imaging atmospheric Cherenkov telescope and XMM-Newton observations of the
afterglow. Simultaneous observation between Swift XRT and XMM-Newton produce
consistent results, showing a break in the lightcurve at T+~15ks. Together,
these four observatories provide unusually broad spectral coverage of the
prompt emission and detailed X-ray follow-up of the afterglow for two weeks
after the burst trigger. Simultaneous spectral fits of K-W with BAT and BAT
with XRT data indicate that an absorbed broken powerlaw is often a better fit
to GRB flares than a simple absorbed powerlaw. These spectral results together
with the rapid temporal rise and decay of the flares suggest that flares are
produced in internal shocks due to late time central engine activity.Comment: 22 pages, 6 tables, 10 figures; Submitted to the Astrophysical
Journa
Multi-epoch Doppler tomography and polarimetry of QQ Vul
We present multi-epoch high-resolution spectroscopy and photoelectric polarimetry of the long-period polar (AM Herculis star) QQ Vul. The blue emission lines show several distinct components, the sharpest of which can unequivocally be assigned to the illuminated hemisphere of the secondary star and used to trace its orbital motion. This narrow emission line can be used in combination with Nai-absorption lines from the photosphere of the companion to build a stable long-term ephemeris for the star: inferior conjunction of the companion occurs at HJD = 244 8446.4710(5)+E×0. d 15452011(11). The polarization curves are dissimilar at different epochs, thus supporting the idea of fundamental changes of the accretion geometry, e.g. between one- and two-pole accretion modes. The linear polarization pulses display a random scatter by 0.2 phase units and are not suitable for the determination of the binary period. The polarization data suggest that the magnetic (dipolar) axis has a co-latitude of 23 ◦ , an azimuth of −50 ◦, and an orbital inclination between 50 ◦ and 70 ◦. Doppler images of blue emission and red absorption lines show a clear separatio
The Far-Ultraviolet Spectrum and Short Timescale Variability of AM Herculis from Observations with the Hopkins Ultraviolet Telescope
Using the Hopkins Ultraviolet Telescope (HUT), we have obtained 850-1850
angstrom spectra of the magnetic cataclysmic variable star AM Her in the high
state. These observations provide high time resolution spectra of AM Her in the
FUV and sample much of the orbital period of the system. The spectra are not
well-modelled in terms of simple white dwarf (WD) atmospheres, especially at
wavelengths shortward of Lyman alpha. The continuum flux changes by a factor of
2 near the Lyman limit as a function of orbital phase; the peak fluxes are
observed near magnetic phase 0.6 when the accreting pole of the WD is most
clearly visible. The spectrum of the hotspot can be modelled in terms of a 100
000 K WD atmosphere covering 2% of the WD surface. The high time resolution of
the HUT data allows an analysis of the short term variability and shows the UV
luminosity to change by as much as 50% on timescales as short as 10 s. This
rapid variability is shown to be inconsistent with the clumpy accretion model
proposed to account for the soft X-ray excess in polars. We see an increase in
narrow line emission during these flares when the heated face of the secondary
is in view. The He II narrow line flux is partially eclipsed at secondary
conjunction, implying that the inclination of the system is greater than 45
degrees. We also present results from models of the heated face of the
secondary. These models show that reprocessing on the face of the secondary
star of X-ray/EUV emission from the accretion region near the WD can account
for the intensities and kinematics of most of the narrow line components
observed.Comment: 19 pp., 12 fig., 3 tbl. To appear in The Astrophysical Journal. Also
available at http://greeley.pha.jhu.edu/papers/amherpp.ps.g
The prompt to late-time multiwavelength analysis of GRB 060210
We present our analysis of the multiwavelength photometric & spectroscopic
observations of GRB 060210 and discuss the results in the overall context of
current GRB models. All available optical data underwent a simultaneous
temporal fit, while X-ray and gamma-ray observations were analysed temporally &
spectrally. The results were compared to each other and to possible GRB models.
The X-ray afterglow is best described by a smoothly broken power-law with a
break at 7.4 hours. The late optical afterglow has a well constrained single
power-law index which has a value between the two X-ray indices, though it does
agree with a single power-law fit to the X-ray. An evolution of the hardness of
the high-energy emission is demonstrated and we imply a minimum host extinction
from a comparison of the extrapolated X-ray flux to that measured in the
optical. We find that the flaring gamma-ray and X-ray emission is likely due to
internal shocks while the flat optical light curve at that time is due to the
external shock. The late afterglow is best explained by a cooling break between
the optical and X-rays and continued central engine activity up to the time of
the break. The required collimation corrected energy of ~ 2x10^52 erg, while at
the high end of the known energy distribution, is not unprecedented.Comment: 8 pages, 4 figures, accepted to Astronomy & Astrophysics after minor
change
Swift observations of the 2006 outburst of the recurrent nova RS Ophiuchi: I. Early X-ray emission from the shocked ejecta and red giant wind
RS Ophiuchi began its latest outburst on 2006 February 12. Previous outbursts
have indicated that high velocity ejecta interact with a pre-existing red giant
wind, setting up shock systems analogous to those seen in Supernova Remnants.
However, in the previous outburst in 1985, X-ray observations did not commence
until 55 days after the initial explosion. Here we report on Swift observations
covering the first month of the 2006 outburst with the Burst Alert (BAT) and
X-ray Telescope (XRT) instruments. RS Oph was clearly detected in the BAT 14-25
keV band from t=0 to days. XRT observationsfrom 0.3-10 keV, started at
3.17 days after outburst. The rapidly evolving XRT spectra clearly show the
presence of both line and continuum emission which can be fitted by thermal
emission from hot gas whose characteristic temperature, overlying absorbing
column, , and resulting unabsorbed total flux decline monotonically
after the first few days. Derived shock velocities are in good agreement with
those found from observations at other wavelengths. Similarly, is in
accord with that expected from the red giant wind ahead of the forward shock.
We confirm the basic models of the 1985 outburst and conclude that standard
Phase I remnant evolution terminated by days and the remnant then
rapidly evolved to display behaviour characteristic of Phase III. Around t=26
days however, a new, luminous and highly variable soft X-ray source began to
appear whose origin will be explored in a subsequent paper.Comment: 20 pages, 4 figures (2 updated), accepted by Ap
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