ORCID Profile
0000-0003-2325-8509
Current Organisations
Midnapore City College
,
Jadavpur University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Oxford University Press (OUP)
Date: 18-01-2008
Publisher: American Astronomical Society
Date: 22-08-2003
DOI: 10.1086/379003
Publisher: Springer Science and Business Media LLC
Date: 31-10-2022
Publisher: EDP Sciences
Date: 28-06-2006
Publisher: Springer Science and Business Media LLC
Date: 14-11-2021
Publisher: Cold Spring Harbor Laboratory
Date: 06-07-2020
DOI: 10.1101/2020.07.05.20146324
Abstract: Coronavirus Disease 2019 (COVID-19) started in Wuhan province of China in November 2019 and within a short time, it was declared as a worldwide pandemic by the World Health Organisation due to the very fast worldwide spread of the virus. There were a few studies that look for the correlation with infected in iduals and different environmental parameters using early data of COVID-19 but there was no study that deal with the variation of effective reproduction number and environmental factors. Effective reproduction number is the driving parameter of the spread of a pandemic and it is important to study the effect of various environmental factors on effective reproduction numbers to understand the effect of those factors on the spread of the virus. We have used time-dependent models to investigate the variation of different time-dependent driving parameters of COVID-19 like effective reproduction number and contact rate using data from India as a test case. India is a large population country that was highly affected due to the COVID-19 pandemic and has a wide span of different temperature and humidity regions and is ideal for such study. We have studied the impact of temperature and humidity on the spread of the virus of different Indian states using time-dependent epidemiological models SIRD, and SEIRD for a long time scale. We used a linear regression method to look for any dependency between the effective reproduction number with the relative humidity, absolute humidity, and temperature. The effective reproduction number showed a negative correlation with both relative and absolute humidity for most of the Indian states, which are statistically significant. This implies that relative and absolute humidity may have an important role in the variation of effective reproduction numbers. There was no conclusive evidence of a correlation between effective reproduction numbers and average air temperature.
Publisher: Oxford University Press (OUP)
Date: 02-2010
Publisher: Elsevier BV
Date: 08-2022
DOI: 10.1016/J.LSSR.2022.04.002
Abstract: Amino acids are the essential keys that contribute to the study of the formation of life. The simplest amino acid, glycine (NH2CH2COOH), has been searched for a long time in the interstellar medium, but all surveys of glycine have failed. Since the detection of glycine in the interstellar medium was extremely difficult, we aimed to search for the precursor of glycine. After detailed searches of the in idual prebiotic molecular species, we successfully identified the emission lines of possible glycine precursor molecule amino acetonitrile (NH2CH2CN) towards the hot molecular core G10.47 + 0.03 using the Atacama Large Millimeter/Submillimeter Array. The estimated statistical column density of amino acetonitrile was (9.10 ± 0.7) × 10
Publisher: Oxford University Press (OUP)
Date: 28-05-2012
Publisher: World Scientific Publishing Company
Date: 02-2006
Publisher: Oxford University Press (OUP)
Date: 15-09-2010
Publisher: Elsevier BV
Date: 08-2019
Publisher: Oxford University Press (OUP)
Date: 12-09-2023
Publisher: American Astronomical Society
Date: 02-11-2020
Publisher: Springer Science and Business Media LLC
Date: 11-2022
Publisher: Cambridge University Press (CUP)
Date: 2014
DOI: 10.1017/S1743921313009460
Abstract: We have measured HI absorption distance to the youngest Galactic supernova remnant G1.9+0.3. Absorption by known anomalous velocity features near the Galactic centre (GC) puts a lower limit on its distance from Sun as 10 kpc, 2 kpc further away from the GC. We have found a small diameter (1.6′) shell like structure G354.4+0.0, that shows polarised emission in the NVSS. Based on its morphology, angular size, HI distance and its spectrum between 1.4 GHz and 330 MHz, it is perhaps the second youngest SNR in the Galaxy that is expanding in a dense environment of an HII region surrounding it. Our pilot observation of the inner Galactic 4th quadrant within 337° l 354° with a fixed Galactic latitude of 0.37° has confirmed G345.1−0.2 as an SNR.
