Apparent Fragmentation of P/2013 TL117 (Lemmon)
ATel #14182; Michael S. P. Kelley, Quanzhi Ye (U. Maryland) on behalf of the Zwicky Transient Facility Collaboration
on 16 Nov 2020; 18:02 UT
Distributed as an Instant Email Notice Comets
Credential Certification: Quanzhi Ye (qye@umd.edu)
Comet P/2013 TL117 (Lemmon), recently recovered under the temporary designation P/2020 U1 (MPEC 2020-U231, CBET #4874), has developed a morphology consistent with a small fragmentation event. The Zwicky Transient Facility (ZTF; Bellm et al. 2019, PASP, 131, a8002) has been observing the comet's ephemeris position since 2020 July 17 UTC. The comet was below the typical ZTF detection limits (r>20 to 21 mag, 5σ limit) until 2020 September 16 UTC, after which it is detected in most r-band frames. Photometry measured with a 3" radius aperture (equivalent to 1200 to 2500 km at the comet's distance) is tabulated below, calibrated to the PS1 catalog (Tonry et al. 2012, ApJ, 750, 99). From these data, we estimate a g-r color of 0.47±0.02 mag.
Starting on 2020 October 18 UTC, the comet's appearance was clearly more extended towards position angle 120° E of N. This extension has slowly evolved into a separate but diffuse component. On 2020 November 12 UTC, the component was ~5" (~2000 km) away from the brightest centroid, approximately along position angle 130° E of N (the ZTF camera has a pixel scale of 1.0"). Assuming a separation of 1" on 2020 October 18, the component, which may be a single fragment or a fragment swarm, has a projected velocity of ~0.8 m/s with respect to the primary. There are no apparent outbursts in our data, however, we do have a 9-day gap in coverage between 2020 October 4 and 13 UTC, during which we cannot rule out any small events. Follow-up imaging is encouraged to test the longevity of the component and the potential for additional components to become apparent.
A ZTF image of the comet can be found here.
Date rh Delta Phase F m unc
-------------- ---- ----- ----- - ----- ----
2020-09-17.436 1.67 1.14 36.0 r 20.35 0.19
2020-09-19.427 1.66 1.11 36.3 r 20.46 0.17
2020-09-20.487 1.65 1.10 36.5 r 20.17 0.11
2020-09-20.515 1.65 1.10 36.5 g 20.61 0.16
2020-09-22.471 1.63 1.07 36.8 r 20.17 0.12
2020-09-22.489 1.63 1.07 36.8 r 20.03 0.10
2020-09-22.515 1.63 1.07 36.8 g 20.57 0.15
2020-09-23.375 1.62 1.05 36.9 r 19.96 0.13
2020-09-23.387 1.62 1.05 36.9 r 20.19 0.14
2020-09-24.392 1.61 1.04 37.1 r 19.84 0.11
2020-09-25.404 1.60 1.03 37.2 r 19.82 0.08
2020-09-25.432 1.60 1.03 37.2 g 20.42 0.14
2020-09-26.527 1.59 1.01 37.4 r 19.88 0.10
2020-09-28.468 1.58 0.98 37.7 g 20.29 0.12
2020-09-28.488 1.58 0.98 37.7 r 19.90 0.09
2020-09-29.456 1.57 0.97 37.9 r 19.60 0.10
2020-09-30.482 1.56 0.96 38.1 r 19.57 0.10
2020-10-02.344 1.55 0.93 38.4 r 19.48 0.15
2020-10-03.457 1.54 0.92 38.6 g 19.74 0.17
2020-10-03.484 1.54 0.92 38.6 r 19.37 0.10
2020-10-03.485 1.54 0.92 38.6 r 19.66 0.13
2020-10-04.383 1.53 0.91 38.7 r 19.47 0.13
2020-10-13.456 1.46 0.80 40.5 g 19.43 0.06
2020-10-15.384 1.44 0.78 40.9 r 18.95 0.05
2020-10-15.422 1.44 0.78 40.9 g 19.48 0.07
2020-10-17.449 1.43 0.75 41.4 g 19.38 0.07
2020-10-19.369 1.41 0.73 41.9 r 18.74 0.05
2020-10-19.429 1.41 0.73 41.9 g 19.19 0.04
2020-10-21.425 1.40 0.71 42.4 g 19.15 0.04
2020-10-21.445 1.40 0.71 42.4 r 18.68 0.04
2020-10-27.347 1.36 0.66 44.0 r 18.55 0.07
2020-10-29.491 1.34 0.64 44.7 g 18.99 0.07
2020-10-29.510 1.34 0.64 44.7 r 18.50 0.04
2020-10-31.477 1.33 0.62 45.3 r 18.53 0.05
2020-10-31.520 1.33 0.62 45.3 g 18.82 0.09
2020-11-03.492 1.31 0.60 46.3 g 18.76 0.08
2020-11-03.515 1.31 0.60 46.3 r 18.38 0.05
2020-11-04.477 1.30 0.59 46.6 r 18.31 0.06
2020-11-04.517 1.30 0.59 46.6 g 18.87 0.09
2020-11-12.454 1.25 0.55 49.5 g 18.82 0.04
2020-11-12.466 1.25 0.55 49.5 r 18.34 0.03
