J/A+A/632/L6 AT 2018hso light curves and spectra (Cai+, 2019)
The transitional gap transient AT 2018hso:
new insights into the luminous red nova phenomenon.
Cai Y-Z., A. Pastorello, M. Fraser, Prentice S.J., Reynolds T.M.,
Cappellaro E., Benetti S., Morales-Garoolo A., Reguitti A., Elias-Rosa N.,
Brennan S., Callis E., Cannizzaro G., Fiore A., Gromadzki M.,
Galindo-Guil F.J., Gall C., Heikkilae T., Mason E., Moran S., Onori F.,
Sagues Carracedo A., Valerin G.
<Astron. Astrophys. 632, L6 (2019)>
=2019A&A...632L...6C 2019A&A...632L...6C (SIMBAD/NED BibCode)
ADC_Keywords: Supernovae ; Stars, variable ; Photometry, SDSS ;
Photometry, UBVRI ; Photometry, infrared ; Spectroscopy
Keywords: binaries: close - stars: winds, outflows - stars: massive -
supernovae: individual: AT 2018hso -
supernovae: individual: AT 2017jfs -
supernovae: individual: NGC4490-2011OT1
Abstract:
The absolute magnitudes of luminous red novae (LRNe) are intermediate
between those of novae and supernovae (SNe), and show a relatively
homogeneous spectro-photometric evolution. Although they were thought
to derive from core instabilities in single stars, there is growing
support for the idea that they are triggered by binary interaction
that possibly ends with the merging of the two stars.
AT 2018hso is a new transient showing transitional properties between
those of LRNe and the class of intermediate-luminosity red transients
(ILRTs) similar to SN 2008S. Through the detailed analysis of the
observed parameters, our study support that it actually belongs to the
LRN class and was likely produced by the coalescence of two massive
stars.
We obtained ten months of optical and near-infrared photometric
monitoring, and 11 epochs of low-resolution optical spectroscopy of AT
2018hso. We compared its observed properties with those of other ILRTs
and LRNe. We also inspected the archival Hubble Space Telescope (HST)
images obtained about 15 years ago to constrain the progenitor
properties.
The light curves of AT 2018hso show a first sharp peak
(reddening-corrected Mr=13.93mag), followed by a broader and
shallower second peak that resembles a plateau in the optical bands.
The spectra dramatically change with time. Early-time spectra show
prominent Balmer emission lines and a weak [CaII] doublet, which is
usually observed in ILRTs. However, the strong decrease in the
continuum temperature, the appearance of narrow metal absorption
lines, the great change in the Hα strength and profile, and the
emergence of molecular bands support an LRN classification. The
possible detection of a MI∼8mag source at the position of AT 2018hso
in HST archive images is consistent with expectations for a pre-merger
massive binary, similar to the precursor of the 2015 LRN in M101.
We provide reasonable arguments to support an LRN classification for
AT 2018hso. This study reveals growing heterogeneity in the
observables of LRNe than has been thought previously, which is a
challenge for distinguishing between LRNe and ILRTs. This suggests
that the entire evolution of gap transients needs to be monitored to
avoid misclassifications.
Description:
Photometry tables for a peculiar luminous red nova AT 2018hso.
