Observations of 8567 1996HW1 was carried
out over 12 nights in July, August and September
of 2008.@The synodic period was determined
as 8.7458 } 0.0002 hr with a mean amplitude
of 1.04 } 0.02 mag was derived. .
Minor planet 8567 1996HW1 was discovered
by Spacewatch-Steward Observatory,
Kitt Peak-Spacewatch
in April 1996. This is an Amor asteroid
with
a diameter of 2.5 - 5.6 km (Near Earth
Objects
- Dynamic Site). The latest list of
rotational
parameters (Harris and Warner, 2006)
has
8.7573hr with an amplitude 0.25 mag.
Photometric data for 8567 1996HW1 were
collected
using a 0.4 m Newtonian telescope,
a SBIG
ST-8E camera, and R filter (UBVRI)
with guided
exposure times ranging from 120 seconds
to
360 seconds at Hamanowa Astronomical
Observatory.
The image scale was 2.0 arc-seconds
per pixel
and camera temperature held at -15c
for all
measurements. The sky condition was
good
over the whole observation period.
All images
were dark subtracted and flat-fielded
before
measuring using IRAF (Tody 1986) and
Stella
Image ver, 5 (Astro Arts). Data were
collected
by light travel time from the asteroid
to
the Earth, and times are for mid-exposure.
We also used Cyclocode (B. Dermawan
2003)
to determine the period.
The phase changes as the observation
time
progresses because 8567 1996HW1 is
NEO. Therefore,
we used data of September 8, 9 and
10 where
few phase-changes occur to make a period
clear. Analysis of this data set showed
a
yielded rotation period of 8.7458 }
0.0003
day. Figure 1 is created by applying
a sought
period to all observation data and
shows
the phase of the curve be behind, by
observation
time's progressing. The data of all
days
must revise a difference in the period
which
is caused by the change of phase-angle.
Because
8567 1996 HW1 of the observation period
showed
a big magnitude variation, an offset
value
was mainly fixed by the change element
in
the celestial-longitude. Figure 2 is
created
by applying this offset and is correcting
the difference of the phase well. The
peak
to peak amplitude was the 0.7 mag in
the
early stages of the observation, in
the middle
was 0.9 mag, and it increased from
the observation
on September 8th to the 1.04 mag.
Table 1 The aspect data of 8567 1996HW1,
and the offset value which used for the correction.
Dates
2008 |
Phase |
PAB
Long, |
PAB
Lat, |
‡™PAB
Long, |
revision quantity
for period (day)
|
| Jul, 28 |
31.3631 |
316.7111 |
17.8763 |
0 |
0 |
| Aug, 07 |
31.4459 |
329.7445 |
17.3887 |
-13.0334 |
-0.013193 |
| Aug, 08 |
31.4226 |
330.6043 |
17.2823 |
-13.8932 |
-0.014063 |
| Aug, 17 |
30.7631 |
338.8282 |
15.6950 |
-22.1171 |
-0.022388 |
| Sep, 08 |
25.4081 |
1.2706 |
5.5059 |
-44.5596 |
-0.045105 |
| Sep, 09 |
25.1743 |
2.2857 |
4.8469 |
-45.5746 |
-0.046133 |
| Sep, 10 |
24.9589 |
3.2936 |
4.1797 |
-46.5825 |
-0.047153 |
| Sep, 12 |
24.5884 |
5.2846 |
2.8283 |
-48.5735 |
-0.049168 |
| Sep, 16 |
24.1041 |
9.1474 |
0.1095 |
-52.4363 |
-0.053078 |
| Sep, 22 |
23.9063 |
14.5707 |
-3.7996 |
-57.8596 |
-0.058568 |
| Oct, 01 |
23.9367 |
21.7312 |
-8.7578 |
-65.0201 |
-0.065816 |
| Oct, 02 |
23.9170 |
22.4567 |
-9.2244 |
-65.7456 |
-0.066551 |
|
