J/ApJ/870/13 K2 light curve alternative analysis of ASASSN-18bt (Shappee+, 2019)
Seeing double: ASASSN-18bt exhibits a two-component rise in the early-time K2
light curve.
Shappee B.J., Holoien T.W.-S., Drout M.R., Auchettl K., Stritzinger M.D.,
Kochanek C.S., Stanek K.Z., Shaya E., Narayan G. (The ASAS-SN), Brown J.S.,
Bose S., Bersier D., Brimacombe J., Chen P., Dong S., Holmbo S., Katz B.,
Munoz J.A., Mutel R.L., Post R.S., Prieto J.L., Shields J., Tallon D.,
Thompson T.A., Vallely P.J., Villanueva S. (The ATLAS), Denneau L.,
Flewelling H., Heinze A.N., Smith K.W., Stalder B., Tonry J.L., Weiland H.,
Barclay T., Barentsen G., Cody A.M., Dotson J., Foerster F., Garnavich P.,
Gully-Santiago M., Hedges C., Howell S., Kasen D., Margheim S., Mushotzky R.,
Rest A., Tucker B.E., Villar A., Zenteno A. (The Kepler Spacecraft Team),
Beerman G., Bjella R., Castillo G., Coughlin J., Elsaesser B., Flynn S.,
Gangopadhyay R., Griest K., Hanley M., Kampmeier J., Kloetzel R., Kohnert L.,
Labonde C., Larsen R., Larson K.A., McCalmont-Everton K.M., McGinn C.,
Migliorini L., Moffatt J., Muszynski M., Nystrom V., Osborne D., Packard M.,
Peterson C.A., Redick M., Reedy L.H., Ross S.E., Spencer B., Steward K.,
Van Cleve J.E., Vinicius de Miranda Cardoso J., Weschler T.,
Wheaton A. (The Pan-STARRS), Bulger J., Chambers K.C., Flewelling H.A.,
Huber M.E., Lowe T.B., Magnier E.A., Schultz A.S.B., Waters C.Z., Willman M.,
Baron E., Chen Z., Derkacy J.M., Huang F., Li L., Li W., Li X., Mo J.,
Rui L., Sai H., Wang L., Wang L., Wang X., Xiang D., Zhang J., Zhang J.,
Zhang K., Zhang T., Zhang X., Zhao X., Brown P.J., Hermes J.J., Nordin J.,
Points S., Sodor A., Strampelli G.M., Zenteno A.
<Astrophys. J. 870, 13 (2019)>
=2019ApJ...870...13S 2019ApJ...870...13S (SIMBAD/NED BibCode)
ADC_Keywords: Photometry; Optical; Supernovae
Keywords: supernovae: individual: (ASASSN-18bt, SN 2018oh)
Abstract:
On 2018 February 4.41, the All-Sky Automated Survey for SuperNovae
(ASAS-SN) discovered ASASSN-18bt in the K2 Campaign 16 field. With a
redshift of z=0.01098 and a peak apparent magnitude of Bmax=14.31,
ASASSN-18bt is the nearest and brightest Supernovae Ia type (SNe Ia)
yet observed by the Kepler spacecraft. Here we present the discovery
of ASASSN-18bt, the K2 light curve, and prediscovery data from ASAS-SN
and the Asteroid Terrestrial-impact Last Alert System. The K2
early-time light curve has an unprecedented 30-minute cadence and
photometric precision for an SN Ia light curve, and it unambiguously
shows a ∼4 day nearly linear phase followed by a steeper rise. Thus,
ASASSN-18bt joins a growing list of SNe Ia whose early light curves
are not well described by a single power law. We show that a
double-power-law model fits the data reasonably well, hinting that two
physical processes must be responsible for the observed rise. However,
we find that current models of the interaction with a nondegenerate
companion predict an abrupt rise and cannot adequately explain the
initial, slower linear phase. Instead, we find that existing published
models with shallow 56Ni are able to span the observed behavior and,
with tuning, may be able to reproduce the ASASSN-18bt light curve.
Regardless, more theoretical work is needed to satisfactorily model
this and other early-time SNe Ia light curves. Finally, we use Swift
X-ray nondetections to constrain the presence of circumstellar
material (CSM) at much larger distances and lower densities than
possible with the optical light curve. For a constant-density CSM,
these nondetections constrain ρ<4.5x105cm-3 at a radius of
4x1015cm from the progenitor star. Assuming a wind-like environment,
we place mass loss limits of dM/dt<8x10-6M☉/yr for
νw=100km/s, ruling out some symbiotic progenitor systems. This
work highlights the power of well-sampled early-time data and the need
for immediate multiband, high-cadence follow-up for progress in
understanding SNe Ia.
