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We present optical and ultraviolet photometry, and low resolution optical spectroscopy of the broad-line type Ic supernova SN 2014ad in the galaxy PGC 37625 (Mrk 1309), covering the evolution of the supernova during $-$5 to +87 d with respect to the date of maximum in $B$-band. A late phase spectrum obtained at +340 d is also presented. With an absolute $V$ band magnitude at peak of $M_{V}$ = $-$18.86 $\pm$ 0.23 mag, SN 2014ad is fainter than Gamma Ray Burst (GRB) associated supernovae, and brighter than most of the normal and broad-line type Ic supernovae without an associated GRB. The spectral evolution indicates the expansion velocity of the ejecta, as measured using the Si\,{\sc ii} line, to be as high as $\sim$ 33500 km\,s$^{-1}$ around maximum, while during the post-maximum phase it settles down at $\sim$ 15000 km\,s$^{-1}$. The expansion velocity of SN 2014ad is higher than all other well observed broad-line type Ic supernovae except the GRB associated SN 2010bh. The explosion parameters, determined by applying the Arnett's analytical light curve model to the observed bolometric light curve, indicate that it was an energetic explosion with a kinetic energy of $\sim$ (1 $\pm$ 0.3)$\times$10$^{52}$ ergs, a total ejected mass of $\sim$ (3.3 $\pm$ 0.8) M$_\odot$, and $\sim$ 0.24 M$_\odot$ of $^{56}$Ni was synthesized in the explosion. The metallicity of the host galaxy near the supernova region is estimated to be $\sim$ 0.5 Z$_\odot$., 15 pages, 17 figures and 4 tables. Accepted for publication in MNRAS main journal

We present optical photometric (upto $\sim$410 days since $B$$_{max}$) and spectroscopic (upto $\sim$157 days since $B$$_{max}$) observations of a Type Iax supernova (SN) 2014dt located in M61. SN 2014dt is one of the brightest and closest (D $\sim$ 20 Mpc) discovered Type Iax SN. SN 2014dt best matches the light curve evolution of SN 2005hk and reaches a peak magnitude of $M$$_B$ $\sim$-18.13$\pm$0.04 mag with $\Delta m_{15}$ $\sim$1.35$\pm 0.06$ mag. The early spectra of SN 2014dt are similar to other Type Iax SNe, whereas the nebular spectrum at 157 days is dominated by narrow emission features with less blending as compared to SNe 2008ge and 2012Z. The ejecta velocities are between 5000 to 1000 km sec$^{-1}$ which also confirms the low energy budget of Type Iax SN 2014dt as compared to normal Type Ia SNe. Using the peak bolometric luminosity of SN 2005hk we estimate $^{56}$Ni mass of $\sim$0.14 M$_{\odot}$ and the striking similarity between SN 2014dt and SN 2005hk implies that a comparable amount of $^{56}$Ni would have been synthesized in the explosion of SN 2014dt., Comment: 12 figures, 7 tables, Accepted for publication in MNRAS

We present optical photometric and spectroscopic results of supernova SN 2004ab, a highly reddened normal type Ia supernova. The total reddening is estimated as $E(B-V)$ = 1.70 $\pm$ 0.05 mag. The intrinsic decline rate parameter, $\Delta m_{15}(B)_\text{true}$ is 1.27 $\pm$ 0.05, and $B$-band absolute magnitude at maximum $M_{B}^{\text{max}}$ is $-$19.31 $\pm$ 0.25 mag. The host galaxy NGC 5054 is found to exhibit anomalous extinction with very low value of $R_V$ = 1.41 $\pm$ 0.06 in the direction of SN 2004ab. Peak bolometric luminosity is derived as $\log L_\text{bol}^\text{max}$ = 43.10 $\pm$ 0.07 erg\,s$^{-1}$. The photospheric velocity measured from absorption minimum of Si\,{\sc ii} $\lambda$6355 line shows a velocity gradient of $\dot{v}$ = 90 km\,s$^{-1}$\,d$^{-1}$, indicating that SN 2004ab is a member of the high velocity gradient (HVG) subgroup. The ratio of strength of Si\,{\sc ii} $\lambda$5972 and $\lambda$6355 absorption lines, $\cal R$(Si\,{\sc ii}) is estimated as 0.37, while their pseudo equivalent widths suggest that SN 2004ab belongs to broad line (BL) type subgroup., Comment: 13 pages, 5 tables, 16 figures, accepted for publication in MNRAS

We present results of optical broad-band and narrow-band Halpha observations of a sample of forty nearby early-type galaxies. The majority of sample galaxies are known to have dust in various forms viz. dust lanes, nuclear dust and patchy/filamentary dust. A detailed study of dust was performed for 12 galaxies with prominent dust features. The extinction curves for these galaxies run parallel to the Galactic extinction curve, implying that the properties of dust in these galaxies are similar to those of the Milky-Way. The ratio of total to selective extinction (Rv) varies between 2.1 and 3.8, with an average of 2.9 +/- 0.2, fairly close to its canonical value of 3.1 for our Galaxy. The average relative grain size /a_Gal of dust particles in these galaxies turns out to be 1.01 +/- 0.2, while dust mass estimated using optical extinction lies in the range 10^2 to 10^4 M(sun) . The Halpha emission was detected in 23 out of 29 galaxies imaged through narrow- band filters with the Halpha luminosities in the range 10^38 - 10^41 erg s^-1. The mass of the ionized gas is in the range 10^3-10^5 M(sun). The morphology and extent of ionized gas is found similar to those of dust, indicating possible coexistence of dust and ionized gas in these galaxies. The absence of any apparent correlation between blue luminosity and normalized IRAS dust mass is suggestive of merger related origin of dust and gas in these galaxies., Comment: 28 pages, 6 figures; Accepted for publication in New Astronomy. Please cite this article in press as: Kulkarni, S., et al. New Astron. (2014), http://dx.doi.org/10.1016/j.newast.2014.01.003

We present a study of the properties of star-forming regions within a sample of 7 Wolf-Rayet (WR) galaxies. We analyze their morphologies, colours, star-formation rate (SFR), metallicities, and stellar populations combining broad-band and narrow-band photometry with low-resolution optical spectroscopy. The $UBVRI$ observations were made through the 2m HCT (Himalayan Chandra Telescope) and 1m ARIES telescope. The spectroscopic data were obtained using the Hanle Faint Object Spectrograph Camera (HFOSC) mounted on the 2m HCT. The observed galaxies are NGC 1140, IRAS 07164+5301, NGC 3738, UM 311, NGC 6764, NGC 4861 and NGC 3003. The optical spectra have been used to search for the faint WR features, to confirm that the ionization of the gas is consequence of the massive stars, and to quantify the oxygen abundance of each galaxy using several and independent empirical calibrations. We detected the broad features originated by WR stars in NGC 1140 and NGC 4861 and used them to derive their population of massive stars. Using our H$\alpha$ images we have identified tens of regions within these galaxies, for which we derived the SFR. For all regions we found that the most recent star-formation event is 3 - 6 Myr old. We used the optical broad-band colours in combination with Starburst99 models to estimate the internal reddening and the age of the dominant underlying stellar population within all these regions. Knots in NGC 3738, NGC 6764 and NGC 3003 generally show the presence of an important old (400 - 1000 Myr) stellar population. However, the optical colours are not able to detect stars older than 20 - 50 Myr in the knots of the other four galaxies. This fact suggests both the intensity of the starbursts and that the star-formation activity has been ongoing for at least some few tens of million years in these objects., Comment: 22 Pages, 14 Figures, accepted for publication in MNRAS

