J/ApJ/954/155 Type IIP supernova SN 2018gj follow-up obs. (Teja+, 2023)
SN 2018gj: a short Plateau Type II supernova with persistent blueshifted Ha
emission.
Teja R.S., Singh A., Sahu D.K., Anupama G.C., Kumar B., Nakaoka T.,
Kawabata K.S., Yamanaka M., Takey A., Kawabata M.
<Astrophys. J., 954, 155 (2023)>
=2023ApJ...954..155T 2023ApJ...954..155T
ADC_Keywords: Supernovae; Photometry, UBVRI; Ultraviolet; Spectra, optical
Keywords: Observational astronomy ; Type II supernovae ;
Hydrodynamical simulations ; Red supergiant stars
Abstract:
We present an extensive, panchromatic photometric (UV, optical, and
near-IR) and low-resolution optical spectroscopic coverage of a Type
IIP supernova SN 2018gj that occurred on the outskirts of the host
galaxy NGC 6217. From the V-band light curve, we estimate the plateau
length to be ∼70±2days, placing it among the very few well-sampled
short plateau supernovae (SNe). With V-band peak absolute magnitude
MV≤-17.0±0.1mag, it falls in the middle of the luminosity
distribution of the Type II SNe. The color evolution is typical to
other Type II SNe except for an early elbow-like feature in the
evolution of V-R color owing to its early transition from the plateau
to the nebular phase. Using the expanding photospheric method, we
present an independent estimate of the distance to SN 2018gj. We
report the spectral evolution to be typical of a Type II SNe. However,
we see a persistent blueshift in emission lines until the late nebular
phase, not ordinarily observed in Type II SNe. The amount of
radioactive nickel (56Ni) yield in the explosion was estimated to be
0.026±0.007M☉. We infer from semianalytical modeling, nebular
spectrum, and 1D hydrodynamical modeling that the probable progenitor
was a red supergiant with a zero-age-main-sequence mass ≤13M☉.
In the simulated hydrodynamical model light curves, reproducing the
early optical bolometric light curve required an additional radiation
source, which could be the interaction with the proximal circumstellar
matter.
Description:
The discovery of SN 2018gj, in the outskirts of the barred spiral
galaxy NGC 6217 (about 122" or ∼11kpc away from the center of the host
galaxy; Figure 1), was reported on 2018 January 14 (2458132.91 JD).
We started an extensive follow-up campaign in optical--near-IR (NIR)
photometry and spectroscopy, which continued for about 300 days after
the discovery. An imager cum spectrograph, the Himalaya Faint Object
Spectrograph (HFOSC) mounted on the 2m Himalayan Chandra Telescope
(HCT) of the Indian Astronomical Observatory (IAO), Hanle, India, was
used for optical photometry and spectroscopy.
Near Infrared (NIR) data were acquired with the Hiroshima Optical and
Near-InfraRed Camera (HONIR) installed at the 1.5m Kanata Telescope
operated by the Hiroshima Astrophysical Science Center of Hiroshima
University.
Further, we supplemented our photometry data using public archive
images from the UltraViolet/Optical Telescope (UVOT) on board Neil
Gehrels Swift Observatory in the UVW2, UVM2, UVW1, UVU, UVB, and UVV
bands. We also obtained photometry in ATLAS-o band (AB-magnitude) from
ATLAS forced photometry server.
The low-resolution spectroscopic (∼10Å) data was obtained with
HFOSC using a setup consisting of 1.92" slit with grisms,
Gr7 (3800-6840Å) and Gr8 (5800-9350Å) during 2018-Jan-14
(JD2458132.5) to 2018-Oct-31 (JD2458423.1).
We study the spectral evolution spanning 31 epochs over the
photospheric phase to the nebular phase beginning +5 days
spanning 295 days post-explosion (Figure 8; see Section 4).
