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Raghvendra Sahai

Photo of Raghvendra Sahai

Address:

4800 Oak Grove Drive
M/S 183-900

Pasadena, CA 91109

Phone:

818.354.0452

Fax:

818.393.9088

Curriculum Vitae:

Click here

Member of:

Interstellar and Heliospheric Physics

Biography

Dr. Sahai's research has focused on the physics and chemistry of mass-loss in dying stars, the births of new stars in irradiated environments, and the accretion phase in the lives of massive stars, using both spectroscopic and continuum techniques, radio and infrared wavelengths. His most recent research interests include study the UV emission from exoplanet host-star systems using archival data form GALEX and new observations with the Hubble Space Telescope. He has over 140 published articles in these areas. He is a frequent invited speaker at conferences on evolved stars.

For his research, Dr. Sahai proposes new studies with, and/or uses archival data from NASA's Great Observatories (e.g., James Webb Space Telescope, Hubble Space Telescope, Chandra X-Ray Observatory, GALEX, Spitzer Space Telecope) and the Atacama Large Millimeter Array, to investigate the circumstellar environaments of young and dying stars, as well as exoplanet-host stars, with high angular and/or spectral resolution and/or at wavelengths only accessible from space. He is an expert at building detailed models, constrained by multiwavelength data, for studying individual objects, as well as object classes.

Dr. Sahai leads the science justification for a new compact space-based spectroscopic instrument concept to study the faint Universe (e.g., the Circum-Galactic Medium) at JPL.

In the past, he has led and/or participated in several space-based astrophysics mission and instrument concept studies such as a Probe-Class UV and optical observatory, SmallSat UV observatories to investigate accretion activity and binarity in dying stars and the star-planet interaction in exoplanet host stars, an infrared high-contrast coronagraphic imaging camera to search for planetary and brown dwarf companions around nearby stars, and circumstellar matter in young, main-sequence and dying stars (as part of the Design Reference Mission for the JWST). He was a member of the Science Team for the ECLIPSE coronagraphic telescope concept for a DISCOVERY-class mission to search for extra-solar giant planets.

He is a full member of the American Astronomical Society and the International Astronomical Union, and a founding member of the European Astronomical Society.

Education

  • Ph.D., California Institute of Technology (1985)
  • MS (Physics, First Class with Distinction), Indian Institute of Technology, Kanpur, India (1978)

Professional Experience

  • Jet Propulsion Laboratory / California Institute of Technology (1992-Present)
    • Principal Research Scientist (2008-Present)
    • Research Scientist, Senior A (2002-2008)
    • Research Scientist (1995-2001)
    • NHST Science Working Group (2002-2003)
    • Member, Science Team, HST's Wide Field and Planetary Camera 2 (1995-1999)
    • National Research Council Senior Resident Research Associate (1992-1995)
  • University of Gothenburg, Sweden (1986-1992)
    • Docent (1990-1992)
    • Post-doctoral Research Associate (1986-1990)
  • University of Texas, Austin, Post-doctoral Research Associate (1985-1986)
  • University of Texas, Austin, Robert A. Welch Foundation Fellow (1984-1985)

Funded Proposals

  • Co-I on NASA Minority University Research and Education Project Award (2015-20) to Cal State University (CSU), Los Angeles
  • 3 PI JPL Research & Technology Development Awards (2013,2014,2017)
  • 4 PI and 2 co-I XMM-Newton (ESA/NASA) GO program awards (2007-2017)
  • 30 PI and 9 co-I NASA Hubble Space Telescope GO program awards (1998-2021)
  • 1 co-I & US PI JWST Cycle 1 award (2021)
  • 2 co-I JWST Cycle 1 awards (2021)
  • 4 PI and 1 co-I SOFIA GO program awards (2011-2017)
  • 9 PI and 2 co-I NASA Chandra X-Ray Observatory GO program awards (2001-2015)
  • 3 PI and 1 co-I ESA/NASA Herschel Space Observatory GO program awards (2010-2012)
  • 3 PI and 5 co-I NASA Spitzer Space Telescope GO program awards (2004-2006)
  • 2 PI NASA Long Term Space Astrophysics 5-yr awards (1998-2003, 2005-2010)
  • 2 PI NASA GALEX GO program awards (2004, 2008)
  • 5 PI NASA Astrophysics Data Program 3-yr awards (2004-2007, 2010-2014, 2013-2016, 2017-2021
  • 6 co-I NASA Astrophysics Data Program 3-yr award (2021)