Publisher: Springer Science and Business Media LLC
Date: 28-02-2023
Publisher: Oxford University Press (OUP)
Date: 11-07-2009
Publisher: Oxford University Press (OUP)
Date: 31-01-2022
Abstract: We made a detailed study of the timing and spectral properties of the X-ray pulsar 1A 0535+262 during the recent giant outburst in 2020 November and December. The flux of the pulsar reached a record value of ∼12.5 Crab as observed by Swift/BAT (15–50 keV) and the corresponding mass accretion rate was ∼6.67 × 1017 g s−1 near the peak of the outburst. There was a transition from the subcritical to the supercritical accretion regime which allows exploring different properties of the source in the supercritical regime. A q-like feature was detected in the hardness–intensity diagram during the outburst. We observed high variability and strong energy dependence of pulse profiles during the outburst. Cyclotron Resonant Scattering Feature (CRSF) was detected at ∼44 keV from the NuSTAR energy spectrum in the subcritical regime and the corresponding magnetic field was B ≃ 4.9 × 1012 G. The energy of the CRSF was shifted towards lower energy in the supercritical regime. The luminosity dependence of the CRSF was studied and during the supercritical regime, a negative correlation was observed between the line energy and luminosity. The critical luminosity was ∼6 × 1037erg s−1 above which a state transition occurred. A reversal of correlation between the photon index and luminosity was observed near the critical luminosity. The NuSTAR spectra can be described by a composite model with two continuum components, a blackbody emission, cut-off power law, and a discrete component to account for the iron emission line at 6.4 keV. An additional cyclotron absorption feature was included in the model.
Publisher: Oxford University Press (OUP)
Date: 05-07-2022
Abstract: Hybrid Morphology Radio Sources (HyMoRS) are a very rare subclass of radio galaxies with apparent mixed FR morphology, i.e. these galaxies seem to have an FR-I structure on one side of the core and an FR-II structure on the other side of the core. We systematically searched for HyMoRS using Very Large Array (VLA) Faint Images of the Radio Sky at Twenty-cm (FIRST) survey with 1400 MHz frequency and identified 33 candidate HyMoRS. Our finding significantly increased the known s le size of HyMoRS. HyMoRS may play an essential role in understanding the interaction of jets with the interstellar medium and the much-debated topic of the FR dichotomy. We identified optical counterparts for 29 sources in our catalogue. In our s le of sources, one source (J1106+1355) had quasar-like behaviour. Four sources were BRCLG (Brightest Cluster Galaxies) and six were LRG (Luminous Red Galaxies). We have estimated the spectral index and radio luminosity of HyMoRS in our catalogue, when possible. We found that J1136–0328 was the most luminous source in our s le (log L = 27.01 W Hz−1sr−1). It was also the farthest HyMoRS (with a redshift z = 0.82) in our s le. With the help of a large s le size of discovered sources, various statistical properties of detected galaxies were studied.
Publisher: Springer Science and Business Media LLC
Date: 04-2019
Publisher: Springer Science and Business Media LLC
Date: 12-08-2022
Publisher: Springer Science and Business Media LLC
Date: 05-2023
Publisher: Cold Spring Harbor Laboratory
Date: 06-2021
DOI: 10.1101/2021.05.30.21258040
Abstract: India is one of the countries in the world which is badly affected by the Covid-19 second wave. Assembly election in four states and a union territory of India was taken place during March-May 2021 when the Covid-19 second wave was close to its peak and affected a huge number of people. We studied the impact of assembly election on the effective contact rate and the effective reproduction number of Covid-19 using different epidemiological models like SIR, SIRD, and SEIR. We also modeled the effective reproduction number for all election-bound states using different mathematical functions. We separately studied the case of all election-bound states and found all the states shown a distinct increase in the effective contact rate and the effective reproduction number during the election-bound time and just after that compared to pre-election time. States, where elections were conducted in single-phase, showed less increase in the effective contact rate and the reproduction number. The election commission imposed extra measures from the first week of April 2021 to restrict big c aign rallies, meetings, and different political activities. The effective contact rate and the reproduction number showed a trend to decrease for few states due to the imposition of the restrictions. We also compared the effective contact rate, and the effective reproduction number of all election-bound states and the rest of India and found all the parameters related to the spread of virus for election-bound states are distinctly high compared to the rest of India.
Publisher: Oxford University Press (OUP)
Date: 12-10-2022
Abstract: Active galactic nucleus (AGN) feedback during galaxy merger has been the most favoured model to explain black hole–galaxy co-evolution. However, how the AGN-driven jet/wind/radiation is coupled with the gas of the merging galaxies, which leads to positive feedback, momentarily enhanced star formation, and subsequently negative feedback, a decline in star formation, is poorly understood. Only a few cases are known where the jet and companion galaxy interaction leads to minor off-axis distortions in the jets and enhanced star formation in the gas-rich minor companions. Here, we briefly report one extraordinary case, RAD12, discovered by RAD@home citizen science collaboratory, where for the first time a radio jet–driven bubble (∼ 137 kpc) is showing a symmetric reflection after hitting the incoming galaxy which is not a gas-rich minor but a gas-poor early-type galaxy in a major merger. Surprisingly, neither positive feedback nor any radio lobe on the counter jet side, if any, is detected. It is puzzling if RAD12 is a genuine one-sided jet or a case of radio lobe trapped, compressed and re-accelerated by shocks during the merger. This is the first imaging study of RAD12 presenting follow-up with the Giant Metrewave Radio Telescope, archival MeerKAT radio data and Canada-France-Hawaii Telescope optical data.
