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Amanda Walker-LaFollette, Lauren Biddle, Cassandra Lejoly

Graduating Astronomy Major Research Symposium

On Thursday. April 24, at 3:45pm, a regular weekly research colloquium will be held, this time featuring four of our matriculating senior undergraduates. Lauren Biddle, Spencer Wallace, Amanda Walker-LaFollette, and Cassandra Lejoly will speak. Their abstracts are below. Please do join us. Pictured are Amanda Walker-LaFollette (left), Lauren Biddle (center), and Cassandra Lejoly (right). Not pictured, Spencer Wallace.

Lauren Biddle
It is important to explore the diversity of characteristics of ice giants to understand the nature and evolution of this class of planets. We present a homogeneous analysis of 12 new and 9 previously published broadband photometric observations of the Uranus-sized extrasolar planet GJ 3470b, which belongs to the growing sample of sub-Jovian bodies orbiting M dwarfs. The consistency of our analysis explains some of the discrepancies between previously published results and provides updated constraints on the planetary parameters. Our data are also consistent with previous transit observations of this system. The physical properties of the transiting system can only be constrained as well as the host star is characterized, so we provide new spectroscopic measurements of GJ 3470 from 0.33 to 2.42 μm to aid our analysis. We also perform a second analysis of the transmission spectrum of the entire ensemble of transit observations to date, supporting the existence of a H2 dominated atmosphere exhibiting a strong Rayleigh scattering slope.

Spencer Wallace
Current mixing length theories fail to properly address the interactions that occur between convective and stably stratified regions in stars. Purely local, static criteria such as Schwarzchild and Ledoux do not account for the mixing that occurs at the convective boundaries. We propose a dynamic boundary condition, based on the properties of the turbulent convective flow near the boundary, and describe how we implemented such a mixing mechanism in the MESA stellar evolution code. We also briefly consider how turbulence near the convective boundary affects semiconvective mixing.

Amanda Walker-LaFollette
We conducted a survey of the 63 starless and prestellar cores in the Perseus molecular cloud to study the kinematics of the cores using the Arizona Radio Observatory 12m telescope. We observed the cores in HCN and H13CN and looked for blue asymmetry in the line profile, a sign of infall. We classified the line profiles based on whether there is a clear asymmetry or skew in the profile. Blue asymmetric infall profiles across an entire starless and prestellar core population are rare. Comparing to the number of class II protostars in Perseus we estimated the lifetime of collapsing prestellar cores to be (0.25 - 1.6)×105yrs, which is 0.74 - 4.7 times longer than the gravitational freefall time. This could indicate that some of the infall candidates are tracing larger scale flows.

Cassandra Lejoly
I will present the periods of repeatability of individual coma features in Comet 1P/Halley measured using the position angle at different spatial distances from the nucleus in consequent cycles. I found that separate features appear to have different periods of repeatability within the same images, perhaps depending on the corresponding source regions on the nucleus. The periods of repeatability of coma morphologies will be presented as a function of time from the perihelion. I will also discuss the current work being done on the outflow velocities of the dust as well as the comprehensive modeling of the comet’s features.

2014 Outstanding Graduate Student Awardees

This year’s Department of Astronomy awards to outstanding graduate students, one in each of three categories, are the following:

Scholarship: Kathryn Decker French
Service: Kate Follette
Teaching: Megan Kiminki

Further, Kate Follette received the 2014 Outstanding Service Award for the entire College of Science, which was presented by Associate Dean Elliott Cheu to Kate in a special ceremony on Apr 16th.

Please join me in congratulating these students on their awards.

-Buell Jannuzi


Reporter Tom Beal fills us in on the latest from LSST and OSIRIS-REx

Two Tucson-based space science projects are moving from design to construction. OSIRIS-REx, the asteroid sampling mission being led by the University of Arizona’s Lunar and Planetary Laboratory, has been cleared by NASA to begin building a spacecraft, flight instruments, ground system and launch support facilities. The Large Synoptic Survey Telescope has passed its design review. Money for construction is in this year’s federal budget and a July date has been set for construction, pending final approval by the National Science Board in early May.

In Memory of Father Bill Stoeger, SJ, PhD, of the Vatican Observatory

Memorial Mass and Reception for Father William R. Stoeger, S.J., on Tuesday, April 22, at 5:00 pm at the Benedictine Monastery, 800 N. Country Club Road, Tucson AZ.
Priests who wish to concelebrate please bring an alb and white stole.
Please pass this invitation on to other friends of Father Bill Stoeger.
Inquiries to Fr. Chris Corbally

This remembrance was written by Jose Funes, the director of the Vatican Observatory, which has offices at Steward Observatory:

We are deeply saddened to announce the passing of Father Bill Stoeger, S.J.

He was called home to the Lord yesterday evening at the Sacred Heart Jesuit Center in Los Gatos, California. The Jesuit Community of the Vatican Observatory has lost a brother, a friend and an outstanding scientist.

Bill Stoeger was a staff scientist for the Vatican Observatory Research Group in Tucson, specializing in theoretical cosmology, high-energy astrophysics, and interdisciplinary studies relating to science, philosophy and theology. The eight volumes of the Vatican Observatory and the Center for Theology and the Natural Sciences series on "God's Action in the World" attest magnificently to this broad-based work.

His sensitivity to others was shown in finding the right words for special Masses, in the regular calls he received to give retreats, and in the lives of the very many people to whom he gave spiritual direction. Bill's goodness, and his genius, never ceased to move those around him. He was one of the few who could excel not only at understanding and working with the mathematics of the Big Bang but also at directing retreats for religious men and women.

The funeral mass was held at 10:00 AM on Friday March 28 at the Sacred Heart Jesuit Center in Los Gatos, CA.

Image courtesy NASA/Chris Gunn.

Engineers Install Near Infrared Camera into the Heart of Webb Telescope

NIRCam is provided by the University of Arizona and Lockheed Martin Advanced Technology Center.

NSF Graduate Research Fellowship

Please join our director, Buell Jannuzi in congratulating Benjamin Rackham, newly awarded an NSF Graduate Research Fellowship. Ben’s proposed research, entitled “Strange New Worlds: Exploring the Super-Earth / Hot Neptune Transition through Transmission Spectroscopy”, uses the Magellan and MMT telescopes to study the atmospheric properties of low-mass exoplanets. By pushing the envelope of ground-based transmission spectroscopy, his observations will set the stage for the detailed characterization of the low-mass exoplanets NASA’s TESS satellite will discover in the years ahead.

Buell Jannuzi, Director Steward Observatory


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