IGO Publications
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Item Optical Spectroscopy of Candidates of Young Stellar Objects in NGC 1333(2001-01-01) Itoh, Yoichi; Gupta, Ranjan; Oasa, YumikoWe carried out low-resolution optical spectroscopy of 14 low-luminosity young stellar object (YSO) candidates in the NGC 1333 cluster. These objects were previously identified by the near-infrared imaging survey. Eleven objects were confirmed as YSOs by the H line emission. Strengths of the H emission are correlated with the near-infrared excesses of the objects. Spectral types of all YSOs are estimated to be M-type, indicative of low-mass. Comparisons of the results of our spectroscopic observations and the previous photometric observations with evolutionary tracks on the HR diagram suggest two objects to be young brown dwarfs.Item Photometric Study ofWUMa Type Binaries in the Old Open Cluster Berkeley 39(2009-07-06) Sriram, K; Y, Ravi Kiron; P, Vivekananda RaoThe study of W UMa binary systems give a wealth of information about its nature as well as about its parent body (if any), like clusters. In this paper, we present the I passband photometric solutions of fourWUMa binaries in the open cluster Berkeley 39 using the latest version of W–D program. The result shows that, two binary systems are W-subtype W UMa binary systems and another two systems are H-subtype W UMa binary systems. No third body is found in any of the four systems. We found a correlation between the period and mass-ratio as well as temperature and mass-ratio for the respective variables which is similar to the relationship between mass ratio and total mass of the contact binaries as shown by van’t Veer (1996) and Li et al. (2008).Item Optical variability of radio-intermediate quasars(2009-10-08) Goyal, Arti; Krishna, Gopal; Joshi, S; etWe report the results of our intensive intranight optical monitoring of 8 opti- cally bright ‘radio-intermediate quasars’ (RIQs) having flat or inverted radio spectra. The monitoring was carried out in R-band on 25 nights during 2005- 09. On each night only one RIQ was monitored for a minimum duration of ∼ 4 hours (the average being 5.2 hours per night). Using the CCD as an N-star photometer, an intranight optical variability (INOV) detection threshold of ∼ 1–2% was achieved for the densely sampled differential light curves (DLCs) de- rived from our data. These observations amount to a large increase over those reported hitherto for this rare and sparsely studied class of quasars which can, however, play an important role in understanding the link between the dominant varieties of powerful AGN, namely the radio-quiet quasars (RQQs), radio-loud quasars (RLQs) and blazars. Despite the probable presence of rela- tivistically boosted nuclear jets, inferred from their flat/inverted radio spectra, clear evidence for INOV in our extensive observations was detected only on one night. Also, flux variation between two consecutive nights was clearly seen for one of the RIQs. These results demonstrate that as a class, RIQs are much less extreme in nuclear activity compared to blazars. The availability in the literature of INOV data for another 2 RIQs conforming to our selection crite- ria allowed us to enlarge the sample to 10 RIQs (monitored on a total of 42 nights for a minimum duration of ∼ 4 hours per night). The absence of large 2 Goyal et al. amplitude INOV (ψ > 3%) persists in this enlarged sample. This extensive database has enabled us to arrive at the first estimate for the INOV Duty Cy- cle (DC) of RIQs. The DC is found to be small (∼ 9%), increasing to ∼ 14% if the two cases of ‘probable’ INOV are included. The corresponding value is known to be ∼ 60% for BL Lacs and ≈ 15% for both RLQs and RQQs, if they too are monitored for & 4 − 6 hours in each session. Our observations also provide information about the long-term optical variability (LTOV) of RIQs, which is found to be fairly common and reaches typical amplitudes of ≈ 0.1- mag. The light curves of these RIQs are briefly discussed in the context of a theoretical framework proposed earlier for linking this rare kind of quasars to the much better studied dominant classes of quasars.Item SDSS J092712.64+294344.0: recoiling black hole or merging galaxies?