Multi-wavelength Space Research Articles

PECULIARITIES OF THE DISTRIBUTION AND DETECTION OF COSMIC RAYS, GAMMA-RAY BURSTS, AND OTHER HIGH-ENERGY SOURCES

The importance of using databases of scientific space missions for fundamental astrophysical research is demonstrated. Based on the spacecraft data and the obtained solutions of the transport equation, the estimates of level of the cosmic rays modulation in the heliospheric magnetic fields were made. Based on the archives of ground-based and space telescope observations in the radio and optical ranges, the radio properties of a sample of isolated active galactic nuclei in the nearby Universe have been systematized. Opportunities that may arise from the databases of future multiwavelength space missions are also considered.

Simultaneous X-ray/UV Observations of Ultraluminous X-ray Source Holmberg II X-1 with Indian Space Mission Astrosat

We present the results of 8 epochs of simultaneous UV and X-ray observations of the highly variable ultraluminous X-ray source (ULX) Holmberg II X-1 with AstroSat -- Indian multiwavelength space satellite. During the entire observation period from late 2016 to early 2020, Holmberg II X-1 showed a moderate X-ray luminosity of $8\times10^{39}$ erg/s and a hard power-law spectrum with $\Gamma \lesssim 1.9$. Due to low variability of the object in X-rays (by a factor 1.5) and insignificant variability in the UV range (upper limit $\approx25$%) we could not find reliable correlation between flux changes in these ranges. Inside each particular observation, the X-ray variability amplitude is higher, it reaches a factor of 2-3 respect to the mean level at the time scales of $\sim10$ ks or even shorter. We discussed our results in terms of three models of a heated donor star, a heated disk and a heated wind, and estimated the lower limit to the variability which would allow to reject at least part of them.

Study of dynamical status of the globular cluster NGC 1851 using ultraviolet imaging telescope

We present the study of dynamical status of the globular cluster NGC 1851. A combination of multi-wavelength space and ground-based data sets are used for the present analysis. In order to select the genuine cluster members, we used the astro-photometric data available from HST and GAIA-DR2 catalogs. The BSS radial distribution of the cluster is plotted from the center of the cluster to the outskirts. The radial distribution of BSS shows a central peak, followed by a dip at the intermediate radii (\(r_\mathrm{min}\sim 90''\)) and a rising trend in the outskirts. We also estimated \(A^{+}_{rh}\) parameter as 0.391 ± 0.006 to validate the findings of the radial distribution study. On the basis of the minima in the BSS radial distribution and the value of \(A^{+}_{rh}\) parameter, we conclude that NGC 1851 belongs to Family II classification and is an intermediate dynamical state cluster.

Imaging and photometric studies of NGC 1316 (Fornax A) using Astrosat/UVIT

We present imaging and photometric studies of the radio galaxy NGC 1316 (Fornax~A) using high spatial resolution near-ultraviolet (NUV) and far-ultraviolet (FUV) imaging telescopes of the first Indian multi-wavelength space observatory {\it AstroSat}. The residual maps of UV emission obtained from the subtraction of smooth models witness peculiar features within the central few kpc (1-2 kpc) region. The spatial correspondence between the radio emission maps and FUV imaging study reveal that the UV emitting sources are displaced away from the centre by the AGN outburst (radio jet). The presence of rims and clumpy structures in the outskirt of this galaxy delineate that the galaxy has acquired a large fraction of gas through merger-like events and is still in the process of settling. The estimates of the star formation rates (SFR) using FUV and NUV luminosities are found to be 0.15 M$_\odot$yr$^{-1}$ and 0.36 M$_\odot$yr$^{-1}$, respectively, and provide the lower limit due to the screen effect. The estimated lower rates of SFR in this galaxy probably represent its quenching due to the AGN driven outflows emanating from the central engine of NGC 1316.

AstroSat science support cell

AstroSat is India's first dedicated multi-wavelength space observatory launched by the Indian Space Research Organisation (ISRO) on 28 September 2015. After launch, the AstroSat Science Support Cell (ASSC) was set up as a joint venture of ISRO and the Inter-University Centre for Astronomy and Astrophysics (IUCAA) with the primary purpose of facilitating the use of AstroSat, both for making observing proposals and for utilising archival data. The ASSC organises meetings, workshops and webinars to train users in these activities, runs a help desk to address user queries, provides utility tools and disseminates analysis software through a consolidated web portal. It also maintains the AstroSat Proposal Processing System (APPS) which is deployed at ISSDC, a software platform central to the workflow management of AstroSat operations. This paper illustrates the various aspects of ASSC functionality.

Towards a BRICS Optical Transient Network (BRICS-OTN).

