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  • 10:47 PM, Monday, 20 Sep 2021

Department of Earth and Space Sciences
Dr. Resmi Lekshmi
Associate Professor


PhD in Astrophysics. Joint Astronomy Program, Indian Institute of Science, Bangalore.

  • Post-doctoral fellow, Institut d’Astrophysique de Paris, France.
  • Post-doctoral fellow, Tata Institute of fundamental Research, Bombay, India.

Research Work / Area

I use theoretical modelling and observational techniques to study astrophysical sources, especially the bright energetic explosions called Gamma Ray Bursts and a class of “active galaxies” called Blazars.  My broad areas of interest are High Energy Astrophysics, Radiation processes in astrophysical contexts, Relativistic sources, X-ray and gamma-ray astronomy.

Funded Project

DST funded project on the "Physics of radio bright Gamma-Ray Burst afterglows" (EMR/2016/007127).

Area of Interest

(Art-house) Movies, Trekking, Travelling, Birding, Photography, River kayaking.


  • Cospar Capacity Building Fellowship to work on Fermi Gamma Ray Space Telescope observaions (at GSFC and UAH, Alabama).
  • Young Astronomer Award for year 2005, by Astronomical Society of India.
  • Research Fellowship, year 1999. Council for Scientific and Industrial Research, India.
  • JNCASR Summer Research Fellowship, 1999. (at IUCAA on Galactic dynamics)

Membership in Professional Bodies

Life-member, Astronomical Society of India (ASI)

Co-coordinator, SKA-India Working group for Transients

Member, Indigo Consortium


N E W S !!!

Electromagnetic follow-up of the first binary neutron star merger (GW170817) detected by Ligo.

Our group searched for the radio afterglow of the associated Gamma Ray Burst with GMRT and ALMA. See the Indigo press release of the event, with emphasize on the Indian contribution here. We used ALMA and GMRT limits to draw the structure and energetics of the  burst. See the list of publications for more details.


DST funded PhD position (Deadline 14 Dec 2017 17:00hrs IST) to work on Gamma Ray Bursts and EM counterparts of GW events





Gamma Ray Bursts

The first afterglow of a Gamma Ray Burst (Costa+ 1997, Van Paradijs+ 1997)

Gamma Ray Bursts (GRBs) are the most energetic explosions in the universe known so far. They were discovered serendipitously 4 decades ago by Vela military satellites launched by the USA to monitor nuclear test ban treaty.  Since then our understanding of these bursts have improved tremendously. Now we believe that GRBs result from the gravitational collapse leading to the formation of a stellar mass blackhole. GRBs are broadly divided into two classes : long (duration) GRBs and short GRBs. The long ones, where the gamma-ray flash may last for up to 100s to 1000s of seconds is thought to be produced by the collapse of a single massive star while the short ones (duration <~ 2s) are considered to be due to the merger of a compact object binary via orbital energy loss through gravitational waves.


Blazars (in blue) in the 2nd yr catalog of Fermi Large Area Telescope (LAT) observations. Fermi LAT has broadened our knowledge of blazar population (Image from ASDC, Italy)

Blazars are a class of active galaxies. Most galaxies are normal. Their emission is mostly the cumulative light from all their stars and intervening gas/dust clouds. But some peculiar galaxies emit almost 5 orders of magnitude more energy than a typical galaxy. The spectrum of the emitted radiation does not resemble a typical stellar black-body. These galaxies are collectively known as “active galaxies”, where most of their energy release is believed to be due to gravitational heating by a Supermassive black-hole. Blazars are the extreme class where most of the emission we receive is believed to be arriving from a relativistic jet launched by the black-hole.


Kuntal Misra, ARIES, Nainital, India.

Bing Zhang,  Univ. of Nevada Las Vegas, USA.

S Sahayanathan, BARC, Bombay, India.

K G Arun, CMI, Chennai, India.

Archana Pai, IIT-Bombay, India.

Undergrad projects

I encourage motivated undergrad students for short term projects. Prefer students with (i) an understanding of basic special relativity OR/AND (ii) aptitude towards numerical programing in python or fortran. Exposure to Radiation Processes in Astrophysics is an advantage.

Projects involve (i) GRB physics, (ii) non-thermal radiation processes.

