J/ApJ/902/46 LCO network light curves of SN Ia 2018gv (Yang+, 2020)
The young and nearby normal type Ia supernova 2018gv: UV-optical observations
and the earliest spectropolarimetry.
Yang Y., Hoeflich P., Baade D., Maund J.R., Wang L., Brown P.J.,
Stevance H.F., Arcavi I., Burke J., Cikota A., Clocchiatti A., Gal-Yam A.,
Graham M.L., Hiramatsu D., Hosseinzadeh G., Howell D.A., Jha S.W.,
McCully C., Patat F., Sand D.J., Schulze S., Spyromilio J., Valenti S.,
Vinko J., Wang X., Wheeler J.C., Yaron O., Zhang J.
<Astrophys. J., 902, 46 (2020)>
=2020ApJ...902...46Y 2020ApJ...902...46Y
ADC_Keywords: Supernovae; Photometry, UBVRI
Keywords: Spectro-polarimetry ; Galaxies ; Type Ia supernovae
Abstract:
The nondetection of companion stars in SN Ia progenitor systems lends
support to the notion of double-degenerate systems and explosions
triggered by the merging of two white dwarfs. This very asymmetric
process should lead to a conspicuous polarimetric signature. By
contrast, observations consistently find very low continuum
polarization as the signatures from the explosion process largely
dominate over the pre-explosion configuration within several days.
Critical information about the interaction of the ejecta with a
companion and any circumstellar matter is encoded in the early
polarization spectra. In this study, we obtain spectropolarimetry of
SN 2018gv with the ESO Very Large Telescope at -13.6 days relative to
the B-band maximum light, or ∼5 days after the estimated explosion-the
earliest spectropolarimetric observations to date of any SN Ia. These
early observations still show a low continuum polarization
(≤0.2%) and moderate line polarization (0.30±0.04% for the
prominent SiIIλ6355 feature and 0.85±0.04% for the
high-velocity Ca component). The high degree of spherical symmetry
implied by the low-line and continuum polarization at this early epoch
is consistent with explosion models of delayed detonations and is
inconsistent with the merger-induced explosion scenario. The dense UV
and optical photometry and optical spectroscopy within the first
∼100 days after the maximum light indicate that SN 2018gv is a normal
SN Ia with similar spectrophotometric behavior to SN 2011fe.
Description:
SN 2018gv was discovered at UT 2018 January 15 16:21:06.
Follow-up spectroscopy on UT 2018 January 16 12:41:15
(Siebert+ 2018TNSCR..75....1S 2018TNSCR..75....1S) reveals that SN 2018gv was a very
young, normal SN Ia, at ∼11-13 days before the maximum luminosity. We
measure its J2000.0 coordinates on the images obtained by the Sinistro
cameras on Las Cumbres Observatory (LCO) Global Network of 1m
telescopes to be RAJ2000=08:05:34.58, DEJ2000=-11:26:16.77.
SN2018gv exploded 346W and 3915S of the nucleus of the host spiral
galaxy NGC2525 (see Figure 1).
Throughout the paper, we used a redshift of z=0.00527±0.00004 for
SN2018gv together with the adopted Hubble constant of
H0=73.24±1.74km/s/Mpc.
Extensive UBg'Vr'i' photometry was obtained with the Sinistro cameras
on the LCO network of 1m telescopes.
