J/A+A/708/A60 GRB 180728A and SN 2018fip (Rossi+ 2026)
GRB 180728A and SN 2018fip: The nearest high-energy cosmological gamma-ray burst
with an associated supernova.
Rossi A., Izzo L., Maeda K., Schady P., Malesani D.B., Kann D.A.,
Klose S., Amati L., D'Avanzo P., de Ugarte Postigo A., Heintz K.E.,
Kumar A., Lipunov V., Martin-Carrillo A., Melandri A.,
Nicuesa Guelbenzu A.M., Oates S.R., Schulze S., Selsing J.,
Starling R.L.C., Stratta G., Vlasenko D., Balanutsa P., Brivio R.,
D'Elia V., Milvang-Jensen B., Palazzi E., Perley D.A., Rau A.,
Sollerman J., Tanvir N.R., Zafar T.
<Astron. Astrophys. 708, A60 (2026)>
=2026A&A...708A..60R 2026A&A...708A..60R (SIMBAD/NED BibCode)
ADC_Keywords: Supernovae ; Photometry ; Spectroscopy ; Optical ; Infrared
Keywords: gamma-ray bursts: general - supernovae: general -
supernovae: individual: SN 2018fip -
gamma-ray burst: individual: GRB 180728A
Abstract:
The long GRB 180728A, at a redshift of z=0.1171, stands out due to its
high isotropic energy of Egamma,iso∼2.5x1051erg, in contrast with
most events at redshift z<0.2. We analyze the properties of GRB
180728A's prompt emission, afterglow, and associated supernova SN
2018fip, comparing them with other GRB-SN events. This study employs a
dense photometric and spectroscopic follow-up of the afterglow and the
SN up to 80 days after the burst, supported by image subtraction to
remove the presence of a nearby bright star, and modelling of both the
afterglow and the supernova. GRB 180728A lies on the
Ep,i-Egamma,iso plane occupied by classical collapsar events, and
the prompt emission is one of the most energetic at z<0.2 after GRB
030329 and GRB 221009A. The afterglow of GRB 180728A is less luminous
than that of most long GRBs, showing a shallow early phase that
steepens around 5 hours (0.2 days). The GRB exploded in an irregular,
low-mass, blue, star-forming galaxy, typical of low-z collapsar
events. Because of the relatively faint afterglow, the light curve
bump of SN 2018fip dominates the optical emission already after ∼3
days and is one of the best sampled to date. The strong suppression
below ∼4000 angstrom and a largely featureless continuum in the early
6--9 days spectra favor aspherical two-component ejecta with a
high-velocity collimated component (>20000km/s), dominant early-on,
and a more massive, low-velocity component, which dominates at much
later epochs. Our findings indicate that asymmetries need to be
considered in order to better understand GRB-SNe. In any case, SN
2018fip shares many characteristics with typical GRB-SNe. Its kinetic
energy is below the common range of 1052-1053erg and does not
correlate with the high energy of the GRB, highlighting the diversity
of the GRB-SN energy budget partition.
Description:
Observations of the afterglow of GRB 180728A and its associated SN
2018fip. X-Shooter, UVOT, and GROND data result from subtracting the
constant emission from the host and the nearby star, while the
remaining UVOT bands, REM and MASTER data are not affected noticeably
by additional components.
Objects:
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RA (2000) DE Designation(s)
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16 54 15.48 -54 02 40.3 GRB 180728A = SN 2018fip
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec3.dat 49 395 Photometry of the afterglow of GRB 180728A
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Byte-by-byte Description of file: tablec3.dat
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Bytes Format Units Label Explanations
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1- 9 F9.6 d Time Time since GRB trigger (days) (1)
12 A1 --- l_mag Upper limit flag on mag
13- 18 F6.3 mag mag AB magnitude in Filter (2)
22- 27 F6.3 mag e_mag ?=-1 magnitude in Filter error (3)
31- 35 A5 --- Filter Filter used (4)
37- 49 A13 --- Tel/Inst Telescope/Instrument used
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Note (1): Midtimes are derived logarithmically,
t=10^[(log(t1-t0)+log(t2-t0))/2],
hereby t_{1,2} are the absolute start and stop times,
t_0 is the Swift trigger time.
Note (2): All data are in AB magnitudes and not corrected for Galactic
foreground extinction.
Note (3): Negative errors (e.g., -1) indicate upper limits
Note (4): Filters are J, H, Ks, CR, u, b, v, r', i', z', uvm2, uvw1, uvw2
and white. CR is the MASTAER Clear filter.
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Acknowledgements:
Andrea Rossi, andrea.rossi(at)inaf.it
(End) Andrea Rossi [INAF-OAS], Patricia Vannier [CDS] 27-Jan-2026