Browsing IIAP Publications by Title

Now showing items 5362-5381 of 5544

Variability of sunspot cycle QBO and total ozone over high altitude Western Himalayan regions

Shantikumar, N. S (Elsevier B.V., 2011-10)

Long-term trend of total column ozone at high altitude region in Ladakh is studied, using a total ozone mapping spectrometer and an ozone monitoring instrument during 1979–2008. In the region, total ozone exhibits seasonality ...
Variability of the solar chromospheric network over the solar cycle

Kariyappa, R; Sivaraman, K. R (Springer, 1994-06)

From a large sample of the Kodaikanal spectroheliograms in the Ca II K line we have studied the variations in the intensity of the network elements over two solar cycles and have estimated their contribution to the overall ...
Variable circumstellar activity of V351 Orionis

Choudhury, R; Bhatt, H. C; Pandey, G (EDP Sciences, 2011-02)

Context. Emission and absorption line profiles which are formed in the interaction of pre-main sequence stars and their circumstellar environment are found to be variable at various timescales. Aims. We investigate the ...
Variable mass accretion and failed wind explain changing-look phenomena in NGC 1365

Mondal, Santanu; Adhikari, T. P; Hryniewicz, K; Stalin, C. S; Pandey, Ashwani (EDP Sciences, 2022-06)

Changing-look active galactic nuclei (CLAGNs) show a complex nature in their X-ray spectral shape and line-of-sight column-density variation. The physical mechanisms responsible for these variations are unclear. Here, we ...
THE VARIABLE STAR POPULATION IN THE GLOBULAR CLUSTER NGC 6934

Yepez, M. A; Ferro, A. A; Muneer, S; Giridhar, S (Instituto de Astronomia, 2018-04)

We report an analysis of new V and I CCD time-series photometry of the globular cluster NGC 6934. Through the Fourier decomposition of the RR Lyrae light curves the mean values of [Fe/H] and the distance of the cluster ...
Variable stars in M37

Dar, A. A; Parihar, P. S; Saleh, P; Malik, M. A (IOP Publishing, 2018-12)

The CCD photometric observations of open star cluster M37 (NGC 2099) were carried out up to a limiting magnitude of V ~ 20 in both B and V filters to search for variable stars using a 2k Ã— 4k CCD and the 1.3 m telescope ...
Variable stars in NGC 4147 revisited: RR Lyrae stars new CCD VI photometry and physical parameters

Arellano Ferro, A; Rojas Galindo, F. C; Muneer, S; Giridhar, S (Universidad Nacional Autonoma De Mexico, 2018-10)

We have calculated the physical parameters of the RR Lyrae stars in the globular cluster NGC 4147 via the Fourier decomposition of their light curves, using new data and well-established semi-empirical calibrations and ...
Variable stars in Palomar 13; an evaporating globular cluster

Yepez, M. A; Ferro, A. A; Schoeder, K. P; Muneer, S; Giridhar, S; Allen, C (Elsevier B.V, 2019-08)

We present new CCD VI photometry of the distant globular cluster Pal 13. Fourier decomposition of the light curves of the three cluster member RRab stars lead to estimations of [Fe/H] = −1.65, and a distance of 23.67 ± ...
Variable Stars in Palomar 13; an Evaporating Globular Cluster

Yepez, M. A; Ferro, A. Arellano; Schröder, K. P.; Muneer, S; Giridhar, Sunetra; Allen, Christine (Astronomical Society of the Pacific, 2021-06)

We present new CCD VI photometry of the globular cluster Pal 13. Fourier decomposition of the light curves of RRab stars lead to estimations of [Fe/H]ZW = -1.65±0.15, and a distance to the cluster of 23.67±0.57 kpc. A ...
The variable stars in the compact halo globular cluster NGC 5634 visited again

Ferro, A. A; Michel, R; Yepez, M. A; Muneer, S; Bustos Fierro, I. H; Prudil, Z (Oxford University Press on behalf of Royal Astronomical Society, 2025-08)

We present new time-series CCD VR photometry of the globular cluster NGC 5634. We aim to use the known RR Lyrae stars, members of the cluster, as indicators of mean metallicity and distance. Accurate coordinates, periods, ...
Variable Stars in the Globular Cluster NGC 288: [Fe/H] and Distance

Ferro, A. A; Bramich, D.M; Giridhar, S; Jaimes, R. F; Kains, N; Kuppuswamy, K (Copernicus Foundation for Polish Astronomy, 2013-12)

A search for variable stars in the globular cluster NGC 288 was carried out using a time-series of CCD images in the V and I filters. The photometry of all stellar sources in the field of view of our images, down to V≈19 ...
Variable stars in the globular cluster NGC 7492. New discoveries and physical parameter determination

Figuera Jaimes, R; Arellano Ferro, A; Bramich, D. M; Giridhar, S; Kuppuswamy, K (EDP Sciences, 2013-08)

Aims. We have performed a photometric V,R,I CCD time-series analysis with a baseline of about eight years of the outer-halo globular cluster NGC 7492 with the aim of searching for new variables and using these (and the ...
A "variable" stellar object in a variable blue nebula V-V 1-7

Kameswara Rao, N; Gilra, D. P (The Observatory, 1981-08)
Variables in Globular Cluster NGC 5024

Safonova, M; Stalin, C. S (IOP Publishing, 2011-12)

We present the results of a commissioning campaign to observe Galactic globular clusters for the search of microlensing events. The central 10' × 10' region of the globular cluster NGC 5024 was monitored using the 2 m ...
The variation in area of hydrogen absorption markings with longitude

Salaruddin, M (Government Observatory, Madras, 1932-04-19)
Variation in continuum brightness and equivalent widths of lines in sunspot penumbrae

Bhatnagar, A (Springer - Verlag, 1966)

Variations in the continuum brightness and in the equivalent widths of lines have been observed in the sunspot penumbral spectra. Darker regions in the continuum of the penumbrae show widening of lines, while the brighter ...
Variation in the network flux as derived from the Calcium K-line profiles as function of latitude and solar cycle phase

Singh, J; Gholami, I; Muneer, S (Elsevier, 2004)

We have obtained the Calcium K-line profiles, on daily basis, at all latitudes, while integrating the spectrum over the visible longitudes of the Sun by moving a ~340 mm solar image at a uniform speed in the E-W direction ...
Variation in the width of transition region network boundaries

Raju, K. P (Springer, 2016-12)

The transition region network seen in solar extreme ultraviolet (EUV) lines is the extension of the chromospheric network. The network appears as an irregular web-like pattern over the solar surface outside active regions. ...
Variation of chromospheric features as a function of latitude and time using Ca-K spectroheliograms for solar cycles 15 - 23: Implications for meridional flow

Devi, Pooja; Singh, J; Chandra, Ramesh; Priyal, Muthu; Joshi, Reetika (Springer, 2021-03)

We have analyzed the Ca-K images obtained at Kodaikanal Observatory as a function of latitude and time for the period of 1913 - 2004 covering Solar Cycles 15 to 23. We have classified the chromospheric activity into plage, ...
Variation of Emission LineWidth in Mid and High-Latitude Corona

Krishna Prasad, S; Singh, J; Banerjee, D (Springer, 2013-02)

Spectroscopic studies of the solar corona, using the high spatial and spectral resolution 25-cm corona graph at the Norikura Solar Observatory for equatorial off-limb observations, indicated that the variation of radiance ...

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