A5067934334- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Dark Matter and Cosmic Phenomena
- Particle physics theoretical and experimental studies
- Cosmology and Gravitation Theories
- Adaptive optics and wavefront sensing
- Solar and Space Plasma Dynamics
- Computational Physics and Python Applications
- Optical Systems and Laser Technology
- Metabolomics and Mass Spectrometry Studies
- Syphilis Diagnosis and Treatment
- Laser-Plasma Interactions and Diagnostics
- High-pressure geophysics and materials
- Alkaline Phosphatase Research Studies
- HIV, Drug Use, Sexual Risk
- Advanced optical system design
- Lysosomal Storage Disorders Research
- Dermatological and Skeletal Disorders
Merck & Co., Inc., Rahway, NJ, USA (United States)
2025
Indian Institute of Astrophysics
2021-2024
Peking University
2017-2023
Kavli Institute for Theoretical Sciences
2017-2023
Inter-University Centre for Astronomy and Astrophysics
2015-2017
Michigan Technological University
2015
Aryabhatta Research Institute of Observational Sciences
2011-2014
Technical University of Darmstadt
2012
Government Medical College
2002-2004
Sultan Qaboos University Hospital
1998
Abstract The rare case of changing-look (CL) active galactic nuclei (AGNs), with the appearance or disappearance broad Balmer emission lines within a few years, challenges our understanding AGN unified model. We present sample 21 new CL AGNs at <?CDATA $0.08\lt z\lt 0.58$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.08</mml:mn> <mml:mo><</mml:mo> <mml:mi>z</mml:mi> <mml:mn>0.58</mml:mn> </mml:math> , which doubles number such objects known to...
We present the accretion disk size estimates for a sample of 19 active galactic nuclei (AGN) using optical $g$, $r$, and $i$ band light curves obtained from Zwicky Transient Facility (ZTF) survey. All AGN have reliable supermassive black hole (SMBH) mass based on previous reverberation mapping measurements. The multi-band are cross-correlated, lag is estimated Interpolated Cross-Correlation Function (ICCF) method Bayesian {\sc javelin} code. As expected reprocessing arguments, $g-r$ lags...
Background. Concern about the emergence of antibiotic-resistant strains and morbidity and/or mortality related to rheumatic fever heart disease has been a continuous impetus for development safe, effective vaccine against group A Streptococcus (GAS). To date, >120 GAS M types are known, as identified by serological typing. In general, serum immunoglobulin G directed hypervariable NH2 terminal portion protein leads complement fixation opsonophagocytosis homologous streptococcal serotype...
We present the results of extensive multiband intranight optical monitoring BL Lacertae during 2010–2012. was very active in this period and showed intense variability almost all wavelengths. extensively observed it for a total 38 nights; on 26 them, observations were done quasi-simultaneously B, V, R I bands (totalling 113 light curves), with an average sampling interval around 8 min. significant variations hour-like time-scales 19 nights different bands. did not find any evidence...
We present Data Releases 4 and 5 of the quasar catalog from survey by Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST), which includes quasars observed between 2015 September 2017 June. There are a total 19,253 identified visual inspections spectra. Among them, 11,458 were independently discovered LAMOST, in 3296 reported SDSS DR12 DR14 after our began, while remaining 8162 new discoveries LAMOST. provide emission line measurements for Hα, Hβ, Mg ii, and/or C iv 18,100...
How would negative energy density affect a classic Friedmann cosmology? Although never measured and possibly unphysical, certain realizations of quantum field theories leaves the door open for such possibility. In this paper we analyze evolution universe comprising varying amounts forms. Negative components have normalized densities, $\Omega < 0$. They include phantom with an equation state parameter $w<-1$, cosmological constant: $w=-1$, domain walls: $w=-2/3$, cosmic strings: $w=-1/3$,...
Abstract A complete and pure sample of quasars with accurate redshifts is crucial for quasar studies cosmology. In this paper, we present CatNorth, an improved Gaia Data Release 3 (Gaia DR3) candidate catalog more than 1.5 million sources in the π sky built data from Gaia, Pan-STARRS1, CatWISE2020. The XGBoost algorithm used to reclassify original DR3 candidates as stars, galaxies, quasars. To construct training/validation sets classification, carefully two different master stellar samples...
