J/ApJ/743/118 BVRIJHK photometry of the 2008 OT in NGC 300 (Humphreys+, 2011)
The photometric and spectral evolution of the 2008 luminous optical transient
in NGC 300.
Humphreys R.M., Bond H.E., Bedin L.R., Bonanos A.Z., Davidson K.,
Berto Monard L.A.G., Prieto J.L., Walter F.M.
<Astrophys. J., 743, 118 (2011)>
=2011ApJ...743..118H 2011ApJ...743..118H
ADC_Keywords: Galaxies, IR ; Photometry, UBVRI ; Photometry, infrared ;
Stars, variable
Keywords: galaxies: individual (NGC 300) - galaxies: stellar content -
stars: individual (NGC 300 OT2008-1) - stars: variables: general -
stars: winds, outflows - supernovae: general
Abstract:
The 2008 optical transient in NGC 300 is one of a growing class of
intermediate-luminosity transients that brighten several orders of
magnitude from a previously optically obscured state. The origin of
their eruptions is not understood. Our multi-wavelength photometry and
spectroscopy from maximum light to more than a year later provide a
record of its post-eruption behavior. We describe its changing
spectral energy distribution, the evolution of its absorption- and
emission-line spectrum, the development of a bipolar outflow, and the
rapid transition from a dense wind to an optically thin ionized wind.
In addition to strong, narrow hydrogen lines, the F-type
absorption-line spectrum of the transient is characterized by strong
CAII and [CAII] emission. The very broad wings of the CAII triplet and
the asymmetric [CAII] emission lines are due to strong Thomson
scattering in the expanding ejecta. Post-maximum, the hydrogen and
CaII lines developed double-peaked emission profiles that we attribute
to a bipolar outflow. Between approximately 60 and 100 days after
maximum, the F-type absorption spectrum, formed in its dense wind,
weakened and the wind became transparent to ionizing radiation. We
discuss the probable evolutionary state of the transient and similar
objects such as SN 2008S and conclude that they were most likely
post-red supergiants or post-asymptotic giant branch stars on a blue
loop to warmer temperatures when the eruption occurred. These objects
are not luminous blue variables.
Description:
The outburst was discovered by Monard (2008IAUC.8946....1M 2008IAUC.8946....1M) at
broadband magnitude 14.3, using his 0.3m telescope equipped with a CCD
camera, on a frame obtained on 2008 May 14 (UT). An earlier frame,
taken on 2008 April 24, and examined after discovery of the eruption,
showed the transient at ∼16.3mag. It was fainter than 18mag on 2008
February 8, and on all previous monitoring observations obtained by
Monard.
Our program of systematic photometric monitoring began on 2008 May 15.
These data were obtained by Chilean service observers with the 1.3m
SMARTS telescope at CTIO with the ANDICAM optical/near-IR direct
camera, which simultaneously obtains optical frames with a CCD
detector and near-IR frames with an IR detector. We used the BVRI
filters of the Johnson-Kron-Cousins system in the optical and standard
JHK filters for the near-IR.
Objects:
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RA (2000) DE Designation(s)
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00 54 34.16 -37 38 28.6 NAME NGC 300 OT2008-1 = NGC 3030OT
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table6.dat 66 110 SMARTS 1.3-m ANDICAM and Bronberg photometry of
NGC 300 OT2008-1
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See also:
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2013)
J/ApJ/715/1094 : Census of self-obscured massive stars (Khan+, 2010)
J/ApJ/705/1364 : MIR catalog of point sources in M33 (Thompson+, 2009)
J/AJ/128/1167 : ARAUCARIA project : NGC 300 Variables. II (Gieren+, 2004)
J/MNRAS/350/679 : BV photometry of NGC 300 variables (Mennickent+, 2004)
J/PASP/114/298 : BVI photometry in NGC 300 (Pietrzynski+, 2002)
Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 9 F9.3 d HJD Heliocentric Julian Date; HJD-2400000
11- 17 F7.3 d Day Elapsed days
19- 24 F6.3 mag Bmag ? The B band magnitude (1)
26- 31 F6.3 mag Vmag ? The V band magnitude (1)
33- 38 F6.3 mag Rmag ? The R band magnitude (1)
40- 45 F6.3 mag Imag ? The I band magnitude (1)
47- 52 F6.3 mag Jmag ? The J band magnitude (1)
54- 59 F6.3 mag Hmag ? The H band magnitude (1)
61- 66 F6.3 mag Kmag ? The K band magnitude (1)
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Note (1): First three lines are Bronberg (Klein Karoo Observatory)
discovery and pre-discovery observations, taken to be Landolt R
magnitudes. All other data from 1.3-m ANDICAM frames. Typical errors
are ±0.02-0.04mag until end of 2008 (HJD{~=}54830), increasing
thereafter to approximately ±0.1-0.2 mag as the transient faded.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 06-May-2013