J/ApJ/915/121 Type Ic SN2018gep phot. & sp. follow-up (Pritchard+, 2021)
The exotic type Ic broad-lined supernova SN 2018gep: blurring the line between
supernovae and fast optical transients.
Pritchard T.A., Bensch K., Modjaz M., Williamson M., Thone C.C., Vinko J.,
Bianco F.B., Bostroem K.A., Burke J., Garcia-Benito R., Galbany L.,
Hiramatsu D., Howell D.A., Izzo L., Kann D.A., McCully C., Pellegrino C.,
de Ugarte Postigo A., Valenti S., Wang X., Wheeler J.C., Xiang D.,
Sarneczky K., Bodi A., Cseh B., Tarczay-Nehez D., Kriskovics L., Ordasi A.,
Pal A., Szakats R., Vida K.
<Astrophys. J., 915, 121 (2021)>
=2021ApJ...915..121P 2021ApJ...915..121P
ADC_Keywords: Photometry, UBVRI; Ultraviolet; Spectra, optical; Supernovae
Keywords: Core-collapse supernovae ; Supernovae ; Transient sources ;
Ultraviolet transient sources ; Time domain astronomy
Abstract:
In the last decade a number of rapidly evolving transients have been
discovered that are not easily explained by traditional supernova
models. We present optical and UV data on one such object, SN 2018gep,
that displayed a fast rise with a mostly featureless blue continuum
around peak, and evolved to develop broad features typical of an
SNIc-bl while retaining significant amounts of blue flux throughout
its observations. This blue excess is most evident in its near-UV
flux, which is over 4 mag brighter than other stripped-envelope
supernovae, and is still visible in optical g-r colors. Its fast rise
time of trise,V=5.6±0.5days puts it squarely in the emerging class
of Fast Evolving Luminous Transients, or Fast Blue Optical Transients.
With a peak absolute magnitude of Mv=-19.53±0.23mag it is on the
extreme end of both the rise time and peak magnitude distribution for
SNe Ic-bl. These observations are consistent with a simple SN Ic-bl
model that has an additional form of energy injection at early times
that drives the observed rapid, blue rise. We show that SN 2018gep and
the literature SN iPTF16asu have similar photometric and spectroscopic
properties and that they overall share many similarities with both SNe
Ic-bl and Fast Evolving Transients. Based on our SN 2018gep host
galaxy data we derive a number of properties, and we show that the
derived host galaxy properties for both SN 2018gep and iPTF16asu are
consistent with the SNe Ic-bl and gamma-ray burst/supernova sample
while being on the extreme edge of the observed Fast Evolving
Transient sample.
Description:
SN 2018gep/ZTF18abukavn was first discovered on
UT 03:55:17 2018 September 09 (JD=2458370.6634) by
Ho+ (2018TNSTR1357....1H 2018TNSTR1357....1H) as part of the partnership ZTF survey
(Bellm+ 2019PASP..131a8002B 2019PASP..131a8002B).
The ZTF public survey observed SN 2018gep between 2018 September 8 and
28 in the r-ZTF and g-ZTF filters.
The Global Supernova Project (GSP) obtained additional Las Cumbres
Observatory (LCO) BVgri-band follow-up data with the Sinistro and
Spectral cameras on 1m and 2m telescopes, respectively. Science
observations were taken between 2018 September 22 and 2018 October 30
with template photometry taken between 2019 January 22 and 26.
Additional photometric observations were collected with the 0.6/0.9m
Schmidt telescope at Piszkesteto Mountain Station of Konkoly
Observatory, Hungary, using the 4kx4k FLI CCD equipped with
Johnson-Cousins-Bessel BVRI filters.
Observations with the Neil Gehrels Swift Observatory
Ultra-Violet/Optical Telescope began on 14:02:56 2018 September 9
(∼0.5day after discovery) using three optical (u, b, v) and three UV
filters (uvw2, uvm2, uvw1: λc=1928, 2246, 2600Å,
respectively. Regular observations continued through 2018 October 3
with a final observation obtained on 2018 October 29.
We obtained optical spectroscopy of the SN as well as its host galaxy
and list the journal of our spectroscopic observations in Table 2.
Additional observations of the location of SN 2018gep and its host
galaxy were obtained by two different telescopes at 1.5-2 months after
the explosion. One was obtained via Director's Discretionary Time (PI:
Bensch) using the Potsdam MultiAperture Spectrophotometer (PMAS),
which is an IFU instrument, mounted on the 3.5m telescope at the
Centro Astronomico Hispano en Andalucia (CAHA). The other was with
the Low-Resolution Imaging Spectrometer (LRIS) at the 10m W. M. Keck
Observatory on Maunakea, Hawaii, as part of the LCO-GSP follow-up
program (PI: Valenti), using a long-slit aperture.