High cadence ultraviolet, optical and near-infrared photometric and low-resolution spectroscopic observations of the peculiar Type II supernova (SN) 2018hna are presented. The early phase multiband light curves exhibit the adiabatic cooling envelope emission following the shock breakout up to ~14 days from the explosion. SN~2018hna has a rise time of $\sim$\,88 days in the V-band, similar to SN 1987A. A $\rm^{56}Ni$ mass of ~0.087$\pm$0.004 $\rm M_{\odot}$ is inferred for SN 2018hna from its bolometric light curve. Hydrodynamical modelling of the cooling phase suggests a progenitor with a radius ~50 $\rm R_{\odot}$, a mass of ~14-20 $\rm M_{\odot}$ and explosion energy of ~1.7-2.9$\rm \times$ $\rm 10^{51}\ erg$. The smaller inferred radius of the progenitor than a standard red supergiant is indicative of a blue supergiant progenitor of SN 2018hna. A sub-solar metallicity (~0.3 $\rm Z_{\odot}$) is inferred for the host galaxy UGC 07534, concurrent with the low-metallicity environments of 1987A-like events., 8 pages, 5 figures, Accepted for Publication in ApJ Letters

Optical $UBVRI$ photometry and low resolution spectroscopy of the type IIb supernova SN 2011dh in M51 are presented, covering the first year after the explosion. The light curve and spectral evolution are discussed. The early phase light curve evolution of SN 2011dh is very similar to SN 1993J and SN 2008ax. In the late phase, however, SN 2011dh declines faster than SN 1993J. The late phase decline in the $B$-band is steeper than in the $R$ and $I$ bands, indicating the possibility of dust formation. With a peak $V$-band absolute magnitude of $M_V = -17.123\pm0.18$ mag, SN 2011dh is a marginally faint type IIb event. The reddening corrected colour curves of SN 2011dh are found to be redder than other well studied type IIb supernovae. The bolometric light curve indicates $\sim$ 0.09 M$_\odot$ of $^{56}$Ni is synthesized during the explosion. The HeI lines were detected in the spectra during the rise to maximum. The nebular spectra of SN 2011dh show a box shaped emission in the red wing of the [OI] 6300-6363 \AA\ feature, that is attributed to H$\alpha$ emission from a shock excited circumstellar material. The analysis of nebular spectra indicates that $\sim 0.2$ M$_\odot$ of oxygen was ejected during the explosion. Further, the [CaII]/[OI] line ratio in the nebular phase is $\sim$ 0.7, indicating a progenitor with a main sequence mass of 10-15 M$_\odot$., Comment: Accepted for publication in MNRAS

We present the low-resolution spectroscopic and UBVRI broad-band photometric investigations of the Type IIb supernova (SN) 2011fu, discovered in UGC 01626. The photometric follow-up of this event was initiated a few days after the explosion and covers a period of about 175 d. The early-phase light curve shows a rise, followed by steep decay in all bands, and shares properties very similar to that seen for SN 1993J, with a possible detection of the adiabatic cooling phase. Modelling of the quasi-bolometric light curve suggests that the progenitor had an extended (∼1 × 10 13 cm), low-mass (∼0.1 M ⊙ ) H-rich envelope on top of a dense, compact (∼2 × 10 11 cm), more massive (∼1.1 M ⊙ ) He-rich core. The nickel mass synthesized during the explosion was found to be ∼0.21 M ⊙ , slightly larger than that seen for other Type IIb SNe. The spectral modelling performed with synow suggests that the early-phase line velocities for H and Fe ii features were ∼16000 and ∼14000 km s −1 , respectively. Then, the velocities declined up to day +40 and became nearly constant at later epochs.

We present optical UBVRI photometry and medium-resolution spectroscopy of a transitional Type Ia supernova, SN 2009an, over the period −6 to ∼+150 d from the B maximum. With a Δm 15 (B) = 1.514 ± 0.132, SN 2009an declines faster than normal Type Ia events, but slower than the fast-declining, low-luminosity 1991bg-like events. The B-band absolute magnitude at maximum is −19.02 ± 0.20. The peak bolometric luminosity indicates that 0.41 M☉ of 56 Ni was synthesized during the explosion. The pre-maximum and early post-maximum spectral evolution of SN 2009an is very similar to that in the transitional Type Ia SN 2004eo. High-velocity features in the Ca II near-infrared triplet are seen during the early phases. Similar to the other few objects belonging to this class, SN 2009an exhibits a higher value (~0.4) of the Si II line ratio R(Si II). The velocity gradient of the Si II 6355 A line in the post-maximum epoch (v˙=60 km s −1 d −1 ) is at the boundary between the low-velocity-gradient and high-velocity-gradient groups.

Three Earth-sized planets—receiving similar irradiation to Venus and Earth, and ideally suited for atmospheric study—have been found transiting a nearby ultracool dwarf star that has a mass of only eight per cent of that of the Sun. Theory predicts that terrestrial or rocky planets are likely to be orbiting the lowest-mass stars. This paper reports the detection of a system of three Earth-sized planets transiting a very nearby (12 parsec) ultracool dwarf star of only 8% of the mass of the Sun. The planets are similar in irradiation to Venus and Earth, and particularly well suited for detailed atmospheric characterization. Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as ‘ultracool dwarfs’1. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun2. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks3,4, there should be a large but hitherto undetected population of terrestrial planets orbiting them5—ranging from metal-rich Mercury-sized planets6 to more hospitable volatile-rich Earth-sized planets7. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star8. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.

This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/mnras/stw2253, Supernova (SN) 2015bh (or SNhunt275) was discovered in NGC 2770 on 2015 February with an absolute magnitude of M$_r$ ~ −13.4 mag, and was initially classified as an SN impostor. Here, we present the photometric and spectroscopic evolution of SN 2015bh from discovery to late phases (~1 yr after). In addition, we inspect archival images of the host galaxy up to ~21 yr before discovery, finding a burst ~1 yr before discovery, and further signatures of stellar instability until late 2014. Later on, the luminosity of the transient slowly increases, and a broad light-curve peak is reached after about three months. We propose that the transient discovered in early 2015 could be a core-collapse SN explosion. The pre-SN luminosity variability history, the long-lasting rise and faintness first light-curve peak suggests that the progenitor was a very massive, unstable and blue star, which exploded as a faint SN because of severe fallback of material. Later on, the object experiences a sudden brightening of 3 mag, which results from the interaction of the SN ejecta with circumstellar material formed through repeated past mass-loss events. Spectroscopic signatures of interaction are however visible at all epochs. A similar chain of events was previously proposed for the similar interacting SN 2009ip.

