J/AJ/154/31 λ Bootis stars: the southern survey I. (Gray+, 2017)
The discovery of λ Bootis stars: the southern survey I.
Gray R.O., Riggs Q.S., Koen C., Murphy S.J., Newsome I.M., Corbally C.J.,
Cheng K.-P., Neff J.E.
<Astron. J., 154, 31-31 (2017)>
=2017AJ....154...31G 2017AJ....154...31G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, peculiar ; Stars, early-type ; Spectral types ;
Effective temperatures ; Abundances ; Reddening
Keywords: circumstellar matter - stars: chemically peculiar -
stars: early-type - stars: emission-line, Be - stars: evolution
Abstract:
The λ Boo stars are a class of chemically peculiar Population I
A-type stars characterized by under-abundances of the refractory
elements, but near-solar abundances of carbon, nitrogen, oxygen, and
sulfur. There is some evidence that λ Boo stars have higher
frequencies of "bright" debris disks than normal A-type stars. The
discovery of four exoplanets orbiting HR8799, a λ Boo star with
a resolved debris disk, suggests that the λ Boo phenomenon may
be related to the presence of a dynamic debris disk, perhaps perturbed
by migrating planets. However, only 64 λ Boo stars are known,
and those stars were discovered with different techniques, making it
problematic to use that sample for statistical purposes, including
determining the frequency of debris disks. The purpose of this paper
is to derive a new sample of λ Boo stars using a technique that
does not lead to biases with respect to the presence of infrared
excesses. Through spectroscopic observations in the southern
hemisphere, we have discovered 33 λ Boo stars and have
confirmed 12 others. As a step toward determining the proportion of
λ Boo stars with infrared excesses, we have used WISE data to
examine the infrared properties of this sample out to 22µm. On this
basis, we cannot conclude that λ Boo stars have a greater
tendency than normal A-type stars to show infrared excesses. However,
observing this sample at longer wavelengths may change that
conclusion, as many λ Boo debris disks are cool and do not
radiate strongly at 22µm.
Description:
Observations were carried out with the South African Astronomical
Observatory (SAAO) SpCCD grating spectrograph, attached to the SAAO
1.9m telescope. Grating 6 was employed, which yields a resolution of
about 2Å/2 pixels and a spectral range from 3600 to 5400Å. Time
was granted for four observing runs of about 5 days each in 2013
December, and 2014 March, June, and September, enabling us to cover
the entire southern sky. A total of 291 program stars, plus a number
of MK standards, were observed over the four runs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 88 207 TYCHO sample: spectral types, models, E(B-V),
and infrared excesses
table2.dat 88 84 Miscellaneous sample: spectral types, models,
E(B-V), and infrared excesses
table3.dat 92 29 TYCHO sample infrared excesses
table4.dat 147 37 Miscellaneous sample infrared excesses
note1.dat 771 13 TYCHO sample: notes on individual stars
note2.dat 1085 15 Miscellaneous sample: notes on individual stars
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See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
J/other/PASA/32.36 : λ Boo star membership evaluations (Murphy+, 2015)
J/MNRAS/410/190 : Young runaway stars within 3kpc (Tetzlaff+, 2011)
J/ApJS/188/473 : Chandra variable guide star catalog (Nichols+, 2010)
J/AJ/140/184 : RAVE double-lined spec. binaries (Matijevic+, 2010)
J/ApJS/168/277 : HK-Survey field HB candidates (Beers+, 2007)
J/AJ/132/161 : NStars project: The southern sample. I. (Gray+, 2006)