Mentoring and Supervision

  • 10/21-todate Jessica Jelke (U. Washington, Seattle, WA), MSP program
  • 01/22-04/22 Kaitlyn Shavelle (Columbia U., New York, NY), MSP program
  • 06/21-12/21 Miranda Chang (UCLA, Los Angeles, CA), MSP Program
  • 09/20-01/21 Cynthia Ibrahim (San Diego State University, San Diego, CA), MSP program
  • 06/20-12/20 Amelia Whitworth (California Istitute of Technology, Pasadena, CA), Caltech SURF & MSP program
  • 06/20-09/20 Antonio Caceres (California Istitute of Technology, Pasadena, CA), Caltech SURF
  • 06/20-03/21 Rabia Husain (U. Texas, Austin, TX), MSP program
  • 01/18-05/18 Cristilyn Cortez (Cal State University, San Bernardino, CA), MSP program
  • 09/17-12/17 Alec Mangan (Iowa State University, Ames, IA), NASA UI program
  • 01/17-06/17 Samantha Scibelli (Stony Brook University, NY), NASA UI program
  • 06/16-08/16 Daniel McAndrew, Caltech, Caltech SURF program
  • 05/16-08/16 Jonathan Barnes, Cal State University (CSU), Los Angeles, MUREP/MIRO program
  • 02/16-06/15 Cristilyn Cortez (Cal State University, San Bernardino), SIRI program
  • 08/15-12/15 Samantha Scibelli (Stony Brook University, NY), NASA UI program
  • 02/15-08/15 Ryan McPeters (College of the Canyons, CA), SIRI and JPL Summer Internship program
  • 06/15-08/15 Kelechi Ikegwu (North Carolina A & T State University), NASA MUREP program
  • 01/15-06/15 Benjamin Stenger (Cal State University Fullerton, CA), Minority Scholar Programs in STEM
  • 06/09-08/15 Elizabeth Toller (MIT, MA), Minority Scholar Programs in STEM
  • 01/14-05/14 Galen Mack-Crane (Occidental College, Eagle Rock, CA), SIRI program
  • 06/13-08/13 Matthew Young (CSU, Los Angeles), California-Arizona Minority Partnership for Astronomy Research and Education (CAMPARE)
  • 01/13-05/13 Skyler Saleebyan (Glendale Community College, Glendale, CA), SIRI program
  • 01/13-05/13 Stoyan Ivanova (Georgia Tech., GA), NASA/USRP Internship program
  • 09/12-12/12 Alyx Stevens (U. Texas, Austin, TX), NASA/USRP Internship program
  • 06/12-07/12 Jennifer Deeb (Bear Creek High School, Lakewood, CO), Cal State University Summer Teacher and Researchers Program
  • 01/12-04/13 Jorge Munoz (Occidental College, Los Angeles, CA), SIRI & Caltech SURF program
  • 09/11-04/14 Alexandra Gruson (Santa Monica Community College, Santa Monica, CA), SIRI program & JPL Research Apprentice program
  • 09/11-12/11 Abigail Azari (Smith College, Northampton, MA), NASA/USRP Internship program
  • 01/11-05/11 Adam Blake (Embry-Riddle Aeronautical University, Daytona Beach, FL), NASA/USRP Internship program
  • 01/11-05/11 Nick Stantzos (Northern Arizona University, Flagstaff, AZ), NASA/USRP Internship program
  • 08/09-11/09 Charlotte Blumenfeld (Columbia University, NY), USRP Internship program
  • 06/09-09/09 Chris Chronopoulos (MIT, MA), Space Grant Student
  • 06/09-09/09 Anna Rosen (University of California, Berkeley, CA), Minority Initiatives Internship Summer Student

