J/A+A/686/A142 NGC 2516 members Surface modulation period (Li+, 2024)
Asteroseismology of the young open cluster NGC 2516.
I. Photometric and spectroscopic observations.
Li G., Aerts C., Bedding T.R., Fritzewski D.J., Murphy S.J., Van Reeth T.,
Montet B.T., Jian M., Mombarg J.S.G., Gossage S., Sreenivas K.R.
<Astron. Astrophys. 686, A142 (2024)>
=2024A&A...686A.142L 2024A&A...686A.142L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, early-type ; Asteroseismology ; Optical
Keywords: asteroseismology - stars: early-type - stars: interiors -
stars: oscillations - stars: rotation
Abstract:
Asteroseismic modelling of isolated stars presents significant
challenges due to the difficulty in accurately determining stellar
parameters, particularly the stellar age. These challenges can be
overcome by observing stars in open clusters whose coeval members
share an initial chemical composition. The light curves from the
all-sky survey by the Transiting Exoplanet Survey Satellite (TESS)
allow us to investigate and analyse stellar variations in clusters
with an unprecedented level of detail for the first time.
We aim to detect gravity-mode oscillations in the early-type
main-sequence members of the young open cluster NGC 2516 to deduce
their internal rotation rates.
We selected the 301 member stars with no more than mild contamination
as our sample. We analysed the full-frame image light curves, which
provide nearly continuous observations in the first and third years of
TESS monitoring. We also collected high-resolution spectra using the
Fiber-fed Extended Range Optical Spectrograph for the g-mode
pulsators, with the aim of assessing the Gaia effective temperatures
and gravities and preparing for future seismic modelling.
By fitting the theoretical isochrones to the colour-magnitude diagram
of a cluster, we determined an age of 102±15Myr and inferred that
the extinction at 550nm (A0) is 0.53±0.0mag. We identified
147 stars with surface-brightness modulations: 24 with gravity
(g-)mode pulsations (γ Doradus or slowly pulsating B-type stars)
and 35 with pressure (p-)mode pulsations (δ Sct stars). When
sorted by colour index, the amplitude spectra of the δ Sct stars
show a distinct ordering and reveal a discernible
frequency-temperature relationship. The near-core rotation rates,
measured from period spacing patterns in two slowly pulsating B-type
(SPB) stars and nine γ Dor stars, reach up to 3d-1. This is at
the high end of the values found from Kepler data of field stars of
similar variability type. The γ Dor stars of NGC 2516 have
internal rotation rates as high as 50% of their critical value,
whereas the SPB stars exhibit rotation rates close to their critical
rate. Although the B-type stars are rotating rapidly, we did not find
long-term brightness and colour variations in the mid-infrared, which
suggests that there are no disc or shell formation events in our
sample. We also discussed the results of our spectroscopic
observations for the g-mode pulsators.
Description:
In this work, we conducted the first asteroseismic study of the young
open cluster NGC 2516 from an observational perspective.
We used the TESS data in Cycle 1 and Cycle 3 to conduct photometry and
obtained the light curves of the member stars.
The surface modulation signals observed in 147 stars offer direct
measurements of surface rotation rates.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 46 147 Surface modulation periods for NGC 2516
cluster member stars in this study
param.dat 355 301 Stellar parameters of the NGC 2516 cluster
member stars
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- TIC TIC number of stars with surface modulations
11- 16 F6.3 --- BP-RP Gaia colour index, BP-RP
18- 23 F6.4 d-1 Freq Measured surface rotation frequency
25- 30 F6.4 d-1 e_Freq Measured surface rotation frequency error
32- 38 F7.5 d Per Period
40- 46 F7.5 d e_Per Period error
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Byte-by-byte Description of file: param.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 source ID
21- 29 I9 --- TIC TIC number
31- 44 F14.10 deg RAdeg Gaia right ascension (ICRS) at Ep=2016.0
46- 59 F14.10 deg DEdeg Gaia declination (ICRS) at Ep=2016.0
61- 70 F10.7 mag Gmag Gaia G band magnitude
72- 80 F9.7 mag e_Gmag Gaia G band magnitude uncertainty
82- 91 F10.7 mag GMAG Gaia G band absolute magnitude,
without the correction of extinction
93-101 F9.7 mag e_GMAG Gaia G band absolute magnitude uncertainty
103-112 F10.7 [Lsun] logL log of luminosity, calculated by Gaia
effective temperature, with the bolometric
correction and extinction correction.
Use with caution
114-122 F9.7 [Lsun] e_logL log of luminosity uncertainty
124-130 F7.1 K Teff Effective temperature provided by Gaia.
Use with caution
132-136 F5.1 K e_Teff Effective temperature uncertainty (1)
138-147 F10.7 mag BP-RP Gaia colour index
149-157 F9.7 mag e_BP-RP Gaia colour index uncertainty
159-165 F7.1 K Teffsp Effective temperature by FEROS spectra,
better than Tegg, only available for nine
stars
167-172 F6.1 K e_Teffsp ?=9999 Effective temperature by FEROS
spectra uncertainty
174-185 F12.7 [Lsun] logLsp ?=9999 log of luminosity calculated by
Teffsp, with the bolometric correction and
extinction correction, better than logL
187-198 F12.7 [Lsun] e_logLsp ?=9999 log of luminosity calculated by
Teffsp uncertainty
200-207 F8.3 [cm/s2] logg ?=9999 Surface gravity by FEROS spectra,
only available for nine stars
209-216 F8.3 [cm/s2] e_logg ?=9999 Surface gravity uncertainty
218-223 F6.1 km/s vsini ?=9999 Projected equatorial velocity by
FEROS spectra, only available for nine stars
225-230 F6.1 km/s e_vsini ?=9999 Projected equatorial velocity
uncertainty
232-239 F8.3 [-] [M/H] ?=9999 Metallicity by FEROS spectra,
only available for nine stars
241-248 F8.3 [-] e_[M/H] ?=9999 Metallicity by FEROS spectra
uncertainty
250-255 F6.1 km/s RVsp ?=9999 Radial velocity by FEROS spectra,
only available for nine stars
257-262 F6.1 km/s e_RVsp ?=9999 Radial velocity by FEROS spectra
uncertainty
264-270 F7.2 km/s Vmic ?=9999 Microturbulent velocity by FEROS
spectra, only available for nine stars
272-292 F21.16 km/s e_Vmic ?=9999 Microturbulent velocity by FEROS
spectra uncertainty
294-299 F6.1 d-1 S/N ?=9999 Signal-to-noise ratio of the FEROS
spectra
301-306 F6.1 --- Pi0 ?=9999 Asymptotic spacing of g modes,
measured by g modes,
only available for 11 stars
308-313 F6.1 --- e_Pi0 ?=9999 Asymptotic spacing of g modes
uncertainty
315-324 F10.5 d-1 dP/dt ?=9999 Near-core rotation rate, measured by
g modes, only available for 11 stars
326-335 F10.5 d-1 e_dP/dt ?=9999 Near-core rotation rate uncertainty
337-345 F9.4 --- Per ?=9999 Surface rotation period measured by
surface modulations
347-355 F9.4 --- e_Per ?=9999 Surface rotation period uncertainty
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Note (1): A uncertainty value of '100' means the temperature is absent by Gaia,
so we use the temperature from the TIC input catalog
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 05-Aug-2024