Comet C/2019 L2 (NEOWISE)

Jana P. Chesley (Jet推進研究所)の通報によると、6月11-12日UT、Near-Earth Object Wide-field 
Infrared Survey Explorer (NEOWISE:地球近傍天体広域赤外線探査衛星、以前のWISE:広域赤外線探
査衛星;CBET 4225参照)で得た赤外線画像から彗星を発見した。光学波長による光度は過去のWISEと
NEOWISE彗星の観測から推定される。
明らかな彗星活動は、3.4と4.6ミクロン両方に存在し、後者のイメージは、1′のコマは丸いようだ。
小惑星センターのPCCP webpageに公表後、R. S. McMillan (Spacewatch 0.9-m f/3 reflector, 
Kitt Peak; 6月13.4日UT,  薄く、変わりやすい雲を通して得た画像のスタックから、1".1のシーイ
ングでこの天体は少し拡散して、南西に向かって3" の尾らしいものが見える。r光度は18.3-19.1等)
らCCD位置観測者によって彗星状と観測された。

発見位置は次のとおり、

     2019 UT             R.A. (2000) Decl.       Mag.
     June 11.78358   22 38 00.69   +23 02 30.0   18
          11.84903   22 37 47.85   +23 03 45.8
          11.91435   22 37 34.98   +23 05 00.7
          11.97981   22 37 21.95   +23 06 15.6
          12.11058   22 36 56.27   +23 08 43.7

楕円軌道要素と位置推算表は次のとおり、

Orbital elements:
    C/2019 L2 (NEOWISE)
Epoch 2019 Mar. 18.0 TT = JDT 2458560.5
T 2019 Apr. 1.79062 TT                                  MPCLINUX
q   1.6192058            (2000.0)            P               Q
n   0.00825554     Peri.   18.62113     +0.98634649     -0.12996330
a  24.2459455      Node    12.52265     -0.12369784     -0.99012558
e   0.9332175      Incl.  152.19413     +0.10871727     +0.05254407
P 119
From 101 observations 2019 June 11-27, mean residual 0".7.

    C/2019 L2 (NEOWISE)
Epoch 2019 Apr. 27.0 TT = JDT 2458600.5
T 2019 Apr. 1.79144 TT                                  MPCLINUX
q   1.6192068            (2000.0)            P               Q
n   0.00826042     Peri.   18.62158     +0.98634522     -0.12997333
a  24.2364004      Node    12.52252     -0.12370761     -0.99012416
e   0.9331911      Incl.  152.19396     +0.10871769     +0.05254600
P 119
From 101 observations 2019 June 11-27, mean residual 0".7.

Ephemeris:
Date    TT    R. A. (2000) Decl.     Delta      r    Elong.  Phase   m1
2019 05 29    23 13 04.2 +18 42 27   1.8181  1.7804    71.6    32.7  19.8
...
2019 06 13    22 33 56.7 +23 25 53   1.5445  1.8672    91.3    32.9  19.7
...
2019 06 21    22 02 14.2 +25 52 25   1.4196  1.9190   102.7    31.1  19.6
...
2019 06 27    21 32 26.5 +27 21 53   1.3453  1.9600   111.4    28.9  19.6
2019 06 28    21 26 58.7 +27 33 51   1.3350  1.9670   112.8    28.4  19.6
2019 06 29    21 21 22.9 +27 44 44   1.3254  1.9740   114.2    28.0  19.6
...
2019 07 05    20 45 23.3 +28 23 22   1.2830  2.0172   122.2    25.3  19.6
...
2019 07 13    19 54 00.6 +27 48 22   1.2735  2.0769   129.8    22.1  19.7
...
2019 07 28    18 28 31.9 +22 45 54   1.4081  2.1948   129.1    21.1  20.2

     This object was reported as cometary by J. P. Chesley (C51) in discovery
images obtained on 2019 June 11 UT, who noted that it showed clear cometary
activity in both the 3.4 micron and 4.6 micron bands.  At 4.6 microns, the
coma appeared circular, extending 1 arcmin in diameter.  Other reports of
cometary features are summarized below:

OC   Date     Reporter           Coma    Tail
691  June 13  R. S. McMillan             ~3"
N55  June 13  D. W. E. Green       5"    ~5" in P.A. 140      (29 x 40s)
204  June 17  L. Buzzi            11"    
G40  June 21  B. Lutkenhoner       6"                         (34 x 50s)
104  June 23  P. Bacci            11"                         (120 x 30s)
695  June 23  A. F. Tubbiolo             in P.A. 280
K88  June 24  K. Sarneczky        10"    12" in P.A. 190      (5 x 60s)
658  June 25  D. D. Balam         11"    
Z84  June 26  E. Schwab                  in P.A. 280
I52  June 26  R. A. Kowalski      10"
B96  June 27  E. Bryssinck        14"    17" in P.A. 193

(CBET 4641、MPEC 2019-M93)