Abstract Details
| Name: Sireesha Chamarthi Affiliation: Indian Institute of Astrophysics Conference ID: ASI2016_627 Title : Towards Radial Velocity Measurements with Iodine Absorption Cell on VBT Echelle Spectrograph Authors and Co-Authors : Ravinder K. Banyal, U. Lemke, S. Sriram, K. Ravi and Gajendra Pandey Abstract Type : Poster Abstract Category : Instrumentation and Techniques Abstract : Instrumental drift is a major source of errors in high precision spectroscopy in astronomy. Changing environmental conditions at the observatory can cause a nightly drift in the spectrograph exceeding several 100m/s to few km/s. In addition, calibration errors may arise from different optical paths traversed by the reference beam (from arc lamps) and the star light. Note that, the two exposures are not simultaneous and results in spurious shifts as well as distortions in both the dispersion and the PSF due to spectrograph flexure, detector movement, and several other unknowns. A self-calibrating gas absorption cell placed in the light path can eliminate some of these errors. We are implementing the Iodine (I2) absorption cell technique to improve the radial velocity precision of our Echelle spectrograph attached to the 2.3m Vainu Bappu Telescope at Kavalur. The superimposed narrow I2 absorption lines allow us a) to model the instrument profile of the spectrograph and b) to extract the tiny Doppler shift in the stellar spectra. A high resolution template of the Iodine gas is required to accurately model the instrument profile of the spectrograph. We have used a Fourier Transform Spectrograph (FTS) facility of BARC at Mumbai to obtained a high resolution ( R> 100,000) scan of the gas cell. In this presentation, our completed work on mechanical design, temperature controller and hardware interface of the I2 cell will be discussed. We will also present our analysis of the I2 FTS data, relevant statistics and algorithm used for compiling a line list for the Kavalur spectrograph. Some preliminary results of solar spectra and bright stars observations with Iodine cell will also be discussed. Finally, we will give an outline of our approach to develop radial velocity analysis code for the Iodine cell. |