Ultra Violet Imaging Telescope (UVIT) on ASTROSAT

Kumar, Amit; Ghosh, S. K.; Hutchings, J. B.; Kamath, Pritish; Srinivasan, Kathiravan; Pathakoti, Mahesh; Murthy, Jayant; Nagbhushana, S.; Pati, A. K.; Rao, Mukund; Rao, N. Kameswara; Sriram, S.; Tandon, S. N.

doi:10.1117/12.924507

Cited by 69 publications

(31 citation statements)

References 2 publications

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“…UVIT is primarily an imaging telescope on board AstroSat and consists of 3 channels in visible and ultraviolet(UV): VIS (320-550 nm), NUV (200-300 nm) and FUV (130-180 nm) wavelengths provided with absolute spatial resolution (FWHM < 1.8") images in a field of view ∼ 28 ′ (Kumar et al 2012;Annapurni et al 2016;Tandon et al 2017). The detail information on the detectors and the UVIT filetrs are available at the AstroSat UVIT website 3 .…”

Section: Uvitmentioning

confidence: 99%

Unravelling the unusually curved X-ray spectrum of RGB J0710 + 591 using AstroSat observations

Goswami

Sinha

Chandra

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We report the analysis of simultaneous multi-wavelength data of the high energy peaked blazar RGB J0710+591 from the LAXPC, SXT and UVIT instruments on-board AstroSat. The wide band X-ray spectrum (0.35 -30 keV) is modelled as synchrotron emission from a non-thermal distribution of high energy electrons. The spectrum is unusually curved, with a curvature parameter β p ∼ 6.4 for a log parabola particle distribution, or a high energy spectral index p 2 > 4.5 for a broken power-law distribution. The spectrum shows more curvature than an earlier quasi-simultaneous analysis of Swift -XRT/NuSTAR data where the parameters were β p ∼ 2.2 or p 2 ∼ 4. It has long been known that a power-law electron distribution can be produced from a region where particles are accelerated under Fermi process and the radiative losses in acceleration site decide the maximum attainable Lorentz factor, γ max . Consequently, this quantity decides the energy at which the spectrum curves steeply. We show that such a distribution provides a more natural explanation for the AstroSat data as well as the earlier XRT/NuSTAR observation, making this as the first well constrained determination of the photon energy corresponding to γ max . This in turn provides an estimate of the acceleration time-scale as a function of magnetic field and Doppler factor. The UVIT observations are consistent with earlier optical/UV measurements and reconfirm that they plausibly correspond to a different radiative component than the one responsible for the X-ray emission.

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Section: Uvitmentioning

confidence: 99%

Unravelling the unusually curved X-ray spectrum of RGB J0710 + 591 using AstroSat observations

Goswami

Sinha

Chandra

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…There are 5 payloads on the satellite with spectral coverage from the hard X-ray (0.5 -100 keV) to the optical (Singh et al 2014). We will focus on data from the Ultraviolet Imaging Telescope (UVIT) (Kumar et al 2012). The UVIT consists of two 35cm Ritchey-Chrètien telescopes with one channel dedicated to the far ultraviolet (FUV: 1250 -1830Å) and the other split between the near ultraviolet (NUV: 1900 -3040Å) and the visible (VIS: 3040 -5500Å) through the use of a dichroic beam splitter.…”

Section: Uvit Observations and Datamentioning

confidence: 99%

“…Only very nearby bright galaxies provide the opportunity to study star-forming regions in detail. In this paper, we have used the recently launched Ultraviolet Imaging Telescope (UVIT) instrument (Kumar et al 2012;Tandon et al 2017) on-board the As-troSat multi-wavelength mission (Agrawal 2006;Singh et al 2014;Agrawal 2017) to do a deep study of the star-forming regions in the nearby spiral galaxy NGC 2336. Our aim is to characterize the spatially resolved star-forming knots in the disk of this galaxy, determine their SFRs and study their properties.…”

Section: Introductionmentioning

confidence: 99%

A study of the star forming regions in the spiral galaxy NGC 2336 using the Ultraviolet Imaging Telescope (UVIT)

Rahna

Das

Murthy

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present a far-UV (FUV) and near-UV (NUV) imaging study of recent star formation in the nearby spiral galaxy NGC 2336 using the Ultraviolet Imaging Telescope (UVIT). NGC 2336 is nearly face-on in morphology and has a multi-armed, branching spiral structure which is associated with star forming regions distributed mainly along the spiral arms and the co-rotation ring around the bar. We have identified 72 star forming knots in the disk, of which only two are in the inter-arm regions and 6 in the co-rotation ring. We have tabulated their positions and estimated their luminosities, sizes, star formation rates, colors, ages and masses. The ages and masses of these star forming knots were estimated using the Starburst99 stellar evolutionary synthesis models. The star forming knots have FUV and NUV mean sizes of 485 pc and 408 pc respectively and mean stellar masses of 9.8 ×10 5 M that range from 5.6 ×10 5 to 1.1 ×10 6 M . Their star formation rates vary from 6.9 ×10 −4 to 2.2 ×10 −2 M /yr in NUV and from 4.5 ×10 −4 to 1.8 ×10 −2 M /yr in FUV. The FUV-NUV colour of the knots is found to be bluest in the central region and becomes progressively redder as the radius increases. Our results suggest that star formation in disks with spiral structure is driven by the spiral density wave and is best traced by UV imaging as it encompasses clusters spanning a wide range of star forming ages and stellar masses.

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“…CIS have become increasingly relevant within astronomical imaging and have already been implemented in several projects including the Ultra Violet Imaging Telescope (UVIT) of ASTROSAT 4 . CMOS sensors can provide a greater level of on-chip functionality, including signal processing and timing control.…”

Section: Cmos Image Sensorsmentioning

confidence: 99%

Low voltage electron multiplying CCD in a CMOS process

2016

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Low light level and high-speed image sensors as required for space applications can suffer from a decrease in the signal to noise ratio (SNR) due to the photon-starved environment and limitations of the sensor's readout noise. The SNR can be increased by the implementation of Time Delay Integration (TDI) as it allows photoelectrons from multiple exposures to be summed in the charge domain with no added noise. Electron Multiplication (EM) can further improve the SNR and lead to an increase in device performance. However, both techniques have traditionally been confined to Charge Coupled Devices (CCD) due to the efficient charge transfer required. With the increase in demand for CMOS sensors with equivalent or superior functionality and performance, this paper presents findings from the characterisation of a low voltage EMCCD in a CMOS process using advanced design features to increase the electron multiplying gain. By using the CMOS process, it is possible to increase chip integration and functionality and achieve higher readout speeds and reduced pixel size. The presented characterisation results include analysis of the photon transfer curve, the dark current, the electron multiplying gain and analysis of the parameters' dependence on temperature and operating voltage.

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Ultra Violet Imaging Telescope (UVIT) on ASTROSAT

Cited by 69 publications

References 2 publications

Unravelling the unusually curved X-ray spectrum of RGB J0710 + 591 using AstroSat observations

Unravelling the unusually curved X-ray spectrum of RGB J0710 + 591 using AstroSat observations

A study of the star forming regions in the spiral galaxy NGC 2336 using the Ultraviolet Imaging Telescope (UVIT)

Low voltage electron multiplying CCD in a CMOS process

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