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Announcements of Opportunity
SURF@JPL: Announcements of Opportunity
Announcements of Opportunity are posted by JPL technical staff for the SURF@JPL program. Each AO indicates whether or not it is open to non-Caltech students. If an AO is NOT open to non-Caltech students, please DO NOT contact the mentor.
Announcements of Opportunity are posted as they are received. Please check back regularly for new AO submissions!
**Students applying for JPL projects should complete a SURF@JPL application instead of a "regular" SURF application.
**Students pursuing opportunities at JPL must be U.S. citizens or U.S. permanent residents.
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Circumstellar Matter (Jets, Disks and Torii) in Young and Dying Stars
(JPL AO No. 14247)
|Mentor URL:||https://science.jpl.nasa.gov/people/Sahai/ (opens in new window)|
The research opportunities offered here cover three diverse studies as
follows: (1) the formation of young stars, (2) the death of Sun-like
stars, and (3) the ultraviolet properties of planet-hosting Sun-like
(1) 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.
(2) As these stars reach the end of their lives (as red giant stars),
they carry out much of their interesting nucleosynthesis (e.g.
production of the biogenic elements C & N), and through extensive
mass-loss, disperse nucleosynthetic products and dust into the
interstellar medium. The red giants then transform into planetary
nebulae with a dazzling variety of shapes that not only pose a serious
challenge to professional astronomers in finding a mechanism to produce
their shapes, but also make them immensely appealing to the public (as
evident by their frequent appearance in popular astronomy magazines).
Many of these results have attracted wide public attention and have
been published in public media. An outstanding example of these
phenomena is the coldest object in the Universe, the Boomerang Nebula.
(3) A new area of my research is focussed on the planets found in
extra-solar systems interacting with their host star: this star-planet
interaction (SPI) is poorly understood, but quite important. Archival UV
observations are being used to investigate this process.
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, the Chandra
X-Ray Observatory (CXO), GALEX, and more recently, TESS. 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
birth and deaths of Sun-like stars, and the star-planet interaction in
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. One student is a co-author on one,
and lead author on a 2nd follow-up paper in the Astrophysical Journal,
and continues scientific collaboration with me after joining graduate
school, which is expected to lead to more major publications.
Specific research goals include work on:
(1) the physical and chemical structure of free-floating evaporating
gaseous globules that birth stars in irradiated environments.
(2) the role and origin of highly collimated jets in stellar death (jets
are an exciting, dramatic and integral feature of many astrophysical
environments, yet are very poorly understood), and the formation of
large masses of mm-sized grains in equatorial disks or torii.
(3) the star-planet interaction (SPI) and the temporal variability of
the UV fluxes of stars with detected planets.
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
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
12. "The Coldest Place in the Universe: Probing the Ultra-Cold Outflow and Dusty Disk
in the Boomerang Nebula", Sahai, R., Vlemmings, W.~H.~T., Nyman, L.-A.2017,
ApJ, 841, 110
13. "A molecular-line study of the interstellar bullet engine IRAS 05506+2414",
Sahai, R., Lee, C.-F., Sanchez Contreras, C. , et al. 2017, ApJ, 850, 158
14. "Observing Planetary and Pre-Planetary Nebulae with the James Webb Space
Telescope", Sahai, R., 2020, Galaxies 8, 61
15. "The Rapidly Evolving Asymptotic Giant Branch Star, V Hya: ALMA Finds a Multiring
Circus with High-velocity Outflows", Sahai, R., Huang, P.-S., Scibelli, S., et al.
2022, ApJ, 929
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"
3. "ALMA REVEALS GHOSTLY SHAPE OF COLDEST PLACE IN THE UNIVERSE"
2013, Oct. 24, National Radio Astronomy Observatory
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: .|
This AO can be done under the following programs:
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