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Second Major Outburst in Four Days

As I am sure you already know, ISON underwent a major outburst peaking on November 15th, which gradually declined over the next several days. It appears that a second, even larger, outburst is under way. The chronology of events as posted at comets-ml:

From ejehin on Nov 13

TRAPPIST : ISON outburst !
Dear all,
Very good news, TRAPPIST ISON production rates (all gas species) have been x2 in only 24 hours !
We now reach about 2E28 mol/s for Q(OH) at 10.000 km.
It looks like an outburst is going on, as the increase was not as fast the last 4 nights,
We now see also jets in OH bands same location as those of CN and C2.
AfRho from dust continuum is only rising a bit,
R and V broad band flux have also increased by factor 2,
We should be able to get images until Nov. 18, but window is only 20 minutes now and comet below 15 deg,
Clear skies,
Emmanuel Jehin

From biver_nicolas on Nov 14

RE: TRAPPIST : ISON outburst !
ISON is visible to the Naked Eye!!
Just 40min ago before clouds came in again (it snowed here yesterdy evening), I saw ISON with naked eye and adverted vision (good dark sky from Pico Veleta, SQM=21.14 to 20.9 in the zodiacal light).
It is about m1=6.3 to 6.5, estimated from naked eye and binculars (nearly starlike).
I saw it quickly in the Celestron 8, very condensed and hard to make out a structure, but the beginning of the tail does not look (yet) much brighter than the days before.
(I estimated ISON to m1=7.4 yesterday 13.22-Nov and 8.1 on the 12.2-Nov.)
Nicolas

From ejehin on Nov 14

TRAPPIST update : major outburst ongoing !
Dear all,
We had a hard time this morning to observe ISON, which is lower and closer to the Sun, but it was so bright we are saturating the broad band filters in 10s and plenty of flux in 20s with the narrow band filters.
To our suprise the change has been huge in the last 24 hours ! We are reaching 1E29 mol/s in OH, an increase close a factor 8 of the amount of gas released in space, since 24 hours !
The AfRho has also increased by the same factor (it is now 2400cm), so dust is finally released too, even if the level stays quite low compare to other comets.
Two jets are now also visible in OH band (coming from water dissociation) and also faint ones in the dust continuum at the same position as the CN and C2 jets previously reported.
There is no indication yet of disruption, the inner coma is very sharp (4 arcsec) and round in the dust continuum windows and there is no other special features in the coma.
This is the early phase of the outburst as the dust is still close to the nucleus and we should still expect a large increase of the magnitude and the coma diameter if more dust is released in the coming days.
The comet will become rapidly visible naked eye if the outburst last a few more days !
Best regards,
Emmanuel

From e48d5e092c3a74bb8dc8987a056172ad on Nov 14

Comet ISON (C/2012 S1) From Pasadena CA
I observed comet ISON from Pasadena, CA this morning, 16 minutes after the start of astronomical twilight, sun elevation -14.6˚. Scattered cirrus was present as was suburban light pollution. I used a 70mm refractor at 20X, timed the drift of the coma to measure the diameter, and used the Beyer method of magnitude estimation with TK reference stars:
2013 Nov. 14.552 m1=5.8, Coma dia.=1.25' DC=7
The coma was circular and well defined, of a deep blue-green color and the central condensation was bright and nearly starlike. It resembled a circular planetary nebula around a central star as seen through a giant telescope.
The tail was not seen.
Yesterday (11-13-2013), ISON appeared ghostly in the same equipment. This morning, it appeared the same size, but bright and easy to see!
Anthony Cook
Astronomical Observer
Griffith Observatory

From Man-To Hui on Nov 15

Dramatic Morphological Change of C/2012 S1
Hi all,
We (Quanzhi Ye, Man-To Hui and Xing Gao) noticed a dramatic morphological change of comet C/2012 S1 (ISON) observed via the 0.35-m f/6.9 Schmidt telescope + unfiltered QHY9 CCD at Xingming Observatory C42 from Nov 13.99 UT to 14.99 UT. Seven delicate (plasma) tails are visible from P.A. 275 to 320 deg (0 deg at north) in the Nov. 14 images. In comparison there were only two obvious in the Nov 13 images. After applying the azimuthal median filter to images from both dates, we saw two intense jets in P.A. 0 deg and 220 deg in the Nov 14 images, both slightly skewed to the anti-solar direction and measured ~34-arcsec in length. The two jets were absent in the Nov. 13 images. Images could be found at http://flic.kr/p/hyyTwX (Nov 13) and http://flic.kr/p/hyyUhK (Nov 14). What we found has been reported to CBET.
Cheers,
Man-To Hui (Cantonese)
Wentao Xu, Wen-Tao Hsu (Mandarin Chinese)
Astrosite: comethunter.lamost.org
Blog: pachacoti.wordpress.com

From Jakub Cerny on Nov 15

Re: Dramatic Morphological Change of C/2012 S1
Hi,
very nice report!
Missing presence of any synchronic feature inside coma ruling out any disintegration process. The jets looking like health turn-on of nucleus, which remaining mostly intact.
Best regards,
Jakub Cerny

From ejehin on Nov 19

TRAPPIST ISON update : new outburst !
Dear all,
Since our last report and major outburst on Nov. 14, the ISON production rates were dropping. We lost about a factor 2 in all measured quantities in 4 days.
No sign of breakup in the images.The dust features in our pictures seem to be linked to the active regions identified earlier in C2 and CN.
But this morning 19.37 Nov UT, we found ISON very active again !
All the production rates have been x ~6 since last night, while the AfRho, maesuring the quantity of dust, was only x ~2.
This looks to us to be the start of a new outburst linked to the active regions, as the jets are today strong again.
Our campain is unfortunately nearly over with TRAPPIST, but we will try to point it again the next couple of nights and confirm this new rise.
Is there new visual estimates ?
ESO picture of the week : http://www.eso.org/public/images/potw/
TRAPPIST news : http://www.orca.ulg.ac.be/TRAPPIST/Trappis...News.html#new25
Cheers,
Emmanuel Jehin

[MahFL]

I am going to try spot it tomorrow am, skies are currently clear.