The evolution of the spin rate of Comet 9P/Tempel 1 through two perihelion passages (in 2000 and 2005) is determined from 1922 Earth-based observations taken over a period of 13 year as part of a World-Wide observing campaign and from 2888 observations taken over a period of 50 days from the Deep Impact spacecraft. We determine the following sidereal spin rates (periods): 209.023 +/- 0.025 degrees/dy (41.335 +/- 0.005 h) prior to the 2000 perihelion passage, 210.448 +/- 0.016 degrees/dy (41.055 +/- 0.003 h) for the interval between the 2000 and 2005 perihelion passages, 211.856 +/- 0.030 degrees/dy (40.783 +/- 0.006 h) from Deep Impact photometry just prior to the 2005 perihelion passage, and 211.625 +/- 0.012 degrees/dy (40.827 +/- 0.002 h) in the interval 2006-2010 following the 2005 perihelion passage. The period decreased by 16.8 +/- 0.3 min during the 2000 passage and by 13.7 +/- 0.2 min during the 2005 passage suggesting a secular decrease in the net torque. The change in spin rate is asymmetric with respect to perihelion with the maximum net torque being applied on approach to perihelion. The Deep Impact data alone show that the spin rate was increasing at a rate of 0.024 +/- 0.003 degrees/dy/dy at JD2453530.60510 (i.e., 25.134 dy before impact), which provides independent confirmation of the change seen in the Earth-based observations. The rotational phase of the nucleus at times before and after each perihelion and at the Deep Impact encounter is estimated based on the Thomas et al. (Thomas et al. [2007]. Icarus 187, 4-15) pole and longitude system. The possibility of a 180 error in the rotational phase is assessed and found to be significant. Analytical and physical modeling of the behavior of the spin rate through of each perihelion is presented and used as a basis to predict the rotational state of the nucleus at the time of the nominal (i.e., prior to February 2010) Stardust-NExT encounter on 2011 February 14 at 20:42. We find that a net torque in the range of 0.3-2.5 x 10(7) kg m(2) s(-2) acts on the nucleus during perihelion passage. The spin rate initially slows down on approach to perihelion and then passes through a minimum. It then accelerates rapidly as it passes through perihelion eventually reaching a maximum post-perihelion. It then decreases to a stable value as the nucleus moves away from the Sun. We find that the pole direction is unlikely to precess by more than similar to 1 degrees per perihelion passage. The trend of the period with time and the fact that the modeled peak torque occurs before perihelion are in agreement with published accounts of trends in water production rate and suggests that widespread H(2)O out-gassing from the surface is largely responsible for the observed spin-up. (C) 2011 Elsevier Inc. All rights reserved.

We present observational data for Comet 9P/Tempel 1 taken from 1997 through 2010 in an international collaboration in support of the Deep Impact and Stardust-NExT missions. The data were obtained to characterize the nucleus prior to the Deep Impact 2005 encounter, and to enable us to understand the rotation state in order to make a time of arrival adjustment in February 2010 that would allow us to image at least 25% of the nucleus seen by the Deep Impact spacecraft to better than 80 m/pixel, and to image the crater made during the encounter, if possible. In total, similar to 500 whole or partial nights were allocated to this project at 14 observatories worldwide, utilizing 25 telescopes. Seventy percent of these nights yielded useful data. The data were used to determine the linear phase coefficient for the comet in the R-band to be 0.045 +/- 0.001 mag deg(-1) from 1 degrees to 16 degrees. Cometary activity was observed to begin inbound near r similar to 4.0 AU and the activity ended near r similar to 4.6 AU as seen from the heliocentric secular light curves, water-sublimation models and from dust dynamical modeling. The light curve exhibits a significant pre- and post-perihelion brightness and activity asymmetry. There was a secular decrease in activity between the 2000 and 2005 perihelion passages of similar to 20%. The post-perihelion light curve cannot be easily explained by a simple decrease in solar insolation or observing geometry. CN emission was detected in the comet at 2.43 AU pre-perihelion, and by r = 2.24 AU emission from C-2 and C-3 were evident. In December 2004 the production rate of CN increased from 1.8 x 10(23) mol s(-1) to Q(CN) = 2.75 x 10(23) mol s(-1) in early January 2005 and 9.3 x 10(24) mol s(-1) on June 6, 2005 at r = 1.53 AU. (C) 2011 Elsevier Inc. All rights reserved.

Optical $UBVRI$ photometry and medium resolution spectroscopy of the type Ib supernova SN 2009jf, during the period $\sim -15$ to +250days with respect to the $B$ maximum are reported. The light curves are broad, with an extremely slow decline. The early post-maximum decline rate in the $V$ band is similar to SN 2008D, however, the late phase decline rate is slower than other studied type Ib supernovae. With an absolute magnitude of $M_{V} = -17.96\pm0.19$ magnitude at peak, SN 2009jf is a normally bright supernova. The peak bolometric luminosity and the energy deposition rate via $^{56}$Ni $\rightarrow$ $^{56}$Co chain indicate that $\sim {0.17}^{+0.03}_{-0.03}$ M$_{\odot}$ of $^{56}$Ni was ejected during the explosion. He\,I 5876 \AA\ line is clearly identified in the first spectrum of day $\sim -15$, at a velocity of $\sim 16000$ km sec$^{-1}$. The [O\,I] 6300-6364 \AA\ line seen in the nebular spectrum has a multi-peaked and asymmetric emission profile, with the blue peak being stronger. The estimated flux in this line implies $\ga 1.34$ M$_\odot$ oxygen was ejected. The slow evolution of the light curves of SN 2009jf indicates the presence of a massive ejecta. The high expansion velocity in the early phase and broader emission lines during the nebular phase suggest it to be an explosion with a large kinetic energy. A simple qualitative estimate leads to the ejecta mass of M$_{\rm ej} = 4-9$ M$_\odot$, and kinetic energy E$_{\rm K} = 3-8 \times 10^{51}$ erg. The ejected mass estimate is indicative of an initial main-sequence mass of $\ga 20- 25$ M$_\odot$.

We present ground-based and HST optical observations of the optical transients (OTs) of long-duration Gamma Ray Bursts (GRBs) 060729 and 090618, both at a redshift of z = 0.54. For GRB 060729, bumps are seen in the optical light curves (LCs), and the late-time broadband spectral energy distributions (SEDs) of the OT resemble those of local type Ic supernovae (SNe). For GRB 090618, the dense sampling of our optical observations has allowed us to detect well-defined bumps in the optical LCs, as well as a change in colour, that are indicative of light coming from a core-collapse SN. The accompanying SNe for both events are individually compared with SN1998bw, a known GRB-supernova, and SN1994I, a typical type Ic supernova without a known GRB counterpart, and in both cases the brightness and temporal evolution more closely resemble SN1998bw. We also exploit our extensive optical and radio data for GRB 090618, as well as the publicly-available SWIFT -XRT data, and discuss the properties of the afterglow at early times. In the context of a simple jet-like model, the afterglow of GRB 090618 is best explained by the presence of a jet-break at t-to > 0.5 days. We then compare the rest-frame, peak V -band absolute magnitudes of all of the GRB and X-Ray Flash (XRF)-associated SNe with a large sample of local type Ibc SNe, concluding that, when host extinction is considered, the peak magnitudes of the GRB/XRF-SNe cannot be distinguished from the peak magnitudes of non-GRB/XRF SNe.