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
16 32 02.31 +78 12 40.8 SN 2018gj = ZTF18aaxljll
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 78 42 UBVRI photometric magnitudes of SN 2018gj
table4.dat 88 5 Swift/UVOT photometry for SN 2018gj
table5.dat 56 42 JHKs photometric magnitudes of SN 2018gj
table6.dat 41 31 Log of spectroscopic observations of SN 2018gj
sp/* . 31 31 epochs HCT-HFOSC spectra in ASCII format
(Data behind Figure 8)
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See also:
II/183 : UBVRI Photometric Standards (Landolt 1992)
VII/233 : 2MASS All-Sky Extended Source Catalog (XSC) (IPAC/UMass, 2003-2006)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/333/231 : O-M stars model atmospheres (Bessell+ 1998)
J/MNRAS/372/1315 : UBVRI photometry of SN 2004et (Sahu+, 2006)
J/AJ/131/2245 : BATC photometry of SN2004dj (Zhang+, 2006)
J/AJ/137/4517 : UVOT light curves of supernovae (Brown+, 2009)
J/MNRAS/394/2266 : SN 2005cs one-year photometry (Pastorello+, 2009)
J/MNRAS/395/1409 : Type II-P SN progenitor constraints (Smartt+, 2009)
J/MNRAS/408/827 : Simulations of supernova explosions (Dessart+, 2010)
J/A+A/537/A141 : UBVRI light curves of SN 2009E (Pastorello+, 2012)
J/ApJ/756/173 : Phot. of type IIn SNe 2005ip and 2006jd (Stritzinger+, 2012)
J/MNRAS/433/1871 : UBVRI griz light curves of SN 2012aw (Bose+, 2013)
J/MNRAS/436/774 : Core collapse supernovae (type Ibc) (Eldridge+, 2013)
J/A+A/555/A142 : Spectra of 5 Type II supernovae (Inserra+, 2013)
J/A+A/555/A10 : Light curves of 5 type IIn supernovae (Taddia+, 2013)
J/MNRAS/442/844 : BVRI light curves of type II-P supernovae (Faran+, 2014)
J/MNRAS/438/L101 : First month on SN 2013ej (Valenti+, 2014)
J/ApJ/799/208 : Type IIP supernovae from Pan-STARRS1 (Sanders+, 2015)
J/MNRAS/450/3137 : Optical/NIR light curves of SN 2009ib (Takats+, 2015)
J/AJ/151/33 : UBVRIz LCs of 51 Type II supernovae (Galbany+, 2016)
J/ApJ/820/33 : R-band light curves of type II supernovae (Rubin+, 2016)
J/MNRAS/459/3939 : Type II supernova light curves (Valenti+, 2016)
J/ApJ/885/43 : UBVRI & ugriz phot. of supernova SN 2017gmr (Andrews+, 2019)
J/MNRAS/488/4239 : SNe II & IIb optical light curves comparison (Pessi+, 2019)
J/ApJ/895/31 : Photometric obs. of Type II SN 2018ivc (Bostroem+, 2020)
J/A+A/655/A105 : 3 SN multiwavelength light curves (Sollerman+, 2021)
J/A+A/655/A90 : SN 2020cxd multi-photometry (Yang+, 2021)
J/ApJ/930/34 : HCT spectroscopic obs. of type IIP SN 2020jfo (Teja+, 2022)
J/ApJ/952/119 : SNII in ZTF 1st phase survey sp. follow-up (Bruch+, 2023)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "Y/M/D" Date Observation Date (UT)
12- 16 F5.1 d JD [132.5/423.1] Julian Date, JD-2458000
18- 23 F6.1 d Phase [4.7/295.3] Phase (with reference to the
explosion date, JD2458127.8)
25- 29 F5.2 mag Umag [14/20.6]? HFOSC/HCT U-band
(Johnson-Cousins-Glass) magnitude at Date
31- 34 F4.2 mag e_Umag [0.01/0.05]? Uncertainty in Umag
36- 40 F5.2 mag Bmag [14.7/20.8]? HFOSC/HCT B-band
