J/ApJ/887/169 UV-Opt light curves of the type Ic SN 2018gep (Ho+, 2019)
Evidence for late-stage eruptive mass loss in the progenitor to SN2018gep, a
broad-lined Ic supernova: pre-explosion emission and a rapidly rising luminous
transient.
Ho A.Y.Q., Goldstein D.A., Schulze S., Khatami D.K., Perley D.A., Ergon M.,
Gal-Yam A., Corsi A., Andreoni I., Barbarino C., Bellm E.C.,
Blagorodnova N., Bright J.S., Burns E., Cenko S.B., Cunningham V., De K.,
Dekany R., Dugas A., Fender R.P., Fransson C., Fremling C., Goldstein A.,
Graham M.J., Hale D., Horesh A., Hung T., Kasliwal M.M., Kuin N.P. M,
Kulkarni S.R., Kupfer T., Lunnan R., Masci F.J., Ngeow C.-C., Nugent P.E.,
Ofek E.O., Patterson M.T., Petitpas G., Rusholme B., Sai H., Sfaradi I.,
Shupe D.L., Sollerman J., Soumagnac M.T., Tachibana Y., Taddia F.,
Walters R., Wang X., Yao Y., Zhang X.
<Astrophys. J., 887, 169 (2019)>
=2019ApJ...887..169H 2019ApJ...887..169H
ADC_Keywords: Supernovae; Photometry, ultraviolet; Photometry, ugriz;
Effective temperatures
Keywords: methods: observational ; shock waves ; stars: mass-loss ;
supernovae: individual ; surveys
Abstract:
We present detailed observations of ZTF18abukavn (SN2018gep),
discovered in high-cadence data from the Zwicky Transient Facility as
a rapidly rising (1.4±0.1mag/hr) and luminous (Mg,peak=-20mag)
transient. It is spectroscopically classified as a broad-lined
stripped-envelope supernova (Ic-BL SN). The high peak luminosity
(L_bol≳3x1044erg/s), the short rise time (trise=3days in g band),
and the blue colors at peak (g-r~-0.4) all resemble the high-redshift
Ic-BL iPTF16asu, as well as several other unclassified fast
transients. The early discovery of SN2018gep (within an hour of shock
breakout) enabled an intensive spectroscopic campaign, including the
highest-temperature (Teff≳40000K) spectra of a stripped-envelope
SN. A retrospective search revealed luminous (Mg∼Mr~-14mag)
emission in the days to weeks before explosion, the first definitive
detection of precursor emission for a Ic-BL. We find a limit on the
isotropic gamma-ray energy release E{gamma,iso}<4.9x1048erg, a
limit on X-ray emission LX<1040erg/s, and a limit on radio
emission νLν≲1037erg/s. Taken together, we find that the
early (<10days) data are best explained by shock breakout in a massive
shell of dense circumstellar material (0.02M☉) at large radii
(3x1014cm) that was ejected in eruptive pre-explosion mass-loss
episodes. The late-time (>10days) light curve requires an additional
energy source, which could be the radioactive decay of Ni-56.
Description:
ZTF18abukavn was discovered in an image obtained at
UT 2018 September 9 03:55:18 (start of exposure) as part of the ZTF
extragalactic high-cadence partnership survey (Ho+ 2018ATel12030....1H 2018ATel12030....1H).
We triggered ultraviolet (UV) and optical observations with the
UV/Optical Telescope (UVOT) aboard the Neil Gehrels Swift Observatory,
and observations began 10.2hr after the ZTF discovery.
From Δt∼1day to Δt∼60days, we conducted a photometric
follow-up campaign at UV and optical wavelengths using Swift/UVOT, the
Spectral Energy Distribution Machine (SEDM) mounted on the automated
60 inch telescope at Palomar (P60), the optical imager (IO:O) on the
Liverpool Telescope (LT), and the Lulin 1m Telescope (LOT).
The first spectrum was taken 0.7 day after discovery by the
Spectrograph for the Rapid Acquisition of Transients (SPRAT) on the LT.
Twenty-three optical spectra were obtained from Δt=0.7-61.1days
using SPRAT, the Andalusia Faint Object Spectrograph and Camera
(ALFOSC) on the Nordic Optical Telescope (NOT), the Double
Spectrograph (DBSP) on the 200 inch Hale telescope at Palomar
Observatory, the Low Resolution Imaging Spectrometer (LRIS) on the
Keck I 10m telescope, and the Xinglong 2.16m telescope (XLT+BFOSC) of
NAOC, China.
Swift obtained three UV-grism spectra between UT 2018 September 15
3:29 and 6:58 (Δt∼6.4days) for a total exposure time of 3918s.
We observed the field of SN2018gep with the Karl G. Jansky Very Large
Array (VLA) on three epochs: on 2018 September 14 UT under the Program
ID VLA/18A-242 (PI: D. Perley; Ho+ 2018ATel12056....1H 2018ATel12056....1H), and on
2018 September 25 and 2018 November 23 UT under the Program ID
VLA/18A-176 (PI: A. Corsi). The source was detected in the first two
epochs, but not in the third.
We also obtained three epochs of observations with the AMI large array
(AMI-LA), on UT 2018 September 12, 2018 September 23, and 2018 October
20. All three observations resulted in null detections with 3σ
upper limits.
Finally, we observed at higher frequencies using the Submillimeter
Array (SMA) on UT 2018 September 15 under its target-of-opportunity
program. The project ID was 2018A-S068.
See Section 2.5.