We present a comprehensive multi-wavelength analysis of the young cluster NGC 1624 associated with the H II region Sh2-212 using optical UBVRI photometry, optical spectroscopy and GMRT radio continuum mapping along with the near-infrared (NIR) JHK archival data. Reddening E(B-V) and distance to the cluster are estimated to be 0.76 - 1.00 mag and 6.0 +/- 0.8 kpc, respectively. Present analysis yields a spectral class of O6.5V for the main ionizing source of the region. The distribution of YSOs in (J-H)/ (H-K) NIR colour-colour diagram shows that a majority of them have A_V $\le$ 4 mag. Based on the NIR excess characteristics, we identified 120 probable candidate YSOs in this region which yield a disk frequency of ~ 20%. These YSOs are found to have an age spread of ~ 5 Myr with a median age of ~ 2-3 Myr and a mass range of ~ 0.1 - 3.0 $M_\odot$. A significant number of YSOs are located close to the cluster centre and we detect an enhanced density of reddened YSOs located/projected close to the molecular clumps at the periphery of NGC 1624. This indicates that the YSOs located within the cluster core are relatively older in comparison to those located/projected near the clumps. From the radio continuum flux, spectral class of the ionizing source of the ultra-compact H II region at the periphery of Sh2-212 is estimated to be ~ B0.5V. From optical data, slope of the mass function (MF) $\Gamma$, in the mass range $1.2 \le M/M_{\odot}

We present infrared JHK photometry of the cataclysmic variable SDSS J123813.73-033933.0 (SDSS1238)and analyze it along with optical spectroscopy, demonstrating that the binary system is most probably comprised of a massive white dwarf with Teff=12000+/-1000 K and a brown dwarf of spectral type L4. The inferred system parameters suggest that this system may have evolved beyond the orbital period minimum and is a bounce-back system. SDSS1238 stands out among CVs by exhibiting the cyclical variability (brightenings). These are not related to specific orbital phases of the binary system and are fainter than dwarf novae outbursts, that usually occur on longer timescales. This phenomenon has not been observed extensively and, thus, is poor understood. The new time-resolved, multi-longitude photometric observations of SDSS1238 allowed us to observe two consecutive brightenings and to determine their recurrence time. The period analysis of all observed brightenings during 2007 suggests a typical timescale that is close to a period of ~9.3 hours. However, the brightenings modulation is not strictly periodic, possibly maintaining coherence only on timescales of several weeks. The characteristic variability with double orbital frequency that clearly shows up during brightenings is also analyzed. The Doppler mapping of the system shows the permanent presence of a spiral arm pattern in the accretion disk. A simple model is presented to demonstrate that spiral arms in the velocity map appear at the location and phase corresponding to the 2:1 resonance radius and constitute themselves as a double-humped light curves. The long-term and short-term variability of this CV is discussed together with the spiral arm structure of an accretion disk in the context of observational effects taking place in bounce-back systems., Comment: 24 pages, 9 figures, Accepted for publications in The Astrophysical Journal, typos added

We present optical spectroscopic and photometric observations of supernova (SN) 2008D, associated with the luminous X-ray transient 080109, at >300 days after the explosion (nebular phases). We also give flux measurements of emission lines from the H II region at the site of the SN, and estimates of the local metallicity. The brightness of the SN at nebular phases is consistent with the prediction of the explosion models with an ejected 56Ni mass of 0.07 Msun, which explains the light curve at early phases. The [O I] line in the nebular spectrum shows a double-peaked profile while the [Ca II] line does not. The double-peaked [O I] profile strongly indicates that SN 2008D is an aspherical explosion. The profile can be explained by a torus-like distribution of oxygen viewed from near the plane of the torus. We suggest that SN 2008D is a side-viewed, bipolar explosion with a viewing angle of > 50^{\circ} from the polar direction., 6 pages, 7 figures, Accepted for publication in ApJ

We present a detailed study of the prompt and afterglow emission from Swift GRB 061126 using BAT, XRT, UVOT data and multi-color optical imaging from ten ground-based telescopes. GRB 061126 was a long burst (T_90=191 s) with four overlapping peaks in its gamma-ray light curve. The X-ray afterglow, observed from 26 min to 20 days after the burst, shows a simple power-law decay with alpha_X=1.290 \pm 0.008. Optical observations presented here cover the time range from 258 s (Faulkes Telescope North) to 15 days (Gemini North) after the burst; the decay rate of the optical afterglow shows a steep-to-shallow transition (from alpha_1=1.48 \pm 0.06 to alpha_2=0.88 \pm 0.03) approximately 13 min after the burst. We suggest the early, steep component is due to a reverse shock and show that the magnetic energy density in the ejecta, expressed as a fraction of the equipartion value, is a few ten times larger than in the forward shock in the early afterglow phase. The ejecta might be endowed with primordial magnetic fields at the central engine. The optical light curve implies a late-time break at about 1.5 days after the burst, while there is no evidence of the simultaneous break in the X-ray light curve. We model the broad band emission and show that some afterglow characteristics (the steeper decay in X-ray and the shallow spectral index from optical to X-ray) are difficult to explain in the framework of the standard fireball model. This might imply that the X-ray afterglow is due to an additional emission process, such as late time central engine activity rather than blast-wave shock emission. The possible chromatic break at 1.5 days after the burst would give support to the additional emission scenario., Comment: 14 pages, 10 figures, 1 table; Accepted for publication in ApJ

We present $UBVRI$ CCD photometry and optical spectra of the type Ia supernova SN 2003hx which appeared in the galaxy NGC 2076, obtained till $\sim$ 146 days after the epoch of $B$ band maximum. The supernova reached at maximum brightness in $B$ band on JD 245 2893 $\pm$ 1.0 with an apparent magnitude of 14.92 $\pm$ 0.01 mag which was estimated by making template fits to the light curves. SN 2003hx is an example of a highly reddened supernova with $E(B-V)$ = 0.56 $\pm$ 0.23. We estimate $R_v$ = 1.97 $\pm$ 0.54 which indicates the small size of dust particles as compared to their galactic counterparts. The luminosity decline rate is $\Delta m_{15}(B)$ = 1.17 $\pm$ 0.12 mag and the absolute $B$ band magnitude obtained from the luminosity versus decline rate relation (Phillips et al. 1999) is $M^B_{max}$ = -19.20 $\pm$ 0.18 mag. The peak bolometric luminosity indicates that $\sim$ 0.66 $M_\odot$ mass of $^{56}$ Ni was ejected by the supernova. The spectral evolution indicates the supernova to be a normal type Ia event., Comment: 16 pages, 21 figures, 5 tables, Accepted for publication in MNRAS

Ultraviolet observations using the Solar Blind Channel on the Hubble Space Telescope provide light curves and low resolution spectra of three pulsating white dwarfs in the cataclysmic variables SDSS013132.39-090122.3, SDSSJ161033.64-010223.3 and SDSSJ220553.98+115553.7. The UV light curves show enhanced pulsation amplitudes over those from simultaneous and previous optical photometry, while the UV-optical spectra are fit with white dwarf temperatures near 15,000K. These temperatures place the accreting white dwarfs outside the instability zone for non-interacting DAV white dwarfs and show that the instability strip is complex for accreting white dwarfs.

