Akira Arai

The unprecedented optical outburst of the quasar 3C 454.3 : The WEBT campaign of 2004-2005

Context. The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. The maximum brightness detected was

Early Phase Obserbations of Extermely Luminous Type Ia Supernova 2009dc

R=12.0

The radio delay of the exceptional 3C 454.3 outburst. Follow-up WEBT observations in 2005-2006

, which represents the most luminous quasar state thus far observed (

The WEBT Campaign on the Blazar 3C 279 in 2006

M_B \sim -31.4

Wide-field one-shot optical polarimeter: HOWPol

). Aims. In order to follow the emission behaviour of the source in detail, a large multiwavelength campaign was organized by the Whole Earth Blazar Telescope (WEBT). Methods. Continuous optical, near-IR and radio monitoring was performed in several bands. ToO pointings by the Chandra and INTEGRAL satellites provided additional information at high energies in May 2005. Results. The historical radio and optical light curves show different behaviours. Until about 2001.0 only moderate variability was present in the optical regime, while prominent and long-lasting radio outbursts were visible at the various radio frequencies, with higher-frequency variations preceding the lower-frequency ones. After that date, the optical activity increased and the radio flux is less variable. This suggests that the optical and radio emissions come from two separate and misaligned jet regions, with the inner optical one acquiring a smaller viewing angle during the 2004-2005 outburst. Moreover, the colour-index behaviour (generally redder-when-brighter) during the outburst suggests the presence of a luminous accretion disc. A huge mm outburst followed the optical one, peaking in June-July 2005. The high-frequency (37-43 GHz) radio flux started to increase in early 2005 and reached a maximum at the end of our observing period (end of September 2005). VLBA observations at 43 GHz during the summer confirm the brightening of the radio core and show an increasing polarization. An exceptionally bright X-ray state was detected in May 2005, corresponding to the rising mm flux and suggesting an inverse-Compton nature of the hard X-ray spectrum. Conclusions. A further multifrequency monitoring effort is needed to follow the next phases of this unprecedented event.

Detection of Polarimetric Variations Associated with the Shortest Time-Scale Variability in S5 0716+714

We present early phase observations in optical and near-infrared wavelengths for the extremely luminous Type Ia supernova (SN Ia) 2009dc. The decline rate of the light curve is ?m 15(B) = 0.65 ? 0.03, which is one of the slowest among SNe Ia. The peak V-band absolute magnitude is estimated to be MV = ?19.90 ? 0.15?mag if no host extinction is assumed. It reaches MV = ?20.19 ? 0.19?mag if we assume the host extinction of AV = 0.29?mag. SN 2009dc belongs to the most luminous class of SNe Ia, like SNe 2003fg and 2006gz. Our JHKs -band photometry shows that this SN is also one of the most luminous SNe Ia in near-infrared wavelengths. We estimate the ejected 56Ni mass of 1.2 ? 0.3 M ? for the no host extinction case (and of 1.6 ? 0.4 M ? for the host extinction of AV = 0.29?mag). The C II ?6580 absorption line remains visible until a week after the maximum brightness, in contrast to its early disappearance in SN 2006gz. The line velocity of Si II ?6355 is about 8000?km?s?1 around the maximum, being considerably slower than that of SN 2006gz. The velocity of the C II line is similar to or slightly less than that of the Si II line around the maximum. The presence of the carbon line suggests that the thick unburned C+O layer remains after the explosion. Spectropolarimetric observations by Tanaka et?al. indicate that the explosion is nearly spherical. These observational facts suggest that SN 2009dc is a super-Chandrasekhar mass SN Ia.

OPTICAL AND NEAR-INFRARED POLARIMETRY OF HIGHLY REDDENED Type Ia SUPERNOVA 2014J: PECULIAR PROPERTIES OF DUST IN M82

Context. In spring 2005 the blazar 3C 454.3 was observed in an unprecedented bright state from the near-IR to the hard X-ray frequencies. A mm outburst peaked in June-July 2005, and it was followed by a flux increase at high radio frequencies. Aims. In this paper we report on multifrequency monitoring by the WEBT aimed at following the further evolution of the outburst in detail. In particular, we investigate the expected correlation and time delays between the optical and radio emissions in order to derive information on the variability mechanisms and jet structure. Methods. A comparison among the light curves at different frequencies is performed by means of visual inspection and discrete correlation function, and the results are interpreted with a simple model taking into account Doppler factor variations of geometric origin. Results. The high-frequency radio light curves show a huge outburst starting during the dimming phase of the optical one and lasting more than 1 year. The first phase is characterized by a slow flux increase, while in early 2006 a major flare is observed. The lower-frequency radio light curves show a progressively delayed and fainter event, which disappears below 8 GHz. We suggest that the radio major peak is not physically connected with the spring 2005 optical one, but it is actually correlated with a minor optical flare observed in October-November 2005. This interpretation | involves both an intrinsic and a geometric mechanism. The former is represented by disturbances travelling down the emitting jet, the latter being due to the curved-jet motion, with the consequent differential changes of viewing angles of the different emitting regions.

Discovery of a WZ Sge-Type Dwarf Nova, SDSS J102146.44+234926.3: Unprecedented Infrared Activity during a Rebrightening Phase

Thequasar3C279wasthetargetof anextensivemultiwavelengthmonitoringcampaignfrom2006Januarythrough April. An optical-IR-radio monitoring campaign by the Whole Earth Blazar Telescope (WEBT) collaboration was organized around target-of-opportunity X-ray and soft � -ray observations with Chandra and INTEGRAL in 2006 midJanuary, with additional X-ray coverage by RXTE and Swift XRT. In this paper we focus on the results of the WEBT campaign. Thesource exhibited substantial variability of opticalflux and spectralshape,witha characteristictimescale of a few days. The variability patterns throughout the optical BVRI bands were very closely correlated with each other, while there was no obvious correlation between the optical and radio variability. After the ToO trigger, the optical flux

Optical and Near-Infrared Photometric Observation during the Superoutburst of the WZ Sge-Type Dwarf Nova, V455 Andromedae

For prompt optical polarimetry of gamma-ray burst (GRB) afterglow, we require wide-field imaging polarimeter which can produce both Stokes Q and U parameters from only a single exposure, as well as quickly-moving telescope and enclosure system. HOWPol is an optical imaging polarimeter which provides four linearly polarized images at position angles of 0°, 45°, 90° and 135°, i.e., Stokes I, Q, U, simultaneously. The key device is the wedged double Wollaston prism described by Oliva (1997)1 and Pernechele et al. (2003).2 The images are focused on two 2k×4k fully depleted CCDs. We report the design and development of the optical devices of HOWPol, which will be mounted to the 1.5-m Kanata telescope at Hiroshima University and stand by the GRB alert.

Variable optical polarization during high state in γ-ray loud, narrow-line Seyfert 1 galaxy 1H 0323+342

We present the result of near-infrared and optical observations of the BL Lac object S5 0716