J/MNRAS/492/1008 NGTS clusters survey - I. Rotation in Blanco 1 (Gillen+, 2020)
NGTS clusters survey - I.
Rotation in the young benchmark open cluster Blanco 1.
Gillen E., Briegal J.T., Hodgkin S.T., Foreman-Mackey D., Van Leeuwen F.,
Jackman J.A.G., McCormac J., West R.G., Queloz D., Bayliss D., Goad M.R.,
Watson C.A., Wheatley P.J., Belardi C., Burleigh M.R., Casewell S.L.,
Jenkins J.S., Raynard L., Smith A.M.S., Tilbrook R.H., Vines J.I.
<Mon. Not. R. Astron. Soc., 492, 1008-1024 (2020)>
=2020MNRAS.492.1008G 2020MNRAS.492.1008G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, double and multiple ; Clusters, open ;
Photometry ; Spectral types ; Optical
Keywords: stars: rotation - stars: variables: general - binaries: general -
open clusters and associations: individual: Blanco 1
Abstract:
We determine rotation periods for 127 stars in the ∼115-Myr-old Blanco
1 open cluster using ∼200d of photometric monitoring with the Next
Generation Transit Survey. These stars span F5-M3 spectral types
(1.2M☉≳M≳0.3M☉) and increase the number of known
rotation periods in Blanco 1 by a factor of four. We determine
rotation periods using three methods: Gaussian process (GP)
regression, generalized autocorrelation function (G-ACF), and
Lomb-Scargle (LS) periodogram, and find that the GP and G-ACF methods
are more applicable to evolving spot modulation patterns. Between
mid-F and mid-K spectral types, single stars follow a well-defined
rotation sequence from ∼2 to 10d, whereas stars in photometric
multiple systems typically rotate faster. This may suggest that the
presence of a moderate-to-high mass ratio companion inhibits angular
momentum loss mechanisms during the early pre-main sequence, and this
signature has not been erased at ∼100Myr. The majority of mid-F to
mid-K stars display evolving modulation patterns, whereas most M stars
show stable modulation signals. This morphological change coincides
with the shift from a well-defined rotation sequence (mid-F to mid-K
stars) to a broad rotation period distribution (late-K and M stars).
Finally, we compare our rotation results for Blanco 1 to the similarly
aged Pleiades: the single-star populations in both clusters possess
consistent rotation period distributions, which suggests that the
angular momentum evolution of stars follows a well-defined pathway
that is, at least for mid-F to mid-K stars, strongly imprinted by
∼100Myr.
Description:
NGTS comprises twelve 20-cm wide-field roboticized telescopes situated
at the ESO Paranal Observatory in Chile. The facility is optimized to
detect small exoplanets orbiting K and early M stars (e.g. Bayliss et
al. 2018MNRAS.475.4467B 2018MNRAS.475.4467B; West et al. 2019MNRAS.486.5094W 2019MNRAS.486.5094W, Cat.
J/MNRAS/486/5094), and is designed to achieve mmag photometric
precision across each camera's 2.8° field of view (FoV).
Blanco 1 was observed using a single NGTS camera over a 195-night
baseline between 2017 May 7 and November 18. 201773 exposures were
obtained, at 13s cadence (with 10s exposures), on 134 nights within
this period. Of the 489 Blanco 1 members from Gaia Collaboration et
al. (2018A&A...616A..10G 2018A&A...616A..10G, Cat. J/A+A/616/A10), the NGTS FoV
encompassed 429 stars (88 per cent of the cluster members). The NGTS
band covers the 520-890nm range, and is therefore similar to a
combined R+I filter. We refer the interested reader to Wheatley et al.
(2018MNRAS.475.4476W 2018MNRAS.475.4476W) for further details on the NGTS filter and
pipeline.
The spectral types were estimated using updated information from
Pecaut & Mamajek (2013ApJS..208....9P 2013ApJS..208....9P, Cat. J/ApJS/208/9) based on
their intrinsic G-Ks and GBP-GRP colours.