Publisher: American Astronomical Society
Date: 18-04-2007
DOI: 10.1086/518245
Publisher: Oxford University Press (OUP)
Date: 05-2010
Publisher: EDP Sciences
Date: 11-06-2004
Publisher: American Astronomical Society
Date: 26-08-2013
Publisher: Oxford University Press (OUP)
Date: 24-02-2023
Abstract: The millisecond pulsar MAXI J1816−195 was recently discovered in an outburst by the Monitor of All-sky X-ray Image (MAXI) in 2022 May. We study different properties of the pulsar using data from the Nuclear Spectroscopic Telescope Array (NuSTAR) and the Neutron Star Interior Composition Explorer (NICER) observations. The unstable burning of accreted material on the surface of neutron stars induces thermonuclear (Type-I) bursts. Several such thermonuclear bursts have been detected by MAXI J1816−195 during its outburst. We investigate the evolution of the burst profiles with flux and energy using NuSTAR and NICER observations. During the NuSTAR observation, a total of four bursts were detected from the source. The duration of each burst is around ∼30 s and the ratio of peak to persistent count rate is ∼26 as seen from the NuSTAR data. The burst profiles are modelled using a sharp linear rise and exponential decay function to determine the burst timing parameters. The burst profiles show a relatively long tail at lower energies. The broad-band time-resolved spectra during the burst periods are successfully modelled with a combination of an absorbed blackbody along with a non-thermal component to account for the persistent emission. From our modelling results, we are able to estimate the maximum apparent emitting area of the blackbody of the neutron star to be ∼12.5 km during the peak of the outburst and the maximum distance to the object to be 8.7 kpc. Our findings for the mass accretion rate and the α factor indicate the stable burning of hydrogen via a hot CNO cycle during the bursts.
Publisher: Oxford University Press (OUP)
Date: 21-08-2023
Abstract: Glycolaldehyde (CH2OHCHO) is the simplest monosaccharide sugar in the interstellar medium, and it is directly involved in the origin of life via the ‘RNA world’ hypothesis. We present the first detection of CH2OHCHO towards the hot molecular core G358.93–0.03 MM1 using the Atacama Large Millimetre/Submillimetre Array (ALMA). The calculated column density of CH2OHCHO towards G358.93–0.03 MM1 is (1.52 ± 0.9) × 1016 cm−2 with an excitation temperature of 300 ± 68.5 K. The derived fractional abundance of CH2OHCHO with respect to H2 is (4.90 ± 2.92) × 10−9, which is consistent with that estimated by existing two-phase warm-up chemical models. We discuss the possible formation pathways of CH2OHCHO within the context of hot molecular cores and hot corinos and find that CH2OHCHO is likely formed via the reactions of radical HCO and radical CH2OH on the grain-surface of G358.93–0.03 MM1.
Publisher: Springer Science and Business Media LLC
Date: 12-2011
Publisher: American Astronomical Society
Date: 20-12-2011
Publisher: Springer Science and Business Media LLC
Date: 20-06-2023
Publisher: Oxford University Press (OUP)
Date: 07-12-2022
Abstract: We have studied different timing and spectral properties of the new Galactic X-ray transient Swift J1728.9−3613 using NICER and Swift, discovered by the Burst Alert Telescope on the Neil Gehrels Swift Observatory. The source went through multiple transitions to different spectral states during the outburst, and the complete evolution created a ‘q’-shaped track in the hardness-intensity diagram. A partial hysteresis is also observed in the RMS-intensity diagram, which is another well-defined feature of black hole transients. In soft intermediate states, power-density spectra were dominated by broad-band noise components, and two type-B quasi-periodic oscillations were detected. We have fitted 1–10 keV energy spectra obtained from NICER observations that were performed during the outburst, and the temporal evolution of spectral parameters is studied. A small-scale reflare happened near MJD 58584.69, resulting in finite changes in spectral parameters, and the 1–10 keV averaged flux also increased. We observed that the innermost radius of the accretion disc was almost constant during the soft state and we have measured the mass of the compact object to be ∼4.6 M⊙, considering a non-spinning black hole binary system. The soft-to-hard transition occurred when the bolometric luminosity was 0.01 times the Eddington luminosity. Based on our combined study of the evolution of the timing and spectral properties, we conclude that the new source Swift J1728.9−3613 is a black hole X-ray binary.