Significant abundances of Platinum-group elements (PGE) along with gold have been recorded for the first time from pyroxenite and gabbro in the Mothinamakki-Birolli Suryakalyanigudda layered mafic-ultramafic complex in Uttara Kannada district, Karnataka. The associated path finder elements enrichment such as Cr (45-5000 ppm), Ni (49-3002 ppm), Co (21-434 ppm), Cu (55-10701ppm), V (78-3716 ppm) and Zn (41-1156 ppm) in this layered complex suggest a favorable locale for PGE mineralization. Groove samples from sulphide rich pyroxenite and gabbro have analysed Pt content ranging from 5-405 ppb, Pd 5-593 ppb, Rh 5-106 ppb, Ir 5-18 ppb, Ru 5-20 ppb and Au content

We present multiwavelength observations of the gamma-ray burst GRB 051028 detected by HETE-2 in order to derive its afterglow emission parameters and to determine the reason for its optical faintness when compared to other events. Observations were taken in the optical (2.0m Himalayan Chandra Telescope, 1.34m Tautenburg, 4.2m William Herschel Telescope) and in X-rays (Swift/XRT) between 2.7 hours and 10 days after the onset of the event. The data can be interpreted by collimated emission in a jet with a typical value of $p$ = 2.4 which is moving in an homogeneous interstellar medium and with a cooling frequency nu_{c} still above the X-rays at 0.5 days after the burst onset. GRB 051028 can be classified as a ``gray'' or ``potentially dark'' GRB. On the basis of the combined optical and Swift/XRT data, we conclude that the reason for the optical dimness is not extra absorption in the host galaxy, but rather the GRB taking place at high-redshift.We also notice the very striking similarity with the optical lightcurve of GRB 050730, a burst with a spectroscopic redshift of 3.967, although GRB 051028 is about 3 mag fainter. We suggest that the bump could be explained by multiple energy injection episodes and that the burst is intrinsically faint when compared to the average afterglows detected since 1997. The non-detection of the host galaxy down to R = 25.1 is also consistent with the burst arising at high redshift, compatible with the published pseudo-z of 3.7 +/- 1.8.

著者人数: 59名, Accepted: 2014-08-26, 資料番号: SA1005030000

We present BVRI photometry and optical spectroscopy of SN 2005bf near light maximum. The maximum phase is broad and occurred around 2005 May 7, about forty days after the shock breakout. SN 2005bf has a peak bolometric magnitude M_{bol}=-18.0\pm 0.2: while this is not particularly bright, it occurred at an epoch significantly later than other SNe Ibc, indicating that the SN possibly ejected ~0.31 M_{sun} of 56Ni, which is more than the typical amount. The spectra of SN 2005bf around maximum are very similar to those of the Type Ib SNe 1999ex and 1984L about 25-35 days after explosion, displaying prominent He I, Fe II, Ca II H & K and the near-IR triplet P Cygni lines. Except for the strongest lines, He I absorptions are blueshifted by, Comment: 13 pages, 4 figures. Accepted for publication in ApJ (Letters)

We present optical and UV analysis of the luminous type Ia supernova SN 2012dn covering the period $\sim -$11 to +109 days with respect to the $B$ band maximum, that occurred on JD 2456132.89 $\pm$ 0.19, with an apparent magnitude of $m_{B}^\text{max}$ = 14.38 $\pm$ 0.02. The absolute magnitudes at maximum in $B$ and $V$ bands are $M_{B}^\text{max} = -19.52 \pm 0.15$ and $M_{V}^\text{max} = -19.42 \pm 0.15$, respectively. SN 2012dn is marginally luminous compared to normal type Ia supernovae. The peak bolometric luminosity of $\log L_\text{bol}^\text{max} = 43.27 \pm 0.06$ erg s$^{-1}$ suggests that $0.82 \pm 0.12$ M$_\odot$ of $^{56}$Ni was synthesized in the explosion. The decline rate $\Delta m_{15}(B)_\text{true}= 0.92 \pm 0.04$ mag is lower than that of normal type Ia supernovae, and similar to the luminous SN 1991T. However, the photometric and spectroscopic behaviour of SN 2012dn is different from that of SN 1991T. Early phase light curves in $R$ and $I$ bands are very broad. The $I$ band peak has a plateau-like appearance similar to the super-Chandra SN 2009dc. Pre-maximum spectra show clear evidence of C\,{\sc ii} 6580 \AA\, line, indicating the presence of unburned materials. The velocity evolution of C\,{\ sc ii} line is peculiar. Except for the very early phase ($\sim-$13 d), the C\,{\sc ii} line velocity is lower than the velocity estimated using the Si\,{\sc ii} line. During the pre-maximum and close to maximum phase, to reproduce observed shape of the spectra, the synthetic spectrum code {\sc syn++} needs significantly higher blackbody temperature than those required for normal type Ia events. The photospheric velocity evolution and other spectral properties are similar to those of the carbon-rich SN 2006gz., Comment: Accepted for publication in MNRAS, 19 pages, 20 figures

BACKGROUND Spontaneous bullous serous retinal detachment (RD) with subretinal exudation complicating idiopathic central serous chorioretinopathy (ICSC) is a rare and infrequently described clinical entity. Clinical observations are described on this variant form in 11 patients, the largest series reported to date. METHODS 13 eyes of 11 Indian patients having this entity were followed up clinically and angiographically for 12–24 months (retrospective, longitudinal). None of the patients had any previous history of other diseases nor were they on any medications. Four eyes received laser treatment (group A); nine eyes were not treated (group B). RESULTS All 11 patients were male, aged 23–49 years (median 37 years). The clinical and photographic records revealed subretinal exudation and inferior bullous serous RD complicating ICSC with evidence of large, single or multiple, leaking retinal pigment epithelial detachments (PEDs) in all the cases. In group A, resolution of serous RD occurred in 12 weeks (median) with a visual recovery of ⩾20/30 in three out of four eyes while in group B resolution of serous retinal detachment was observed in 14 weeks (median) with eight out of nine eyes achieving a visual acuity of ⩾20/30. Subretinal fibrosis developed in two eyes in group A and none of the eyes in group B. CONCLUSION The disease is an exaggerated form of ICSC and can occur spontaneously without any history of corticosteroid therapy. Recognition of this atypical presentation is important to avoid inappropriate treatment. These observations suggest that with respect to the duration of the disease and the final visual outcome laser therapy offers no additional benefit over the natural course of this variant form of ICSC.

In this first systematic attempt to characterise the intranight optical variability (INOV) of TeV detected blazars, we have monitored a well defined set of 9 TeV blazars on total 26 nights during 2004-2010. In this R (or V)-band monitoring programme only one blazar was monitored per night for a minimum duration of 4 hours. Using the CCD, an INOV detection threshold of ~ 1-2 % was achieved in the densely sampled DLCs. We have further expanded the sample by including another 13 TeV blazars from literature. This enlarged sample of 22 TeV blazars, monitored on a total of 116 nights (including 55 nights newly reported here), has enabled us to arrive at the first estimate of the INOV duty cycle of TeV detected blazars. Applying the C-test, the INOV DC is found to be 59 %, which decreases to 47 % if only INOV fractional amplitudes above 3 % are considered. These observations also permit, for the first time, a comparison of the INOV characteristics of the two major subclasses of TeV detected BL Lacs, namely LBLs and HBLs, for which we find the INOV DCs to be ~ 63 % and ~ 38 %, respectively. This demonstrates that the INOV differential between LBLs and HBLs persists even when only their TeV detected subsets are considered. Despite dense sampling, the intranight light curves of the 22 TeV blazars have not revealed even a single feature on time scale substantially shorter than 1 hour, even though the inner jets of TeV blazars are believed to have exceptionally large bulk Lorentz factors (and correspondingly stronger time compression). An intriguing feature, clearly detected in the light curve of the HBL J1555+1111, is a 4 per cent `dip' on a 1 hour timescale. This unique feature could have arisen from absorption in a dusty gas cloud, occulting a superluminally moving optical knot in the parsec scale jet of this relatively luminous BL Lacs object.