Abstract We present a catalog of 290 “winged” or X-shaped radio galaxies (XRGs) extracted from the latest (2014 December 17) data release “Very Large Array Faint Images Radio Sky at Twenty centimeter.” have combined these images with their counterparts in TIFR GMRT sky survey 150 MHz, an attempt to identify any low surface brightness emission sources. This has enabled us assemble sample 106 “strong” XRG candidates and 184 “probable” whose designation needs be verified by further...
We present a study of strong intervening absorption systems in the near-IR spectra 31 luminous quasars at $z>5.7$. The quasar were obtained with {\it Gemini} GNIRS that provide continuous wavelength coverage from $\sim$0.9 to $\sim$2.5 $\mu$m. detect 32 Mg II doublet absorbers rest-frame equivalent width $W_r$ ($\lambda2796$) $>1.0$ \AA $2.2 < z 6.0$. Each absorber is confirmed by least two associated Fe lines range $\sim 1600-2600$ \AA. find comoving line density ($dN/dX$) II-bearing...
We investigate the temporal and colour variability of 897 blazars, comprising 455 BL Lacertae objects (BL Lacs) 442 Flat Spectrum Radio Quasars (FSRQs), selected from Roma-BZCAT catalogue, using multi-band light curves Zwicky Transient Facility (ZTF DR6) survey. Assessing characteristics over ~2 year timescales, we found that 18.5 per cent (84 out 455) Lacs showed a stronger bluer when brighter (BWB) trend, whereas 9.0 (41 redder (RWB) trend. The majority (70 cent) showing RWB are host...
We present optical light curves of 19 radio quiet (RQ) broad absorption line (BAL) QSOs and study their rapid variability characteristics. Systematic CCD observations, aided by a careful data analysis procedure, have allowed us to clearly detect any such microvariability exceeding 0.01--0.02 mag. Our observations cover total 13 nights (~72 hours) with each quasar monitored for about 4 hours on given night. sample size is factor three larger than the number radio-quiet BALQSOs previously...
We present the results from our search for HI 21-cm absorption in a sample of 16 strong FeII systems ($W_{\rm r}$(MgII $\lambda2796$) $\ge1.0$ \AA\ and $W_{\rm r}$(FeII $\lambda2600$) or FeII}$ $\ge1$ \AA) at $0.5<z<1.5$ using Giant Metrewave Radio Telescope Green Bank Telescope. report six new detections sample, which have increased known number MgII this redshift range by $\sim50$%. Combining measurements with those literature, we find that detection rate increases FeII}$, being four times...
We propose a radically different picture for X-shaped radio galaxies compared to existing models as transition objects between cold mode accreting low spinning retrograde black holes and prograde holes. The model explains their smaller average hole masses, general aversion cluster isolated environments, the negligible difference in spectral index primary secondary jets despite time formation, absence among most powerful quasars galaxies, connection elusive FRI quasar class, others. key...
Quasars behind the Galactic plane (GPQs) are important astrometric references and valuable probes of gas, yet search for GPQs is difficult due to severe extinction source crowding in plane. In this paper, we present a sample 204 spectroscopically confirmed at |b|<20{\deg}, 191 which new discoveries. This GPQ covers wide redshift range from 0.069 4.487. For subset 230 observed candidates, lower limit purity quasars 85.2%, fraction stellar contaminants 6.1%. Using multicomponent spectral...
We report the kinematic shift and strength variability of C iv broad absorption-line (BAL) trough in two high-ionization X-ray-bright quasi-stellar objects (QSOs): SDSS J085551+375752 (at zem ∼ 1.936) J091127+055054 2.793). Both these QSOs have shown a combination profile shifts appearance disappearance absorption components belonging to single BAL trough. The observed average whole resulted an deceleration ∼−0.7 ± 0.1, −2.0 0.1 cm s−2 over rest-frame time-spans 3.11 2.34 yr for...
