Chariklo.20160824 Occultation August 24, 2016

(last updated 2016 07 19)

finder charts

 

Across the globe pictured above, the three solid lines correspond to the northern limit, centerline, and southern limit of Chariklo's shadow. The northern and southern limits correspond to a radius of 125 km. The upper and lower dashed lines indicate 3-sigma errors. The shaded area represents where the sun is more than 0 degrees below the horizon.
Table 1: Prediction Details
Chariklo Geocentric Mid-time (yyyy month dd hh:mm:ss)

2016 August 24 05:17:18± 00:03:491 UT
Chariklo Minimum Geocentric Separation 0.1521± 0.34641 arcsec
Position Angle (Chariklo relative to the star; measured north through east) +39.24 degrees
Geocentric Velocity 10.92 km/sec
Occultation Star USNOB R magnitude 12.552

1One standard deviation of random error.
2The UCAC bandpass (579-642nm) is between V and R.


Table 2: Reference Star Position
Reference star position:
(USNOB, at epoch of event)		 RA (h:m:s; J2000) Dec (d:m:s; J2000) Notes
Chariklo.20160824 Catalog 18 16 08.5960 ± 0.2030 –33 39 09.680 ± 0.213
Chariklo.20160824 Measured3 18 16 08.4024 ± 0.0174 –33 39 08.156 ± 0.017
From 5 SARA-S frames
Table 3: Projected KBO Offsets from Reference Ephemeris at the Time of the Event
Body RA (arcsec) Dec (arcsec)  
Chariklo

–0.0965 ± 0.5438

 +0.0467 ± 0.047 See Notes 5 and 6

3Measured position corresponds to RA offset of +2.4179 and Dec. offset of +1.5242.

4All "offsets" are defined in the ("corrected" – "reference") or ("observed" – "calculated") sense. The offsets should be added to reference positions to get the measured positions, which we use to calculate the prediction.

4Data analyzed using UCAC2 reference network. A weighted average of the data from the two telescopes was used to calculate the RA and DEC. The errors given are 1 standard deviation.

5The reference positions for Chariklo are those given by JPL Horizon's ephemeris (Chariklo source file: JPL21; Earth center source file: DE405).

6Data from the USNO 61-inch, SMARTS 0.9m, and Lowell 42-inch telescopes over the span of 3 years were reduced with respect to stars in the UCAC2 catalog. A model was developed to fit the residuals obtained from our measured positions compared to that of the object's JPL ephemeris. All residuals obtained from the different telescopes were consistent with the model. The model includes the first-order effects of errors in the orbital elements of Chiron: (i) constant offsets in RA and Dec, (ii) linear (in time) offsets in RA and Dec, and (iii) sinusoidal terms with the Earth's orbital period. The model was propagated to obtain the predicted position and error of the KBO at the time of the occultation. The errors listed for the KBO are 1 standard deviation.

 

Table 4: Site Information

Site
East Longitude
Latitude

Site Altitude6

(km)

Distance7

(km)

Velocity

(km/s)
CTIO
–70 48 54
–30 09 54
2.215
462 N.
11.17
IRTF
–155 28 29
19 49 46
4.182
1184 N.
11.20
Lowell
–111 39 54
35 12 12
2.219
4203 N.
11.24
Geocenter
----------
---------
center of Earth
1639 S.
10.92

6Altitude of each observatory is measured in kilometers above sea level.

7"Distance" refers to the closest approach distance of the "Site" to the center of Chariklo's shadow in the shadow plane. The errors on all closest approach distances are ±3734 km (one standard deviation). "S." means the site is south of the center of Chariklo's shadow. "N." means the site is north of the center of Chariklo's shadow.

Table 5: Chariklo.20160824 Occultation Predictions for Individual Sites

Site
KBO Immersion (UT)9
UT Mid-Time
KBO Altitude
Solar Altitude9

KBO Emersion (UT)9
CTIO
-----------
05:10:03
36
–70
-----------
IRTF
-----------
05:24:00
34
–9
-----------
Lowell
-----------
05:19:51
17
–34
-----------
Geocenter
-----------
05:17:18
-----------
-----------
-----------

9The errors on all times are ±3:49 (3 minutes and 49 seconds; one standard deviation). The solar altitude is given for locations where it is relevant (solar altitude greater than -18°). No entry in the immersion and emersion columns indicates that the occultation is not predicted to be visible at that site.

Last updated by Carlos Zuluaga (czuluaga@mit.edu) 2016-07-19 10:01

Please direct all inquiries to PAL (planetary-astronomy@mit.edu)

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