Prof. Abhijit Chakraborty

The PARAS Project

At PRL I initiated for the first time in India a dedicated program on detection of Extra-Solar Planets using the techniques of precision radial velocity measurements (spectroscopy). The program was started in 2008 under which I designed and build an Echelle Spectrograph under temperature control and Vacuum. The precision radial velocity measurements of stars is obtained using a fiber-fed optical echelle spectrograph at R~67,000 (from 3700A to 9000A). The spectrograph saw first light in April 2010 and after many engineering runs the science observations were started from mid 2012. It is coupled with our 1.2m Telescope at Gurushikar, Mt. Abu. The spectrograph is under vacuum (0.05 to 0.1mbar) and temperature controlled (0.005C at 24.55C). We are also following some of the bright targets between 8th and 10th magnitudes from TESS/K2 candidates that are publicly announced by these programs. The PRL exoplanet program is known as PARAS (Prl Advanced Radial-velocity Abu-sky Search). The PARAS spectograph is used for the first exoplanet discovery by any Indian facility as well as Indian Scientists. Till now, it has produced three exopanet discoveries along with characterization mutiple sub-stellar and stellar objects.

The PARAS-2 Project

In the year 2016, PRL initiated the PRL 2.5m telescope project with state-of-the-art Active Optics systems on the primary mirror and an overall wavefront error of 70nm, which makes it the most precise telescope in terms of image quality in the country. During the factory acceptance test at M/s. AMOS, Belgium facility, 0.3 arcsec FWHM of star images were observed using speckle imaging in the V band. The 2.5m telescope Site acceptance Test was successfully completed in October 2022.

More details about the telescope can be found here.

PARAS-2 is the advanced version of the PARAS (now called PARAS-1) with a resolution of R~110,000, coupled to the telescope with octagonal fibers and the telescope image is controlled by a fast tip/tilt system (working up to 20Hz). PARAS-2 is under an ultra-stable thermal environment (vacuum and temperature control) which is capable of achieving sub-1m/s precision on bright G & K dwarfs.

Details of the PARAS-2 design can be found at PARAS-2 Design.

The first light and intrinstic instrumental stability results of PARAS-2 can be found at: PARAS-2 First light.

Recently, we have discovered a very dense sub-Saturn using PARAS-2: Sub-Saturn from PARAS-2.

Publications

All publications

Important exoplanet or brown-dwarf discoveries from PARAS & PARAS-2:

• “Discovery and characterization of a dense sub-Saturn TOI-6651b”, MNRAS, arxiv:2106.08660, doi: 10.1051/0004-6361/202450934
• “Discovery of a massive giant planet with extreme density around the sub-giant star TOI-4603”, A & A Letters, arxiv:2303.11841, doi: 10.1051/0004-6361/202245608
• “Discovery of an inflated hot Jupiter around a slightly evolved star TOI-1789”, MNRAS, arxiv:2106.08660, doi: 10.1093/mnras/stab2970
• “TOI-503: The First Known Brown-dwarf Am-star Binary from the TESS Mission”, The Astronomical Journal, arxiv:1909.07984, doi: 10.3847/1538-3881/ab7245
• “Evidence of a Sub-Saturn around Epic 211945201”, The Astronomical Journal, arxiv:1805.03466, doi: 10.3847/1538-3881/aac436

Other significant publications from PARAS:

• “Masses and Radii of Four Very Low-mass Stars in F+M Eclipsing Binary Systems”, The Astronomical Journal, arxiv:1805.05841, doi: 10.3847/1538-3881/aac5de
• “Precision wavelength calibration for radial velocity measurements using uranium lines between 3800 and 6900 Å”, JATIS, arxiv:2105.12942, doi: 10.1117/1.JATIS.7.3.038005
• “ State of the Field: Extreme Precision Radial Velocities”, PASP, arxiv:1602.07939, doi: 10.1088/1538-3873/128/964/066001
• “ Evidence for Reflected Light from the Most Eccentric Exoplanet Known”, The Astrophysical Journal, arxiv:1511.08679, doi: 10.3847/0004-637X/821/1/65
• “ Detection of a very low mass star in an eclipsing binary system”, MNRAS, arxiv:1607.03277, doi: 10.1093/mnras/stw1560
• “ Determination of mass and orbital parameters of a low-mass star HD 213597B”, MNRAS, arxiv:1406.1641, doi: 10.1093/mnras/stu1127
• “ The PRL Stabilized High-Resolution Echelle Fiber-fed Spectrograph: Instrument Description and First Radial Velocity Results”, PASP, arxiv:1312.5471, doi: 10.1086/675352

Team Members

Mr. Kapil Kumar Bharadwaj, Scientist/Engineer-SE

Mr. Neelam JSSV Prasad, Scientist/Engineer-SE

Mr. Rishikesh Sharma, Scientist/Engineer-SC

Mr. Kevi Kumar Lad, Scientist/Engineer-SD

Mr. Ashirbad Nayak, Scientist/Engineer-SD

Ms. Nikitha Jithendran, Scientist/Engineer-SC

Mr. Churchil Dwivedi , Scientist/Engineer-SC

Current and Past Students

Current PhD Students

Mr. Sanjay Baliwal, SRF

Mr. Shuhendra Nath Das, SRF

Past PhD Students

Dr. Priyanka Chaturvedi, finished PhD in August 2016, currently an Academic Faculty at TIFR, Mumbai, India.

Dr. Akanksha Khandelwal, finished PhD in August 2024, currently a Post-Doctoral Fellow at Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City, Mexico.

Contact

Prof. Abhijit Chakraborty

Senior Professor, FNASc

Head of Astronomy & Astrophysics Division

Project Director, PRL 2.5m telescope

Physical Research Laboratory, Ahmedabad – 380009, Gujarat, INDIA

Email: [email protected] | [email protected]