(2009-08-31) Vivek, M; Srianand, R.; Noterdaeme, P; et al.We report long-slit spectroscopic observations of SDSS J092712+294344 carried-out at the recently commissioned 2m telescope in IUCAA Girawali Observatory, India. This AGN-like source is known to feature three sets of emission lines at zem = 0.6972, 0.7020 and 0.7128. Different scenarios such as a recoiling black hole after asymmetric emission of gravitational waves, binary black holes and possible merging systems are proposed for this object. We test these scenarios by comparing our spectra with that fromthe Sloan Digital Sky Survey (SDSS), obtained 4 years prior to our observations. Comparing the redshifts of [Oiii]λλ4960,5008 we put a 3σ limit on the relative acceleration to be less than 32 km s−1 yr−1 between different emitting regions. Using the 2D spectra obtained at different position angles we show that the [Oiii]λ5008 line from the zem = 0.7128 component is extended beyond the spectral point spread function.We infer the linear extent of this line emitting region is ∼ 8 kpc.We also find a tentative evidence for an offset between the centroid of the [Oiii]λ5008 line at zem = 0.7128 and the QSO trace when the slit is aligned at a position angle of 299◦. This corresponds to the zem = 0.7128 system being at an impact parameter of ∼1 kpc with respect to the zem = 0.6972 in the north west direction. Based on our observations we conclude that the binary black hole model is most unlikely. The spatial extent and the sizes are consistent with both black hole recoil and merging scenarios.Item TELICS—A Telescope Instrument Control System for Small/Medium Sized Astronomical Observatories(2009-10-12) SRIVASTAVA, MUDIT K.; RAMAPRAKASH, A. N.; Burse, Mahesh P.; et.alFor any modern astronomical observatory, it is essential to have an efficient interface between the telescope and its back-end instruments. However, for small and medium-sized observatories, this requirement is often limited by tight financial constraints. Therefore a simple yet versatile and low-cost control system is required for such observatories to minimize cost and effort. Here we report the development of a modern, multipurpose instrument control system TELICS (Telescope Instrument Control System) to integrate the controls of various instruments and devices mounted on the telescope. TELICS consists of an embedded hardware unit known as a common control unit (CCU) in combination with Linux-based data acquisition and user interface. The hardware of the CCU is built around the ATmega 128 microcontroller (Atmel Corp.) and is designed with a backplane, master-slave architecture. A Qt-based graphical user interface (GUI) has been developed and the back-end application software is based on C/C++. TELICS provides feedback mechanisms that give the operator good visibility and a quick-look display of the status and modes of instruments as well as data. TELICS has been used for regular science observations since 2008 March on the 2 m, f/10 IUCAA Telescope located at Girawali in Pune, India.Item A diffuse bubble-like radio-halo source MRC 0116+111: imprint of AGN feedback in a low-mass cluster of galaxies(2009-07-09) Bagchi, Joydeep; Jacob, Joe; Gopal, Krishna; et al.We present detailed observations of MRC 0116+111, revealing a luminous, mini radiohalo of 240 kpc diameter located at the centre of a cluster of galaxies at redshift z = 0.131. Our optical and multi-wavelength GMRT and VLA radio observations reveal a highly unusual radio source: showing a pair of giant ( 100 kpc diameter) bubble-like diffuse structures, that are about three times larger than the analogous extended radio emission observed in M87 - the dominant central radio galaxy in the Virgo Cluster. However, in MRC 0116+111 we do not detect any ongoing Active Galactic Nucleus (AGN) activity, such as a compact core or active radio jets feeding the plasma bubbles. The radio emitting relativistic particles and magnetic fields were probably seeded in the past by a pair of radio-jets originating in the AGN of the central cD galaxy. The extremely steep high-frequency radio spectrum of the north-western bubble, located 100 kpc from cluster centre, indicates radiation losses, possibly because having detached, it is rising buoyantly and moving away into the putative hot intra-cluster medium. The other bubble, closer to the cluster centre, shows signs of ongoing particle re-acceleration.We estimate that the radio jets which inflated these two bubbles might have also fed enough energy into the intra-cluster medium to create an enormous system of cavities and shock fronts, and to drive a massive outflow from the AGN, which could counter-balance and even quench a cooling flow. Therefore, this source presents an excellent opportunity to understand the energetics and the dynamical evolution of radio-jet inflated plasma bubbles in the hot cluster atmosphere.Item Multi-wavelength observations of afterglow of GRB080319B and the modeling constraints(2009-04-11) Pandey, S.B.; Castro-Tirado, A. J.; Jelinek, M.; et al.Context. We present observations of the afterglow of GRB 080319B at optical, mm and radio frequencies from a few hours to 67 days after the burst. Aims. To