Student-Faculty Programs Office
Summer 2017 Announcements of Opportunity

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Project:  Circumstellar Matter (Jets, Disks and Torii) in Young and Dying Stars
Disciplines:  Astronomy/Astrophysics, Computational/Programming
Mentor:  Raghvendra Sahai, (JPL), Raghvendra.Sahai@jpl.nasa.gov, Phone: (818) 354-0452
Mentor URL:  http://science.jpl.nasa.gov/people/Sahai/  (opens in new window)
Background:  The research opportunity offered is related to the study of circumstellar
matter around young and dying Sun-like stars, and the ultraviolet variability of
planet-hosting Sun-like stars. Low and intermediate mass stars
are born in rotating clouds of gas and dust, and many aspects of this
evolutionary phase are poorly understood.
We are studying a newly-discovered class of isolated stellar nurseries,
free-floating Evaporating gaseous Globules (frEGGs), that are remarkable
astrophysical laboratories for studying the physics of star-formation
processes in irradiated environments.
As these stars reach the end of their lives, they carry out much of their
interesting nucleosyntheses (e.g. production of the biogenic elements C & N),
and through extensive mass-loss, disperse nucleosynthetic products and dust
into the interstellar medium. The dazzling shapes of planetary nebulae make
them not only immensely appealing to the public (as evident by their frequent
appearance in popular astronomy magazines) but also a serious challenge to
professional astronomers in finding a mechanism to produce their shapes. Many
of these results have attracted wide public attention and have been published
by in public media. The study of young and dying stars provides an important
contribution to the part of NASA's ORIGINS program which seeks to understand
the life-cycles of Sun-like stars and the physical mechanisms whereby the
death throes of these stars sow the seeds for the birth of new stars and solar
system.
The planets formed in extra-solar systems can interact with their host star:
this star-planet interaction (SIP) is poorly understood, but quite important.
UV observations can be used to study this process.
Description:  In support of my research on these stars, I have a large number of past and
current observational programs on radio and mm-wave interferometers such as
the JVLA and ALMA, and NASA's space observatories such as the Hubble Space
Telescope (HST), the Spitzer Space Telescope (SST), the Chandra X-Ray
Observatory (CXO), and GALEX. These programs are generating a large amount of
high-quality data, and opportunities exist for motivated students to help with
the analysis and modelling of these data for addressing important scientific
questions related to the death of Sun-like stars.
Specific research goals include work on (1) the physical and chemical
structure of frEGGS, (2) the role and origin of highly collimated jets, which
are an exciting, dramatic and integral feature of many astrophysical
environments, yet are very poorly understood, (3) the formation of large
masses of mm-sized grains equatorial disks/torii, and (4) the star-planet
interaction (SIP) and the temporal variability of the UV fluxes of stars with
detected planets. Motivated and energetic students can expect to be co-authors
on papers presented at the bi-annual meetings of the AAS, and peer-reviewed
journal papers related to their research (in recent years, 9 students have
been co-authors on such papers).
References:  1. "A collimated, high-speed outflow from the dying star V Hydrae",
Sahai, R.; Morris, M.; Knapp, G. R.; Young, K.; Barnbaum, C. 2003,
Nature, 426, 261
2. "Sculpting a Pre-planetary Nebula with a Precessing Jet: IRAS
16342-3814 Sahai, R. et al. 2005, ApJ, 622, L53
3. "Preplanetary Nebulae: An HST Imaging Survey and a New
Morphological Classification System", Sahai, R., Morris, M., S'anchez
Contreras, C., & Claussen, M. 2007,AJ, 134, 2200
4. "Binarity in Cool Asymptotic Giant Branch Stars: A Galex Search for
Ultraviolet Excesses", Sahai, R., Findeisen, K., Gil de Paz, A., &
S'anchez Contreras, C. 2008, ApJ, 689, 1274
5. "High-Velocity Interstellar Bullets in IRAS05506+2414: A Very
Young Protostar?", Sahai, R., Claussen, M., S'anchez Contreras, C.,
Morris, M. & Sarkar, G. 2008, ApJ, 680, 483
6. "An EVLA and CARMA study of dusty disks and torii with large grains
in dying stars", Sahai, R., Claussen, M.J., Schnee, S., Morris,
M.R., & S'anchez Contreras, C. 2011, ApJ, 739, L3
7. "Shocked and Scorched: The Tail of a Tadpole in an Interstellar
Pond", Sahai, R., Morris, M.R., & Claussen, M.J. 2012, ApJ, ApJ, 751, 69
8. "ALMA Observations of the Coldest Place in the Universe: The Boomerang
Nebula", Sahai, R., Vlemmings, W.H.T., Huggins, P.J., Nyman, L.-A., &
Gonidakis, I. 2013, ApJ, 777, 92
9. "Are Large, Cometary-shaped Proplyds Really (Free-floating) Evaporating
Gas Globules?", Sahai, R., Guesten, R., & Morris, M.R. 2012, ApJ, 761, L21
10. "An Extreme High-Velocity Bipolar Outflow in the Pre-Planetary Nebula
IRAS 08005-2356", Sahai, R., & Patel, N.A. 2015, ApJ, 810, L8
11. "A Pilot Deep Survey for X-Ray Emission from fuvAGB Stars", Sahai, R.,
Sanz-Forcada,J., Sanchez Contreras, C. & Stute, M. 2015, ApJ, 810, 77
SELECTED WEB REFERENCES
1. "Boomerang Nebula- the naturally coldest place currently known in
the Universe" http://en.wikipedia.org/wiki/Boomerang_Nebula
2. "Hubble Finds Stars That Go Ballistic"
http://www.physorg.com/news150562469.html
3. "ALMA REVEALS GHOSTLY SHAPE OF COLDEST PLACE IN THE UNIVERSE"
2013, Oct. 24, National Radio Astronomy Observatory
https://public.nrao.edu/news/pressreleases/alma-reveals-coldest-place-in-the-universe
Student Requirements:  1) basic background in Physics and/or Astronomy
2) a reasonable level of computational skill is preferred (e.g.,
some programming language like Fortran, C, C+, IDL, python)
Location / Safety:  Project building and/or room locations: . Student will need special safety training: No.
Programs:  This AO can be done under the following programs:

  Program    Available To
       SURF    both Caltech and non-Caltech students 

Click on a program name for program info and application requirements.


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Problems with or questions about submitting an AO?  Call Jen Manglos of the Student-Faculty Programs Office at (626) 395-2885.
 
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