Service

  • 2022 Hubble Space Telescope Proposal Review Panel Cycle 30, Space Telescope Science Institute
  • 2021 JWST Cycle 1 Review Panel, Space Telescope Science Institute
  • 2021 MIDEX Concept MAGIC Science Review, JPL
  • 2021-2022 ALMA Cycle 8 Suppl., Cycles 9,10 Distributed Proposal Review, Joint ALMA Observatory
  • 2018 2018 Hubble Mid-Cycle Review Panel, Space Telescope Science Institute
  • 2017 ALMA Cycle 5 Proposal Review Committee, Joint ALMA Observatory
  • 2017 Hubble Fellow Selection Committee, Space Telescope Science Institute
  • 2017 Hubble Mid-Cycle Review Panel, Space Telescope Science Institute
  • 2017 Chalmers (Technical University) Academy Fellows Application Review, Knut & Alice Wallenberg Foundation’s (KAW), Sweden
  • 2016 ULTRASAT STMC review, Design Session for UltraSat Instrument STMC 2016-11, JPL
  • 2016 Design Session for Sona Palomar Instrument 2016-07, JPL
  • 2016 Cycle 24 Hubble Space Telescope Mid-Cycle Proposals Review
  • 2016 SOFIA Time Allocation Committee
  • 2016 ALMA Cycle 4 Proposal Review Committee, Joint ALMA Observatory
  • 01/09-05/09 John Caleb Wherry (Austin Peay State University, Clarksville, TN), NASA/USRP Internship program
  • 09/08-12/08 Rachael Ainsworth (U. Tennessee, Knoxville, TN), NASA/USRP Internship program
  • 02/07-08/07 Gregory Villar (CSU, Pomona), Minority Initiatives Internship Summer Student
  • (2008)
  • 02/07-08/07 Mark Rubin (CSU, Northridge, CA), Academic Part Time, (2007)
  • 02/07-08/07 Mark Rubin, Academic Part Time
  • 2005-07 Dr. M. Stute, Caltech Postdoctoral Scholar at JPL
  • 06/06-08/06 Krzysztof Findeisen (Cornell University, Ithaca, NY), Caltech Summer Research Undergraduate Fellow at JPL
  • 2001-03 Dr. C-F. Lee, Postdoctoral Scholar, National Research Council (NRC)
  • 2000-02 Dr. C. Sánchez Contreras, Caltech Postdoctoral Scholar at JPL
  • 1999 D. Ionita-Ariton (Caltech, CA), Caltech Summer Research Undergraduate Fellow at JPL
  • 1997-99 Dr. A. Dayal, Caltech Postdoctoral Scholar at JPL
  • 1995 B. E. Sugerman, Honors Thesis “Models of Kinematic Structure in the Circumstellar Outflows of the AGB Carbon Stars V Hydra Using High-Resolution Spectroscopy of the 4.6 μm CO Lines”, Occidental College
  • 1994 B. E. Sugerman (Occidental College, Eagle Rock, CA), Caltech Summer Research Undergraduate Fellow at JPLFrequent Referee for papers submitted to Astrophysical Journal, Astronomy and Astrophysics & Monthly Notices of the Royal Astronomical Society (1985-present)
  • Chandra Peer Proposal Review Panel Cycle 17 (2015)
  • Herschel Observing Time Allocation Committee (2010, 2011)
  • National Optical Astronomy Observatory (NOAO), Telescope Allocation Committee Member, Scientific Organizing Committee, International Conferences on"Asymmetric Planetary Nebulae VI, IV, and III" (2002-2013)
  • NASA Astrophysics Data Analysis Program [ADAP] Review (2011)
  • JPL Group Supervisor Alternate (2005-2008)
  • JPL Section Promotion Advisory Board Reviews (2002-2005)
  • JPL Research and Technology Development Review (2005)
  • Hubble Space Telescope Proposal Review Panel Cycles 10, 12, 15, 23 (2001-2015)
  • Spitzer Space Telescope Proposal Review Panel Cycle 2 (2005)
  • National Optical Astronomy Observatory (NOAO), Proposal Review Panel (2008)
  • JPL Annual Open House Wide Field Planetary Camera 2 Booth (1995-1998)