(Johnson-Cousins-Glass) magnitude at Date
42- 45 F4.2 mag e_Bmag [0.01/0.04]? Uncertainty in Bmag
47- 51 F5.2 mag Vmag [14.7/20.2] HFOSC/HCT V-band
(Johnson-Cousins-Glass) magnitude at Date
53- 56 F4.2 mag e_Vmag [0.01/0.04] Uncertainty in Vmag
58- 62 F5.2 mag Rmag [14.5/19.23] HFOSC/HCT R-band
(Johnson-Cousins-Glass) magnitude at Date
64- 67 F4.2 mag e_Rmag [0.01/0.05] Uncertainty in Rmag
69- 73 F5.2 mag Imag [14.4/19.01] HFOSC/HCT I-band
(Johnson-Cousins-Glass) magnitude at Date
75- 78 F4.2 mag e_Imag [0.01/0.04] Uncertainty in Imag
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "Y/M/D" Date Observation Date (UT)
12- 16 F5.1 d JD [134.6/142.7] Julian Date, JD-2458000
18- 22 F5.1 d Phase [6.8/14.9] Phase
(with reference to the explosion date,
JD2458127.8)
24- 28 F5.2 mag UVW2 [14/15.5]? Swift/UVOT UVW2-band magnitude at
Date
30- 33 F4.2 mag e_UVW2 [0.03/0.04]? Uncertainty in UVW2
35- 39 F5.2 mag UVM2 [13.9/15.5]? Swift/UVOT UVM2-band magnitude at
Date
41- 44 F4.2 mag e_UVM2 [0.03/0.06]? Uncertainty in UVM2
46- 50 F5.2 mag UVW1 [13.7/14.91]? Swift/UVOT UVW1-band magnitude
at Date
52- 55 F4.2 mag e_UVW1 [0.03/0.04]? Uncertainty in UVW1
57- 61 F5.2 mag Umag [13.7/14.34] Swift/UVOT U-band magnitude at
Date
63- 66 F4.2 mag e_Umag [0.03/0.04] Uncertainty in Umag
68- 72 F5.2 mag Bmag [14.8/15.1] Swift/UVOT B-band magnitude at
Date
74- 77 F4.2 mag e_Bmag [0.03/0.04] Uncertainty in Bmag
79- 83 F5.2 mag Vmag [14.7/15] Swift/UVOT V-band magnitude at Date
85- 88 F4.2 mag e_Vmag [0.04/0.06] Uncertainty in Vmag
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "Y/M/D" Date Observation Date (UT)
12- 16 F5.1 d JD [136.3/332] Julian Date, JD-2458000
18- 23 F6.1 d Phase [8.5/204.2] Phase
(with reference to the explosion date,
JD2458127.8)
25- 29 F5.2 mag Jmag [13.8/17]? HONIR/Kanata J-band
(2MASS-calibrated) magnitude at Date
31- 34 F4.2 mag e_Jmag [0.02/0.3]? Uncertainty in Jmag
36- 40 F5.2 mag Hmag [14/17.64]? HONIR/Kanata H-band
(2MASS-calibrated) magnitude at Date
42- 45 F4.2 mag e_Hmag [0.02/0.3]? Uncertainty in Hmag
47- 51 F5.2 mag Ksmag [14/18]? HONIR/Kanata Ks-band
(2MASS-calibrated) magnitude at Date
53- 56 F4.2 mag e_Ksmag [0.02/0.1]? Uncertainty in Ksmag
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "Y/M/D" Date Date of observation (UT)
12- 16 F5.1 d JD [132.5/423.1] Julian Date, JD-2458000
18- 23 F6.1 d Phase [4.7/295.3] Phase (relative to the explosion
epoch of JD 2458127.8)
25- 28 I4 0.1nm lam1 [3500/5200] Wavelength lower range in Å
29 A1 --- --- [-]
30- 33 I4 0.1nm lam2 [7800/9250] Wavelength upper range in Å
35- 41 A7 --- Grism Grism(s) used
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Byte-by-byte Description of file: sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.4 0.1nm lambda [3900/9000] Wavelength, Angstroms,
no redshift-corrected
11- 21 E11.4 cW/m2/nm Flux [-1.4e-16/10e-15] Calibrated flux,
erg/s/cm2/Å
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Nov-2025