J/MNRAS/537/1763 B-type stars in NGC 6834 (Ruiz Diaz+, 2025)
A comprehensive photometric and spectroscopic study of B-type stars in the
open cluster NGC 6834.
Ruiz Diaz M.A., Aidelman Y.J., Baume G., Granada A.
<Mon. Not. R. Astron. Soc. 537, 1763 (2025)>
=2025MNRAS.537.1763R 2025MNRAS.537.1763R (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, Be ; Photometry ; Optical ;
Equivalent widths ; Rotational velocities
Keywords: stars: emission-line, Be - stars: fundamental parameters -
open clusters and associations: individual (NGC 6834)
Abstract:
This study focuses on the open cluster NGC 6834. Despite being
well-known, its primary parameters show considerable variation. As an
intermediate-age cluster (50-80 million years), it is expected to host
a prominent population of B-type stars, including numerous Be stars.
Fifteen B-type variable stars have already been identified in the
vicinity of the cluster, with four confirmed as Be stars through
spectroscopic observations. Our spectrophotometric analysis aims to
better understand the general and specific properties of NGC 6834,
with particular emphasis on its B-type stars. Photometric data were
gathered from gri images obtained with the Gemini North telescope,
which was completed with several photometric catalogs. Additionally,
109 optical spectra for 89 stars in the cluster's region were
obtained using the GMOS-MOS spectrograph. From the photometric data,
we derive the foreground cluster color excess, E(B-V)=0.62.
Through photometric diagrams, including traditional color-color and
color-magnitude diagrams and those incorporating the reddening-free
$Q$ parameter, we identify new stars with $Hα$ emission. Spectral
classification of 89 stars is achieved, along with estimations of
basic physical parameters, and projected rotational velocities for 64
B-type stars. We identify five new Be stars: NGC 6834 3, 9, and 118 as
cluster members, and NGC 6834 23 and 121 as non-members. The research
contributes to a deeper understanding of the structure of NGC 6834 and
its B-type star population.
Description:
Table 2: Photometric magnitudes and errors for the studied stars,
including coordinates, 2MASS identifications, and the source catalog
of the gri magnitudes (IGAPS, APASS, or GMOS). The table provides
UgriHalpha magnitudes with their respective errors.
Table 4: Fundamental stellar parameters derived in this work,
including spectral type, effective temperature (Teff), surface gravity
(logg) with errors, absolute visual magnitude (MV), bolometric
correction (BC), and intrinsic color ((B-V)0). Also included are
2MASS and Funfschilling (1967ZA.....66..440F 1967ZA.....66..440F) identifications,
g magnitudes from Table 2, and membership classification from
Hunt & Reffert (2023A&A...673A.114H 2023A&A...673A.114H, Cat. J/A+A/673/A114).
Table 5: Absolute griHalpha magnitudes, Extinction AgriHalpha values
and color excesses E(g-r), E(r-Halpha) and E(r-i), as well as the
corresponding coordinates of the stars with spectroscopic
observations. 2MASS and Funfschilling (1967ZA.....66..440F 1967ZA.....66..440F)
identifications are included.
Table 9: Measured equivalent widths (EW) and full width at half
maximum (FWHM) for MgII λ4481Å, HeI λ5875Å, HeI
λ4471Å and HeI λ6678Å along with the derived vsini
values and their errors. 2MASS and Funfschilling (1967ZA.....66..440F 1967ZA.....66..440F)
identifications are included.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 159 40945 Photometric data
table4.dat 102 90 Spectral classification and fundamental parameters
for stars with GMOS spectroscopic observations
table5.dat 137 63 Extinction and absorption values for sample stars
table9.dat 157 89 EW and FWHM measured values for MgII4481Å and
HeIi5875Å, and derived vsini values
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 14 F14.10 deg RAdeg Right ascension (J2000)
16- 28 F13.10 deg DEdeg Declination (J2000)
30- 48 A19 --- Name 2MASS identifier (if available)
