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The Photometric and Spectral Evolution of the 2008 NGC 300 Transient Roberta M. Humphreys University...
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Transcript of The Photometric and Spectral Evolution of the 2008 NGC 300 Transient Roberta M. Humphreys University...
The Photometric and Spectral Evolution of the 2008 NGC 300 Transient
Roberta M. Humphreys
University of Minnesota
Prieto 2008 fromSpitzer 2003, 2007
Discovery April 24, 2008 by Monard
Smarts 1.3m BVRIJHK May 15 – Jun 22, 2009
1.5m spectroscopy May 15 - Jan 22, 2009
Magellan MagE July 6, Aug 30/Sep 1 2008, Jun 05, 2009
The progenitor
Basic Properties
Pre-eruption IR SED => Lsun = 5.5 x 104 Lsun, Mbol = -7.1 mag
Maximum light mv = 14.7 mag => Mv = -12.1 or -12.9 mag, Av = 0.3 or 1.2
Increased luminosity by ~ 100 times or more
Spectrum at max, F-type supergaint abs line + H, Ca II, [Ca II] emission
Total emitted energy ~ 1047 ergs
Mass of progenitor ? 10 – 15 Msun
The Spectral Energy Distribution
7500 K BB, f-f, 715 K dust
R* max = 10AU
Rdust = 1750 AU = 10 light days
Dust survived the initial eruption
L* = 1.3 x 107 Lsun
observed corrected
Evolution of the Spectrum – the Eruption
Berger et al. 2009 Bond et al. 2009
F-type supergiant spectrum expected in an eruption forming optically thick wind
At max – complex Ca II profiles, Vel (em and abs) ~ 400 km/s, FWHM of H ~ 1000 km/s
The Double-Peaked Hydrogen and Ca II Emission Lines
bipolar/asymmetric outflow –
expansion
Ca II primary 79 km/s
secondary 164 km/s
Hydrogen primary 69 km/s
secondary ~ 200 km/s
Evolution of the Spectrum – Post-Eruption
Ca II and [Ca II] Emission
The Asymmetric [Ca II] profiles Thomson scattering
Auer and Van Blerkom 1972 demonstrated effect of electron scattering on profiles in expanding ejecta for recombination lines -- asymmetric profiles with red wings.
Hillier 1991
Other Emission Lines
He I 5876 + other weak em 7065, 6678, 3964, 3888
O I 8446 -- Ly pumping, by flourescence
[O I] 6300, 6363
Fe II
[Fe II]
The Absorption Line Spectrum
O I 7774 (lum sensitive ~ -6.9 Mv )
Sr II, Ca I, Mn I, Ti II, V II
Double Ca II H and K
Ba II : 4554, 4934
Rapid transition from absorption to emission Jul 18 (abs) Sep 08 (em)
Expanding envelope becoming transparent to ionizing radiation
Na I D (also O I 8446, Berger et al. )
Clues from the Velocities
Max . 15 May Em. and abs. ~ 400 km s-1
Post-eruption --
Double-peaked profiles ( abs min.Ca II and H) 200 +/- 2.7 km s-1 (14)
Emission lines (Aug/Sep) 200 +/- 4.4 km s-1 (40)
Absorption lines (July) 180 +/- 1.7 km s-1 (33)
Expected Vel galactic rotation 190 km s-1
Eruption and Post – Eruption
Maximum – redshifted vel ~ 400 km/s expansion ~ 500 km/s,
Post-eruption – 20 – 30d -- shift to lower vel abs and em lines
Initial eruption followed by a dense slowly expanding false photosphere and asymmetrical bipolar outflow
Abs lines weaken, transition to em (Na I and O I)
100d dense wind becomes transparent to ionizing radiation
Thoughts on the nature of the N300 Transient and origin of instability
Progenitor (IR SED) a high mass loss state, tip of AGB or supergiant OH/IR star
lack of IRAC variability, outflow velocity (75 km s-1) post AGB/RSG
Outflow vel. greater than AGB/RSG, lower S Dor vars.
Initial mass -- Lum 10-15Msun, 13-17Msun CMD (Gogarten et al. 2009)
PAH feature/ Ba II? post AGB, proto-PNe, lower initial mass
But no carbon bands: CH, CN, C2
Origin of the ionizing radiation
Intermediate-mass post -AGB/RSG on a blue loop
Other members of this sub-group
SN2008S
SN2010da
SN2010dn
M85 2006 OT?
M31 RV X
At Maximum:
F-type supergiant spectrum, Ca II and [Ca II] em, dusty progenitors, increased 100 – 1000 times in luminosity
NGC 300 2008 OT SN2008s SN2010da
Optically obscured, “cool” transients
Prieto 2008 Prieto et al 2008 Khan et al., Berger et al. 2010
T= 350K BB L = 5.5 x 104 Lsun, Mbol = -7.1 mag
at maximumMv = -12.1 or -12.9 mag
L = 1.1 x 107 Lsun
T= 440K BB
L = 3.5 x 104 Lsun Mbol = -6.8 mag
at maximum Mv = -13.6 mag
L = 3 x 107 Lsun
T= 890 K BB
L = 1.3 x 104 Lsun
Mbol = -5.5 mag
at maximum Mv = -10.4 mag
L = 1.1 x 106 Lsun
In “eruption” increased 100 – 1000 times
SN2010da spectrum
H em, [N II], He I, O I,
Ca II ? No [Ca II] !
He II 4686 !
ATEL 2637 (Chornock & Berger)
The spectra
These are not LBVs !
Outstanding Theoretical Problems in Massive Star Research
A future meeting --
Minnesota Institute for Astrophysics and
Fine Theoretical Physics Institute
University of Minnesota October 2012
IMPOSTOR !
A candidate for membership?
UGC 2773 2009 OT
At max ~ 107 Lsun
Increased 22.8 -> 17.5 mR
Progenitor -7.8 Mv
Color -> ~ A-type 1.3 x 105 Lsun
~ 20Msun (CMD)