My Home Page
I
specialize in near-IR and optical instrumentation, & extra-solar planets
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 is known
as PARAS (Prl Advanced Radial-velocity Abu-sky
Search).
PRL 2.5m Telescope Project and PARAS-2
Project
In the year 2016, the PRL initiated the the PRL 2.5m
telescope project with state of art Active Optics systems on the primary mirror
and overall wave front error of 70nm, which makes is 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 is now
supposed to see the first light early 2022.
PARAS-2
in the line of PARAS will be a new next generation PARAS instrument with
Resolution at R~100,000 and will be coupled to the telescope with octagonal fibers
and the telescope image psf will be controlled by a
fast tip/tilt system (working up to 20Hz). PARAS-2 like PARAS will be under
vacuum and temperature control with target goal of sub-1m/s precision on bright
targets. PARAS is designed and built on the line HARAPS. Details of PARAS-2
design can be found in: PARAS-2
precision radial velocimeter: optical and mechanical
design of a fiber-fed high resolution spectrograph
under vacuum and temperature control 2018SPIE10702E..6GC
The team members of the PARAS/ PARAS2
programs are:
1) Mr.
Kapil Kumar, Engineer SD
2) Mr.
Neelam Prasad, Engineer SD
3) Mr.
Rishikesh Sharma, Scientific Assistant
4) Mr.
Kevi Kumar Lad, Engineer SC
5) Mr.
Ashirbad Nayak, Engineer SC
6) Mr.
Dishendra , Scientific Assistant
Current PhD Student working in the PARAS
Project: Ms. Akanksha Khandelwal,
Senior Research Scholar
Past
PhD Student who worked in the PARAS Project: Dr. Priyanka Chaturvedi,
finished her PhD work in August 2016, currently is a Post-Doctoral Research
Fellow, at TLS, Tautenburg, Germany
Important exoplanet or brown-dwarf discoveries from PARAS:
“TOI-503:
The First Known Brown-dwarf Am-star Binary from the TESS Mission”. The Astronomical
Journal, arXiv:1909.07984 Bibcode:2020AJ....159..151S
doi: 10.3847/1538-3881/ab7245
"Evidence
of a Sub-Saturn around Epic 211945201". The Astronomical Journal. arXiv:1805.03466.
Bibcode:2018AJ....156....3C.
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, 2018AJ....156...27C
Review Article: State of the Field: Extreme Precision
Radial Velocities PASP, 2016PASP..128f6001F
“Evidence for Reflected Light from the
Most Eccentric Exoplanet Known” 2016ApJ...821...65K
“Determination of mass and orbital parameters of a low-mass
star HD 213597B” 2014MNRAS.442.3737C The
workshop was held on Jan 21 & 22 of 2013. Some of the International
participants of the workshop were Prof. Michel Mayor
& Dr. Francesco Pepe from Geneva Observatory, Switzerland, Prof. Alain Leger from IAS, France,
Dr. Suvrath
Mahadevan from Penn State University, US and
Prof. David Latham & Prof. Andrew
Szentgyorgyi from SAO, Harvard University, US. Clicking on their respective
names the presentations of these people can be downloaded. Please note that
these presentations are copyright materials of individual speakers. They should not be used for any
public event or any newspaper printing, or any such events and permission must be taken from these individuals. Other
important publications in the field of Astronomical Instrumentation and related
fields to exoplanets like high contrast imaging: 1) 10-7 contrast ratio at 4.5l/D: New
results obtained in laboratory experiments using nano-fabricated
coronagraph and multi-Gaussian shaped pupil masks. Abhijit Chakraborty, Laird A. Thompson, & Michael
Rogosky, 2005, Optics
Express, vol. 13, Issue 7, p.2394 2) Evidence of Planetesimal Infall
onto the Very Young Herbig Be Star LkHalpha 234. Abhijit
Chakraborty, Jian Ge, & Suvrath Mahadevan, 2004, ApJLetters, 606, 69 3) Unveiling Su Aurigae in the near Infrared:
New high spatial resolution results using Adaptive Optics. Abhijit Chakraborty & Jian Ge 2004, AJ, 127, 2898 4) First high Contrast Imaging using a Gaussian aperture pupil mask. J.H.
Debes, J. Ge, A. Chakraborty, 2002, ApJLetters, 572L, 165. 5) Progress with UnISIS: a Rayleigh
Laser Guided Adaptive Optics System.
2004. L.A. Thompson, S.W. Teare, Y.-H. Xiong, A. Chakraborty, R. Gruendl,
Proc. SPIE., 5490. 6) Design and Performance of a Versatile Penn
State near IR Imager and Spectrograph. Jian Ge, Abhijit Chakraborty, John Debes, Deqing Ren & Jerry Friedman, 2003, SPIE, 4841,
1503. 7) Adaptive Optics High Resolution IR
Spectroscopy with Silicon Grisms and Immersion
Gratings. Jian Ge, Dan McDavitt, Abhijit Chakraborty, John Bernecker &
Shane Miller 2003, SPIE, 4839 Contact: Dr.
Abhijit Chakraborty Professor,
and head of the Astronomy & Astrophysics Division, Project
Director, PRL 2.5m telescope Physical
Research Laboratory Ahmedabad
– 380009 Gujarat,
INDIA e-mail:
abhijit@prl.res.in