Description:
ASASSN-18bt was discovered at RAJ2000=09:06:39.54, DEJ2000=+19:20:17.77
in V-band images obtained by the ASAS-SN unit "Brutus", located on
Haleakala in Hawaii on 2018 February 4.410 UT.
The All-Sky Automated Survey for SuperNovae (ASAS-SN; Shappee+ 2014,
J/ApJ/788/48) is an ongoing project which uses units of four 14cm
lenses on a common mount hosted by the Las Cumbres Observatory global
telescope network at multiple sites around the globe. After expanding
our network in 2017, we currently have five units located in Hawaii,
Chile, Texas, and South Africa, allowing us to observe the entire sky
every ∼20hr, weather permitting, to a depth of g∼18.5mag.
As part of the community effort to support K2 Campaign 16, ASAS-SN was
monitoring the K2 field with an increased cadence. The effort to
monitor the entire K2 field of view multiple times per day was
continued through Campaign 17 and will be extended to monitor the TESS
fields four to six times per day.
We performed forced photometry on the subtracted "Asteroid
Terrestrial-impact Last Alert System" (ATLAS) images of ASASSN-18bt
as described in Tonry+ (2018PASP..130f4505T 2018PASP..130f4505T). ATLAS scans the entire
sky accessible from Hawaii every few days using fully robotic 0.5m
f/2 Wright Schmidt telescopes located on the summit of Haleakala and
at Mauna Loa Observatory. The ATLAS telescopes use two broad filters:
the "cyan" filter (c) covering 420-650nm and the "orange" filter
(o) covering 560-820nm.
Objects:
-----------------------------------------------------
RA (ICRS) DE Designation(s)
-----------------------------------------------------
09 06 39.54 +19 20 17.7 ASASSN-18bt = SN 2018oh
-----------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 37 3654 Photometric observations
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See also :
B/eso : ESO Science Archive Catalog (ESO, 1991-2020)
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
J/ApJ/699/L139 : Spectral parameters of SNe Ia (Wang+, 2009)
J/AJ/139/120 : Low-redshift Type-Ia supernovae (Folatelli+, 2010)
J/ApJ/721/1608 : Absolute UV magnitudes of type Ia SNe (Brown+, 2010)
J/ApJS/200/12 : CfA4: light curves for 94 type Ia SNe (Hicken+, 2012)
J/other/Sci/340.170 : Classifications of 188 SNe Ia (Wang+, 2013)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJ/799/105 : KELT light curve of the M82 SN 2014J (Siverd+, 2015)
J/MNRAS/453/3649 : Photometric data for ASASSN-15ed (Pastorello+, 2015)
J/ApJ/826/144 : Follow-up observations of SNIa ASASSN-14lp (Shappee+, 2016)
J/MNRAS/455/2918 : Photom. & line luminosities for ASASSN-14li (Holoien+, 2016)
J/MNRAS/463/3813 : ASASSN-15oi UBVI M2W1W2 light curves (Holoien+, 2016)
J/A+A/607/A127 : 2014-2017 photom. for ASASSN-13db (Sicilia-Aguilar+, 2017)
J/ApJ/836/25 : Swift UVOT light curves of ASASSN-15lh (Margutti+, 2017)
J/A+A/610/A14 : ASASSN-15lh MUSE host spectroscopy (Kruehler+, 2018)
J/A+A/629/A57 : Supernova ASASSN-14jb light curves and spectra (Meza+, 2019)
J/MNRAS/490/718 : 109 SNe & their 104 hosts properties (Barkhudaryan+, 2019)
J/ApJ/870/L1 : K2 obs. of type Ia supernova SN 2018oh (Dimitriadis+, 2019)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.3 d JD Julian date of the observation; JD-2450000
10- 11 A2 --- Band Magnitude band of observation (K2, V, g, o) (1)
13 A1 --- l_mag Limit flag on magnitude
15- 20 F6.3 mag mag [14.2/21.2] Apparent magnitude
22- 26 F5.3 mag e_mag [0.001/0.8]? Error on mag
28- 37 A10 --- Tel Telescope identifier (ASAS-SN, ATLAS, K2)
--------------------------------------------------------------------------------
Note (1): V-band photometry is calibrated in the Vega magnitude system. The
Kepler and SDSS g-band photometry are calibrated in the AB magnitude
system.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Li et al. 2019ApJ...870...12L 2019ApJ...870...12L
Dimitriadis et al. 2019ApJ...870L...1D 2019ApJ...870L...1D Cat. J/ApJ/870/L1
(End) Prepared by [AAS], Coralie Fix [CDS] 20-Jan-2020