J/A+A/633/A146 Radial velocities of stars in NGC 2546 (Alejo+, 2020)
The nature of NGC 2546: not one but two open clusters.
Alejo A.D., Gonzalez J.F., Veramendi M.E.
<Astron. Astrophys. 633, A146 (2020)>
=2020A&A...633A.146A 2020A&A...633A.146A (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Binaries, spectroscopic ; Radial velocities
Keywords: binaries: spectroscopic - stars: chemically peculiar -
open clusters and associations: individual: NGC 2546 -
techniques: radial velocities - surveys: Gaia
Abstract:
As part of a broader project on the role of binary stars in clusters,
we present a spectroscopic study of the open cluster NGC 2546, which
is a large cluster lacking previous spectroscopic analysis.
We report the finding of two open clusters in the region of NGC 2546.
For the two star groups, we determine radial velocity, parallax,
proper motion, reddening, distance modulus, and age, using our
spectroscopic observations and available photometric and astrometric
data, mainly from Gaia Data Release 2 (Gaia DR2). We also determine
the orbit of four spectroscopic binaries in these open clusters.
From mid-resolution spectroscopic observations for 28 stars in the
NGC 2546 region, we determined radial velocities and evaluate velocity
variability. To analyze double-lined spectroscopic binaries, we used a
spectral separation technique and fit the spectroscopic orbits using a
least-squares code.
The presence of two stellar groups is suggested by the radial velocity
distribution and confirmed by available photometric and astrometric
data. We applied a multi-criteria analysis to determine cluster
membership, and we obtained kinematic and physical parameters of the
clusters.
NGC 2546 is actually two clusters, NGC 2546A and NGC 2546B, the are
not physically related to each other. NGC 2546A has an age of about
180Myr and a distance of 950pc. It has a half-number radius of 8pc
and contains about 480 members brighter than G=18 mag. NGC 2546B is a
very young cluster (<10Myr) located at a distance of 1450pc. It is a
small cluster with 80 members and a half-number radius of 1.6pc.
Stars less massive than 2.5 solar masses in this cluster would be pre-
main-sequence objects. We detected four spectroscopic binaries and
determined their orbits. The two binaries of NGC 2546A contain
chemically peculiar components: HD 68693 is composed of two mercury-
manganese stars and HD 68624 has a Bp silicon secondary. Among the
most massive objects of NGC 2546B, there are two binary stars:
HD 68572, with P=124.2d, and CD -37 4344 with P=10.4d.
Description:
The spectroscopic analysis of NGC 2546 is based on 177 spectra
collected between the years 2000 and 2018. These observations were
carried out using the 2.15m telescope and the REOSC echelle
spectrograph at the CASLEO, San Juan, Argentina. The spectra cover the
wavelength range 3700-6300Å with a resolving power R=12400. The
data were reduced by using standard tasks of the NOAO/IRAF package.
The final steps of the data processing included combination of the
echelle orders, spectrum normalization, cosmic rays remotion, and
heliocentric velocity correction.
Radial velocity measurements for 28 bright stars in the region of
NGC 2546 are presented. The sample includes 25 spectroscopic single
stars (Table 2) whose velocities were measured by cross-correlations,
and three double-lined spectroscopic binaries (Table 3) for which a
spectral disentangling technique was applied.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 32 28 List of studied stars
table2.dat 25 123 Radial velocities of 25 single-lined stars
table3.dat 39 54 Radial velocities of 3 double-lined binaries
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Star Star identification number
5- 6 I2 h RAh Right ascension (J2000)
8- 9 I2 min RAm Right ascension (J2000)
11- 15 F5.2 s RAs Right ascension (J2000)
17 A1 --- DE- Declination sign (J2000)
18- 19 I2 deg DEd Declination (J2000)
21- 22 I2 arcmin DEm Declination (J2000)
24- 27 F4.1 arcsec DEs Declination (J2000)
29 A1 --- Flag [sd] Flag (1)
31- 32 I2 --- NRV Number of radial velocity measurements,
in table2 (single) or table3 (double)
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Note (1): Flag as follows:
s = single-lined star, RV in table2.dat
d = double-lined star, RV in table3.dat
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Star Star identification number
5- 13 F9.4 d HJD Heliocentric Julian Date (HJD-2450000)
15- 19 F5.2 km/s RV Radial velocity
21- 25 F5.2 km/s e_RV Radial velocity error
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Star Star identification number
5- 13 F9.4 d HJD Heliocentric Julian Date (HJD-2450000)
15- 20 F6.2 km/s RVA Radial velocity of component A
22- 26 F5.2 km/s e_RVA Error on RVA
28- 33 F6.2 km/s RVB Radial velocity of component B
35- 39 F5.2 km/s e_RVB Error on RVB
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Acknowledgements:
Antonio Damian Alejo, aalejo(at)unsj-cuim.edu.ar
(End) Antonio Damian Alejo [UNSJ, Argentina], Patricia Vannier [CDS] 22-Dec-2019