LCO optical spectra were taken with the FLOYDS spectrographs mounted
on the 2m Faulkes Telescope North and South at Haleakala, USA, and
Siding Spring, Australia, respectively, through the Global Supernova
Project.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
08 05 34.58 -11 26 16.7 SN2018gv = AT 2018gv
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 137 114 Las Cumbres Observatory (LCO) UBg'Vr'i' photometry
of SN2018gv
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See also:
VI/135 : All-sky spectrally matched Tycho2 stars (Pickles+, 2010)
J/AJ/133/403 : Light curve of 11 type Ia supernovae (Garg+, 2007)
J/ApJ/699/L139 : Spectral parameters of SNe Ia (Wang+, 2009)
J/AJ/139/120 : Low-redshift Type-Ia supernovae (Folatelli+, 2010)
J/ApJ/733/124 : Cepheids in M101 observed with HST (Shappee+, 2011)
J/ApJ/745/74 : Pre-maximum spectra of type Ia SNe (Folatelli+, 2012)
J/MNRAS/425/1819 : Berkeley supernova Ia program. II. (Silverman+, 2012)
J/other/NewA/20.30 : BVRI light curves of 3 SN (Munari+, 2013)
J/A+A/554/A27 : 2011fe spectrophotometric time series (Pereira+, 2013)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/MNRAS/438/L101 : First month on SN 2013ej (Valenti+, 2014)
J/MNRAS/446/3895 : The rising light curves of Type Ia SNe (Firth+, 2015)
J/MNRAS/451/1973 : Type Ia SNe igh-velocity features (Silverman+, 2015)
J/ApJ/813/30 : UV-Optical LCs of the SNIa iPTF14bdn (Smitka+, 2015)
J/AJ/149/171 : 2MASS galaxy group catalog (Tully, 2015)
J/ApJS/219/13 : SNe Ia light curves for the LSQ-CSP sample (Walker+, 2015)
J/ApJS/220/20 : Si and Ca high-velocity features in SNe Ia (Zhao+, 2015)
J/AJ/152/102 : Flux conversions for Swift/UVOT filters (Brown+, 2016)
J/ApJ/826/56 : HST/WFC3 obs. of Cepheids in SNIa host gal. (Riess+, 2016)
J/AJ/151/125 : Optical and UV photometry of SN 2013dy (Zhai+, 2016)
J/A+A/608/A146 : Southern Hemisphere ISM FORS2 spectropol. (Bagnulo+, 2017)
J/AJ/154/211 : CSP (DR3): photometry of low-z SNe Ia (Krisciunas+, 2017)
J/ApJ/853/62 : Opt. & NIR spectra and LCs of SN2016ija (Tartaglia+, 2018)
J/ApJ/870/L1 : K2 obs. of type Ia SN 2018oh (Dimitriadis+, 2019)
J/ApJ/870/13 : K2 LC alternative analysis of ASASSN-18bt (Shappee+, 2019)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 9 F9.3 d MJD-U [58134.8/58264.8]? Modified Julian date of
U band observation (JD-2400000.5)
11- 16 F6.3 mag Umag [12.45/17.47]? U band magnitude
18- 22 F5.3 mag e_Umag [0.002/0.112]? Uncertainty in Umag
24- 32 F9.3 d MJD-B [58134/58287]? Modified Julian date of
B band observation (JD-2400000.5)
34- 39 F6.3 mag Bmag [12.81/17.41]? B band magnitude
41- 45 F5.3 mag e_Bmag [0.001/0.031]? Uncertainty in Bmag
47- 55 F9.3 d MJD-V [58134/58287]? Modified Julian date of
V band observation (JD-2400000.5)
57- 62 F6.3 mag Vmag [12.86/17.19]? V band magnitude
64- 68 F5.3 mag e_Vmag [0.002/0.03]? Uncertainty in Vmag
70- 78 F9.3 d MJD-gp [58134/58287]? Modified Julian date of
g' band observation (JD-2400000.5)
80- 85 F6.3 mag gpmag [12.81/17.05]? g' band magnitude
87- 91 F5.3 mag e_gpmag [0.001/0.018]? Uncertainty in gpmag
93-101 F9.3 d MJD-rp [58134/58287]? Modified Julian date of
r' band observation (JD-2400000.5)
103-108 F6.3 mag rpmag [12.93/17.66]? r' band magnitude
110-114 F5.3 mag e_rpmag [0.001/0.033]? Uncertainty in rpmag
116-124 F9.3 d MJD-ip [58134/58287]? Modified Julian date of
i' band observation (JD-2400000.5)
126-131 F6.3 mag ipmag [13.47/18.06]? i' band magnitude
133-137 F5.3 mag e_ipmag [0.002/0.118]? Uncertainty in ipmag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 29-Mar-2022