J/A+A/344/943 Sh 138 BVRIJHK photometry (Deharveng+ 1999)
Sh 138: a compact HII region excited by a very young cluster
Deharveng L., Zavagno A., Nadeau D., Caplan J., Petit M.
<Astron. Astrophys. 344, 943 (1999)>
=1999A&A...344..943D 1999A&A...344..943D (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Photometry, UBVRIJKLMNH ; Clusters, open
Keywords: pre-main sequence - ISM:: HII regions -
ISM: individual objects: Sh 138 -
Galaxy: open clusters and associations: individual: Sh 138 -
infrared: stars
Abstract:
We present a photometric and spectroscopic study of the compact
HII region Sh 138 and its associated stellar cluster. The positions and
BVRIJHK magnitudes are obtained for more than 400 stars over a field
of about 4' square centred on the HII region. Sh 138 is excited by a
cluster of young massive stars. At the cluster's very centre are at
least four O-B2 stars separated by less than 4". The brightest of
these, both in the visible and the near infrared, exhibits a spectrum
similar to those of the more massive Herbig Ae/Be stars. This star,
our No. 183, is overluminous by a factor of 2.5 in the visible and
four in the near IR with respect to the O9.5V star required to account
for the ionization level of the HII region. However star 183's
position in the J-H versus H-K diagram does not indicate a near-IR
excess. We suggest that this star is a young massive object belonging
to a binary or multiple system. The stellar cluster associated with Sh
138 is very reminiscent of the Orion Trapezium cluster: it is
centrally peaked around several massive stars, and is dense - more
than 550stars/pc2 at its centre. The visual extinction in the
cluster varies between 5mag and more than 35mag; large variations are
observed over very small scales (for example, more than 20mag over
less than 4" among the central massive stars).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 96 424 Coordinates and photometry of all the stars
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Running number of the star
5- 10 F6.3 arcmin Xpos tangential coordinate (1)
12- 17 F6.3 arcmin Ypos tangential coordinate (1)
19- 20 I2 h RAh [22] Right ascension (J2000.0)
22- 23 I2 min RAm Right ascension (J2000.0)
25- 29 F5.2 s RAs Right ascension (J2000.0)
31 A1 --- DE- Declination sign (J2000.0)
32- 33 I2 deg DEd Declination (J2000.0)
35- 36 I2 arcmin DEm Declination (J2000.0)
38- 41 F4.1 arcsec DEs Declination (J2000.0)
43- 47 F5.2 mag Vmag ? V magnitude
49- 53 F5.2 mag B-V ? B-V colour index
55- 59 F5.2 mag V-R ? V-R colour index
61- 65 F5.2 mag R-I ? R-I colour index
67- 71 F5.2 mag V-I ? V-I colour index
73- 77 F5.2 mag Kmag ? K magnitude
79- 83 F5.2 mag J-K ? J-K colour index
85- 89 F5.2 mag J-H ? J-H colour index
91- 95 F5.2 mag H-K ? H-K colour index
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Note (1): Xpos and Ypos are with respect to RA=22h32m45.6s, Dec=58°28'16.8"
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Acknowledgements: James Caplan
(End) Patricia Bauer [CDS] 01-Feb-1999