14 research outputs found
Studying the Imaging Characteristics of Ultra Violet Imaging Telescope (UVIT) through Numerical Simulations
Ultra-Violet Imaging Telescope (UVIT) is one of the five payloads aboard the
Indian Space Research Organization (ISRO)'s ASTROSAT space mission. The science
objectives of UVIT are broad, extending from individual hot stars, star-forming
regions to active galactic nuclei. Imaging performance of UVIT would depend on
several factors in addition to the optics, e.g. resolution of the detectors,
Satellite Drift and Jitter, image frame acquisition rate, sky background,
source intensity etc. The use of intensified CMOS-imager based photon counting
detectors in UVIT put their own complexity over reconstruction of the images.
All these factors could lead to several systematic effects in the reconstructed
images. A study has been done through numerical simulations with artificial
point sources and archival image of a galaxy from GALEX data archive, to
explore the effects of all the above mentioned parameters on the reconstructed
images. In particular the issues of angular resolution, photometric accuracy
and photometric-nonlinearity associated with the intensified CMOS-imager based
photon counting detectors have been investigated. The photon events in image
frames are detected by three different centroid algorithms with some energy
thresholds. Our results show that in presence of bright sources, reconstructed
images from UVIT would suffer from photometric distortion in a complex way and
the presence of overlapping photon events could lead to complex patterns near
the bright sources. Further the angular resolution, photometric accuracy and
distortion would depend on the values of various thresholds chosen to detect
photon events.Comment: Submitted to PASP, 16 Pages, 9 figure
UNICS - An Unified Instrument Control System for Small/Medium Sized Astronomical Observatories
Although the astronomy community is witnessing an era of large telescopes,
smaller and medium sized telescopes still maintain their utility being larger
in numbers. In order to obtain better scientific outputs it is necessary to
incorporate modern and advanced technologies to the back-end instruments and to
their interfaces with the telescopes through various control processes. However
often tight financial constraints on the smaller and medium size observatories
limit the scope and utility of these systems. Most of the time for every new
development on the telescope the back-end control systems are required to be
built from scratch leading to high costs and efforts. Therefore a simple, low
cost control system for small and medium size observatory needs to be developed
to minimize the cost and efforts while going for the expansion of the
observatory. Here we report on the development of a modern, multipurpose
instrument control system UNICS (Unified Instrument Control System) to
integrate the controls of various instruments and devices mounted on the
telescope. UNICS consists of an embedded hardware unit called Common Control
Unit (CCU) and Linux based data acquisition and User Interface. The Hardware of
the CCU is built around the Atmel make ATmega 128 micro-controller and is
designed with a back-plane, Master Slave architecture. The Graphical User
Interface (GUI) has been developed based on QT and the back end application
software is based on C/C++. UNICS provides feedback mechanisms which give the
operator a good visibility and a quick-look display of the status and modes of
instruments. UNICS is being used for regular science observations since March
2008 on 2m, f/10 IUCAA Telescope located at Girawali, Pune India.Comment: Submitted to PASP, 10 Pages, 5 figure
Exploring the short-term variability of H and H emissions in a sample of M dwarfs
The time scales of variability in active M dwarfs can be related to their
various physical parameters. Thus, it is important to understand such
variability to decipher the physics of these objects. In this study, we have
performed the low resolution (5.7\AA) spectroscopic monitoring of 83 M
dwarfs (M0-M6.5) to study the variability of H / H emissions;
over the time scales from 0.7 to 2.3 hours with a cadence of 3-10
minutes. Data of a sample of another 43 late-type M dwarfs (M3.5-M8.5) from the
literature are also included to explore the entire spectral sequence. 53 of the
objects in our sample (64\%) show statistically significant short-term
variability in H. We show that this variability in 38 of them are most
likely to be related to the flaring events. We find that the early M dwarfs are
less variable despite showing higher activity strengths
(L/L \& L/L), which saturates around
10 for M0-M4 types. Using archival photometric light curves from
TESS and Kepler/K2 missions, the derived chromospheric emission (\ha and \hb
emission) variability is then explored for any plausible systematics with
respect to their rotation phase. The variability indicators clearly show higher
variability in late-type M dwarfs (M5-M8.5) with shorter rotation periods (2
days). For 44 sources, their age has been estimated using StarHorse project and
possible correlations with variability have been explored. The possible causes
and implications for these behaviors are discussed.Comment: There are 35 pages including 18 pages of supplementary material. The
manuscript is accepted for publication in MNRA
First Results from MFOSC-P : Low Resolution Optical Spectroscopy of a Sample of M dwarfs within 100 parsecs
Mt. Abu Faint Object Spectrograph and Camera (MFOSC-P) is an in-house
developed instrument for Physical Research Laboratory (PRL) 1.2m telescope at
Mt. Abu India, commissioned in February 2019. Here we present the first science
results derived from the low resolution spectroscopy program of a sample of M
Dwarfs carried out during the commissioning run of MFOSC-P between
February-June 2019. M dwarfs carry great significance for exoplanets searches
in habitable zone and are among the promising candidates for the observatory's
several ongoing observational campaigns. Determination of their accurate
atmospheric properties and fundamental parameters is essential to constrain
both their atmospheric and evolutionary models. In this study, we provide a low
resolution (R500) spectroscopic catalogue of 80 bright M dwarfs (J10)
and classify them using their optical spectra. We have also performed the
spectral synthesis and minimisation techniques to determine their
fundamental parameters viz. effective temperature and surface gravity by
comparing the observed spectra with the most recent BT-Settl synthetic spectra.
Spectral type of M dwarfs in our sample ranges from M0 to M5. The derived
effective temperature and surface gravity are ranging from 4000 K to 3000 K and
4.5 to 5.5 dex, respectively. In most of the cases, the derived spectral types
are in good agreement with previously assigned photometric classification.Comment: Accepted for Publication in MNRA
Technology Pipeline for Large Scale Cross-Lingual Dubbing of Lecture Videos into Multiple Indian Languages
Cross-lingual dubbing of lecture videos requires the transcription of the
original audio, correction and removal of disfluencies, domain term discovery,
text-to-text translation into the target language, chunking of text using
target language rhythm, text-to-speech synthesis followed by isochronous
lipsyncing to the original video. This task becomes challenging when the source
and target languages belong to different language families, resulting in
differences in generated audio duration. This is further compounded by the
original speaker's rhythm, especially for extempore speech. This paper
describes the challenges in regenerating English lecture videos in Indian
languages semi-automatically. A prototype is developed for dubbing lectures
into 9 Indian languages. A mean-opinion-score (MOS) is obtained for two
languages, Hindi and Tamil, on two different courses. The output video is
compared with the original video in terms of MOS (1-5) and lip synchronisation
with scores of 4.09 and 3.74, respectively. The human effort also reduces by
75%