155 research outputs found
Kiso observations for 20 GRBs in HETE-2 era
We have established a GRB follow-up observation system at Kiso observatory
(Japan) in 2001. Since the east Asian area had been blank for the GRB follow-up
observational network, this observational system is very important in studying
the temporal and spectral evolution of early afterglows. Using this system, we
have performed quick observations for optical afterglows from early phase based
on HETE-2 and INTEGRAL alerts. Thanks to the quick follow-up observation
system, we have been able to use the Kiso observatory in 20 events, and conduct
their follow-up observations in optical and near infrared wavelengths.Comment: 5 pages, 4 figure. Accepted for publication into "il nuovo cimento".
Proceeding of the 4th Rome GRB conference, eds. L. Piro, L. Amati, S. Covino,
B. Gendr
Early (0.3 day) R-band light curve of the optical afterglow of GRB030329
We observed the optical afterglow of the bright gamma-ray burst GRB030329 on
the nights of 2003 March 29, using the Kiso observatory (the University of
Tokyo) 1.05 m Schmidt telescope. Data were taken from March 29 13:21:26 UT to
17:43:16 (0.072 to 0.253 days after the burst), using an -band filter. The
obtained -band light curve has been fitted successfully by a single power
law function with decay index of . These results remain
unchanged when incorporating two early photometric data points at 0.065 and
0.073 days, reported by Price et al.(2003) using the SSO 40 inch telescope, and
further including RTT150 data (Burenin et al. 2003) covering at about 0.3 days.
Over the period of 0.065-0.285 days after the burst, any deviation from the
power-law decay is smaller than 0.007 mag. The temporal structure reported
by Uemura et al. (2003) does not show up in our -band light curve.Comment: 9 pages, 2 figures, 1 table, accepted for publication in ApJ
Testing the External Shock Model of Gamma-Ray Bursts using the Late-Time Simultaneous Optical and X-ray Afterglows
We study the ``normal'' decay phase of the X-ray afterglows of gamma-ray
bursts (GRBs), which follows the shallow decay phase, using the events
simultaneously observed in the R-band. The classical external shock model -- in
which neither the delayed energy injection nor time-dependency of shock
micro-physics is considered -- shows that the decay indices of the X-ray and
R-band light curves, and , obey a certain
relation, and that in particular, should be
larger than -1/4 unless the ambient density increases with the distance from
the central engine. For our selected 14 samples, we have found that 4 events
violate the limit at more than the 3 level, so that a fraction of
events are outliers of the classical external shock model at the ``normal''
decay phase.Comment: Accepted for publication in ApJL. 12 page, 2 figures, 2 table
Multi-band optical follow-up observations of GRB 020813 at KISO and Bisei observatories
Observations were made of the optical afterglow of GRB020813 (Fox, Blake &
Price, 2002) with the KISO observatory 1.05 m Schmidt telescope and the Bisei
astronomical observatory 1.01 m telescope. Four-band (, and )
photometric data points were obtained from 2002, August 13 10:52 to 16:46 UT,
or 0.3460.516 days after the burst. In order to investigate the early-time
(1 day) evolution of the afterglow, four-band light curves were produced by
analyzing the data taken at these two astronomical observatories, as well as
publicly released data taken by the Magellan Baade telescope (Gladders and
Hall, 2002c). The light curves can be approximated by a broken power law, of
which the indices are approximately 0.46 and 1.33 before and after a break at
0.2 days, respectively. The optical spectral index stayed approximately
constant at 0.9 over 0.17 4.07 days after the burst. Since the
temporal decay index after the break and the spectral index measured at that
time are both consistent with those predicted by a spherical expansion model,
the early break is unlikely to be a jet break, but likely to represent the end
of an early bump in the light curve as was observed in the optical afterglow of
GRB021004.Comment: 12 pages, 3 figures, 2 tables, accepted for publication in ApJ
The History of the Mysterious Eclipses of KH 15D II. Asiago, Kiso, Kitt Peak, Mt. Wilson, Palomar, Tautenburg and Rozhen Observatories, 1954-97
The unusual pre-main-sequence binary star named KH 15D undergoes remarkably
deep and long-lasting periodic eclipses. Some clues about the reason for these
eclipses have come from the observed evolution of the system's light curve over
the last century. Here we present UBVRI photometry of KH 15D based on
photographic plates from various observatories, ranging in time from 1954 to
1997. The system has been variable at the ~1 mag level since at least 1965.
There is no evidence for color variations, with a typical limit of Delta(B-V) <
0.2 mag. We confirm some previously published results that were based on a
smaller sample of plates: from approximately 1965 to 1990, the total flux was
modulated with the 48-day orbital period of the binary, but the maximum flux
was larger, the fractional variations were smaller, and the phase of minimum
flux was shifted by almost a half-cycle relative to the modern light curve. All
these results are consistent with the recently proposed theory that KH 15D is
being occulted by an inclined, precessing, circumbinary ring.Comment: 10 pages, 3 figures, 3 tables, accepted for publication in
Astronomical Journa
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