Issue |
Astron. Astrophys. Suppl. Ser.
Volume 140, Number 3, December II 1999
|
|
---|---|---|
Page(s) | 309 - 326 | |
DOI | https://doi.org/10.1051/aas:1999425 | |
Published online | 15 December 1999 |
A survey of blue –
objects in the galaxy M 33
Special Astrophysical Observatory of the Russian AS, Nizhnij Arkhyz 357147, Russia
Received:
18
June
1999
Accepted:
19
July
1999
For the purposes of a search for SS 433 type objects, LBV stars and
hypergiants in M 33, we have carried out a photometry of blue stars in
Hα images of this galaxy. From 2332 listed OB stars,
we have isolated 549 objects,
which have Hα excess over stars of the same V magnitude.
Among them 81 emission stars (s) have been selected. About 60%
of isolated objects found to be extended in , among them
154 diffuse (d) and
180 bubble–type (b) nebulae. 117 objects are compact (c) and faint
sources. These groups are different in colour indices,
fluxes, surface
brightness and sizes. The most probable size of the
nebulae is
pc. There is evidence that their properties and location
in the galaxy
are defined by interstellar gas pressure and related to
spiral arms. The d objects are H II regions with an embedded star.
The b objects are probably envelopes around WR stars or SN remnants.
Among s–type objects we isolated a group of 20 brightest stars, which in
their average properties fit well to the parameters of blue hypergiants
or LBV–type stars. The stars of intermediate brightness follow very
well to blue Ia supergiants. The interstellar absorption derived from
brightest
stars is
.
We classify the faintest stars as blue Ib supergiants, their average
absorption is
. They are restricted in
number by the limiting stellar magnitude in the original sample.
Key words: nearby galaxies: stellar content: individual (M 33): stars: early type / H∝ excess
© European Southern Observatory (ESO), 1999