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ∼16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO2-driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production. Fil: Meech, K. J.. Institute for Astronomy; Estados Unidos Fil: A’Hearn, M. F.. University of Maryland; Estados Unidos Fil: Adams, J. A.. Cornell University; Estados Unidos Fil: Bacci, P.. Centro Astronomico di Libbiano; Italia Fil: Bai, J.. Chinese Academy of Sciences; China Fil: Barrera, L.. Universidad Metropolitana de Ciencias de la Educacion; Chile Fil: Battelino, M.. Swedish Space Corporation; Suecia Fil: Bauer, J. M.. Jet Propulsion Laboratory; Estados Unidos Fil: Becklin, E.. Stratospheric Observatory for Infrared Astronomy; Estados Unidos Fil: Bhatt, B.. Indian Institute of Astrophysics; India Fil: Biver, N.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia Fil: Bockelee Morvan, D.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia Fil: Bodewits, D.. University of Maryland; Estados Unidos Fil: Bohnhardt, H.. Gobierno de la Republica Federal de Alemania. Max Planck Institut Fur Astrophysik; Alemania Fil: Boissier, J.. Inst. di Radioastronomia; Italia Fil: Bonev, B. P.. Catholic University of America; Estados Unidos Fil: Borghini, W.. Osservatorio Astronomico Naturalistico di Casasco; Italia Fil: Brucato, J. R.. Osservatorio Astrofisico di Arcetri; Italia Fil: Bryssinck, E.. Brixiis Observatory; Bélgica Fil: Buie. M. W.. Southwest Research Institute; Estados Unidos Fil: Canovas, H.. Utrecht University; Países Bajos Fil: Castellano, D.. Unione Astrofili Italiani; Italia Fil: Charnley, S. B.. National Aeronautics And Space Administration; Estados Unidos Fil: Chen, W. P.. National Taiwan Normal University; Corea del Sur Fil: Chiang, P.. Korea Astronomy and Space Science Institute; Corea del Sur Fil: Choi, Y. J.. Korea Astronomy and Space Science Institute; Corea del Sur Fil: Christian, D. J.. California State University; Estados Unidos Fil: Chuang, Y. L.. National Taiwan Normal University; Corea del Sur Fil: Cochran, A. L.. University of Texas; Estados Unidos Fil: Melita, Mario Daniel. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

We report the results of our intensive intranight optical monitoring of 8 `radio-intermediate quasars' (RIQs) having flat or inverted radio spectra. The monitoring was carried out in {\it R-} band on 25 nights during 2005-09. An intranight optical variability (INOV) detection threshold of $\sim$ 1--2% was achieved for the densely sampled differential light curves (DLCs). 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 relativistically boosted nuclear jets, clear evidence for INOV in our extensive observations was detected only on one night. 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 criteria allowed us to enlarge the sample to 10 RIQs (monitored on a total of 42 nights for a minimum duration of $\sim 4$ hours per night). The absence of large amplitude INOV $(��> 3%)$ persists in this enlarged sample. This extensive database has enabled us to arrive at the first estimate for the INOV Duty Cycle (DC) of RIQs. The DC is found to be small ($\sim$ 9%). The corresponding value is known to be $\sim 60%$ for BL Lacs and $\approx 15%$ for RLQs and RQQs. On longer-term, the RIQs are found to be fairly variable with typical amplitudes of $\approx$ 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., 35 pages, 2 figures, 3 tables, accepted for publication in MNRAS

We present the result of our extensive intranight optical monitoring of the well known low-energy peaked BL Lac (LBL) object PKS 0735+178. This long-term follow-up consists of $R$-band monitoring for a minimum duration of $\sim 4$ hours, on 17 nights spanning 11 years (1998-2008). Using the CCD as an N-star photometer, a detection limit of around 1% was attained for the intra-night optical variability (INOV). Remarkably, an INOV amplitude of $\geq 3%$ on hour-like time scale was not observed on any of the 17 nights, even though the likelihood of a typical LBL showing such INOV levels in a single session of $\ga 4$ hours duration is known to be high ($\sim50%$). Our observations have thus established a peculiar long-term INOV quiescence of this radio-selected BL Lac object. Moreover, the access to unpublished optical monitoring data of similarly high sensitivity, acquired in another programme, has allowed us to confirm the same anomalous INOV quiescence of this LBL all the way back to 1989, the epoch of its historically largest radio outburst. Here, we present observational evidence revealing the very unusual INOV behaviour of this classical BL Lac object and discuss this briefly in the context of its other known exceptional properties., 24 pages, 4 figures, 2 tables; Accepted for publication in MNRAS

We present optical UBVRI photometric and spectroscopic data of the type Ibn supernova SN 2006jc, until the onset of the dust forming phase. The optical spectrum shows a blue continuum and is dominated by the presence of moderately narrow (velocity ~2500 km/s) He I emission lines superimposed over a relatively weak supernova spectrum. The helium lines are produced in a pre-existing He rich circumstellar shell. The observed helium line fluxes indicate the circumstellar shell is dense, with a density of ~10^9 - 10^{10} cm^{-3}. The helium mass in this shell is estimated to be, Comment: Accepted for publication in MNRAS

Photometric and spectral evolution of the Type Ic supernova SN 2007ru until around 210 days after maximum are presented. The spectra show broad spectral features due to very high expansion velocity, normally seen in hypernovae. The photospheric velocity is higher than other normal Type Ic supernovae. It is lower than SN 1998bw at $\sim$ 8 days after the explosion, but is comparable at later epochs. The light curve evolution of SN 2007ru indicates a fast rise time of 8$\pm$3 days to $B$ band maximum and post-maximum decline more rapid than other broad-line Type Ic supernovae. With an absolute $V$ magnitude of -19.06, SN 2007ru is comparable in brightness with SN 1998bw and lies at the brighter end of the observed Type Ic supernovae. The ejected mass of \Nifs is estimated to be $\sim0.4\Msun$. The fast rise and decline of the light curve and the high expansion velocity suggest that SN 2007ru is an explosion with a high kinetic energy/ejecta mass ratio ($E_{\rm K}/M_{\rm {ej}}$). This adds to the diversity of Type Ic supernovae. Although the early phase spectra are most similar to those of broad-line SN 2003jd, the [OI] line profile in the nebular spectrum of SN 2007ru shows the singly-peaked profile, in contrast to the doubly-peaked profile in SN 2003jd. The singly-peaked profile, together with the high luminosity and the high expansion velocity, may suggest that SN 2007ru could be an aspherical explosion viewed from the polar direction. Estimated oxygen abundance 12 + log(O/H) of $\sim$8.8 indicates that SN 2007ru occurred in a region with nearly solar metallicity., 9 pages, 10 figures, emulateapj style, later observations are included, accepted for publication in the Astrophysical Journal

We present a theoretical model for supernova (SN) 2008D associated with the luminous X-ray transient 080109. The bolometric light curve and optical spectra of the SN are modelled based on the progenitor models and the explosion models obtained from hydrodynamic/nucleosynthetic calculations. We find that SN 2008D is a more energetic explosion than normal core-collapse supernovae, with an ejecta mass of Mej = 5.3 +- 1.0 Msun and a kinetic energy of E = 6.0 +- 2.5 x 10^{51} erg. The progenitor star of the SN has a 6-8 Msun He core with essentially no H envelope (< 5 x 10^{-4} Msun) prior to the explosion. The main-sequence mass of the progenitor is estimated to be Mms =20-25 Msun, with additional systematic uncertainties due to convection, mass loss, rotation, and binary effects. These properties are intermediate between those of normal SNe and hypernovae associated with gamma-ray bursts. The mass of the central remnant is estimated as 1.6 - 1.8 Msun, which is near the boundary between neutron star and black hole formation., 13 pages, 10 figures, Accepted for publication in ApJ, typos corrected

