14 research outputs found
From Chilly Climate to Warm Reception: Experiences and Good Practices for Supporting LGBTQ Students in STEM
Lesbian, gay, bisexual, transgender, and queer/questioning students (LGBTQ) face unique challenges during their university or college careers, and while society has generally become more accepting of sexual and gender minorities (SGM) over the past decade, students still often face chilly or outright hostile campus climates, as well as institutional and departmental policies and practices that create barriers to their learning and feeling of belonging in their classrooms and on their campuses. Research suggests that these issues are particularly pervasive in the disciplines of Science, Technology, Engineering and Mathematics (STEM), and there is some evidence to suggest that LGBTQ individuals are underrepresented in these fields, at least in the STEM federal agency workforce (Cech, 2015). In this work, I review the research pertaining to LGBTQ university and community college students in STEM fields, including departmental and campus climate, departmental and institutional policies, and student outcomes. I investigate the evidence for policy and intervention options, and synthesize the recommendations from the literature that can help to support SGM students in classrooms, departments, and institutions of higher education
The Mid-Infrared Spectrum of the Short Orbital Period Polar EF Eridani from the Spitzer Space Telescope
We present the first mid-infrared (5.5-14.5 micron) spectrum of a highly
magnetic cataclysmic variable, EF Eridani, obtained with the Infrared
Spectrograph on the Spitzer Space Telescope. The spectrum displays a relatively
flat, featureless continuum. A spectral energy distribution model consisting of
a 9500 K white dwarf, L5 secondary star, cyclotron emission corresponding to a
B~13 MG white dwarf magnetic field, and an optically thin circumbinary dust
disk is in reasonable agreement with the extant 2MASS, IRAC, and IRS
observations of EF Eri. Cyclotron emission is ruled out as a dominant
contributor to the infrared flux density at wavelengths >3 microns. The
spectral energy distribution longward of ~5 microns is dominated by dust
emission. Even longer wavelength observations would test the model's prediction
of a continuing gradual decline in the circumbinary disk-dominated region of
the spectral energy distribution.Comment: To be published in The Astrophysical Journa
Design and Construction of Absorption Cells for Precision Radial Velocities in the K Band using Methane Isotopologues
We present a method to optimize absorption cells for precise wavelength
calibration in the near-infrared. We apply it to design and optimize methane
isotopologue cells for precision radial velocity measurements in the K band. We
also describe the construction and installation of two such cells for the
CSHELL spectrograph at NASA's IRTF. We have obtained their high-resolution
laboratory spectra, which we can then use in precision radial velocity
measurements and which can also have other applications. In terms of obtainable
RV precision methane should out-perform other proposed cells, such as the
ammonia cell (NH) recently demonstrated on CRIRES/VLT. The
laboratory spectra of Ammonia and the Methane cells show strong absorption
features in the H band that could also be exploited for precision Doppler
measurements. We present spectra and preliminary radial velocity measurements
obtained during our first-light run. These initial results show that a
precision down to 20-30 m s can be obtained using a wavelength interval
of only 5 nm in the K band and S/N150. This supports the prediction that
a precision down to a few m s can be achieved on late M dwarfs using the
new generation of NIR spectrographs, thus enabling the detection of terrestrial
planets in their habitable zones. Doppler measurements in the NIR can also be
used to mitigate the radial velocity jitter due to stellar activity enabling
more efficient surveys on young active stars.Comment: accepted PASP, Apr 2012 (in press). Preprint version with 36 pages, 9
Figures, 2 Table
Observations of V592 Cassiopeiae with the Spitzer Space Telescope - Dust in the Mid-Infrared
We present the ultraviolet-optical-infrared spectral energy distribution of
the low inclination novalike cataclysmic variable V592 Cassiopeiae, including
new mid-infrared observations from 3.5-24 microns obtained with the Spitzer
Space Telescope. At wavelengths shortward of 8 microns, the spectral energy
distribution of V592 Cas is dominated by the steady state accretion disk, but
there is flux density in excess of the summed stellar components and accretion
disk at longer wavelengths. Reproducing the observed spectral energy
distribution from ultraviolet to mid-infrared wavelengths can be accomplished
