J/ApJ/734/67 Circumstellar emission measures with Keck (Millan-Gabet+, 2011)
Exozodiacal dust levels for nearby main-sequence stars: a survey with the Keck
Interferometer Nuller.
Millan-Gabet R., Serabyn E., Mennesson B., Traub W.A., Barry R.K.,
Danchi W.C., Kuchner M., Stark C.C., Ragland S., Hrynevych M., Woillez J.,
Stapelfeldt K., Bryden G., Colavita M.M., Booth A.J.
<Astrophys. J., 734, 67 (2011)>
=2011ApJ...734...67M 2011ApJ...734...67M
ADC_Keywords: Interferometry ; Stars, nearby ; Infrared sources
Keywords: circumstellar matter - techniques: high angular resolution -
zodiacal dust
Abstract:
The Keck Interferometer Nuller (KIN) was used to survey 25 nearby
main-sequence stars in the mid-infrared, in order to assess the
prevalence of warm circumstellar (exozodiacal) dust around nearby
solar-type stars. The KIN measures circumstellar emission by spatially
blocking the star but transmitting the circumstellar flux in a region
typically 0.1-4AU from the star. We find one significant detection
(η Crv), two marginal detections (γ Oph and α Aql),
and 22 clear non-detections. Using a model of our own solar system's
zodiacal cloud, scaled to the luminosity of each target star, we
estimate the equivalent number of target zodis needed to match our
observations. Our three zodi detections are η Crv (1250±260),
γ Oph (200±80), and α Aql (600±200), where the
uncertainties are 1σ. The 22 non-detected targets have an
ensemble weighted average consistent with zero, with an average
individual uncertainty of 160 zodis (1σ). These measurements
represent the best limits to date on exozodi levels for a sample of
nearby main-sequence stars. A statistical analysis of the population
of 23 stars not previously known to contain circumstellar dust
(excluding η Crv and γ Oph) suggests that, if the
measurement errors are uncorrelated (for which we provide evidence)
and if these 23 stars are representative of a single class with
respect to the level of exozodi brightness, the mean exozodi level for
the class is <150 zodis (3σ upper limit, corresponding to 99%
confidence under the additional assumption that the measurement errors
are Gaussian). We also demonstrate that this conclusion is largely
independent of the shape and mean level of the (unknown) true
underlying exozodi distribution.
Description:
Observations of the 25 systems targeted (2 "high dust": with known
debris disk emission and 23 "low dust": without known debris disk
emission) took place in service mode during the period 2008
February-2009 January, over 32 nights; at the Keck Interferometer
Nuller (KIN), in N band (8.0-13.0um). Table 1 describes our list of
observed targets, including all the brightnesses relevant to the
various KIN subsystems, and the stellar parameters relevant to our
modeling approach.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 131 25 Target list
table3.dat 93 78 Log of observations and calibrated leak data
(wideband channel 8-9 microns)
table4.dat 66 234 Number of zodis for each observation and each
zodi disk orientation
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See also:
V/130 : Geneva-Copenhagen Survey of Solar neighbourhood III (Holmberg+, 2009)
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
V/89 : Ages, Metallicities, Galactic Orbit of F stars (Marsakov+ 1995)
J/ApJS/181/62 : Survey of young solar analogs (Metchev+, 2009)
J/ApJ/705/89 : IRS spectra of solar-type stars (Lawler+, 2009)
J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008)
J/ApJ/660/1556 : Characterization of dusty debris disks (Rhee+, 2007)
J/ApJ/636/1098 : Debris disks around solar-type stars (Bryden+, 2006)
J/ApJ/620/1010 : Spitzer 24µm photometry of A dwarfs (Rieke+, 2005)
J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)
