KANATA ObsLog

■ [blazar] S5 0716+714 : detection of a flare

We update the data of S5 0716+714. We can see a flare clearly between JD=2454747 and 4760. Also the color V-J was blue when the object was brightening.

■ [blazar] PKS 0048-097 : Bright

The figure shows the light curve of the object in V band (red point) and the time variation of the V-J color (green point). The object has become bright since JD=2454757, and the magnitude of the object reached about 14.9 mag. In addition, the color has become blue. The feature is called as the "bluer-when-brighter".

■ [blazar] H 1722+119 : light curve

We started observation of H 1722+119 on 2008 July 11. . The figure shows the light curve of the object in V band. The magnitude of its quiescence is 15.77 mag.(SIMBAD). The object tend to be brightening.

■ [blazar] PKS 2155-304 : light curve & color

We report our observation of PKS 2155-304. The figure shows the light curve of the object in V band and V-J color variation. The object shows a fading trend but the color still remains blue.

■ [XRB] V4641 Sgr: still on the quiescent level

After some cloudy days, we have just restarted our observation of V4641 Sgr. Tonight observation (24 Oct) shows the object apparently stays on its quiescent level.

■ [blazar] AO 0235+164 ; faded

We have continued to observe AO 0235+164. The figure shows the light curve of the object in V band. The magnitude of the flare in JD=2454755 was reached in about 15 mag. After the peak of the flare, the magnitude was faded to 15.7 mag in 6 days. The object is, however, still in the bright state.

■ [blazar] PKS 0048-097 : remain active

We started observation PKS 0048-097 on 2008 Oct. 2. The mag. of the object in V band is 15.2-15.7 during our 1-month observation. It has been recorded as 17.3 mag.(by SIMBAD). Once the object reached a maximum on Oct. 9. After that the object tended to become faint but it tend to become bright again in these 4 days.

■ [XRB] V4641 Sgr: return to quiescence?

We have just finished tonight (21 Oct.) observation of V4641 Sgr. The object is almost on the quiescent ellipsoidal modulation, as can be seen in the above light curve.

■ [XRB] V4641 Sgr: activity update

The object remains at the slightly active state since the last report. It has kept 0.1-0.2 mag brighter than its quiescent level as can be seen in the above light curve. Tonight (20 Oct.), the object is almost on the quiscent level. The activity may be weakening.

■ [blazar] 3C 371 : light curve (V, J, Ks band)

We have observed 3C 371 since 7 July 2008. The figure shows the light curves of the object in V, J and Ks bands. The amplitudes of variations in V and Ks bands might be larger than those of J band. That behavior is mysterious if the optical-infrared emission is dominated by a single component of the synchrotron emission. The object tend to be bright.

■ [blazar] S5 0716+714 : active state

We have observed to S5 0716+714 since 26 May 2008. The figure shows the light curve in V band and V-J color variation. The object has been active since 1 week ago, and also the color of the object has become blue.

■ [blazar] PKS 1749+096 : variation of color

The figure shows the light curve of PKS 1749+096 in V band and a V-J color. The color of the second flare is bluer than that of the first flare. In the recent 7 days, the magnitude of the object faded but the color is still blue.

■ [XRB] V4641 Sgr active

As noticed by Dr. Yamaoka in vsnet-alert 10580, the black hole X-ray binary, V4641 Sgr is currently active in X-rays. The above figures show the light curves of our observation (the red points) and the model of the ellipsoidal modulation (the green lines) (Upper panel: 7 - 17 Oct, lower panel: 16 - 26 Aug). On 14 and 16 Oct, the object was ~0.1-0.15 mag brighter than its quiescent level, although it was on the quiescent ellipsoidal modulation on 9 Oct and in August. The object is, thus, active also in the optical regime.

On 15 Oct, it was rather close to its quiescent level, as can be seen in the upper figure. At that time, the object was in the secondary minimum of the ellipsoidal modulation. In that phase, the secondary star of V4641 Sgr can hide the active region in the accretion disk around the black hole. The relatively low level on 15 Oct may be due to the partial eclipse of the central active region.

■ [blazar] AO 0235+164 : Fermi and our data

The figure shows the light curves of AO 0235+164 in GeV gamma-ray region and V band. These light curves in both gamma-ray and optical regions are variable by a factor of four and sixteen. The optical variation is, hence, larger than the gamma-ray one. The gamma-ray and optical light curves seem not to show a clear positive correlation.

■ [blazar] 1ES 1959+650 : light curve and color

We have been observed 1ES 1959+650 since 7 July '08. The figure shows the light curve of the object in V band and a V-J color. There is a clear correlation between the brightness and the color.

■ [blazar] PKS 2155-304 ; fading trend

PKS 2155-304 is the one of the brightest and famous blazars. We have observed the object since 9 Jul. 2008. The figure shows a light curve in V band and a V-J color variation. The magnitude of the object faded and the amplitude was about 0.7 mag.. There were some short flares which tended to be blue. The color has gradually become red except for the flares.

■ [blazar] AO 0235+164 : rebrightening

The figure shows the light curve of the object in V band from 12 Oct. 2008. The object had a first flare at 23 Sep., and now has a second flare.

■ [blazar] PKS 0048-097 ; brightening

The figure shows the light curve of PKS 0048-097 in V band and the time series of the polarization degree in the same band. The object became bright, and the magnitude of the object reached about 15.3 mag. on 7 Oct. 2008 in V band. The object is usually at about 16 mag. in V band. It is now in a bright state. The average of the polarization degree was about 5 %. The polarization degree was variable.

■ [blazar] AO 0235+164 ; Faded the flare

The figure shows the light curve of AO 0235+164. The object had beed brightened since we started observing the object. However, the object have recently been faded. The amplitude of the faded magnitude was about 1.6 mag. in V band.

■ [blazar] PKS 1749+096 : brightening

We have been observed PKS 1749+096 since 18 July '08. The figure shows the light curve of the object. The object became bright from 10 September more than about 1.2 mag. We continue to observe the object.

■ [blazar] 3C 66A : update the data

We have been observed 3C 66A since 9 Jul. 2008. Although the magnitude of this object had gradually decreased until 19 Sep., the object have become bright. Atel #1755 also reported this behaviour. The V-J color became bluer when the object became bright. We continue to observe the object.