1. Department of Earth and Space Sciences, Indian Institute of Space Science & Technology, Thiruvananthapuram 695547, Kerala, India
2. Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
3. Department of Physics, Yale University, New Haven, CT 06520, USA
4. Department of Astronomy, Yale University, New Haven, CT 06520, USA
5. Department of Astronomy & Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
6. Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007, Maharashtra, India