Objects:
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RA (2000) DE Designation(s)
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11 33 51.96 +53 07 07.10 AT 2018hso
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 119 56 Optical (BVugriz) light curves of AT 2018hso
tablea2.dat 61 12 Near-infrared (NIR) JHK light curves of
AT 2018hso
list.dat 143 11 List of fits files
fits/* . 11 Individual fits files
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 "date" Date Date of observation (yyyy/mm/dd)
12- 20 F9.3 d MJD Modified Julian Date
22 A1 --- l_Bmag Limit flag on Bmag
23- 28 F6.3 mag Bmag ? Johnson-Cousins B band magnitude
30- 34 F5.3 mag e_Bmag ? Johnson-Cousins B band magnitude error
36 A1 --- l_Vmag Limit flag on Vmag
37- 42 F6.3 mag Vmag ? Johnson-Cousins V band magnitude
44- 48 F5.3 mag e_Vmag ? Johnson-Cousins V band magnitude error
50 A1 --- l_umag Limit flag on umag
51- 56 F6.3 mag umag ? Sloan u band magnitude
58- 62 F5.3 mag e_umag ? Sloan u band magnitude error
64 A1 --- l_gmag Limit flag on gmag
65- 70 F6.3 mag gmag ? Sloan g band magnitude
72- 76 F5.3 mag e_gmag ? Sloan g band magnitude error
78 A1 --- l_rmag Limit flag on rmag
79- 84 F6.3 mag rmag ? Sloan r band magnitude
86- 90 F5.3 mag e_rmag ? Sloan r band magnitude error
92 A1 --- l_imag Limit flag on imag
93- 98 F6.3 mag imag ? Sloan i band magnitude
100-104 F5.3 mag e_imag ? Sloan i band magnitude error
106-111 F6.3 mag zmag ? Sloan z band magnitude
113-117 F5.3 mag e_zmag ? Sloan z band magnitude error
119 I1 --- Tel [1/4] Telescope numerical code (1)
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Note (1): Telescope numerical code as follows:
1 = ZTF (https://www.ztf.caltech.edu) data from the Palomar 1.2-m Oschin
Telescope equipped with ZTF-Cam, taken from Lasair (Smith et al., 2019;
Lasair: https://lasair.roe.ac.uk/object/ZTF18acbwfza) and
Transient Name Server (TNS; https://wis-tns.weizmann.ac.il/object/2018hso)
2 = The 2m fully automatic Liverpool Telescope
(LT; http://telescope.livjm.ac.uk) equipped with IO:O, located at Roque
de los Muchachos Observatory (La Palma, Canary Islands, Spain)
3 = The 2.56m Nordic Optical Telescope (NOT; http://www.not.iac.es) equipped
with ALFOSC, located at Roque de los Muchachos Observatory
(La Palma, Canary Islands, Spain)
4 = The 10.4m Gran Telescopio Canarias (GTC; http://www.gtc.iac.es) with
OSIRIS, located at Roque de los Muchachos Observatory
(La Palma, Canary Islands, Spain)
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 "date" Date Date of observation (yyyy/mm/dd)
12- 20 F9.3 d MJD Modified Julian Date
22- 27 F6.3 mag Jmag NIR J band magnitude
29- 33 F5.3 mag e_Jmag NIR J band magnitude error
35- 40 F6.3 mag Hmag ? NIR H band magnitude
42- 46 F5.3 mag e_Hmag ? NIR H band magnitude error
48- 53 F6.3 mag Kmag ? NIR K band magnitude
55- 59 F5.3 mag e_Kmag ? NIR K band magnitude error
61 I1 --- Tel [1] Telescope numerical code (1)
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Note (1): Telescope numerical code as follows:
1 = NOTCAM: The 2.56m Nordic Optical Telescope (NOT) equipped with NOTCAM,
located at Roque de los Muchachos Observatory
(La Palma, Canary Islands, Spain).
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Nx Number of pixels along X-axis
6 I1 --- Ny ? Number of slices, for the multi-spectra
8- 30 A23 "datime" Obs.date Observation date
32- 38 F7.2 0.1nm blambda Lower value of wavelength interval
40- 47 F8.2 0.1nm Blambda Upper value of wavelength interval
49- 55 F7.5 0.1nm dlambda Wavelength resolution
57- 58 I2 Kibyte size Size of FITS file
60-110 A51 --- FileName Name of FITS file, in subdirectory fits
112-143 A32 --- Title Title of the FITS file
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Acknowledgements:
Yongzhi Cai, yongzhi.cai(at)studenti.unipd.it
(End) Patricia Vannier [CDS] 25-Nov-2019