We present a preliminary analysis of an extensive set of optical observations of the Type Ia SN 2005hk. We show that the evolution of SN 2005hk closely follows that of the peculiar SN 2002cx. SN 2005hk is more luminous than SN 2002cx, while still under-luminous compared to normal Type Ia supernovae. The spectrum at 9 days before maximum is dominated by conspicuous Fe III and Ni III lines, and the Si II 6355 line is also clearly visible. All these features have low velocity (~6000 km/s). The near maximum spectra show lines of Si II, S II, Fe II, Fe III, as well as other intermediate mass and iron group elements. Analysis with the code for synthetic spectra SYNOW indicates that all these spectral lines have similar velocities., 6 pages, 3 figures, submitted to the proceedings of the conference``The Multicoloured Landscape of Compact Objects and their Explosive Origins'', 2006 June 11--24, Cefalu, Sicily, to be published by AIP

We present early-time optical and near-infrared photometry of supernova (SN) 2005cf. The observations, spanning a period from about 12 days before to 3 months after maximum, have been obtained through the coordination of observational efforts of various nodes of the European Supernova Collaboration and including data obtained at the 2m Himalayan Chandra Telescope. From the observed light curve we deduce that SN 2005cf is a fairly typical SN Ia with a post-maximum decline (Delta m_15(B) = 1.12) close to the average value and a normal luminosity of M_B,max = -19.39+/-0.33. Models of the bolometric light curve suggest a synthesised 56Ni mass of about 0.7 solar masses. The negligible host galaxy interstellar extinction and its proximity make SN 2005cf a good Type Ia supernova template., Comment: 17 pages, 11 figures, MNRAS, in press

We present broad band optical afterglow observations of a long duration GRB 060124 using the 1.04-m Sampurnanand Telescope at ARIES, Nainital and the 2.01-m HCT at IAO, Hanle, including the earliest ground based observations in R band for this GRB. We determine the decay slope of the light curve at different bands and examine the reality of a proposed jet break. We use data from our observations as well as others reported in the literature to construct light curves in different bands and make power law fits to them. The spectral slope of the afterglow emission in the optical band is estimated. Our first R-band observations were taken $\sim 0.038$~d after burst. We find that all available optical data after this epoch are well fit by a single power law, with a temporal flux decay index $\alpha\sim 0.94$. We do not find any evidence of a jet break within our data, which extend till $\sim 2$~d after the burst. The X-ray light curve, however, shows a distinct break around 0.6 day. We attribute this break to a steepening of the electron energy spectrum at high energies. We conclude that the above measurements are consistent with the picture of a standard fireball evolution with no jet break within $t\sim 2$~days after the burst. This sets a lower limit of $3\times 10^{50}$~erg to the total energy released in the explosion., Comment: Accepted for publication in A&A

We report optical extinction properties of dust for a sample of 26 early-type galaxies based on the analysis of their multicolour CCD observations. The wavelength dependence of dust extinction for these galaxies is determined and the extinction curves are found to run parallel to the Galactic extinction curve, which implies that the properties of dust in the extragalactic environment are quite similar to those of the Milky Way. For the sample galaxies, value of the parameter $R_V$, the ratio of total extinction in $V$ band to selective extinction in $B$ & $V$ bands, lies in the range 2.03 - 3.46 with an average of 3.02, compared to its canonical value of 3.1 for the Milky Way. A dependence of $R_V$ on dust morphology of the host galaxy is also noticed in the sense that galaxies with a well defined dust lane show tendency to have smaller $R_V$ values compared to the galaxies with disturbed dust morphology. The dust content of these galaxies estimated using total optical extinction is found to lie in the range $10^4$ to $10^6 \rm M_{\sun}$, an order of magnitude smaller than those derived from IRAS flux densities, indicating that a significant fraction of dust intermixed with stars remains undetected by the optical method. We examine the relationship between dust mass derived from IRAS flux and the X-ray luminosity of the host galaxies.The issue of the origin of dust in early-type galaxies is also discussed., 12 pages, 6 figures. Accepted for publication in Astronomy & Astrophysics

GRB 050730 is a long duration high-redshift burst (z=3.967) discovered by Swift. The afterglow shows variability and is well monitored over a wide wavelength range. We present comprehensive temporal and spectral analysis of the afterglow of GRB 050730 including observations from the millimeter to X-rays. We use multi-wavelength afterglow data to understand the temporal and spectral decay properties with superimposed variability of this high redshift burst. Five telescopes were used to study the decaying afterglow of GRB 050730 in the B, V, r', R, i', I, J and K photometric pass bands. A spectral energy distribution was constructed at 2.9 hours post-burst in the K, J, I, R, V and B bands. X-ray data from the satellites Swift and XMM-Newton were used to study the afterglow evolution at higher energies. The early afterglow shows variability at early times and shows a steepening at ~0.1 days (8.6 ks) in the B, V, r', R, i', I, J and K passbands. The early afterglow light curve decayed with alpha_1 = -0.60+/-0.07 and alpha_2 = -1.71+/-0.06 based on R and I band data. A millimeter detection of the afterglow around 3 days after the burst shows an excess in comparison to predictions. The early X-ray light curve observed by Swift is complex and contains flares. At late times the X-ray light curve can be fit by a powerlaw alpha_x = -2.5+/-0.15 which is steeper than the optical light curve. A spectral energy distribution (SED) was constructed at \~2.9 hours after the burst. An electron energy index, p, of ~ 2.3 was calculated using the SED and the photon index from the X-ray afterglow spectra and indicates that the synchrotron cooling frequency nu_c is above observed frequencies., Comment: 12 pages, 10 figures, Accepted for publication in A&A. Typo corrected in revision

We present a detailed study of the post-outburst phase of McNeil's nebula (V1647 Ori) using optical B,V,R,I and NIR J,H,K photometric and low resolution optical spectroscopic observations. The observations were carried out with the HFOSC, NIRCAM, TIRCAM and NICMOS cameras on the 2m HCT and 1.2m PRL telescopes during the period 2004 Feb-2005 Dec. The optical/NIR observations show a general decline in brightness of the exciting source of McNeil's nebula (V1647 Ori). Our recent optical images show that V1647 Ori has faded by more than 3 mags since Feb 2004. The optical/NIR photometric data also show a significant variation in the mags (Delta V = 0.78 mag, Delta R = 0.44 mag, Delta I = 0.21 mag, Delta J = 0.24 mag and Delta H = 0.20 mag) of V1647 Ori within a period of one month, which is possibly undergoing a phase similar to eruptive variables, like EXors or FUors. The optical spectra show a few features such as strong Halpha emission with blue-shifted absorption and the CaII IR triplet (8498A, 8542A and 8662A) in emission. As compared to the period just after outburst, there is a decrease in the depth and extent of the blue-shifted absorption component, indicating a weakening in the powerful stellar wind. The presence of the CaII IR triplet in emission confirms that V1647 Ori is a PMS star. The long-term, post-outburst photometric observations of V1647 Ori suggest an EXor, rather than an FUor event. An optical/IR comparison of the region surrounding McNeil's nebula shows that the optical nebula is more widely and predominantly extended to the north, whereas the IR nebula is relatively confined (dia ~ 60 arcsec), but definitely extended, to the south, too., Comment: 25 pages (4 figures in JPEG format), Accepted for the publication in MNRAS. Preprint is also available at: http://www.tifr.res.in/~ojha/McNeil.html

