Echeclus.20200122

January 22, 2020

Prediction Last Updated: January 07, 2019

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Across the globe pictured, the three solid black lines correspond to the northern limit, centerline, and southern limit of the Echeclus shadow. The Northern and Southern limits correspond to a radius of 32 km. The dashed lines indicate 3-sigma errors. The shaded area on the globe represents where the sun is more than 0 degrees below the horizon. The shadow paths on the globe are an approximation at the geocentric close approach time; they disregard the Earth rotation during the event.



Table 1: Prediction Details
Echeclus Geocentric Mid-time (hh:mm:ss)

January 22, 2020 01:44:46 ± 00:00:11. UT1
Prediction pred1.0_v1.0
Echeclus apparent magnitude 19.4
Occultation Star Gaia DR2 G magnitude 15.359532
Occultation Star Gaia DR2 rp magnitude 14.486599
Occultation Star Gaia DR2 bp magnitude 16.145884
Echeclus Minimum Geocentric Separation 0.7502 ± 0.0129 arcsec1
Position Angle (Echeclus relative to the star; measured north through east) -177.76

1One standard deviation of random error




Table 2: Reference Star Position
Reference star position:
(Gaia DR2)		 RA (h:m:s; J2000) Dec (d:m:s; J2000) Notes
Echeclus.20200122 (Catalog; epoch of occ) 04:51:35.9221 ± 0.0004 17:48:18.7787 ± 0.0002
proper motion applied up to the time of the event
Echeclus.20200122 (Measured) - -

Potential Star Duplicity:

Unknown



Table 3: Projected KBO Offsets from Reference Ephemeris at the Time of the Event
Body RA (arcsec) Dec (arcsec)  
Echeclus

-0.0118 ± 0.0207

-0.2516 ± 0.0129 See Notes 5 and 6

2Measured position corresponds to RA offset of 0. and Dec. offset of 0.

3All "offsets" are degined 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.

4The reference positions for Echeclus are those given by JPL Horizon's ephemeris (Echeclus source file: JPL#87 ; Earth center source file: DE431)

5Data from various telescope were reduced with respect to the Gaia DR2 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 the object: (i) constant offsets in RA and Dec, (ii) linear (in time) offsets in RA and Dec, and (iii) potential sinusoidal terms with companion's 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)
Cerro Calan
-70 32 48
-33 23 48
0.86
227 S
11.5
CTIO
-70 48 54
-30 09 54
2.215
3 N
11.51
Las Campanas
-70 42 00
-29 00 30
2.282
90 N
11.51
Geocentric
..........
..........
-6378.14
4711 N
11.11

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

7"Distance" refers to the closest approach of the "Site" to the center of Echeclus's shadow in the shadow plane. The errors on all closest approach distances are ±81 km (one standard deviation). "S." means the site is south of the center of Echeclus's shadow. "N." means the site is north of the center of Echeclus's shadow.




Table 5: Echeclus Occultation Predictions for Individual Sites
Site
KBO Immersion (UT)8
UT Mid-Time
KBO Altitude
Solar Altitude8
KBO Emersion (UT)8
Cerro Calan
........
01:44:02
38.6
-20.19
........
CTIO
01:44:02.264
01:44:05
41.93
-22.19
01:44:07.800
Las Campanas
........
01:44:04
43.07
-23.02
........
Geocentric
........
01:44:46
........

8The errors on all times are ± 0:11. (11. seconds; one standard deviation). The solar altitude is given for locations where it is relevant (solar altitude greater than -18 deg). No entry in the immersion and emersion columns indicates that the occultation is not predicted to be visible at that site.



Webpage generated by Carlos Zuluaga (czuluaga@mit.edu) on January 07, 2020

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

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