The Photometric and Spectral Evolution of the 2008 NGC 300 Transient
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The Photometric and Spectral Evolution of the 2008 NGC 300 Transient. Roberta M. Humphreys University of Minnesota. Discovery April 24, 2008 by Monard. Smarts 1.3m BVRIJHK May 15 – Jun 22, 2009 1.5m spectroscopy May 15 - Jan 22, 2009

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The Photometric and Spectral Evolution of the 2008 NGC 300 Transient

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The photometric and spectral evolution of the 2008 ngc 300 transient

The Photometric and Spectral Evolution of the 2008 NGC 300 Transient

Roberta M. Humphreys

University of Minnesota

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

Prieto 2008from

Spitzer 2003, 2007


The photometric and spectral evolution of the 2008 ngc 300 transient

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 photometric and spectral evolution of the 2008 ngc 300 transient

The Spectral Energy Distribution

7500 K BB, f-f, 715 K dust

L* = 1.3 x 107 Lsun

R* max = 10AU

Rdust = 1750 AU = 10 light days

Dust survived the initial eruption

observed

corrected


The photometric and spectral evolution of the 2008 ngc 300 transient

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 Ha ~ 1000 km/s


The photometric and spectral evolution of the 2008 ngc 300 transient

Evolution of the Spectrum – Post-Eruption

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


The photometric and spectral evolution of the 2008 ngc 300 transient

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


The photometric and spectral evolution of the 2008 ngc 300 transient

Other Emission Lines

The Absorption Line Spectrum

He I 5876 + other weak em 7065, 6678, 3964, 3888

O I 8446 -- Ly b pumping, by flourescence

[O I] 6300, 6363

Fe II

[Fe II]

O I 7774 (lum sensitive ~ -6.9 Mv )

Sr II, Ca I, Mn I, Ti II, V II

Ba II : 4554, 4934

Na I D (also O I 8446, Berger et al. )

Double Ca II H and K

Expanding envelope becoming transparent to ionizing radiation

Rapid transition from absorption

to emission

Jul 18 (abs)  Sep 08 (em)


The photometric and spectral evolution of the 2008 ngc 300 transient

Clues from the Velocities

Expected Vel galactic rotation 190 km s-1

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)


The photometric and spectral evolution of the 2008 ngc 300 transient

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


The photometric and spectral evolution of the 2008 ngc 300 transient

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


The photometric and spectral evolution of the 2008 ngc 300 transient

Intermediate-mass post -AGB/RSG on a blue loop


The photometric and spectral evolution of the 2008 ngc 300 transient

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


The photometric and spectral evolution of the 2008 ngc 300 transient

Optically obscured, “cool” transients

NGC 300 2008 OT SN2008s SN2010da

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 maximum

Mv = -12.1 or -12.9 mag

L = 1.1 x 107 Lsun

T= 440K BB

L = 3.5 x 104Lsun

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


The photometric and spectral evolution of the 2008 ngc 300 transient

The spectra

SN2010da spectrum

H em, [N II], He I, O I,

Ca II ? No [Ca II] !

He II 4686 !

ATEL 2637 (Chornock & Berger)


The photometric and spectral evolution of the 2008 ngc 300 transient

These are not LBVs !


The photometric and spectral evolution of the 2008 ngc 300 transient

A future meeting --

Outstanding Theoretical Problems in Massive Star Research

Minnesota Institute for Astrophysics and

Fine Theoretical Physics Institute

University of Minnesota

October 2012

IMPOSTOR !


The photometric and spectral evolution of the 2008 ngc 300 transient

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)


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