We present UBV CCD photometry and low-resolution spectra of stars in the field of the young open cluster NGC 146. UBV photometry of 434 stars were used to estimate the E(B$-$V) reddening of 0.55 $\pm$ 0.04 mag and BV photometry of 976 stars were used to estimate a distance modulus of (m$-$M)$_0$ = 12.7 $\pm$0.2 mag, corresponding to a distance of 3470$^{+335}_{-305}$ pc. We estimated 10 -- 16 Myr as the turn-off age for the upper main sequence of the cluster using isochrones and synthetic colour magnitude diagrams. We identified two B type stars with H$_\alpha$ in emission and located on the MS using slit-less spectra. A higher resolution spectrum of the brighter Be star indicated the presence of a number of emission lines, with some lines showing the signature of gas infall. This star was found to be located in the region of Herbig Ae/Be stars in the (J$-$H) vs (H$-$K) colour-colour diagram. Thus, we identify this star as a Herbig Be star. On the other hand, 54 stars were found to show near infrared excess, of which 17 were found to be located in the region of Herbig Ae/Be stars and 18 stars were found to be located in the region of Be stars in the NIR colour-colour diagram. Thus NGC 146 is a young cluster with a large number of intermediate mass pre-main sequence stars. The turn-on age of the cluster is found to be $\sim$ 3 Myr. Though NGC 146 shows an older turn off, the bulk of stars in this cluster seems to belong to the younger population of 3 Myr., Comment: 13 pages, 20 figures, To appear in A & A

We present radio, millimeter and optical observations of the afterglow of GRB030329. UBVR_{C}I_{C} photometry is presented for a period of 3 hours to 34 days after the burst. Radio monitoring at 1280 MHz has been carried out using the GMRT for more than a year. Simultaneous millimeter observations at 90 GHz and 230 GHz have been obtained from the Swedish-ESO Submillimeter Telescope (SEST) and the IRAM-PdB interferometer over more than a month following the burst. We use these data to constrain the double jet model proposed by Berger et al. (2003) for this afterglow. We also examine whether instead of the two jets being simultaneously present, the wider jet could result from the initially narrow jet, due to a fresh supply of energy from the central engine after the ``jet break''., Comment: 31 pages, 5 figures, Accepted for publication in A&A main journal. Table 2 will be available only through the electronic version of the journal

Optical and near-infrared spectroscopic observations of the fast nova V1494 Aquilae 1999 #2 covering various phases -- early decline, transition and nebular -- during the first eighteen months of its post-outburst evolution are presented in this paper. During this period, the nova evolved in the P_fe P_fe^o C_o spectral sequence. The transition from an optically thick wind to a polar blob - equatorial ring geometry is seen in the evolution of the spectral line profiles. There is evidence of density and temperature stratification in the ejecta. Physical conditions in the ejecta have been estimated based on our observations., Comment: 9 pages, 10 figures, to be published in MNRAS

著者人数: 209名, Accepted: 2005-09-01, 資料番号: SA1004082000

The UBVRI photometric follow-up of SN 2011fu has been initiated a few days after the explosion, shows a rise followed by steep decay in all bands and shares properties very similar to that seen in case of SN 1993J, with a possible detection of the adiabatic cooling phase at very early epochs. The spectral modeling performed with SYNOW suggests that the early-phase line velocities for H and Fe ii features were ~ 16000 km s−1 and ~ 14000 km s−1, respectively. Studies of rare class of type IIb SNe are important to understand the evolution of the possible progenitors of core-collapse SNe in more details.

UBVRI photometry and low resolution optical spectroscopy of the type IIb SN 2011dh in M51 are presented, covering the first year after the explosion. The peak absolute magnitude in V-band of −17.12±0.18 mag indicates SN 2011dh to be a normal bright type IIb event. The peak quasi-bolometric luminosity indicates that ~ 0.06 M⊙ of 56Ni was synthesized in the explosion. The He I lines were detected in the spectra much before the maximum light in B-band. The nebular spectra of SN 2011dh show a box shaped emission in the red wing of [OI] 6300, 6363 line due to Hα emission excited because of shock-wave interaction. The analysis of the nebular spectra indicates a progenitor with a main sequence mass of 10-15 M⊙.

UBVRI photometry and optical spectra of type Ia supernova SN 2003du obtained at the Indian Astronomical Observatory for nearly a year since discovery are presented. The apparent magnitude at maximum was B=13.53 +/- 0.02 mag, and the colour (B-V) = -0.08 +/- 0.03 mag. The luminosity decline rate, Delta(m_{15}(B)) = 1.04 +/- 0.04 mag indicates an absolute B magnitude at maximum of M_B = -19.34 +/- 0.3 mag and the distance modulus to the parent galaxy as mu=32.89 +/- 0.4.The light curve shapes are similar, though not identical, to those of SNe 1998bu and 1990N, both of which had luminosity decline rates similar to that of SN 2003du and occurred in spiral galaxies. The peak bolometric luminosity indicates that 0.9 Msun mass of 56Ni was ejected by the supernova. The spectral evolution and the evolution of the Si II and Ca II absorption velocities closely follows that of SN 1998bu, and in general, is within the scatter of the velocities observed in normal type Ia supernovae. The spectroscopic and photometric behaviour of SN 2003du is quite typical for SNe Ia in spirals. A high velocity absorption component in the Ca II (H & K) and IR-triplet features, with absorption velocities of ~20,000 km/s and ~22,000 km/s respectively, is detected in the pre-maximum spectra of days -11 and -7., 10 pages, 10 figures; Accepted for publication in A&A

The CCD magnitudes in Johnson $UBV$ and Cousins $RI$ photometric passbands for the afterglow of the long duration GRB 030226 are presented. Upper limits of a few mJy to millimeter wave emission at the location of optical are obtained over the first two weeks. The optical data presented here, in combination with other published data on this afterglow, show an early $R$ band flux decay slope of 0.77$\pm$0.04, steepening to 2.05$\pm$0.04 about 0.65$\pm$0.03 day after the burst. Interpreted as the ``jet break'', this indicates a half opening angle of $\sim 3.2$ degree for the initial ejection, for an assumed ambient density of $\sim 1 {\rm cm}^{-3}$. Broadband spectra show no appreciable evolution during the observations, and indicate the presence of synchrotron cooling frequency $\nu_c$ near the upper edge of the optical band. From the broadband spectra we derive an electron energy distribution index $p = 2.07\pm0.06$ and an intrinsic extinction $E(B - V)\sim0.17$. Millimeter upper limits are consistent with these derived parameters., Comment: 6 pages, 2 figures, Accepted to A&A

We determine Johnson $B,V$ and Cousins $R,I$ photometric CCD magnitudes for the afterglow of GRB 021211 during the first night after the GRB trigger. The afterglow was very faint and would have been probably missed if no prompt observation had been conducted. A fraction of the so-called ``dark'' GRBs may thus be just ``optically dim'' and require very deep imaging to be detected. The early-time optical light curve reported by other observers shows prompt emission with properties similar to that of GRB 990123. Following this, the afterglow emission from $\sim 11$ min to $\sim 33$ days after the burst is characterized by an overall power-law decay with a slope $1.1\pm0.02$ in the $R$ passband. We derive the value of spectral index in the optical to near-IR region to be 0.6$\pm$0.2 during 0.13 to 0.8 day after the burst. The flux decay constant and the spectral slope indicate that optical observations within a day after the burst lies between cooling frequency and synchrotron maximum frequency., Comment: 4 pages, 2 figures, A&A Letters, 408, L21