understand the nature of this brightest explosion based on the observed properties and it’s comparison with the afterglow models. Methods. Present observations along with other published multi-wavelength data have been used to study the light-curves and spectral energy distributions of the burst afterglow. Results. Our results show that the observed features of the afterglow fits equally good with the Inter Stellar Matter and the Stellar Wind density profiles of the circum-burst medium. In case of both density profiles, location of the maximum synchrotron frequency νm is below optical and the value of cooling break frequency νc is below X−rays, ∼ 104 s after the burst. Also, the derived value of the Lorentz factor at the time of naked eye brightness is ∼ 300 with the corresponding blast wave size of ∼ 1018 cm. Conclusions. The numericalItem Analysis of possible anomalies in the QSO distribution of the Flesch & Hardcastle catalogue(2008-01-02) M. L´opez-Corredoira; C. M. Guti´errez; Mohan, V.; Gunthardt, G. I.; Alonso, M. S.Aims. A recent catalogue by Flesch & Hardcastle presents two major anomalies in the spatial distribution of QSO candidates: i/ an apparent excess of such objects near bright galaxies, and ii/ an excess of very bright QSO candidates compared to random background expectations in several regions of the sky. Because anyone of these anomalies would be relevant in a cosmological context, we carried out an extensive analysis of the probabilities quoted in that catalogue. Methods. We determine the nature and redshift of a subsample of 30 sources in that catalogue by analysing their optical spectra (another 11 candidates were identified from existing public databases). These have allowed us to statistically check the reliability of the probabilities QSO status quoted by Flesch & Hardcastle for their candidates. Results. Only 12 of the 41 candidates turned out QSOs (7 of which have been identified here for the first time). Conclusions. The probabilities of the QSOs’ being the candidates given by Flesch & Hardcastle are overestimated for mB ≤ 17 and for objects projected near (≤ 1 arcmin) bright galaxies. This is the cause of the anomalies mentioned above.Item A giant radio jet ejected by an ultramassive black hole in a single-lobed radio galaxy(2004-12-04) Bagchi, Joydeep; Krishna, Gopal; Krause, Marita; Santosh JoshiWe report the discovery of a very unusual, highly asymmetric radio galaxy whose radio jet, the largest yet detected, emits strongly polarized synchrotron radiation and can be traced all the way from the galactic nucleus to the hot spot located 440 kpc away. This jet emanates from an extremely massive black-hole (> 109M⊙) and forms a strikingly compact radio lobe. No radio lobe is detected on the side of the counter-jet, even though it is similar to the main jet in brightness up to a scale of tens of kilo parsecs. Thus, contrary to the nearly universal trend, the brightness asymmetry in this radio galaxy increases with distance from the nucleus. With several unusual properties, including a predominantly toroidal magnetic field, this Fanaroff-Riley type II mega-jet is an exceptionally useful laboratory for testing the role of magnetic field in jet stabilization and radio lobe formationItem Exposure time calculator for IFOSC and sky background estimation(Bull. Astr. Soc. India, 2005-06-22) Chakraborty, Pavan; Das, H.K.; Tandon, S. N.This paper describes a spectroscopy exposure time calculator for the faint object spectrograph, the \IUCAA Faint Object Spectrograph" (IFOSC). It is intended to provide reasonable estimates of exposure times for observations. The background sky brightness is modeled for different phases and angular distance from the Moon. The code automatically calculates the Lunar Ephemerides from the date and time of observations and uses it for sky brightness computations. We adopt a new technique of scaling the Rayleigh and the Mie scattering functions, according to the corresponding extinction terms. This estimation of the sky brightness with moonlight ¯ts reasonably well with the observed sky brightness measured at the IUCAA telescope site. A simple component model is used for the optical elements. Each compo- nent is described by simple wavelength dependent extinction tables. At present, a blackbody/power-law spectrum is chosen as the input spectrum. Model or actual spectrum can also be used. The input blackbody spectrum is computed using the stellar \Spectral type" and scaled by the apparent V magnitude of the star. The programme is easily con¯gurable for di®erent sites and instruments. The code is written in ANSI C and thus portable to any system. A graphically interactive interface using HTML-cgi script has also been developed.