This paper is based on a proposal submitted for a BRICS astronomy flagship program, which was presented at the 2019 meeting of the BRICS Astronomy Working Group, held in Rio de Janeiro from 29 September to 2 October 2019. The future prospects for the detection and study of transient phenomena in the Universe heralds a new era in time domain astronomy. The case is presented for a dedicated BRICS-wide flagship program to develop a network of ground-based optical telescopes for an all-sky survey to detect short lived optical transients and to allow follow-up of multi-wavelength and multi-messenger transient objects. This will leverage existing and planned new facilities within the BRICS countries and will also draw on the opportunities presented by other multi-wavelength space- and ground-based facilities that exist within the BRICS group. The proposed optical network would initially perform followup observations on new transients using existing telescopes. This would later expand to include a new global network of \sim ∼ 70 wide-field 1-m telescopes which will cover the entire sky, simultaneously, with a cadence of less than a few hours. This realization would represent a ground-breaking and unique global capability, presenting many scientific opportunities and associated spin-off benefits to all BRICS countries.

Recommended optical system design for the SSST.

The Southern Spectroscopic Survey Telescope (SSST) is a planned multi-wavelength space survey telescope by China located in Chile. In this paper, we present a feasible optic system design based on wide-field Cassegrain corrector configuration for the SSST of China. Our recommended design has a large field of view (FOV) of $ {2.4^ \circ } \times {2.4^ \circ } $2.4∘×2.4∘ with its image spot size less than 0.3 arcsec in diameter for its full FOV in 80% encircled energy. The atmospheric dispersion effect and actual science requirements are taken into consideration. In addition, a trade-off study is presented. This paper can also provide a reference to the next generation of spectroscopic survey telescopes.

Optical design of the Extreme Coronagraph for Living Planetary Systems instrument for the LUVOIR mission study

The large UV/optical/IR surveyor (LUVOIR) is a concept for a highly capable, multiwavelength space observatory with ambitious science goals. Finding and characterizing a wide range of exoplanets, including those that might be habitable, is a major goal of the study. The ambitious science goals drive the challenges of optical design. This paper will present how the optical design meets the unique challenges for coronagraphs on large telescopes to achieve high contrast for a wide wavelength range from 200 to 2000 nm. Some of these unique challenges include the position and size of occulter masks, deformable mirror placement and separation, tight tolerances on the optical system and each element, and finally, packaging all instruments in a limited space. Three types of modules are designed after the coronagraph to explore the exoplanets and analyze the spectrum of detected exoplanet signals: two imaging cameras, two integral field spectrographs, and one high-resolution spectrometer. All of them work together to provide information to meet scientific challenges in searching for habitable planets. The optical designs, unique challenges, and the solutions for all coronagraph and spectral modules are presented. Their specifications derived from science goals are also presented.

Trigger Simulations for GRB Detection with the Swift Burst Alert Telescope

AbstractUnderstanding the intrinsic cosmic long gamma-ray burst (GRB) rate is essential in many aspects of astrophysics and cosmology, such as revealing the connection between GRBs, supernovae (SNe), and stellar evolution. Swift, a multi-wavelength space telescope, is quickly expanding the GRB category by observing hundreds of GRBs and their redshifts. However, it remains difficult to determine the intrinsic GRB rate due to the complex trigger algorithm adopted by Swift. Current studies of the GRB rate usually approximate the Swift trigger algorithm by a single detection threshold. Nevertheless, unlike the previously flown GRB instruments, Swift has over 500 trigger criteria based on count rates and additional thresholds for localization. To investigate possible systematic biases and further explore the intrinsic GRB rate as a function of redshift and the GRB luminosity function, we adopt a Monte Carlo approach by simulating all trigger criteria used by Swift. A precise estimation of the intrinsic GRB rate is important to reveal the GRB origins and their relation to the black-hole forming SNe. Additionally, the GRB rate at high redshifts provides a strong probe of the star formation history in the early universe, which is hard to measure directly through other methods.

Swift: a Multi-frequency Rapid Response Space Observatory

Swift is a rapid-response, multi-wavelength space observatory dedicated to gamma-ray burst astronomy. The mission, an international collaboration between USA, Italy and UK, is scheduled for launch in October 2004. Swift will carry on-board a wide-field coded-mask gamma-ray camera, a X-ray telescope and a UV-Optical telescope, providing wide and narrow field-of-view instruments capability. The gamma ray camera is expected to detect and image ≈100–150 GRBs per year with a few arcminutes position accuracy. Following a GRB detection the Swift spacecraft will autonomously point its narrow-field telescopes towards the sources within 20-70 seconds to determine arcsec and subarcsec positions accuracy together with detailed spectral and timing information. The accurate positions will be quickly transmitted to the ground thus enabling the timely use of the most advanced ground- and space-based telescopes to gather high quality spectra during the early, brightest phases of the afterglow.