Simultaneous Photometry and Spectroscopy of the B2/E Variable Star HD45677

(1)

SIML.;1TAI{EOUS PHO?OMETRY _AI{DSPECTR.OSCOPY

R,

Barbier, N.

Klutz,

A.

Ins

titut

D tAstrophysique,

Belgiun.

ASSTRÀCT

Light varlations

are

observed

for

HD 45677

_ln the

vlsible, lf

they

are

due Èo obscuration

by

clrcunstellar

patchy

dust

clouds,

part

of

the

stellar

lIV and

vislble

radiatlons

are

back-scattered

inside

the extended atmosphere surrounding

the

star.

The

excitatlon

of

a1l

ats@

and

lons

in

the

envel-ope

is

Èhus

affected,

and

the

resu}t

is

seen qssl

for

the

atoms novi-ng towards

the

observer:

the

lntenslty

variatlong

_of

the blue

emi-sslon wings

of

the

Baloer

lines ln

opposlte phaee wlth

slmultaneous

varlations

of

the

sÈe1lar

flux

are therefore

rrnderstandab1..

The

full

paPer showing

the

data

and

giving correlations

betweeo

equivalenr

width

and magnltudes

and/or colours

ts

presently

in

preparâ!:,j! and

will

be publlshed elsewhere.

DISCUSSION

t

Ë

OF fEE

82(e)

VARIABLE STltt __. ;rn _..",_.-â

TffË

Ë

*

SurdeJ

_{, J.}

SurdeJ and J .

p.

_Srrr,

_-,

_$

Universlte

Ce

Liege,

-"F

_Ë AB s!{

D.

ALLEN: SWINGS:

D.

ALLEN: SWINGS: SMAK: SWINGS: ÂBBYATIGR:

-SWINGS:

If

the

scale

of

your

last

sl1de

1s

rlght, I

donrt

see |É*

the

material- behlnd

the

star

shouldnrt

also

be affeclet

by

the backscatterlng.

The sÈar

isnft blg

eaough to

occult

lt all.

The

great

volume

of

gas

_{in front of}

the

star

absorbô

the

backscaÈtered radiaÈion.

Youtre saylng

_{that it ls opticatty ttri,ct,}

then?

Afunost,

at

least

between

the

sÈar and

the

dust

coodeâ'

satLon reaponsible

for

the

backscattering.

Are there

any

IR data

available

on HD 45677 Ehat coçii be used

to

say more about

the

dust. envelope?

Yes, an energy

dlstrlbuÈlon

of

Lû

456t-7

in

the

visll'r

and

in

the near

infrared

has been published by Sr1n**

and

Allen

(Ap.J.

Lerr.,

L57,

L

41,

1971);

it

shovs

:'f

.=

presence

of

a

strong

IR

excess due

to

theroal

reraci;sl:'

in

a dust

shell (or ring)

surrounding

_æ

45677.

*..é_'a

; :

*

How do you

get

_dust

_near

_{a hot}

_Be

_atar

_l1ke

_HD

45677?

The

strong

p

cygnl

profiles

lndicate

luporÈaut o,qss Loss from

rhe

srar.

_{Ar euffLclently laige ài"a"o"""}

there

_{can be an}_accretl.on_phenooenon_and

formatlon of

eflfns ar

rempererures gOOôx _and

_{Lower. ff,e}

à"sc

will

probably _{appear Ln condensations and}_w111

_not

be

unlfornrly

_dlstributed

_in

_a

_rlng

_around

_the

_obJect.