Teaching Experience

  • Advanced Undergraduate Course in "Stars and Stellar Atmospheres," Chalmers University of Technology and University of Gothenburg, Sweden (1988-1992)
  • Advanced Undergraduate Course in "Astronomical Techniques," Chalmers University of Technology and University of Gothenburg, Sweden (1990-1992)

Selected Awards

  • NASA Exceptional Public Service Medal 2018
  • President's Gold Medal, Best Outgoing Undergraduate Student, Indian Institute of Technology, Kanpur, India (1978)

Selected Publications

  1. A new self-consistent model of circumstellar CO emission for deriving mass-loss rates in red giants. I - The carbon-rich star U Camelopardalis", Sahai, R. 1990, ApJ, 362, 652
  2. Imaging of the Egg Nebula (CRL 2688) with WFPC2/HST: A History of AGB/Post–AGB Mass Loss", Sahai, R., Trauger, J.T., Watson, A.M., Stapelfeldt, K.R. et al. 1998, ApJ, 493, 301
  3. The Etched Hourglass Nebula MYCN 18. I. HUBBLE SPACE TELESCOPE Observations", Sahai, R., Dayal, A., Watson, A.M., Trauger, J.T., et al. 1999, AJ, 118, 468
  4. The Starfish Twins: Two Young Planetary Nebulae with Extreme Multipolar Morphology", Sahai, R. 2000, ApJ, 537, L43
  5. Shaping Proto-Planetary and Young Planetary Nebulae with Collimated Fast Winds", Lee, C-F. & Sahai, R. 2003, ApJ, 586, 319
  6. 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
  7. X-Ray Emission from the Preplanetary Nebula He3-1475", Sahai, R., Kastner, J.H., Morris, M., Frank, A., Blackman, E.G. 2003, ApJ, 599, L87
  8. Magnetohydrodynamic Models of the Knotty, Collimated Jet in He2-90", Lee, C-F. & Sahai, R. 2004, ApJ, 606, 483
  9. Sculpting a Pre-planetary Neula with a Precessing Jet: IRAS 16342-3814", Sahai, R.; Le Mignant, D., Sánchez Contreras, C., Campbell, R. D., Chaffee, F. H. 2005, ApJ, 622, L53.
  10. A Starfish Preplanetary Nebula: IRAS 19024+0044", Sahai, R.; Sánchez Contreras, C., Morris, M. 2005, ApJ, 620, 948
  11. A Massive Bipolar Outflow and a Dusty Torus with Large Grains in the Pre-Planetary Nebula IRAS 22036+5306", Sahai, R., Young, K., Patel, N.A., Sánchez Contreras, C. and Morris, M. 2006, ApJ, 653, 1241
  12. Hydrodynamical Simulations of the Jet in the Symbiotic Star MWC 560. III. Application to X-Ray Jets in Symbiotic Stars", Stute, M., & Sahai, R. 2007, ApJ, 665, 698
  13. Preplanetary Nebulae: An HST Imaging Survey and a New Morphological Classification System", Sahai, R., Morris, M., Sánchez Contreras, C., & Claussen, M. 2007, AJ, 134, 2200
  14. High-Velocity Interstellar Bullets in IRAS05506+2414: A Very Young Protostar?", Sahai, R., Claussen, M., Sánchez Contreras, C., Morris, M. & Sarkar, G. 2008, ApJ, 680, 483
  15. Binarity in Cool Asymptotic Giant Branch Stars: A Galex Search for Ultraviolet Excesses", Sahai, R., Findeisen, K., Gil de Paz, A., & Sánchez Contreras, C. 2008, ApJ, 689, 1274
  16. The Motion of Water Masers in the Pre-Planetary Nebula IRAS 16342-3814", Claussen, M.J., Sahai, R., & Morris, M., 2009, ApJ, 691, 219
  17. Collimated Fast Wind in the Pre-Planetary Nebula CRL 618", Lee, C-F., Hsu, M-C., & Sahai, R. 2009, ApJ, 696, 1630
