IUCAA Preprints
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Item Two dimensional galaxy image decomposition(2015-03-13) Wadadekar, Yogesh; Robbason, Braxton; Kembhavi, A. K.Item Filaments and pancakes in the IRAS 1.2 jy redshift catalogue(2015-03-13) Sathyaprakash, B.S.; Sahni, Varun; Shandarian, Sergei; Fisher, K.B.Item Probing the BLR in AGNs using time variability of associated absorption lines(2015-03-01) Srianand, R.; Shankaranarayanan, S.It is know that most of the clouds producing associated absorption in the spectra of AGNs and quasars do not completely cover the background source (continuum + broad emission line region, BLR). We note that the covering factor derived for the absorption is the fraction of photons occulted by. The absorbing clouds, and is not necessarily the same as the fractional area covered. We show that the variability in absorption lines can be produced by the changes in the covering factor caused by the variation in the continuum and the finite light travel time across the BLR. We discuss how such avariability can be distinguished from the variability caused by other effects and how one can use the variability in the covering factor to probe the BLR.Item Luminosity dependent star-formation history of S0 galaxies: evidence from GALEX-SDSS-2MASS-WISE colours(IUCAA, 2015-02) Barway, Sudhanshu; Wadadekar, Yogesh; Vaghmare, KaustubhItem A multiwavelength view of the ISM in the merger remnant Fornax A galaxy(IUCAA, 2015-02) Deshmukh, Shishir; Tate, B.T.; Vagshette, N. D.Item Spectral properties of XRBs in dusty early-type galaxies(IUCAA, 2015-02) Vagshette, N. D.; Pandge, M. B.; Patil, M. K.Item On the origin of the featureless soft X-ray excess emission from the Seyfert 1 galaxy ESO 198–G24(IUCAA, 2015-02) Laha, Sibasish; Dewangan, Gulab Chand; Kembhavi, A.K.Item Neutral hydrogen at high redshifts as a probe of structure formation : 1. Post COBE analysis of CDM and HDM models(2014-11-23) Subramanian, Kandaswamy; Padmanabhan, T.Item Automated Classification of 2000 Bright IRAS Sources(2011-07-06) Gupta, Ranjan; Singh, Harinder P.; Volk, K.; et al.An Artificial Neural Network (ANN) scheme has been employed that uses a supervised back-propagation algorithm to classify 2000 bright sources from the Calgary database of IRAS (Infrared Astronomical Satellite) spectra in the region 8µm to 23µm. The database has been classified into 17 predefined classes based on the spectral morphology. We have been able to classify over 80 percent of the sources correctly in the first instance. The speed and robustness of the scheme will allow us to classify the whole of the LRS database, containing more that 50,000 sources, in the near future.Item Soft time lags in the X-ray emission of mrk 1040(2011-01-30) Tripathi, Shruti; Misra, Ranjeev; Dewangan, Gulab Chand; et al.Temporal analysis of X-ray binaries and Active Galactic Nuclei have shown that hard X-rays react to variation of soft ones after a time delay. The opposite trend, or soft lag, has only been seen in a few rare Quasi-periodic Oscillations in X-ray binaries and recently for the AGN, 1H 0707-495, on short timescales of ∼ 103 secs. Here, we report analysis of a XMM-Newton observation of Mrk 1040, which reveals that on the dominant variability timescale of ∼ 104 secs, the source seems to exhibit soft lags. If the lags are frequency independent, they could be due to reverberation effects of a relativistically blurred reflection component responding to a varying continuum. Alternatively, they could be due to Comptonization delays in the case when high energy photons impinge back on the soft photon source. Both models can be verified and their parameters tightly constrained, because they will need to predict the photon spectrum, the r.m.s variability and time lag as a function of energy. A successful application of either model will provide unprecedented information on the radiative process, geometry and more importantly the size of the system, which in turn may provide stringent test of strong general relativistic effects.