J/AJ/126/2048 : NStars project: the Northern Sample. I. (Gray+, 2003)
J/A+A/373/625 : uvbyB photometry of lambda Bootis stars (Paunzen+, 2001)
J/ApJ/469/355 : Teff, B-V and BC relation (Flower, 1996)
J/ApJS/96/461 : Far-UV Point Sources from FAUST (Bowyer+ 1995)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- TYC1 [4712/9528] TYC1 of Tycho identifier
6- 10 I5 --- TYC2 [23/5115] TYC2 of Tycho identifier
12 I1 --- TYC3 [1] TYC3 of Tycho identifier
14- 23 A10 --- OName Other identifier
25- 54 A30 --- SpT Spectral type(s) (G1)
56- 60 I5 K Teff [6950/10800] Model effective temperature
62- 64 F3.1 [cm/s2] logg [3.3/4.2] Model log surface gravity
66- 69 F4.1 [Sun] [M/H] [-1.5/0.5] Model metallicity, relative to Sun
71- 75 F5.3 mag E(B-V) [0/0.231] Optical color excess
77- 83 A7 --- IR Infrared excess notes (I, Comp, Comp?, EB, n,
or W4<) (1)
85 A1 --- N [N] Indicates a note on an individual source
in Section 6.1.1 (see note1.dat file)
87- 88 A2 --- SB Indicates a Spectroscopic Binary
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Note (1): The infrared excess notes are defined as follows:
n = No significant infrared excess detected;
I = Infrared excess measurements (see Table3);
W4< = WISE W4 flux upper limit only;
Comp = Infrared excess can be attributed to a cooler companion;
Comp? = Infrared excess can probably be attributed to a cooler companion,
although there is no independent evidence for the existence of
that companion.
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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- 10 A10 --- Name Name (mostly Henry Draper identifier)
12- 21 A10 --- OName Other identifier
23- 52 A30 --- SpT Spectral type(s) (G1)
54- 58 I5 K Teff [6750/11500] Model effective temperature
60- 62 F3.1 [cm/s2] logg [3.3/4.2] Model log surface gravity
64- 67 F4.1 [Sun] [M/H] [-1.5/0.2] Model metallicity, relative to Sun
69- 73 F5.3 mag E(B-V) [0/0.462] Optical color excess
75- 79 A5 --- IR Infrared excess notes (I, I?, Comp, n,
or W4<) (1)
81 A1 --- N [N] Indicates a note on an individual source
in Section 6.2.1 (see note2.dat file)
83 I1 --- Mm ? λ Boo membership evaluation
(1, 2, 3, or 4) (2)
85- 88 A4 --- Note Other notes (EB, SB, VB, and/or u) (G2)
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Note (1): The infrared excess notes are defined as follows:
n = No significant infrared excess detected;
I = Infrared excess measurements (see Table4);
W4< = WISE W4 flux upper limit only;
Comp = Infrared excess can be attributed to a cooler companion;
Comp? = Infrared excess can probably be attributed to a cooler companion,
although there is no independent evidence for the existence of
that companion.
Note (2): λ Boo evaluations given in Murphy et al. 2015
(Cat. J/other/PASA/32.36) are designated as follows:
1 = Member;
2 = Probable member;
3 = Uncertain member;
4 = Non-member;
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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- 4 I4 --- TYC1 [4868/9431] TYC1 of Tycho identifier
6- 10 I5 --- TYC2 [232/3603] TYC2 of Tycho identifier
12 I1 --- TYC3 [1/1] TYC3 of Tycho identifier
14- 40 A27 --- SpT Spectral type
42- 46 A5 --- JHK If an excess is detected in one or more
2MASS bands, that band is noted (G3)
48- 51 F4.2 --- W1 [0.08/0.2]? Infrared excess (E) in WISE W1 band (G4)
53- 55 F3.1 --- Ns1 [3.9/6.8]? Number of standard deviations by which
the observed flux exceeds the theoretical flux
(σ; see Section 5 in the text)
57- 60 F4.2 --- W2 [0.11/0.2]? Infrared excess (E) in WISE W2 band (G4)
62- 64 F3.1 --- Ns2 [5.4/8.4]? Number of standard deviations by which
the observed flux exceeds the theoretical flux