  18. Sculpting an AGB Mass-Loss Envelope into a Bipolar Planetary Nebula: High-Velocity Outflows in V Hydrae", Sahai, R., Sugerman, B.E.K, Hinkle, K. 2009, ApJ, 699, 1015
  19. The Astrosphere of the Asymptotic Giant Branch Star IRC+10216", Sahai, R., & Chronopoulos, C. K.2010, ApJ, 711, L53
  20. The Dusty Circumstellar Disks of B[e] Supergiants in the Magellanic Clouds", Kastner, J. H., Buchanan, C., Sahai, R., Forrest, W. J., & Sargent, B. A. 2010, AJ, 139, 1993
  21. Young Planetary Nebulae: Hubble Space Telescope Imaging and a New Morphological Classification System", Sahai, R., Morris, M. R., & Villar, G. G. 2011, AJ, 141, 134
  22. 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., & Sánchez Contreras, C. 2011, ApJ, 739, L3
  23. Strong Variable Ultraviolet Emission from Y Gem: Accretion Activity in an AGB Star with a Binary Companion?", Sahai, R., Neill, J.D., Gil de Paz, A., & Sánchez Contreras, C. 2011, ApJ, 740, L39
  24. Shocked and Scorched: The Tail of a Tadpole in an Interstellar Pond", Sahai, R., Morris, M. R., & Claussen, M. J. 2012, ApJ, 751, 69
  25. Probing the mass and structure of the Ring Nebula in Lyra with SOFIA/GREAT observations of the [CII] 158 micron line", Sahai, R., Morris, M. R., Werner, M. W., Guesten, R., Wiesemeyer, H., & Sandell, G. 2012, A & A, 542, L20
  26. Are Large, Cometary-shaped Proplyds Really (Free-floating) Evaporating Gas Globules?", Sahai, R., Güsten, R., & Morris, M. R. 2012, ApJ Let, 761, L21
  27. OPACOS: OVRO Post-AGB CO (1-0) Emission Survey. I. Data and Derived Nebular Parameters", Sánchez Contreras, C., & Sahai, R. 2012, ApJS, 203, 16
  28. IRAS 19520+2759: a 105Lsun massive young stellar object driving a collimated outflow", Palau, A., Sánchez Contreras, C., Sahai, R., Sánchez-Monge, Á., & Rizzo, J. R. 2013, MNRAS, 428, 1537
  29. Mapping the Central Region of the PPN CRL 618 at Sub-arcsecond Resolution at 350 GHz", Lee, C.-F., Yang, C.-H., Sahai, R., & Sanchez Contreras, C. 2013, ApJ, 770, 153
  30. Multiple Fast Molecular Outflows in the Pre-planetary Nebula CRL 618 ", Lee, C.-F., Sahai, R., Sánchez Contreras, C., Huang, P.-S., & Hao Tay, J. J. 2013, ApJ, 777, 37
  31. ALMA Observations of the Coldest Place in the Universe: The Boomerang Nebula", Sahai, R., Vlemmings, W. H. T., Huggins, P. J., Nyman, L.-Å., & Gonidakis, I. 2013, ApJ, 777, 92
  32. Sahai, R. 2013, “From AGB Stars to Aspherical Planetary Nebulae An Observational Per- spective”, invited review, in Asymmetric Planetary Nebulae VI, conference held Nov. 4–8, 2013, Riviera Maya, Mexico (http://adsabs.harvard.edu/abs/2014apn6.confE..87S)
  33. Mid-infrared Imaging of the Bipolar Planetary Nebula M2-9 from SOFIA", Werner, M. W., Sahai, R., Davis, J., et al. 2014, ApJ, 780, 156
  34. The Astrosphere of the Asymptotic Giant Branch Star CIT 6, Sahai, R., & Mack-Crane, G. P. 2014, AJ, 148, 74
  35. 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
  36. An Extreme High-Velocity Bipolar Outflow in the Pre-Planetary Nebula IRAS 08005-2356, Sahai, R., & Patel, N.~A. 2015, ApJ, 810, L8