by including a circumbinary disk composed of cool dust, with a maximum inner
edge temperature of ~500 K. The total mass of circumbinary dust in V592 Cas
(~10^21 g) is similar to that found from recent studies of infrared excess in
magnetic CVs, and is too small to have a significant effect on the long-term
secular evolution of the cataclysmic variable. The existence of circumbinary
dust in V592 Cas is possibly linked to the presence of a wind outflow in this
system, which can provide the necessary raw materials to replenish the
circumbinary disk on relatively short timescales, and/or could be a remnant
from the common envelope phase early in the formation history of the system.Comment: Accepted for publication in the Astrophysical Journa
Nova-like Cataclysmic Variables in the Infrared
Novalike cataclysmic variables have persistently high mass transfer rates and prominent steady state accretion disks. We present an analysis of infrared observations of twelve novalikes obtained from the Two Micron All Sky Survey, the Spitzer Space Telescope, and the Wide-field Infrared Survey Explorer All Sky Survey. The presence of an infrared excess at >3-5 microns over the expectation of a theoretical steady state accretion disk is ubiquitous in our sample. The strength of the infrared excess is not correlated with orbital period, but shows a statistically significant correlation (but shallow trend) with system inclination that might be partially (but not completely) linked to the increasing view of the cooler outer accretion disk and disk rim at higher inclinations. We discuss the possible origin of the infrared excess in terms of emission from bremsstrahlung or circumbinary dust, with either mechanism facilitated by the mass outflows (e.g., disk wind/corona, accretion stream overflow, and so on) present in novalikes. Our comparison of the relative advantages and disadvantages of either mechanism for explaining the observations suggests that the situation is rather ambiguous, largely circumstantial, and in need of stricter observational constraints.Peer reviewe
A high-precision near-infrared survey for radial velocity variable low-mass stars using CSHELL and a methane gas cell
We present the results of a precise near-infrared (NIR) radial velocity (RV) survey of 32 low-mass stars with spectral types K2-M4 using CSHELL at the NASA InfraRed Telescope Facility in the K band with an isotopologue methane gas cell to achieve wavelength calibration and a novel, iterative RV extraction method. We surveyed 14 members of young (≈25-150 Myr) moving groups, the young field star ϵ Eridani, and 18 nearby (<25 pc) low-mass stars and achieved typical single-measurement precisions of 8-15 m s-1with a long-term stability of 15-50 m s-1 over longer baselines. We obtain the best NIR RV constraints to date on 27 targets in our sample, 19 of which were never followed by high-precision RV surveys. Our results indicate that very active stars can display long-term RV variations as low as ∼25-50 m s-1 at ≈2.3125 μm, thus constraining the effect of jitter at these wavelengths. We provide the first multiwavelength confirmation of GJ 876 bc and independently retrieve orbital parameters consistent with previous studies. We recovered RV variabilities for HD 160934 AB and GJ 725 AB that are consistent with their known binary orbits, and nine other targets are candidate RV variables with a statistical significance of 3σ-5σ. Our method, combined with the new iSHELL spectrograph, will yield long-term RV precisions of ≲5 m s-1 in the NIR, which will allow the detection of super-Earths near the habitable zone of mid-M dwarfs
Measuring the rotational periods of isolated magnetic white dwarfs
We present time-series photometry of 30 isolated magnetic white dwarfs, surveyed with the Jacobus Kapteyn Telescope between 2002 August and 2003 May. We find that 9 were untestable due to varying comparison stars, but of the remaining 21, 5 (24%) are variable with reliably derived periods, while a further 9 (43%) are seen to vary during our study, but we were unable to derive the period. We interpret the variability to be the result of rotation of the objects. We find no correlation between rotation period and mass, temperature, magnetic field, or age. We have found variability in 9 targets with low magnetic field strengths and temperatures low enough for partially convective atmospheres, which we highlight as candidates for polarimetry to search for starspots. Most interestingly, we have found variability in one target, PG1658+441, which has a fully radiative atmosphere in which conventional starspots cannot form, but a magnetic field strength that is too low to cause magnetic dichroism. The source of variability in this target remains a mystery