We test three methods: Lomb-Scargle (LS) periodogram, generalized
autocorrelation function (G-ACF), and Gaussian process (GP) regression
(See section 3). These differ in their assumptions and complexity, and
hence in their appropriateness for estimating rotation periods from
photometric rotational modulation.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 166 127 Identification, photometric, multiplicity, and
period information for periodic Blanco 1 stars
table2.dat 96 43 Identification, photometric, and multiplicity
information for Blanco 1 stars without a
detected period
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/ApJS/208/9 : Intrinsic colors and temperatures of PMS stars (Pecaut+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [626/20343] Internal NGTS object identifier
7- 25 I19 --- GaiaDR2 Gaia DR2 source identifier
27- 28 I2 h RAh Right ascension (J2000)
30- 31 I2 min RAm Right ascension (J2000)
33- 38 F6.3 s RAs Right ascension (J2000)
40 A1 --- DE- Declination sign (J2000)
41- 42 I2 deg DEd Declination (J2000)
44- 45 I2 arcmin DEm Declination (J2000)
47- 52 F6.3 arcsec DEs Declination (J2000)
54- 58 F5.2 mag NGTSmag NGTS 520-890nm band magnitude (G1)
60- 64 F5.2 mag Gmag Gaia DR2 G band magnitude (G1)
66- 70 F5.2 mag BPmag Gaia DR2 BP band magnitude (G1)
72- 76 F5.2 mag RPmag Gaia DR2 RP band magnitude (G1)
78- 82 F5.2 mag Ksmag Ks-band magnitude (G1)
84- 87 F4.2 mag G-Ks G-Ks colour index (G1)
89- 92 A4 --- SpType Spectral type (G2)
94- 95 A2 --- Mult [c/r/cr/ ] Method used to determine the
multiplicity of the system (G3)
97-102 F6.2 10-3 ampdata Amplitude of the data (1)
104-109 F6.2 10-3 ampGP Amplitude of the GP model (1)
111-118 F8.5 d PGP Period estimate from GP regression
120-126 F7.5 d E_PGP Upper 1-σ error on PGP
128-134 F7.5 d e_PGP Lower 1-σ error on PGP
136-143 F8.5 d PLS Period estimate from Lomb-Scargle
145-152 F8.5 d PGACF ? Period estimate from G-ACF
154-157 A4 --- Method Method selected for final period (GP, LS or
GACF) (2)
159-166 F8.5 d Padop Period adopted
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Note (1): The amplitude is defined as the 10-90th percentile spread
Note (2): Method as follows:
GP = Gaussian process regression
LS = Lomb-Scargle periodogram
GACF = Generalized autocorrelation function
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- ID [3284/18932] Internal NGTS object identifier
7- 25 I19 --- GaiaDR2 Gaia DR2 source identifier
27- 28 I2 h RAh Right ascension (J2000)
30- 31 I2 min RAm Right ascension (J2000)
33- 38 F6.3 s RAs Right ascension (J2000)
40 A1 --- DE- Declination sign (J2000)
41- 42 I2 deg DEd Declination (J2000)
44- 45 I2 arcmin DEm Declination (J2000)
47- 52 F6.3 arcsec DEs Declination (J2000)
54- 58 F5.2 mag NGTSmag NGTS 520-890nm band magnitude (G1)
60- 64 F5.2 mag Gmag Gaia DR2 G band magnitude (G1)
66- 70 F5.2 mag BPmag Gaia DR2 BP band magnitude (G1)
72- 76 F5.2 mag RPmag Gaia DR2 RP band magnitude (G1)
78- 82 F5.2 mag Ksmag Ks-band magnitude (G1)
84- 88 F5.2 mag G-Ks G-Ks colour index (G1)
90- 93 A4 --- SpType Spectral type (G2)
95- 96 A2 --- Mult [c/r/cr/ ] Method used to determine the
multiplicity of the system (G3)
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Global Notes:
Note (G1): The magnitudes and colours quoted are as observed (not dereddened)
Note (G2): Spectral types are based purely on dereddened G-Ks colours and are
therefore estimates only. The spectral types of stars listed as B9*
are suspect because this is the earliest spectral type for which
G-Ks colours (and corresponding spectral types) are available. We
therefore advise caution when interpreting these.
Note (G3): Method as follows:
c = Colour-magnitude diagram
r = Radial velocity
cr = System that was highlighted as a likely multiple system by both methods
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 13-Mar-2023