  37. High-Speed Bullet Ejections during the AGB to Planetary Nebula Transition: HST Observations of the Carbon Star, V Hydrae, Sahai, R., Scibelli, S., & Morris, M.R. 2016, ApJ, 827, 92
  38. ALMA Observations of the Water Fountain Pre-planetary Nebula IRAS 16342-3814: High-velocity Bipolar Jets and an Expanding Torus, Sahai, R., Vlemmings, W.~H.~T., Gledhill, T., Sanchez Contreras, C,. Lagadec, E,. Nyman, L.-AA, and Quintana-Lacaci, G. 2017, ApJ (Letters), 835, L13
  39. The large-scale nebular pattern of a superwind binary in an eccentric orbit, Kim, H., Trejo, A., Liu, S.-Y., Sahai, R., Taam, R.E., Morris, M.R., Hirano, N., Hsieh, I.-T 2017, Nature Astronomy, 1, 0060
  40. 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.-AA 2017, ApJ, 841, 11
  41. A molecular-line study of the interstellar bullet engine IRAS 05506+2414, Sahai, R., Lee, C.-F., Sanchez Contreras, C. , Patel, N., Morris, M., and Claussen, M., 2017, ApJ,  850, 158
  42. The Herschel Planetary Nebula Survey (HerPlaNS). A Comprehensive Dusty Photoionization Model of NGC6781, M. Otsuka, T. Ueta, P.A.M. van Hoof, Sahai, R., I. Aleman, A.A. Zijlstra, Y-H. Chu, E. Villaver, M. L. Leal-Ferreira, J. Kastner, R. Szczerba, K.M. Exter, 2017, ApJS, 231, 22
  43. “Binarity and Accretion in AGB Stars: HST/STIS Observations of UV Flickering in Y Gem”, Sahai, R., Sánchez Contreras, Mangan. A., Sanz-Forcada, J., Muthumariappan., C., and Claussen, M.J., 2018, ApJ, 860, 105
  44. “High-velocity Bullets from V Hydrae, an Asymptotic Giant Branch Star in Transition: Ejec-tion History and Spatio-kinematic Modeling”, Scibelli, S., Sahai, R., & Morris, M. R. 2019, ApJ, 870, 117
  45. “Observing Planetary and Pre-Planetary Nebulae with the James Webb Space Telescope”, Sahai, R., 2020, Galaxies 8, 61
  46. “ALMA reveals the coherence of the magnetic field geometry in OH 231.8+4.2”, Sabin, L., Sahai, R., Vlemmings, W. H. T., et al. 2020, MNRAS, 495, 4297
  47. “Evolution from Spherical AGB Wind to Multipolar Outflow in Pre-planetary Nebula IRAS 17150-3224”, Huang, P.-S., Lee, C.-F., Sahai, R., 2020, ApJ, 889, 85
  48. “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., Morris, M. R., Hinkle, K., Lee, C.-F. 2022, ApJ, 929 (doi:10.3847/1538-4357/ac568a)
  49. “A Study of the Dusty Disks and Shells around Post-RGB Stars in the LMC”, Sarkar, G., & Sahai, R., 2022, ApJ, 940, 54. doi:10.3847/1538-4357/ac8d03
  50. “Understanding High-Energy (UV and X-ray) Emission from AGB Stars – Episodic Accretion in Binary Systems”, Sahai, R., Sanz-Forcada, J., Guerrero, M., Ortiz, R., Contreras, C. S. 2022. Galaxies 10, 62
  51. The Binary and the Disk: The Beauty is Found within NGC3132 with JWST", Sahai, R., Bujarrabal, V., Quintana-Lacaci, G., et al. 2023, ApJ, 943, 110. doi:10.3847/1538-4357/aca7ba
  52. Faint but Not Forgotten. I. First Results from a Search for Astrospheres around AGB Stars in the Far-ultraviolet", Sahai, R. & Stenger, B. 2023, AJ, 165, 229. doi:10.3847/1538-3881/acccf2