J/ApJS/152/261 : Chromospheric Ca II emission in nearby stars (Wright+, 2004)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Target name
15- 17 A3 --- --- [HIP]
18- 23 I6 --- HIP Hipparcos designation
25- 30 A6 --- SpT MK spectral type (1)
32- 33 I2 h RAh Hour of right ascension (J2000)
35- 36 I2 min RAm Minute of right ascension (J2000)
38- 41 F4.1 s RAs Second of right ascension (J2000)
43 A1 --- DE- Sign of declination (J2000)
44- 45 I2 deg DEd Degree of declination (J2000)
47- 48 I2 arcmin DEm Arcminute of declination (J2000)
50- 53 F4.1 arcsec DEs Arcsecond of declination (J2000)
55- 57 F3.1 mag Vmag V-band magnitude (1)
59- 61 F3.1 mag Jmag J-band magnitude (1)
63- 65 F3.1 mag Kmag K-band magnitude (1)
67- 70 F4.1 Jy N N band (8.0-13.0um) flux from KIN
(Keck Interferometer Nuller)
72- 76 F5.2 pc Dist Star distance (1)
78- 81 F4.2 Rsun R* Star radius (1)
83- 88 F6.3 Lsun L* Star luminosity (1)
90- 93 I4 K T* Star temperature (1)
95- 97 F3.1 mas theta Apparent iameter θ from NExScI/fBol
(validated with surface brightness relations)
99-101 F3.1 mas e_theta theta uncertainty
103-106 F4.2 Gyr Age ? Age or lower limit in age if range given
107 A1 --- --- [-]
108-111 F4.1 Gyr Age2 ? Upper limit in age if range given
113-116 F4.2 AU RHz Radius of the center of the habitable zone
118-129 A12 --- Comm Comment
131 I1 --- r_Age ? Age reference (2)
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Note (1): Stellar data from NStED.
Note (2): Age reference as follows:
1 = Valenti & Fischer 2005, Cat. J/ApJS/159/141;
2 = Wright et al. 2004, Cat. J/ApJS/152/261;
3 = Mamajek & Hillenbrand 2008, Cat. J/ApJ/687/1264;
4 = Rieke et al. 2005, Cat. J/ApJ/620/1010;
5 = Vizier online data catalog V/89 (Marsakov & Shevelev 1995BICDS..47...13M 1995BICDS..47...13M);
6 = Holmberg et al. 2009, Cat. V/130;
7 = Rhee et al. 2007, Cat. J/ApJ/660/1556;
8 = Bryden et al. 2006, Cat. J/ApJ/636/1098
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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- 13 A13 --- Name Source name
15- 25 A11 "YYYY/MMM/DD" Date UT date of the observation
27- 31 F5.2 h HA Hour Angle
33- 39 F7.4 m u The u long baseline spatial frequency
41- 47 F7.4 m v The v long baseline spatial frequency
49- 57 F9.6 --- Lcal Measured calibrated leak (G1)
59- 66 F8.6 --- e_Lcal Formal uncertainty in Lcal
68- 75 F8.6 --- sigL External uncertainty in Lcal
77- 84 F8.6 --- L* Leak expected from target star (G1)
86- 93 F8.6 --- e_L* Uncertainty in L*
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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- 13 A13 --- Name Source name
15- 25 A11 "YYYY/MMM/DD" Date UT date of the observation
27- 31 F5.2 h HA Hour Angle
33- 36 F4.1 deg i Disk inclination
38- 42 F5.1 deg PA Disk position angle
44- 47 I4 --- zij "Leak" measured in zodis (G1) (1)
49- 52 I4 --- e_zij Uncertainty in zodis from formal error in
leak (G1)
54- 56 I3 --- sigj Uncertainty in zodis from external error
in leak (G1)
58- 60 I3 --- sig* Uncertainty in zodis from the error in
stellar leak (G1)
62- 66 F5.2 AU Rhl Half-light radius
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Note (1): a "zodi" is the unit used to measure the brightness distribution
of a zodiacal dust disk in external planetary systems: at 1zodi, the
dust has the same optical depth at 1 AU and radial density profile as
in the solar system. The values zij are given for each observation and
for each disk orientation.
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Global Notes:
Note (G1): the "leak" or "flux leakage" measures the transmitted flux due
to dust surrounding the central target stars; it is the inverse of
"null depth", i.e. leak=0.01 corresponds to a null depth of 100:1.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 23-Nov-2012