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The international campaign "Photometry and Spectroscopy" of P Cygni. ASPA. Active Spectroscopy in Astronomy. Ernst Pollmann eMail: [email protected] http://www.astrospectroscopy.de. 1. LBV - Characteristics

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Aspa

The international campaign

"Photometry and Spectroscopy"

of P Cygni

ASPA

Active Spectroscopy

in Astronomy

Ernst Pollmann

eMail: [email protected]

http://www.astrospectroscopy.de


Aspa

1


Aspa

  • LBV - Characteristics

    • the most absolute massive and brightest supergiants withmore than 50 solar masses. They go through a very unstable phase with

    • strong variations in brigthness, in color and in their spectra

    • Gravity and pressure don´t keep balanced

    • The stars are unstable

    • They develop strong solar wind (10-3  solar masses per year)

    • Envelope around the star

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Photometric Variability

Irregular brigthness variations

Small rapid changes at about 0.01 mag in few hours

Slow changes in the order of 2 mag in years to decades Occasional strong brightness outbursts

AG Carinae

R127

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Spectrum of P Cygni

HeI 6678

4


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Stellar wind of P Cygni

to the observer

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Spectrum of P Cygni

HeI 6678

6


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Time behavior of the Hα-Emission (Equivalent width)

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Period Analysis

Main period 1211 d

Phase plot

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Photometric V-Variation and Variation of the Hα-EW (Markova)

EW

V

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V (photometr.) [mag]

HαEW [Ǻ]

V (photometr.) [mag]

HαEW [Ǻ]

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  • The EW of a line is a measure of

    • the frequency of a element

    • the density of the gas

    • the temperatur of the layer in which it is developed

  • The Equivalent width indicates how much intensity an absorption line takes away from the continuum or an emission line adds to the continuum

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Intensität

Kontinuum

Wellenlänge [Å]

8000

7000

6000

5000

4000

3000

2000

Kontinuum

1000

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From the definition of EW

and the relation between stellar magnitudes and continuum flux variations

F2 / F1 = 10-0.4 (m2-m1)

it follows

the line flux is F = C * EW / 10 (0.4 Vphot)

Here is C a constant factor. In practice, we correct EW with a simple division by 10(0.4*Vphot)

Then the derived quantity is not the line flux in physical units, but a quantity proportional to the physical line flux, corrected for continuum variations

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Evidence of the independency of line flux F & V(photometr.)

F = EW/10^(0.4*V)

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The intrinsic Hα-line flux from Nov./2008 until today

16


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Stellar wind of P Cygni

to the observer

17


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The HeI6678-line in the spectrum of P Cygni

He6678-Region

18


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EW time behavior of the HeI 6678 absorption

Variable mass loss rate ?

19


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