Publisher: Elsevier BV
Date: 08-2022
Publisher: Springer International Publishing
Date: 2018
Publisher: Oxford University Press (OUP)
Date: 25-08-2022
Abstract: We present a list of tailed radio galaxies using the Tata Institute of Fundamental Research (TIFR) Giant Metrewave Radio Telescope (GMRT) Sky Survey Alternative Data Release 1 (TGSS ADR1) at 150 MHz. We visually examined 5336 image fields and found 264 tailed radio galaxies. Tailed radio galaxies are classified as wide-angle tailed (WAT) galaxies or narrow-angle tailed (NAT) galaxies, based on the angle between the two jets of the galaxy. Our s le of tailed radio galaxies included 203 WAT- and 61 NAT-type sources. These newly identified tailed sources are significant additions to the list of known tailed radio galaxies. The source morphology and luminosity features of the various galaxies and their optical identifications are presented. Other radio properties and general features of the sources are also discussed.
Publisher: Oxford University Press (OUP)
Date: 21-09-2005
Publisher: AIP
Date: 2008
DOI: 10.1063/1.3009482
Publisher: American Astronomical Society
Date: 24-02-2010
Publisher: Sissa Medialab
Date: 28-08-2006
DOI: 10.22323/1.033.0020
Publisher: American Astronomical Society
Date: 15-04-2009
Publisher: Springer Science and Business Media LLC
Date: 29-06-2023
Publisher: Sissa Medialab
Date: 07-08-2007
DOI: 10.22323/1.056.0009
Publisher: Oxford University Press (OUP)
Date: 11-04-2022
Abstract: A small subclass of radio galaxies, exhibiting a pair of secondary low-surface-brightness radio lobes oriented at an angle to the primary high-surface-brightness lobes, is the group known as X-shaped radio galaxies (XRGs). In some cases, it is seen that less luminous secondary lobes emerge from the edges of the primary high-brightness lobes, giving a Z-symmetric morphology. These objects are known as Z-shaped radio galaxies (ZRGs). From the Tata Institute of Fundamental Research (TIFR) Giant Metrewave Radio Telescope (GMRT) Sky Survey at 150 MHz, we present systematic search results for XRGs and ZRGs. We identified a total of 58 radio sources, out of which 40 are XRGs and 18 are ZRGs. Taking advantage of the large s le size of XRGs and ZRGs reported in the current work, different properties of XRGs and ZRGs are studied. Out of 58 XRGs and ZRGs presented here, 19 (32 per cent) are FR I and 33 (57 per cent) are FR II radio galaxies. For four XRGs and three ZRGs, the morphology is so complex that they could not be classified. We have estimated the radio luminosity and spectral index of newly discovered winged radio galaxies and made a comparative study with previously detected XRGs and ZRGs. Most of the XRGs show a steep spectral index between 150 and 1400 MHz and only 14 per cent of the sources show a flat spectrum, but for ZRGs a good proportion of the sources (36 per cent) show a flat spectrum.
Publisher: IOP Publishing
Date: 07-2020
DOI: 10.1088/1742-6596/1579/1/012021
Abstract: Using the 144 MHz Low-Frequency Array (LOFAR) telescope, We undelook a search for Miscellaneous Radio Galaxies (MRGs) whose morphological structures are different from known structures. Reseaons of study of these type sources due to their unique and peculiar morphology. Here, we report four MRGs from LOFAR Two Metre Sky Survey first data release (LoTSS DR1) at 144 MHz frequency. The MRS is identified manual visual search (MVS) from LoTSS DR1 data catalogue. We also check their radio morphology from other surveys like The NRAO VLA Sky Survey (NVSS) at 1400 MHz. The corresponding optical counterparts are also identified from Sloan Digital Sky Survey (SDSS), where available. We have estimated different physical parameters like spectral index, radio luminosity, radio power of these MRGs.
Publisher: Springer Science and Business Media LLC
Date: 04-2023
Publisher: Springer Science and Business Media LLC
Date: 09-2022
Publisher: IOP Publishing
Date: 07-2020
DOI: 10.1088/1742-6596/1579/1/012023
Abstract: Miscellaneous Radio Galaxies (MRGs) are very rare kind of radio galaxies that exhibit unusual and different jet alignment and orientation from a typical radio galaxy. The peculiar and unique morphology of this type of radio source makes them a special case of study. In this paper, we report the identification of fifteen MRGs from VLA Faint Images of the Radio Sky at Twenty-Centimeters (VLA FIRST) Survey. The MRGs are identified manually by visual inspection of the FIRST database (December, 2017). The in idual radio morphology of each sources are cross-checked at different frequencies from other surveys like TIFR GMRT Sky Survey at 150 MHz and Westerbork Northern Sky Survey at 325 MHz. We also identify the associated optical counterparts from the Sloan Digital Sky Survey (SDSS), where available. The different physical parameters like spectral index and radio luminosity of these MRGs are also estimated. An overview on the origin of these unique sources are also drawn.
Location: Australia
No related grants have been discovered for Sabyasachi Pal.