(σ; see Section 5 in the text)
66- 69 F4.2 --- W3 [0.1/1.16]? Infrared excess (E) in WISE W3 band (G4)
71- 74 F4.1 --- Ns3 [2.7/12]? Number of standard deviations by which
the observed flux exceeds the theoretical flux
(σ; see Section 5 in the text)
76- 79 F4.2 --- W4 [0.2/2.4]? Infrared excess (E) in WISE W4 band (G4)
81- 83 F3.1 --- Ns4 [2/6.1]? Number of standard deviations by which
the observed flux exceeds the theoretical flux
(σ; see Section 5 in the text)
85 A1 --- l_W4 [<] Upper limit flag on W4
87 A1 --- N [N] Indicates a note on an individual source
in Section 6.1.1 (see note1.dat file)
89- 92 A4 --- Note Other notes (d, d?, EB, and/or SB) (G2)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name (mostly Henry Draper identifier)
12- 39 A28 --- SpT Spectral type
41- 45 A5 --- JHK If an excess is detected in one or more
2MASS bands, that band is noted (G3)
47- 86 A40 --- n_JHK Note on JHK
88- 92 F5.2 --- W1 [0.1/12]? Infrared excess (E) in WISE W1 band (G4)
94- 97 F4.1 --- Ns1 [4/27]? Number of standard deviations by which
the observed flux exceeds the theoretical
flux (σ; see Section 5 in the text)
99-103 F5.2 --- W2 [0.1/29]? Infrared excess (E) in WISE W2 band (G4)
105-108 F4.1 --- Ns2 [2.3/40]? Number of standard deviations by which
the observed flux exceeds the theoretical
flux (σ; see Section 5 in the text)
110-115 F6.2 --- W3 [0.1/208]? Infrared excess (E) in WISE W3 band (G4)
117-121 F5.1 --- Ns3 [4.4/155]? Number of standard deviations by which
the observed flux exceeds the theoretical
flux (σ; see Section 5 in the text)
123-129 F7.2 --- W4 [0.1/2199]? Infrared excess (E) in WISE W4 band (G4)
131-135 F5.1 --- Ns4 [2.3/181]? Number of standard deviations by which
the observed flux exceeds the theoretical
flux (σ; see Section 5 in the text)
137 A1 --- l_W4 [<] Upper limit flag on W4
139 A1 --- N [N] Indicates a note on an individual source
in Section 6.2.1 (see note2.dat file)
141-147 A7 --- Note Other notes (Algol, d, EB, EB?, d?, or/and VB) (G2)
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Byte-by-byte Description of file: note1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [TYC]
5- 8 I4 --- TYC1 TYC1 of Tycho identifier
9 A1 --- --- [-]
10- 14 I5 --- TYC2 TYC2 of Tycho identifier
15 A1 --- --- [-]
16 I1 --- TYC3 TYC3 of Tycho identifier
18-771 A754 --- Note Notes
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Byte-by-byte Description of file: note2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star name
12-1085 A1074 --- Note Notes
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Global Notes:
Note (G1): The full spectral type of a λ Bootis star consists of three
spectral types: the hydrogen-line type, the Ca II K-line type, and a
metallic-line type; a luminosity class; and the designation "λ Boo".
Stars that appear to be mild λ Boo stars are designated as
"(λ Boo)". Very mild members of the class have designations
"((λ Boo))".
Note (G2): Double star designations are designated as follows:
EB = Eclipsing Binary;
SB = Spectroscopic Binary;
VB = Visual Binary;
u = uvbyβ-selected (λ Boo) candidate;
d = The observed infrared excess can be attributed to the presence of a
cooler companion;
d? = The infrared excess is consistent with the presence of a cool
companion, although no independent evidence for that companion exists.
Note (G3): If an excess is detected in the J-band, the theoretical flux
distribution is normalized to the flux in the Johnson or Tycho V-band.
Note (G4): Measured as E=(Fobserved-Ftheoretical)/Ftheoretical).
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 02-Oct-2017