J/A+A/705/A89 12P/Pons-Brooks magnitude and activity (Vander Donckt+, 2026)
Photometric and spectroscopic monitoring of the outbursting Halley-type comet
12P/Pons-Brooks.
Vander Donckt M., Jehin E., Aravind K., Adami C., Hmiddouch S., Manfroid J.,
Ganesh S., Benkhaldoun Z., Delsanti A.
<Astron. Astrophys. 705, A89 (2026)>
=2026A&A...705A..89V 2026A&A...705A..89V (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Comets ; Abundances ; Optical
Keywords: techniques: photometric - techniques: spectroscopic -
comets: general - comets: general -
comets: individual: 12P/Pons-Brooks
Abstract:
Comet 12P/Pons-Brooks is a Halley-type comet known for its outbursting
activity during its previous perihelia in 1883 and 1953. Its strong
activity and favourable observing geometry gave a great opportunity to
study this outburst-prone comet during its 2024 return with modern
instruments. We aim to study the activity and composition of
12P/Pons-Brooks during its 2024 passage through long-slit spectroscopy
and narrow- and broad-band photometry and imaging.
The photometric survey contains over 130 nights of observation with
TRAPPIST-North and -South from May 6, 2023 (rh=4.62au, inbound), to
September 7, 2024 (rh=2.06au, outbound). We collected images with
broad- band Johnson-Cousins filters (BVRcIc) and narrow-band HB
filters (OH, CN, C2, C3, NH, and dust continuum). We obtained
long-slit low-resolution spectra at the Observatoire de Haute Provence
with the MISTRAL instrument on the night of March 23, 2024, at a
heliocentric distance of 0.94au. The spectra were used to analyse the
emissions from the different molecular bands.
We detect nine strong outbursts, with an approximate two-week
periodicity; OH production rate reaching values above 1029
molecules/s and A(0)fρ dust activity proxy above 105cm. Dust
images show the formation of a double-horned-shaped coma and the
expansion of a dust shell in the days following the strongest
outbursts. The gas-to-dust ratio behaviour during these events differs
from other observations of outbursting comets closer to the Sun, while
outbursts rather share similarities with the centaur comet
29P/Schwassmann-Wachmann's. The analysis of CN jets between 1.02 and
2.13au suggests a nucleus rotation period of either 29.45h or 58.90h
and a gas ejection velocity of 1.03±0.09km/s. From the MISTRAL
spectra, emission bands from C2, NH2, and CN were observed, as
well as H2 O+ in the anti-sunward direction.
Description:
append1.dat contains the Rc broad-band magnitude and colour indices in
a 5'' radius aperture for B-V, V-Rc, and Rc-Ic.
append2.dat contains the molecular production rates (OH, NH, CN, C2,
and C3) from the narrow-band filters and A(0)fρ dust activity
proxy from the broad- band filters (B, V, Rc, and Ic) and the
measured fluxed used to calculate production rates and dust activity
proxies.
object:
------------------------------------------------------------------------
Code Name Elem q e i H1
(d) (AU) (deg) (mag)
------------------------------------------------------------------------
12P P/Pons-Brooks 2451628.5 0.7791566 0.9541391 74.861249 7.61
------------------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 96 131 Magnitude and colour indices
tablea2.dat 280 131 Production rates and A(0)fρ dust activity proxy
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 "date" UTdate UT date
15- 21 F7.2 d deltaT Time to reach perihelion
23- 26 F4.2 au rh Heliocentric distance
28- 31 F4.2 au delta Geocentric distance
33- 34 A2 --- Obs Observatory,
TS: TRAPPIST-South; TN: TRAPPIST-North
36 A1 --- l_Rcmag Limit flag on Rc
37- 41 F5.2 mag Rcmag Rc magnitude
44- 47 F4.2 mag e_Rcmag ? Rc magnitude error
49 A1 --- l_FRc Limit flag on Rc
50- 56 F7.2 10-18W/m2/nm FRc Rc flux (10-16erg/cm2/s/Å)
59- 63 F5.2 10-18W/m2/nm e_FRc ? Rc flux error (10-16erg/cm2/s/Å)
65- 68 F4.2 mag B-V ?=- B-V colour index
71- 74 F4.2 mag e_B-V ?=- B-V colour index error
76- 79 F4.2 mag V-Rc ?=- V-Rc colour index
82- 85 F4.2 mag e_V-Rc ?=- V-Rc colour index error
87- 90 F4.2 mag Rc-Ic ?=- Rc-Ic colour index
