The field of exoplanets is highly competitive and demanding, given that detecting exoplanets involves observing millions of bright stars across a vast expanse of the sky. It necessitates the continuous monitoring of potential planet candidates, precise milli-magnitude photometry during planetary transits, and the determination of their radial-velocity variations with a precision of a few tens of meters per second. This type of study is best conducted through international collaboration. A significant portion of my exoplanetary research has been conducted within the SuperWASP collaboration, which has successfully identified over a hundred transiting exoplanets. With the goal of playing a pivotal role in advancing planetary science in India, I have actively participated in transit observations and data analysis of exoplanets using the 1.3-m Devasthal Fast Optical Telescope (DFOT), 2-m Himalayan Chandra Telescope (HCT), and 3.6-m Devasthal Optical Telescope (DOT). Our group collaborates with a global network to analyze photometric transit light curves, engaging in data analysis, modeling, and simulation. More recently, we initiated a long-term collaborative program on the 3.6-m DOT with the SPEARNET project, involving scientists from the UK, India, and Thailand. This initiative aims to conduct transmission spectroscopy of close-in giant exoplanets, providing valuable insights into their planetary atmospheres. Publications
The exploration of Galactic open clusters holds paramount significance in unraveling the intricacies of star formation history and understanding the characteristics of their parent star clusters. These systems play a crucial role in testing stellar models, providing vital insights into our comprehension of stellar evolution. At ARIES Nainital, we have initiated a comprehensive and long-term observational survey program aimed at conducting a photometric study of numerous understudied or inadequately explored star clusters within the Galaxy. In addition to scrutinizing the overall characteristics of these open clusters, we delve into the study of variable stars within some of these clusters. Understanding the nature of their variability serves as a valuable constraint on stellar pulsation models. Eclipsing binaries identified within these open clusters offer an alternative means of determining the distance to these stellar groups. Our investigations cover a broad spectrum, ranging from photometric (optical to mid-infrared) to space-based data, whenever available. For instance, the analysis of the NGC6866 cluster involved a comprehensive examination utilizing both ground-based observations and high-precision data from the Kepler satellite. This study revealed more than 178 variable stars within the cluster, including several new Delta-Scuti and Gamma-Dor type variables. Additionally, an asteroseismic study of the cluster unveiled a groundbreaking observation: hot stars extending up to A-spectral type follow a period-color relation, marking a significant finding. In our recent long-term variability analysis of clusters NGC 1960 and NGC 559, we identified over 150 periodic variables, further enriching our understanding of the dynamic nature of these clusters. Publications
Stars exhibit diverse forms of variability throughout their evolution, characterized by fluctuations in brightness and varying timescales. Photometric variability is thought to arise from several physical mechanisms, including stellar pulsation, rotational effects with an uneven distribution of cool spots, variable hot spots, obscuration by circumstellar disks, eclipsing events, and eruptions. The exploration of variable stars is of utmost importance as it provides a unique opportunity to delve into the interiors of stars, verifying stellar evolution theories and offering constraints that enhance our understanding of the structure and evolution of the Galaxy. In Nainital, we have embarked on a long-term project dedicated to the survey of variable stars within open star clusters in the Milky Way Galaxy. This initiative involves extensive time-series CCD observations conducted using telescopes ranging from 1 meter to 2 meters in size. Our ongoing efforts have resulted in the identification of hundreds of diverse variable stars within these regions. Additionally, I conduct a comprehensive study of the spatial and age distributions of Cepheids in the Local Group of galaxies. This research aims to unravel the processes of star formation and evolution within these galaxies, contributing valuable insights to our broader understanding of stellar dynamics across cosmic scales. Publications
Since 2006, my research has been dedicated to investigating the Galactic structure based on a substantial archival sample of Galactic open clusters. Additionally, I have collaborated on a joint research project with Russian partners, focusing on the Galactic disk and Galactic structure. This collaborative effort is supported by the Department of Science & Technology, Government of India, and the Russian Foundation for Basic Research in Moscow. Within the framework of this project, we have extensively studied archival data on open star clusters, aiming to comprehend the distribution of clusters in the Galaxy and explore the Galactic structure. A statistical analysis of a large number of star clusters in the Galaxy becomes imperative for probing the Galactic disk and structure, particularly in the solar neighborhood, given that the majority of detected clusters are located within 3 kpc of the Sun. Our investigations have yielded significant results, enabling us to determine crucial parameters such as scale height, solar displacement, and local mass density. This information is instrumental in gaining insights into the behavior of the Galactic disk in the solar neighborhood. The geometrical characteristics of a substantial number of clusters have provided a deeper understanding of the large-scale spatial properties of cluster systems within the Galaxy. Publications
Dr. Yogesh C. Joshi
Scientist-F
Aryabhatta Research Institute of Observational Sciences (ARIES)
Ministry of Science and Technology, Govt. of India
Nainital-263001
India
Office Room: 125
New Building, First Floor
Office Phone: +91-(0)5942-270754
Office Extn.: 754
Email: yogesh@aries.res.in
Last modified Thursday, 01 March 2024