We observed the position of SN2018gep with Swift/XRT from
Δt∼0.4-14days. The source was not detected in any epoch.
We obtained two epochs of observations with the Advanced CCD Imaging
Spectrometer on the Chandra X-ray Observatory via our approved program
(Proposal No. 19500451; PI: Corsi). The first epoch began at 9:25 UTC
on 2018 10 October (Δt∼15days) under ObsId 20319 (integration
time 12.2ks), and the second began at 21:31 UTC on 2018 December 4
(Δt∼70days) under ObsId 20320 (integration time 12.1ks). No
X-ray emission is detected at the location of SN2018gep in either
epoch. See Section 2.6.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
16 43 48.2 +41 02 43 ZTF18abukavn = SN 2018gep
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 94 21 Physical evolution of AT2018gep from blackbody fits
table5.dat 44 480 Optical and ultraviolet photometry for SN2018gep
--------------------------------------------------------------------------------
See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)
II/317 : The CFHTLS Survey (T0007 release) (Hudelot+ 2012)
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman- McCarthy+, 2012)
J/A+A/448/955 : Abundances of em. galaxies in SDSS-DR3 (Izotov+, 2006)
J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)
J/ApJ/702/226 : Swift/UVOT panchromatic obs. of SN 2008D (Modjaz+, 2009)
J/other/Nat/463.513 : Radio observations of SN 2009bb (Soderberg+, 2010)
J/ApJ/760/L33 : Photometry of the Ic supernova PTF12gzk (Ben-Ami+, 2012)
J/MNRAS/421/3027 : Statisical study of galaxy dust emissions (Bourne+, 2012)
J/ApJ/747/L5 : R-band observations of PTF 10vgv (Corsi+, 2012)
J/A+A/558/A131 : Model spectra of hot stars at pre-SN stage (Groh+, 2013)
J/A+A/559/A114 : Updated O3N2 and N2 abundance indicators (Marino+, 2013)
J/MNRAS/429/3330 : AMI Galactic Plane Survey at 16GHz. I. (Perrott+, 2013)
J/ApJ/782/42 : Panchromatic observations of PTF11qcj (Corsi+, 2014)
J/ApJ/794/23 : Pan-STARRS1 transients optical photometry (Drout+, 2014)
J/ApJS/211/13 : 2nd Fermi/GBM GRB catalog (4yr) (von Kienlin+, 2014)
J/A+A/573/A12 : SN1993J sp. 100-500d post-explosion (Jerkstrand+, 2015)
J/A+A/581/A125 : UV/Optical/NIR spectroscopy GRB hosts (Kruehler+, 2015)
J/ApJ/819/35 : LCs of four transients from PTF & SNLS (Arcavi+, 2016)
J/A+A/593/A68 : PTF12os & iPTF13bvn spectra and LCs (Fremling+, 2016)
J/ApJ/832/108 : Spectral data of Type Ic & Ic-bl SNe (Modjaz+, 2016)
J/ApJ/836/5 : Abundances of LAMOST giants from APOGEE DR12 (Ho+, 2017)
J/ApJ/851/107 : iPTF 16asu photometry follow-up (Whitesides+, 2017)
J/other/Sci/362.201 : iPTF 14gqr (SN 2014ft) photometry (De+, 2018)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.2 d MJD [58370.2/58407.85] Modified Julian Date
(JD-2400000.5)
10- 14 F5.2 d dt [0.05/37.7] Time from explosion, days
16- 22 F7.3 10+15cm Rph [20/304] Black-body (photospheric) radius
24- 29 F6.3 10+15cm e_Rph [4.9/86] Lower uncertainty on Rph
31- 36 F6.3 10+15cm E_Rph [7.8/96] Upper uncertainty on Rph
38- 43 F6.3 K Teff [4.2/46.5] Black-body effective temperature
45- 50 F6.3 K e_Teff [0.3/14] Lower uncertainty on Teff
52- 57 F6.3 K E_Teff [0.3/16.1] Upper uncertainty on Teff
59- 67 E9.3 10-7W Lbol [335700000/74270000000] Bolometric Luminosity
69- 77 E9.3 10-7W e_Lbol Lower uncertainty on Lbol
79- 87 E9.3 10-7W E_Lbol [115400000/85580000000] Upper uncertainty
on Lbol
89- 92 F4.2 --- chi2 [0/5.53] Reduced χ2
94- 94 I1 --- dof [0/8] Fit degrees of freedom
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 F12.4 d JD [2458370.6/2458429.6] Julian date of observation
14- 18 F5.2 d dt [0.02/59] Elapsed time for transient
20- 27 A8 --- Tel Telescope/Instrument used (1)
29- 32 A4 --- Filt Filter used
34- 38 F5.2 mag omag [15.19/26.7]? Observed AB magnitude in Filt
40- 44 F5.2 mag e_omag [0.01/76.3] Uncertainty in omag
--------------------------------------------------------------------------------
Note (1): Telescope as follows:
P48+ZTF = Zwicky Transient Facility (ZTF) with the 48 inch Samuel Oschin
Telescope (P48) at Palomar Observatory (179 occurrences)
UVOT = The Neil Gehrels Swift Observatory UV/Optical Telescope
(108 occurrences)
LT = The optical imager (IO:O) on the Liverpool Telescope
(106 occurrences)
LOT = The Lulin 1m Telescope (44 occurrences)
P60+SEDM = The Spectral Energy Distribution Machine mounted on the automated
60 inch telescope at Palomar (P60; 43 occurrences)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 28-May-2021