93- 96 F4.2 mag e_Rc-Ic ?=- Rc-Ic colour index error
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 "date" UTdate UT date
15- 21 F7.2 d deltaT time to reach perihelion
23- 26 F4.2 au rh heliocentric distance
28- 31 F4.2 au delta geocentric distance
33- 34 A2 --- Obs Observatory,
TS: TRAPPIST-South; TN: TRAPPIST-North
36 A1 --- l_OH Limit flag on OH
37- 40 I4 10+26s-1 OH ?=- OH production rate (1026molecules/s)
43- 45 I3 10+26s-1 e_OH ? OH production rate error
(1026molecules/s)
47- 51 F5.2 10+26s-1 NH ?=- NH production rate (1026molecules/s)
53- 56 F4.2 10+26s-1 e_NH ? NH production rate error
(1026molecules/s)
58- 62 F5.2 10+26s-1 CN ?=- CN production rate (1026molecules/s)
64- 67 F4.2 10+26s-1 e_CN ? CN production rate error
(1026molecules/s)
69- 73 F5.2 10+26s-1 C2 ?=- C2 production rate (1026molecules/s)
75- 78 F4.2 10+26s-1 e_C2 ? C2 production rate error
(1026molecules/s)
80- 83 F4.2 10+26s-1 C3 ?=- C3 production rate (10^26 molecules/s)
85- 88 F4.2 10+26s-1 e_C3 ? C3 production rate error
(1026molecules/s)
90 A1 --- l_B Limit flag on B
91- 95 I5 cm B ?=- B-band A(0)fρ dust activity proxy
97-100 I4 cm e_B ? B-band A(0)fρ dust activity proxy
error
102 A1 --- l_V Limit flag on V
103-107 I5 cm V ?=- V-band A(0)fρ dust activity proxy
109-111 I3 cm e_V ? V-band A(0)fρ dust activity proxy
error
113 A1 --- l_Rc Limit flag on Rc
114-118 I5 cm Rc ?=- Rc-band A(0)fρ dust activity proxy
120-122 I3 cm e_Rc ? Rc-band A(0)fρ dust activity proxy
error
124 A1 --- l_Ic Limit flag on Ic
125-129 I5 cm Ic ?=- Ic-band A(0)fρ dust activity proxy
131-133 I3 cm e_Ic ? Ic-band A(0)fρ dust activity proxy
error
135 A1 --- l_FOH Limit flag on FOH (1)
136-143 F8.2 10-17W/m2 FOH ? Measured OH flux used to calculate
production rate (1)
145-151 F7.2 10-17W/m2 e_FOH ? Measured OH flux used to calculate
production rate error (1)
153-159 F7.2 10-17W/m2 FNH ? Measured NH flux used to calculate
production rate (1)
161-166 F6.2 10-17W/m2 e_FNH ? Measured NH flux used to calculate
production rate error (1)
168-175 F8.2 10-17W/m2 FCN ? Measured CN flux used to calculate
production rate (1)
177-183 F7.2 10-17W/m2 e_FCN ? Measured CN flux used to calculate
production rate error (1)
185-192 F8.2 10-17W/m2 FC2 ? Measured C2 flux used to calculate
production rate (1)
194-199 F6.2 10-17W/m2 e_FC2 ? Measured C2 flux used to calculate
production rate error (1)
201-208 F8.2 10-17W/m2 FC3 ? Measured C3 flux used to calculate
production rate (1026molecules/s) (1)
210-216 F7.2 10-17W/m2 e_FC3 ? Measured C3 flux used to calculate
production rate error (1)
218 A1 --- l_FB Limit flag on FB
219-226 F8.2 10-18W/m2/nm FB ? Measured B-band flux used to calculate
A(0)fρ dust activity proxy (1)
228-233 F6.2 10-18W/m2/nm e_FB ? Measured B-band flux used to calculate
A(0)fρ dust activity proxy error (1)
235 A1 --- l_FV Limit flag on FV
236-243 F8.2 10-18W/m2/nm FV ? Measured V-band flux used to calculate
A(0)fρ dust activity proxy (1)
245-250 F6.2 10-18W/m2/nm e_FV ? Measured V-band flux used to calculate
A(0)fρ dust activity proxy error (1)
252 A1 --- l_FRc Limit flag on FRc
253-259 F7.2 10-18W/m2/nm FRc ? Measured Rc-band flux used to calculate
A(0)fρ dust activity proxy (1)
261-265 F5.2 10-18W/m2/nm e_FRc ? Measured Rc-band flux used to calculate
A(0)fρ dust activity proxy error (1)
267 A1 --- l_FIc Limit flag on FIc
268-274 F7.2 10-18W/m2/nm FIc ? Measured Ic-band flux used to calculate
A(0)fρ dust activity proxy (1)
276-280 F5.2 10-18W/m2/nm e_FIc ? Measured Ic-band flux used to calculate
A(0)fρ dust activity proxy error (1)
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Note (1): Fluxes used to calculate A(0)frho are given in
10-16erg/cm2/s1/Å. Fluxes used to calculate production rates
are given in 10-14erg/cm^2/s, after dust subtraction correction and
corrected for the whole emission band by the gamma factor given by
Farnham et al., 2000Icar..147..180F 2000Icar..147..180F.
--------------------------------------------------------------------------------
Acknowledgements:
Mathieu Vander Donckt, mathieu.vanderdonckt(at)uliege.be
(End) Patricia Vannier [CDS] 17-Nov-2025