J/ApJ/910/42 LCs and spectroscopic observations of AT2018cow (Xiang+, 2021)
The peculiar transient AT2018cow: a possible origin of a type Ibn/IIn supernova.
Xiang D., Wang X., Lin W., Mo J., Lin H., Burke J., Hiramatsu D.,
Hosseinzadeh G., Howell D.A., McCully C., Valenti S., Vinko J.,
Wheeler J.C., Ehgamberdiev S.A., Mirzaqulov D., Bodi A., Bognar Z.,
Cseh B., Hanyecz O., Ignacz B., Kalup C., Konyves-Toth R., Kriskovics L.,
Ordasi A., Pal A., Sarneczky K., Seli B., Szakats R., Arranz-Heras T.,
Benavides-Palencia R., Cejudo-Martinez D., De la Fuente-Fernandez P.,
Escartin-Perez A., Garcia-de la Cuesta F., Gonzalez-Carballo J.L.,
Gonzalez-Farfan R., Limon-Martinez F., Mantero A., Naves-Nogues R.,
Morales-Aimar M., Ruiz-Ruiz V.R., Soldan-Alfaro F.C., Valero-Perez J.,
Violat-Bordonau F., Zhang T., Zhang J., Li X., Chen Z., Sai H., Li W.
<Astrophys. J., 910, 42 (2021)>
=2021ApJ...910...42X 2021ApJ...910...42X
ADC_Keywords: Supernovae; Photometry, UBVRI; Spectra, optical
Keywords: Supernovae ; Circumstellar matter ; Massive stars ;
Binary stars ; Magnetars ; Time domain astronomy ; Optical observation
Abstract:
We present our photometric and spectroscopic observations of the
peculiar transient AT2018cow. The multiband photometry covers from
peak to ∼70days, and the spectroscopy ranges from 5 to ∼50days. The
rapid rise (tr≲2.9days), high luminosity (MV,peak~-20.8mag), and
fast decline after peak make AT2018cow stand out from any other
optical transients, whereas we find that its light curves show a high
resemblance to those of Type Ibn supernovae. Moreover, the spectral
energy distribution remains at a high temperature of ∼14000K at
t>15days after discovery. The spectra are featureless in the first
10days, while some broad emission lines due to H, He, C, and O emerge
later, with velocity declining from ∼14000 to ∼3000km/s at the end of
our observations. Narrow and weak He I emission lines emerge in the
spectra at t>20days after discovery. These emission lines are
reminiscent of the features seen in interacting supernovae like the
Type Ibn and IIn subclasses. We fit the bolometric light curves with a
model of circumstellar interaction and radioactive decay of 56Ni and
find a good fit with ejecta mass Mej∼3.16M☉, circumstellar
medium (CSM) mass MCSM∼0.04M☉, and ejected 56Ni mass
M56Ni∼0.23M☉. The CSM shell might be formed in an eruptive
mass ejection of the progenitor star. Furthermore, the host
environment of AT2018cow implies a connection of AT2018cow with
massive stars. Combining observational properties and the light-curve
fitting results, we conclude that AT2018cow might be a peculiar
interacting supernova that originated from a massive star.
Description:
The optical photometric observations of AT2018cow were monitored by
several observatories, including the 0.8m Tsinghua University-NAOC
telescope (TNT) at Xinglong Observatory of NAOC (XLT), the AZT-22 1.5m
telescope (AZT) at Maidanak Astronomical Observatory, the telescopes
of the Las Cumbres Observatory network (LCO), and the telescope of
Konkoly Observatory in Hungary (KT). Photometric and spectroscopic
data from LCO were obtained via the Global Supernova Project (GSP). We
also collected early-time photometric data from the Observadores de
Supernovas Group (ObSN) in Spain. The entire data set covers phases
from MJD58286.89 (2018 June 17.89) to MJD58348.74 (2018 August 18.74).
Our first spectrum was taken on 2018 July 21 by the 2.16m telescope at
the XLT. A total of 31 spectra were collected with different
telescopes, including the XLT, the 2m Faulkes Telescope North (FTN) of
the LCO network, and the 9.2m Hobby-Eberly Telescope (HET). The
details of the spectroscopic observations are listed in Table 2.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
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16 16 00.25 +22 16 05.1 AT2018cow = SN 2018cow
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 39 485 Optical photometric observations of AT2018cow
table2.dat 95 32 Log of optical spectroscopy of AT2018cow
sp/* . 31 Individual spectrum in ASCII format
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See also:
B/eso : ESO Science Archive Catalog (ESO, 1991-2022)
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)
J/A+A/627/A106 : HI observations of AT 2018cow (Michalowski+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.4 d MJD [58285.44/58348.75] Observation date
(JD-2400000.5)
12- 17 F6.3 mag omag [13.39/21.37] Observed magnitude in Filt
19- 23 F5.3 mag e_omag [0.006/0.7]? Uncertainty in omag
25- 25 A1 --- Filt Filter (UBVRIgrio)
27- 39 A13 --- r_omag Telescope or reference (1)
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Note (1): Telescope or reference as follows:
ATEL11727 = Smartt et al. (2018ATel11727....1S 2018ATel11727....1S);
ATEL11738 = Fremling et al. (2018ATel11738....1F 2018ATel11738....1F);
AZT = AZT-22 1.5-m telescope at Maidanak Astronomical Obs.;
LCO = Las Cumbres Observatory network;
ObSN = Observadores de Supernovas Group, Spain;
Prentice+2018 = Prentice et al. (2018ApJ...865L...3P 2018ApJ...865L...3P);
TNT = 0.8-m Tsinghua University-NAOC telescope,
Xinglong Observatory of NAOC.
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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 Obs.Y [2018/2019] Year of the observation (UT)
6- 7 I2 "month" Obs.M [6/9] Month of the observation
9- 13 F5.2 d Obs.d [1.57/31.37] Decimal day of the observation
15- 22 F8.2 d MJD [58290.58/58743.1] Modified Julian Date
24- 26 A3 --- Tel Telescope (1)
28- 31 I4 0.1nm lam1 [3500/6440] Wavelength lower range in Å
33- 37 I5 0.1nm lam2 [6970/10300] Wavelength upper range in Å
39- 44 A6 --- Inst Instrument
46- 49 I4 s Exp [300/3600] Exposure time
51 A1 --- n_MJD [a] Flag on spectrum (2)
53- 95 A43 --- FileName Name of the ASCII file in subdirectory "sp/";
column added by CDS
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Note (1): Telescope as follows:
FTN = the 2m Faulkes Telescope North of the LCO network
HET = the 9.2m Hobby-Eberly Telescope
XLT = the 0.8m Tsinghua University-NAOC telescope (TNT)
at Xinglong Observatory of NAOC
Note (2): Note as follows:
a = On 2019 September 17, when AT2018cow had already faded away in the
host galaxy, a spectrum was obtained at the site of AT2018cow by HET.
There are some narrow absorption lines in the resultant spectrum,
which are an artifact of data reduction. A detailed analysis of this
spectrum is presented in Section 4.
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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2- 12 F11.5 0.1nm lambda [3499/10299] Spectrum wavelength,
in Angstrom units
14- 28 E15.8 mW/m2 Flux [-1.9e-16/9.9e-15] Flux in erg/s/cm2 units
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-Aug-2022