J/A+A/616/A124 NGC 3105 UBVR photometry (Alonso-Santiago+, 2018)
NGC 3105: a young open cluster with low metallicity.
Alonso-Santiago J., Marco A., Negueruela I., Tabernero H.M., Castro N.,
Mc Bride V.A., Rajoelimanana A F.
<Astron. Astrophys. 616, A124 (2018)>
=2018A&A...616A.124A 2018A&A...616A.124A (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Photometry, UBVRI
Keywords: open clusters and associations: individual: NGC 3105 -
Hertzsprung-Russell and C-M diagrams - stars: fundamental parameters -
stars: abundances - stars: late-type - stars: emission-line, Be
Abstract:
NGC 3105 is a young open cluster hosting blue, yellow, and red
supergiants. This rare combination makes it an excellent laboratory
for constraining evolutionary models of high-mass stars. It has been
poorly studied, and the fundamental parameters such as its age or
distance are not well defined.
We intend to characterise in an accurate way the cluster and its
evolved stars, for which we derive for the first time atmospheric
parameters and chemical abundances.
We performed a complete analysis combining UBVR photometry with
spectroscopy. We obtained spectra with classification purposes for 14
blue stars and high-resolution spectroscopy for an in-depth analysis
of the six other evolved stars.
We identify 126 B-type likely members within a radius of
2.7±0.6arcmin, which implies an initial mass, Mcl~=4100M☉. We
find a distance of 7.2±0.7kpc for NGC 3105, placing it at
RGC=10.0±1.2kpc. Isochrone fitting supports an age of 28±6Ma,
implying masses around 9.5M{aun} for the supergiants. A high
fraction of Be stars (∼25%) is found at the top of the main sequence
down to spectral type b3. From the spectral analysis we estimate for
the cluster an average vrad=+46.9±0.9km/s and a low metallicity,
[Fe/H]=-0.29±0.22. We also have determined, for the first time,
chemical abundances for Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y, and Ba
for the evolved stars. The chemical composition of the cluster is
consistent with that of the Galactic thin disc. An overabundance of Ba
is found, supporting the enhanced s-process.
NGC 3105 has a low metallicity for its Galactocentric distance,
comparable to typical LMC stars. It is a valuable spiral tracer in a
very distant region of the Carina-Sagittarius spiral arm, a poorly
known part of the Galaxy. As one of the few Galactic clusters
containing blue, yellow, and red supergiants, it is massive enough to
serve as a test bed for theoretical evolutionary models close to the
boundary between intermediate- and high-mass stars.
Description:
UBVR photometry of stars in the field of the cluster NGC 3105 taken
with EFOSC2 on the NTT 3.6-m telescope at the La Silla observatory
(Chile) during three consecutive nights in 2013, from Jan 31 to Feb 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 100 607 UBVR photometry
tablea2.dat 17 126 Spectral types, Q index and colour excess
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See also:
J/MNRAS/327/23 : CCD UBVRI photometry of 7 open star clusters (Sagar+, 2001)
J/A+A/443/157 : CCD photometry in 6 open clusters (Paunzen+, 2005)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/607] ID number
5- 17 F13.9 deg RAdeg Right ascension (J2000)
19- 31 F13.9 deg DEdeg Declination (J2000)
33- 38 F6.3 mag Vmag Johnson V-magnitude band
40- 44 F5.3 mag e_Vmag rms uncertainty on Vmag
46- 50 F5.3 mag B-V Johnson (B-V) colour index
52- 56 F5.3 mag e_B-V rms uncertainty on (B-V)
58- 63 F6.3 mag U-B Johnson (U-B) colour index
65- 69 F5.3 mag e_U-B rms uncertainty on (U-B)
71- 75 F5.3 mag V-R Johnson (V-R) colour index
77- 81 F5.3 mag e_V-R rms uncertainty on (V-R)
83 I1 --- N Number of measurements for each star
85-100 A16 --- 2MASS ?=- 2MASS ID (HHMMSSss+DDMMSSs)
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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- 3 I3 --- ID ID number
5- 9 F5.2 --- Q Q index
11- 12 A2 --- SpType Spectral type
14- 17 F4.2 mag E(B-V) Colour excess
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Acknowledgements:
Javier Alonso-Santiago, javier.alonso(at)ua.es
(End) J. Alonso-Santiago [Univ. Alicante, Spain], P. Vannier [CDS] 07-May-2018