A5041017452- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Astro and Planetary Science
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Adaptive optics and wavefront sensing
- Particle Accelerators and Free-Electron Lasers
- Molecular Spectroscopy and Structure
- Solar and Space Plasma Dynamics
- Advanced X-ray Imaging Techniques
- X-ray Spectroscopy and Fluorescence Analysis
- Calibration and Measurement Techniques
- Laser-Plasma Interactions and Diagnostics
- Technology Assessment and Management
- Spectroscopy and Laser Applications
- Atmospheric Ozone and Climate
- Historical Astronomy and Related Studies
- Mechanics and Biomechanics Studies
- High-pressure geophysics and materials
- Advanced Statistical Modeling Techniques
Indian Institute of Astrophysics
2013-2024
Physical Research Laboratory
1999-2002
We present sub‐arcsecond (0.35–0.9 arcsec), near‐infrared J‐, H‐ and K‐band photometric observations of six fields along the W51 giant molecular cloud (W51 GMC). Our reveal four new, embedded clusters provide a new high‐resolution (0.35 arcsec) view IRS2 (G49.5 − 0.4) region. The cluster associated with G48.9 0.3 is found to be double enclosed in nest nebulosity. construct stellar surface density maps for major GMC. These unveil underlying hierarchical structure. Colour–colour...
We present infrared JHK photometry of the cataclysmic variable (CV) SDSS J123813.73 − 033933.0 and analyze it along with optical spectroscopy, demonstrating that binary system is most probably comprised a massive white dwarf Teff = 12000 ± 1000 K brown spectral type L4. The inferred parameters suggest this may have evolved beyond orbital period minimum bounce-back system. stands out among CVs by exhibiting cyclical variability Zharikov et al. called brightenings. These are not related to...
Optical spectra of the 2006 outburst RS Ophiuchi beginning one day after discovery to over a year are presented here. The spectral evolution is found be similar that in previous outbursts. early-phase dominated by hydrogen and helium (i ii) lines. Coronal nebular lines appear later phases. Emission line widths narrow with time, which interpreted as shock expanding into red giant wind. Using photoionization code cloudy, at nine epochs spanning 14 months peak, thus covering broad range...
ABSTRACT We present low-frequency radio observations of the Galactic symbiotic recurrent nova RS Ophiuchi during its 2021 outburst. The were carried out with upgraded Giant Metrewave Radio Telescope spanning a frequency range 0.15–1.4 GHz 23–287 d post average value optically thin spectral index is α ∼ −0.4 (Fν ∝ να), indicating non-thermal origin emission at observed frequencies. light curves are best represented by shock-driven synchrotron emission, initially absorbed clumpy ionized...
Aims. We study the evolution of recurrent nova U Scorpii during its outburst in 2010.
ABSTRACT The region surrounding the well-known reflection nebula, NGC 7023, illuminated by a Herbig Be star, HD 200775, located in dark cloud L1174 is studied this work. Based on distances and proper motion values from Gaia DR2 of 20 previously known young stellar object (YSO) candidates, we obtained distance 335 ± 11 pc to complex L1172/1174. Using polarization measurements stars projected complex, show additional evidence for be at ∼335 distance. YSO searched comoving sources vicinity...
We present the results of multi-epoch JHK photometry a sample 30 known or suspected symbiotics and related objects. These are first an ongoing programme near-IR monitoring symbiotic stars from Mt. Abu IR Observatory Physical Research Laboratory (PRL).
Abstract Nova Her 2021 or V1674 was one of the fastest novae to be observed so far. We report here results from our timing and spectral studies source at multiple epochs with AstroSat. detection a periodicity in soft X-rays period 501.4–501.5 s which detected high significance after peak super-soft phase, but not far ultraviolet (FUV) band The shape phase-folded X-ray light curves has varied significantly as nova evolved. phase-resolved reveal likely presence various absorption features...
We present the post-maximum optical spectroscopy and infrared photometry of Nova V1425 Aquilae 1995. The data indicate that nova belongs to Fe ii class it formed an optically thin dust shell at a very early phase compared other forming novae same class. total mass is low with dust-to-gas ratio ±10<SUB>-3. spectrum its evolution are similar II novae. An extinction E<SUB>B</SUB> - <SUB>V</SUB> 0.76 derived from He I line ratios distance 2.7 kpc estimated magnitude-decay time relations.</SUB>
JHK photometry of the final helium shell flash object V4334 Sagittarii undertaken during 1996–97 is presented in this paper. The data reveal formation circumstellar dust temperature ∼ 1800 K two years after outburst. Around 5 × 10−10 M⊙ condensed at a distance about 7R⊬ from star. mass Sgr 0.8 and it had radius 70 R⊙ 1997 April–May.
