J/A+A/612/A50 New massive members of Cygnus OB2 (Berlanas+, 2018)
New massive members of Cygnus OB2.
Berlanas S.R., Herrero A., Comeron F., Pasquali A., Motta C.B., Sota A.
<Astron. Astrophys., 612, A50 (2018)>
=2018A&A...612A..50B 2018A&A...612A..50B (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Stars, OB ; Effective temperatures
Keywords: stars: early-type - stars: massive -
open clusters and associations: individual: Cygnus OB2 -
Hertzsprung-Russell and C-M diagrams - Galaxy: stellar content
Abstract:
The Cygnus complex is one of the most powerful star forming regions at
a close distance from the Sun (∼1.4kpc). Its richest OB association
Cygnus OB2 is known to harbor many tens of O-type stars and hundreds
of B-type stars, providing a large homogeneous population of OB stars
that can be analyzed. Many studies of its massive population have been
developed in the last decades, although the total number of OB stars
is still incomplete.
Our aim is to increase the sample of O and B members of Cygnus OB2 and
its surroundings by spectroscopically classifying 61 candidates as
possible OB-type members of Cygnus OB2, using new intermediate
resolution spectroscopy.
We have obtained intermediate resolution (R∼5000) spectra for all of
the OB-type candidates between 2013 and 2017. We thus performed a
spectral classification of the sample using HeI-II and metal lines
rates, as well as the Marxist Ghost Buster (MGB) software for O-type
stars and the IACOB standards catalog for B-type stars.
From the whole sample of 61 candidates, we have classified 42 stars as
new massive OB-type stars, earlier than B3, in Cygnus OB2 and
surroundings, including 11 O-type stars. The other candidates are
discarded as they display later spectral types inconsistent with
membership in the association. We have also obtained visual
extinctions for all the new confirmed massive OB members, placing them
in a Hertzsprung-Russell Diagram using calibrations for Teff and
luminosity. Finally, we have studied the age and extinction
distribution of our sample within the region.
We have obtained new blue intermediate-resolution spectra suitable for
spectral classification of 61 OB candidates in Cygnus OB2 and
surroundings. The confirmation of 42 new OB massive stars (earlier
than B3) in the region allows us to increase the young massive
population known in the field. We have also confirmed the correlation
between age and Galactic longitude previously found in the region. We
conclude that many O and early B stars at B>16mag are still
undiscovered in Cygnus.
Description:
The bulk of stars were observed in July 2016, obtaining spectra of 47
candidates. We have chosen the R1200B grating of IDS (EEV10) on the
Isaac Newton Telescope (INT) in La Palma, which provides a resolution
of ∼5000 at 4500 . The remaining stars were observed in different runs
between 2013 and 2017, at the William Herschel Telescope (WHT) using
the AF2/WYFFOS and ISIS instruments, and at the Gran Telescopio
CANARIAS (GTC) using the OSIRIS instrument. Out of the whole sample,
three of the stars (J20301097+4120088, J20315433+4010067,
J20345785+4143543) belong to the Galactic O-Star Spectroscopic Survey
(GOSSS) catalog (Maiz Apellaniz et al. 2016ApJS..224....4M 2016ApJS..224....4M).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 54 44 Temperatures, luminosities, and individual visual
extinctions derived for the new classified
massive OB stars
tablea2.dat 80 179 Temperatures and luminosities derived for the
known massive OB stars from
Comeron & Pasquali (2012, Cat. J/A+A/543/A101)
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See also:
III/274 : Galactic O-Star Spectroscopic Survey, GOSSS (Sota+, 2014)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Sample Sample (Cygnus OB2 or Surroundings)
14- 30 A17 --- Name Object name
32- 38 A7 --- SpType MK spectral type
40- 44 I5 K Teff Effective temperature
46- 49 F4.2 [Lsun] LogL Luminosity
51- 54 F4.1 mag AV Absorption in V band
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Sample Sample (Cygnus OB2, Cygnus OB9 or Boundaries)
14- 30 A17 --- Name Object name
32- 33 I2 h RAh Right ascension (J2000)
35- 36 I2 min RAm Right ascension (J2000)
38- 43 F6.3 s RAs Right ascension (J2000)
45 A1 --- DE- Declination sign (J2000)
46- 47 I2 deg DEd Declination (J2000)
49- 50 I2 arcmin DEm Declination (J2000)
52- 56 F5.2 arcsec DEs Declination (J2000)
58- 69 A12 --- SpType MK spectral type
71- 75 I5 K Teff Effective temperature
77- 80 F4.2 [Lsun] LogL Luminosity
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 19-Jun-2018