We investigate the dependence of residual rotation measure (RRM) on intervening absorption systems at cosmic distances by using a large sample 539 SDSS quasars in conjunction with available catalog around 21cm wavelength. found an excess extragalactic contribution standard deviation observed RRM about 8.11+/-4.83 Rad/m^2 our MgII absorber as compare to without absorber. Our results suggest that absorbers could contribute enhancement wavelength, was earlier for RM measurements 6cm
In order to find clues the origin of "winged" or "X-shaped" radio galaxies (XRGs) we investigate here parent a large sample 106 XRGs for optical-radio axes alignment, interstellar medium, black hole mass, and large-scale environment. For 41 it was possible determine optical major axis primary strong tendency two be fairly close is confirmed. However, several counter-examples were also found these could challenge widely discussed backflow diversion model wings. Comparison with well-defined...
We investigate the effect of Fe II equivalent width ($W_{2600}$) and fibre size on average luminosity [O II]$\lambda\lambda$3727,3729 nebular emission associated with Mg absorbers (at $0.55 \le z 1.3$) in composite spectra quasars obtained 3 2 arcsec fibres Sloan Digital Sky Survey. confirm presence strong correlations between II] (L$_{[\rm O~II]}$) ($W_{2796}$) redshift absorbers. However, we show L$_{[\rm O~II]}$ surface density suffers from effects. More importantly, for a given strongly...
We present nebular emission associated with 198 strong Mg II absorbers at 0.35 $\le z \le$ 1.1 in the fibre spectra of quasars from Sloan Digital Sky Survey. Measured [O II] luminosities (L$_{[O II]}$) are typical sub-L$^{\star}$ galaxies derived star formation rate (uncorrected for losses and dust reddening) range 0.5-20 ${\rm M_\odot\ yr^{-1}}$. Typically less than $\sim$ 3% systems rest equivalent width, $W_{2796}$ $\ge$ 2 \AA, show L$_{[O II]} \ge 0.3$ L$^{\star}_{[O II]}$. The detection...
We report the discovery of one largest and most distant Giant Radio Galaxy (GRG) in Lynx field which was discovered using deep Metre-wave Telescope (GMRT) 150 MHz observations. The core is detected at also VLA FIRST survey. Spectroscopic observations carried out IUCAA Giravali Observatory(IGO) provided a redshift value 0.57. This later confirmed with data from Sloan Digital Sky Survey (Data Release 12). angular size GRG 5.5 arcmin 0.57, its linear 2.2 Mpc. At this high redshift, only few...
Based on a recently started programme, we report the first search for intranight optical variability (INOV) among radio-quiet 'weak-line-quasars' (RQWLQs). Eight members of this class were observed 13 nights in R band, such that each source was monitored continuously at least once minimum duration about 3.5 h, using installed 130-cm telescope Devasthal, India. Statistical analysis differential light curves carried out two versions F test. INOV data acquired so far, RQWLQ population appears...
We study the average Lyα emission associated with high-z strong (log N(H i) ≥ 21) damped systems (DLAs). report luminosities (LLyα) for full as well various sub-samples based on i), z, (r − colours of QSOs and rest equivalent width Si iiλ1526 line (i.e. W1526). For sample, we find LLyα < 1041(3σ) erg s− 1 a 2.8σ level detection in red part DLA trough. The is found to be higher W1526 its peak, detected at ≥3σ, redshifted by about 300–400 km s−1 respect systemic absorption redshift, seen Lyman...
We explore the potential of ongoing Zwicky-Transient-Facility (ZTF) survey for studying Intra-Night Optical Variability (INOV) active galactic nuclei (AGN), in particular picking rare events large INOV amplitudes, whose detection may require extensive temporal coverage. For this, we have used available high cadence subsets ZTF database to build a well-defined sample 53 blazars (BLs) and another 132 radio-quiet quasars (RQQs), matched blazar redshift-magnitude plane. High-cadence monitoring...
ABSTRACT We investigate the possible presence of quasi-periodic oscillation (QPO) signals in 2103 blazars from Zwicky Transient Facility (ZTF) time-domain survey. detect a low-frequency QPO signal five observed over these 3.8-yr-long optical r-band ZTF light curves. These periods range 144 to 196 d detected at ≳4σ significance levels both Lomb–Scargle periodogram and weighted wavelet Z-transform analyses. find consistent results using phase dispersion minimization technique. A similar peak...