V4643 Sagittarii or Nova 2001 was discovered in outburst at 7.7 mag. on February 24. Here, we present near-infrared results of this fast classical nova obtained the early decline phase March followed by optical observations about one month later. Subsequently also spectra taken later nova's evolution, four months after outburst, when Sgr had entered coronal phase. The are dominated emission lines HI Brackett series and Paschen beta gamma lines. We study cause excitation OI line 1.128 micron...
We discuss the evolution of nova V723 Cassiopeiae 1995 based on JHK photometry covering a period 15 months beginning two following outburst. The first post-outburst flares are covered by these observations.
Optical and near-infrared spectroscopic observations of the fast nova V1494 Aquilae 1999 #2 covering various phases -- early decline, transition nebular during first eighteen months its post-outburst evolution are presented in this paper. During period, evolved P_fe P_fe^o C_o spectral sequence. The from an optically thick wind to a polar blob - equatorial ring geometry is seen line profiles. There evidence density temperature stratification ejecta. Physical conditions ejecta have been...
Context. The presence of three more Herbig Ae/Be (HAeBe) candidates in the Cepheus Flare within a 1.5° radius centered on HD 200775 suggests that star formation is prevalent wider region LDN 1147/1158, 1172/1174, and 1177 clouds. A number young stellar objects (YSOs) are found to be distributed toward these cloud complexes along with HAeBe stars. Various studies clearly indicate ongoing low-mass inside clouds this region. Sources associated less near-infrared excess H α emission raise...
TCP J18224935-2408280 was reported to be in outburst on 2021 May 19. Follow-up spectroscopic observations confirmed that the system a symbiotic star. We present optical spectra obtained from Himalayan Chandra Telescope during 2021-22. The early were dominated by Balmer lines, He I lines and high ionization such as II. In later observations, Raman scattered O VI also identified. Outburst started disc instability, signature of enhanced shell burning expansion photospheric radius white dwarf...
We present low-frequency radio observations of the Galactic symbiotic recurrent nova RS Ophiuchi during its 2021 outburst. The were carried out with upgraded Giant Metrewave Radio Telescope (uGMRT) spanning a frequency range 0.15$-$1.4 GHz 23$-$287 days post average value optically thin spectral index is $\alpha \sim$ $-$0.4 ($F_{\nu} \propto \nu^\alpha$), indicating non-thermal origin emission at observed frequencies. light curves are best represented by shock-driven synchrotron emission,...
The paper demonstrates the spectroscopic and photometric capabilities of Ultra-Violet Imaging Telescope (UVIT) to study T-Tauri stars (TTSs). We present first UVIT/Far-UV spectrum a TTS, TW Hya. Based on C IV line luminosity, we estimated accretion luminosity (0.1 $L_\odot$) mass rate (2.2 $\times$ $10^{-8} M_\odot /yr$) Hya, compared these values with (0.03 (0.6 derived from spectral energy distribution (SED). From SED, derive best-fitted parameters for Hya: $T_{eff}$ = 3900$\pm$50 K,...
Abstract Low resolution optical spectra of the symbiotic star BX Monocerotis in 3500-9000 Å range obtained during 1999–2010 are described. spectrum Mon at all phases is dominated by cool component, with a red continuum and TiO absorption. Emission lines, predominantly due to HI, He I, II, Fe Ca II [O III] seen superimposed on M5III star, variable intensities. observed variations seem be correlated orbital phases.
Using our previously reported observations, we derive some physical parameters of the moderately fast nova V2676 Ophiuchi 2012 # 1. The best-fit CLOUDY model nebular spectrum obtained on 2015 May 8 shows a hot white dwarf source with Tbb = 1.0 x 10^{5} K having luminosity 10^{38} ergs/s. Our abundance analysis that ejecta are significantly enhanced relative to solar, He/H 2.14, O/H 2.37, S/H 6.62 and Ar/H 3.25. mass is estimated be 1.42 10^{-5} Msun. showed pronounced dust formation phase...