Under review
  1. M. Saleem, A. Pai, K. Misra, L. Resmi, and K. G. Arun, Rates of short GRB afterglows in association with binary neutron star mergers., MNRAS in review (astro-ph/1710.06111).
  2. M. Saleem, L. Resmi, K. Misra, A. Pai, and K. G. Arun, Exploring short GRB afterglow parameter space for observations in coincidence with gravitational waves., MNRAS in review (astro-ph/1710.06102).
  3. Nikhil Anand, Mustafa Shahid, and Resmi Lekshmi, Merger delay time distribution of extended emission short GRBs., MNRAS in review (astro-ph/1710.04996)
In Refereed Journals
  1. S. Kim, S. Schulze, L. Resmi, J. Gonzalez-Lopez, et al., ALMA and GMRT constraints on the off-axis Gamma-Ray Burst 170817a from the binary neutron merger GW170817., ApJ Letters, 2017, in press.
  2. Abbott, B. P., Abbott, R., Abbott, T. D., Acernese, F., et al., including Resmi. L., Multi-messenger observations of a binary neutron star merger., ApJ Letters, 2017, 848, 12.
  3. Resmi, L., Radio afterglows of Gamma Ray Bursts., Journal of Astronomy & Astrophysics, 2017, 38, 56.
  4. Chandra, P., G. C. Anupama, K. G. Arun, S. Iyyani et al., including Resmi L., Explosive and radio-selected transients : Transient astronomy with the Square Kilometer Array and its precursors, Journal of Astronomy & Astrophysics, 2016, 37, 30.
  5. Lekshmi Resmi & Bing Zhang, Gamma Ray Bust Reverse Shock Emission in Early Radio Afterglows, ApJ, 2016, 825, 48.
  6. P Kushwaha, S Sahayanathan, L Resmi et al.  Gamma-ray flare of PKS 1222+216 in 2010  : Effect of jet dynamics in the recollimation zone. MNRAS, 2014, 442, 131.
  7. L Resmi, K Misra, G Johannesson, A J Castro-Tirado et al. Comprehensive multi-wavelength modeling of the afterglow of GRB050525A. MNRAS, 2012, 427, 288.
  8. Lekshmi Resmi & Bing Zhang GRB prompt emission variability in synchrotron and synchrotron self-compton lightcurves.   MNRAS, 2012, 426, 1385.
  9. L Resmi & D Bhattacharya Hard electron energy distribution in the relativistic shocks of gamma-ray burst afterglows.  MNRAS, 2008, 388, 144.
  10. A J van der Horst, A Kamble, L Resmi, R A M J Wijers et al. Detailed study of the GRB 030329 radio afterglow deep into the non-relativistic phase.  A&A, 2008, 480, 35.
  11. A Kamble, L Resmi & K Misra  Observations of the Optical Afterglow of GRB050319 : Wind to ISM Transition in View.  ApJL, 2007, 664, 5.
  12. Kuntal Misra, Lekshmi Resmi, Shashi B Pandey, Dipankar Bhattacharya and Ram Sagar.   Optical observations and multiband modelling of the afterglow of GRB041006: Evidence of a hard electron energy spectrum.  BASI, 2005, 33, 487.
  13. L Resmi, C H Ishwara-Chandra, A J Castro-Tirado, D Bhattacharya et al.     Radio, millimeter and optical monitoring of GRB030329 afterglow: Constraining the double jet model.  A&A, 2005, 440, 447.
  14. S. B. Pandey, D. K. Sahu, L. Resmi, R. Sagar et al.   Optical observations of the bright long duration peculiar GRB021004 afterglow. BASI, 2003, 31, 19.
Selected list of talks & presentations
  • Astronomical Society of India meeting, Mohali, March 2014
  • National conference on High energy emission from AGN, Kashmir University, Srinagar (Invited)
  • Journal Club: Dept. of Physics & Astronomy, Univ. of Nevada, Las Vegas, USA, Nov 2009. ‘A closer look at prompt emission variability.’ & ‘Tale of a counter jet’
  • Nanjing GRB Workshop, Nanjing, China, June, 2008. ‘Modelling GRB Afterglows with Hard Electron Energy Spectra’.
  • Atelier AMT, Universitè Montpellier – II, Montpellier, France, April, 2007 “Evolution of Afterglow Modelling.” (Invited)
  • European RTN school on ‘GRBs : The First Three Hours’, Santorini, Greece, September 2005. ‘GMRT observations and modelling of GRB030329 afterglow’.
  • Computational Astrophysics (Jul-Dec 2017)
  • High Energy Astrophysics (Jan - Apr 2018)


Current members

1. Sreelakshmi P Chakyar has joined for PhD program in 2017.

2. Sreelekshmi Mohan is working on her MS thesis since June 2017.


Past members

  1. Koustubh Bhattacharjee (MS thesis)
  2. Suma N Murthy (MS Thesis)
  3. Ashish Mundara (BTech project)
  4. Rahul Dhanak (BTech project)
  5. Prateek Sharma (BTech project)
  6. Siddharth Mallik (BTech project)
  7. Nikhil Anand (informal project)
  8. Mustafa Shahid (informal project)



PhD position at IIST to work on Gamma Ray Bursts and EM counterparts of GW events

Applications are invited for a DST funded PhD position at IIST (Trivandrum) to work with L. Resmi and Kuntal Misra (ARIES) on Radio afterglows of Gamma Ray Bursts ( There will be a major focus on Electromagnetic counterparts of Gravitational Wave events which will be detected in Cycle O3 of AdvLigo/Virgo starting from mid-2018.

The student will focus on data analysis of radio transients and multi-wavelength modelling using data from other wavelengths.  Our group has guaranteed time on the NOrthern Extended Millimeter Array (NOEMA), Atacama Large Millimeter Array (ALMA) and Giant Meter Wave Radio Telescope (GMRT) as part of an international collaboration.

We seek excellent students with a strong background in Physics and interest in Astrophysics. Prior exposure to radio interferometric data analysis is an advantage, but not a necessary qualification. The research scholar is expected to travel to the GMRT facility at Pune, India, for observations and to ARIES, Nainital for collaborative purposes.The deadline for application is 14 Dec 2017, 17:00hrs IST.

Eligibility : (1) MSc in Physics/Astrophysics/Astronomy/Space Science/, or BS-MS in Physics, or equivalent. (2) Candidates should have cleared GATE Physics, or JEST Physics, or UGC-CISR National Eligibility test (in Physics). Selection will be carried out through application screening followed by an interview.

Fellowship :-  The DST funding is for a duration of 3 yrs. Monthly Emolument for the first two years is 25,000 INR and for the last year is 28,000 INR. On-campus accommodation will be provided subject to availability. In the event of non-availability of on-campus housing, HRA as per rules will be provided.   

How to apply?

Application has to be done online. See or

Position code JRF18.

Deadline :- 14 Dec 2017, 17:00 IST


Note that application link at IIST is under “project fellow” category. But the selected candidate will be able to register for the IIST PhD program.