Hatena::Groupkanatatmp

KANATA ObsLog

2011-11-10

[] Optical Transient in UGC 5460 : Characteristics of a Type IIn SN

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We performed photometric and spectroscopic observations of PSN J10081059+5150570 in UGC5460. The spectra exhibit the emission lines of Balmer series. These features are composed of three different velocity components. The broader ones show the FWZI (Full Width of Zero Intensity) of around 10,000 km/s. The narrower ones show that of lower than 700 km/s, respectively. These features indicate that this transient could be classified into Type II"n" SNe or LBV. On the other hand, the light curves indicate the slow rising in optical and near-infrared wavelength. The apparent magnitude reach 14.5 mag in V-band on Nov. 7. The absolute magnitude is roughly estimated to be -16.5 mag. These facts support that PSN J10081059+5150570 should be a Type IIn supernova.

2011-10-07

[] Optical Transient in UGC 5460 : brightening

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We started photometric observations of the optical transient in UGC 5460. This optical transient was spectroscopically classified as an eruption from luminous blue variable (LBV). The light curves indicate the brightening in V, Rc and Ic-band. If the nature of this transient is an eta Car-like object, the light curves may keep the luminous state for more than a year. We will continue the photometric observations of this object.

2011-08-31

[] Type Ia SN 2011ek : rapid decline of line velocity

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We performed the optical photometric and spectroscopic observations of Type Ia SN 2011ek. The line velocity of SiII6355 show a rapid decline until last day. The line velocity of SiII6355 on Aug. 6 reach 15000 km/s. These observational facts indicate that SN 2011ek is classified into high-velocity SNe Ia (Benetti et al. 2005). The depth ratio of SiII5972 to SiII6355 also shows rapid decline. This supports that the ejecta rapidly expands and its temperature become high. We confirm the secondary maximum in I-band. Its luminosity is a bit lower than a typical Type Ia SN. It means that the Fe-group mass would be smaller than a typical Type Ia SN.

2011-08-14

[] Type Ia SN 2011ek : high-velocity features and a possible CII line.

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We have observed Type Ia SN 2011ek since 2011 Aug 6. This SN was discovered on 2011 Aug 4.7 at the nearby galaxy NGC 918 by K. Itagaki. We performed follow-up spectroscopic observations of this SN. This SN was identified as high-velocity Type Ia SN at more 10 days before maximum-light (CBET 2785, 2786). The spectra exhibit high-velocity SiII 5972, 6355 and CaII IR triplet features. The blueshifts of these absorption lines are calculated to be 15000 km/s at Aug 6. These features also exhibit the broader absorption lines than low-velocity SNe Ia. These features are common to high-velocity Type Ia SNe (Benetti et al. 2005, Branch et al. 2006). We also possibly identify the very weak carbon absorption line at 6250A. They may be common features in some Type Ia SNe (Parrent et al. 2011). It may be a signature of the unburnt material of the white dwarf. We also performed phometric observations. The rising time seems to be faster than low-velocity SNe Ia (Ganeshalingam et al .2011). The luminosity still does not reach the maximum-light in B-band. We will observations of this SN.

2011-07-31

[] Possible SN in NGC 3613 : Type Identification

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We performed the spectroscopic observations of the possible SN in NGC 3613 on Jul 30.6. The spectrum exhibits the SII W-shape feature, SiII 5972, SiII 6355, OI 7774 and CaII IR triplet. The line velocity of SiII6355 reached 10000 km/s. The intensity ratio of SiII 5972 to SiII6355 absorption lines estimated to be 0.5, which is comparable of that of SN 1991bg. These profiles are similar to that of SN 1991bg-like object.