• A. N. Ramaprakash

Articles written in Journal of Astrophysics and Astronomy

• Generation of a Near Infra-Red Guide Star Catalog for Thirty-Meter Telescope Observations

The requirements for the production of a near Infra-Red Guide Star Catalog (IRGSC) for Thirty Meter Telescope (TMT) observations are identified and presented. A methodology to compute the expected J band magnitude of stellar sources from their optical (𝑔, 𝑟 , 𝑖 ) magnitudes is developed. The computed and observed J magnitudes of sources in three test fields are compared and the methodology developed is found to be satisfactory for the magnitude range, JVega = 16–22 mag. From this analysis, we found that for the production of final TMT IRGSC (with a limiting magnitude of JVega = 22 mag), we need 𝑔, 𝑟, 𝑖 bands optical data which go up to 𝑖AB ∼ 23 mag. Fine tuning of the methodology developed, such as using Spectral Energy Distribution (SED) template fitting for optimal classification of stars in the fainter end, incorporating spectral libraries in the model, to reduce the scatter, and modification of the existing colour–temperature relation to increase the source density are planned for the subsequent phase of this work.

• A Road Map for the Generation of a Near-Infrared Guide Star Catalog for Thirty Meter Telescope Observations

The near-infrared instruments in the upcoming Thirty Meter Telescope (TMT) will be assisted by a multi conjugate Adaptive Optics (AO) system. For the efficient operation of the AO system, during observations, a near-infrared guide star catalog which goes as faint as 22 mag in ${\rm J}_{{\rm Vega}}$ band is essential and such a catalog does not exist. A methodology, based on stellar atmospheric models, to compute the expected near-infrared magnitudes of stellar sources from their optical magnitudes is developed. The method is applied and validated in JHKs bands for a magnitude range of ${\rm J}_{\rm{Vega}}$ 16--22 mag. The methodology is also applied and validated using the reference catalog of PAN STARRS. We verified that the properties of the final PAN STARRS optical catalog will satisfy the requirements of TMT IRGSC and will be one of the potential sources for the generation of the final catalog. In a broader context, this methodology is applicable for the generation of a guide star catalog for any existing/upcoming near-infrared telescopes.

• A near-infrared camera for iRobo-AO on the IUCAA 2-m telescope

The effect of atmospheric turbulence is gentler at infrared wavelengths than in visible regime. Hence adaptive optics (AO) delivers better performance in the infrared regime. Robotic Adaptive Optics (Robo-AO) is an AO system for medium-sized telescopes jointly built by Caltech, USA and IUCAA, India. It works with minimal overheads and provides good sky coverage in both visible and infrared regime. The ﬁrst version of Robo-AO does not have a high-quality NIR camera. For the second version called iRobo-AO, an NIR camera was developed at IUCAA to accommodate AO-corrected 1.0$^{\prime}$ ﬁeld-of-view in near-infrared bands. It can be used as a science camera as well as a tip-tilt camera. Here we describe the salient features of the NIR camera like optics, optomechanical design, detector control system etc.

• # Journal of Astrophysics and Astronomy

Current Issue
Volume 40 | Issue 5
October 2019

• # Continuous Article Publication

Posted on January 27, 2016

Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019