See Section 2.3.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
16 43 48.21 +41 02 43.4 SN 2018gep = ZTF18abukavn
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 49 163 Photometry of SN 2018gep
table2.dat 106 4 Spectroscopic observations of SN2018gep and
its host galaxy
sp/* . 2 SN2018gep 2m+FLOYDS spectra in FITS format
(data behind Figure 7)
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See also:
J/ApJ/617/240 : Oxygen abund. in the GOODS-North field (Kobulnicky+, 2004)
J/ApJ/702/226 : Swift/UVOT panchromatic obs. of SN 2008D (Modjaz+, 2009)
J/ApJ/747/L5 : R-band observations of PTF 10vgv (Corsi+, 2012)
J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)
J/A+A/559/A114 : Updated O3N2 and N2 abundance indicators (Marino+, 2013)
J/ApJS/213/19 : Optical and near-IR light curves of 64 SNe (Bianco+, 2014)
J/ApJ/794/23 : Pan-STARRS1 transients optical photometry (Drout+, 2014)
J/AJ/147/99 : Spectroscopy of stripped core-collapse SNe (Modjaz+, 2014)
J/A+A/576/A135 : CALIFA DR2 (Garcia-Benito+, 2015)
J/A+A/574/A60 : Light curve templates of SNe Ib/c from SDSS (Taddia+, 2015)
J/ApJ/819/35 : LCs of four transients from PTF & SNLS (Arcavi+, 2016)
J/ApJ/827/90 : Spectroscopy of SNe Ib, IIb and Ic (Liu+, 2016)
J/ApJ/832/108 : Spectral properties of Type Ic & Ic-bl SNe (Modjaz+, 2016)
J/MNRAS/459/3939 : Type II supernova light curves (Valenti+, 2016)
J/ApJ/845/85 : Absorption vel. for 21 super-luminous SNe Ic (Liu+, 2017)
J/ApJ/851/107 : iPTF 16asu photometry follow-up (Whitesides+, 2017)
J/ApJ/860/100 : LCs of 26 hydrogen-poor superluminous SNe (De Cia+, 2018)
J/ApJ/855/107 : PMAS Integral-field SN hosts COmpilation (Galbany+, 2018)
J/ApJ/852/81 : 17 PS1 superluminous SNe LCs + classif. sp. (Lunnan+, 2018)
J/MNRAS/481/894 : Rapidly evolving transients in the DES (Pursiainen+, 2018)
J/ApJ/887/169 : UV-Opt light curves of the type Ic SN 2018gep (Ho+, 2019)
J/ApJ/876/85 : HST observations for LMC Cepheids (Riess+, 2019)
J/MNRAS/482/1545 : Berkeley sample of stripped-envelope SNe (Shivvers+, 2019)
J/ApJ/902/86 : Type Ic SN 2020bvc UV to NIR LCs & opt. spectra (Ho+, 2020)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [0/162] Internal index identifier
5- 22 F18.12 d MJD [58370.62/58420.56] Modified Julian Date
24- 27 A4 --- Filt Filter used
29- 35 F7.4 mag mag [15.66/20.43] Observed magnitude in Filter
37- 41 F5.3 mag e_mag [0.02/0.2] Uncertainty in mag
43- 49 A7 --- Inst Instrument used (1)
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Note (1): Instrument as follows:
UVOT = Swift/UVOT (66 occurrences)
konkoly = the 0.6/0.9m Schmidt telescope at Piszkesteto Mountain Station
of Konkoly Observatory, Hungary (60 occurrences)
LCO = Las Cumbres Observatory with the Sinistro and
Spectral cameras on 1m and 2m telescopes (24 occurrences)
ztf = The Zwicky Transient Facility (13 occurrences)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 yr Date.Y Year of the observation (UT)
6- 7 I2 "month" Date.M Month of the observation (UT)
9- 13 F5.2 d Date.D Decimal date of the observation (UT)
15 A1 --- f_Date b = No SN light, only host galaxy
17- 26 F10.2 d JD [2458372.8/2458520.14] Julian Date
28- 33 F6.1 d tVmax [-3.7/144.6] Days with respect to V-band
maximum (1)
35- 47 A13 --- Inst Instrument (2)
49 A1 --- f_Inst Flag on Inst (3)
51- 54 I4 0.1nm lam1 Wavelength lower range in Å
55 A1 --- --- [-]
56- 60 I5 0.1nm lam2 Wavelength upper range in Å
62- 66 F5.1 deg PA [95.3/250]? Position angle
68- 71 F4.2 --- Airmass [1.3/2.2] Airmass
73- 75 F3.1 arcsec Slit [1/2]? Slit
77- 82 A6 s Exp Exposure time
84-106 A23 --- FileName Name of the FITS file in subdirectory "sp";
column added by CDS
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Note (1): Note that SN 2018gep's rise time in the V-band is
trise,V=5.6±0.5days (see Section 3), such that our first two
spectra were taken 1.9 and 9.9 days after the presumed date of
explosion, respectively.
Note (2): Instrument as follows:
CAHA+PMAS = Potsdam MultiAperture Spectrophotometer mounted on
the 3.5m telescope at the Centro Astronomico Hispano
en Andalucia
Keck+LRIS = Low-Resolution Imaging Spectrometer at the 10m W. M. Keck
Observatory on Maunakea, Hawaii
OGG 2m+FLOYDS = Las Cumbres Observatory (LCO) global telescope network,
2m telescope on Haleakala (FTN).
Note (3): Flag as follows:
c = IFU observations, thus long-slit information such as slit size
and P.A. is not applicable here.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Dec-2022