JHHMMSS.ss+DDMMSS.s
50- 63 A14 --- SourceID IGAPS identifier (if available)
NNNNNN-N-NNNNN
65- 69 A5 --- Source Source catalog of the gri magnitudes
71- 78 F8.3 mag Umag ?=9999.999 U magnitude
80- 87 F8.3 mag e_Umag ?=9999.999 Error in U magnitude
89- 96 F8.3 mag gmag ?=9999.999 g magnitude
98-105 F8.3 mag e_gmag ?=9999.999 Error in g magnitude
107-114 F8.3 mag rmag ?=9999.999 r magnitude
116-123 F8.3 mag e_rmag ?=9999.999 Error in r magnitude
125-132 F8.3 mag imag ?=9999.999 i magnitude
134-141 F8.3 mag e_imag ?=9999.999 Error in i magnitude
143-150 F8.3 mag Hamag ?=9999.999 Halpha magnitude
152-159 F8.3 mag e_Hamag ?=9999.999 Error in Halpha magnitude
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- NGC6834 ? Funfschilling (1967ZA.....66..440F 1967ZA.....66..440F)
identification, NGC 6834 NNN in Simbad
5- 20 A16 --- 2MASS 2MASS identification, HHMMSSss+DDMMSSs
22- 23 I2 h RAh Right ascension (J2000)
25- 26 I2 min RAm Right ascension (J2000)
28- 32 F5.2 s RAs Right ascension (J2000)
34 A1 --- DE- Declination sign (J2000)
35- 36 I2 deg DEd Declination (J2000)
38- 39 I2 arcmin DEm Declination (J2000)
41- 44 F4.1 arcsec DEs Declination (J2000)
46- 50 F5.2 mag gmag g magnitude
52- 59 A8 --- SpType MK spectral type
61- 65 I5 K Teff ? Effective temperature
67- 69 I3 K e_Teff ? Error in effective temperature
71- 75 F5.2 [Sun] logg ? Surface gravity
77- 81 F5.2 [Sun] e_logg ? Error in surface gravity
83- 87 F5.2 mag VMAG ? Absolute visual magnitude
89- 93 F5.2 mag BC ? Bolometric correction
95- 99 F5.2 mag (B-V)0 ? Intrinsic color index
101-102 A2 --- Member [m nm] Membership to the cluster,
m = member, nm = not member
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- ID Funfschilling (1967ZA.....66..440F 1967ZA.....66..440F)
identification, NGC 6834 NNN or 2MASS id
25- 40 A16 --- 2MASS 2MASS identification, HHMMSSss+DDMMSSs
42- 46 F5.2 mag gMAG Absolute g magnitude
48- 52 F5.2 mag Ag Extinction in g band
54- 58 F5.2 mag rMAG Absolute r magnitude
60- 64 F5.2 mag Ar Extinction in r band
66- 70 F5.2 mag iMAG Absolute i magnitude
72- 76 F5.2 mag Ai Extinction in i band
78- 82 F5.2 mag HaMAG Absolute Halpha magnitude
84- 88 F5.2 mag AHa Extinction in Halpha band
90- 94 F5.2 mag E(g-r) Excess in (g-r) colour
96-100 F5.2 mag E(r-Ha) Excess in (r-Ha) colour
102-106 F5.2 mag E(r-i) Excess in (r-i) colour
108-122 F15.11 deg RAdeg Right ascension (J2000)
124-137 F14.11 deg DEdeg Declination (J2000)
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- NGC6834 ? Funfschilling (1967ZA.....66..440F 1967ZA.....66..440F)
identification, NGC 6834 NNN in Simbad
5- 20 A16 --- 2MASS 2MASS ID, HHMMSSss+DDMMSSs
22- 26 F5.2 0.1nm EW4471 ? HeI 4471Å equivalent width
28- 32 F5.2 0.1nm e_EW4471 ? Error in HeI 4471Å equivalent width
34- 38 F5.2 0.1nm FWHM4471 ? HeI 4471Å FWHM
40- 44 F5.2 0.1nm e_FWHM4471 ? Error in HeI 4471Å FWHM
46- 50 F5.2 0.1nm EW4481 ? MgII 4481Å equivalent width
52- 56 F5.2 0.1nm e_EW4481 ? Error in MgII 4481Å equivalent width
58- 62 F5.2 0.1nm FWHM4481 ? MgII 4481Å FWHM
64- 68 F5.2 0.1nm e_FWHM4481 ? Error in MgII 4481Å FWHM
70- 74 F5.2 0.1nm EW5875 ? HeI 5875Å equivalent width
76- 80 F5.2 0.1nm e_EW5875 ? Error in HeI 5875Å equivalent width
82- 87 F6.2 0.1nm FWHM5875 ? HeI 5875Å FWHM
89- 93 F5.2 0.1nm e_FWHM5875 ? Error in HeI 5875Å FWHM
95- 99 F5.2 0.1nm EW6678 ? HeI 6678Å equivalent width
101-105 F5.2 0.1nm e_EW6678 ? Error in HeI 6678Å equivalent width
107-112 F6.2 0.1nm FWHM6678 ? HeI 6678Å FWHM
114-118 F5.2 0.1nm e_FWHM6678 ? Error in HeI 6678Å FWHM
120-122 I3 km/s vsini ? Rotational velocity vsini derived
124-126 I3 km/s e_vsini ? Error in vsini derived
128-142 F15.11 deg RAdeg Right ascension (J2000)
144-157 F14.11 deg DEdeg Declination (J2000)
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Acknowledgements:
Matias Ruiz Diaz, matiruizdiaz(at)fcaglp.unlp.edu.ar
(End) Matias Ruiz Diaz [IALP-UNLP, Argentina] Patricia Vannier [CDS] 11-Feb-2025