J/ApJ/763/L33 Be-B concentrations in rare CB/CH chondrite (Gounelle+, 2013)
Variable and extreme irradiation conditions in the early solar system inferred
from the initial abundance of 10Be in Isheyevo CAIs.
Gounelle M., Chaussidon M., Rollion-Bard C.
<Astrophys. J., 763, L33 (2013)>
=2013ApJ...763L..33G 2013ApJ...763L..33G
ADC_Keywords: Abundances ; Atomic physics ; Solar system
Keywords: meteorites, meteors, meteoroids; protoplanetary disks;
Planet-star interactions; stars: protostars
Abstract:
A search for short-lived 10Be in 21 calcium-aluminum-rich inclusions
(CAIs) from Isheyevo, a rare CB/CH chondrite, showed that only 5 CAIs
had 10B/11B ratios higher than chondritic correlating with the
elemental ratio 9Be/11B, suggestive of in situ decay of this key
short-lived radionuclide. The initial (10Be/9Be)0 ratios vary
between ∼10-3 and ∼10-2 for CAI 411. The initial ratio of CAI 411
is one order of magnitude higher than the highest ratio found in CV3
CAIs, suggesting that the more likely origin of CAI 411 10Be is
early solar system irradiation. The low (26Al/27Al)0
[≤8.9x10-7] with which CAI 411 formed indicates that it was exposed
to gradual flares with a proton fluence of a few 1019protons/cm2,
during the earliest phases of the solar system, possibly the infrared
class 0. The irradiation conditions for other CAIs are less well
constrained, with calculated fluences ranging between a few 1019 and
1020protons/cm2. The variable and extreme value of the initial
10Be/9Be ratios in carbonaceous chondrite CAIs is the reflection
of the variable and extreme magnetic activity in young stars observed
in the X-ray domain.
Description:
The Be-B concentrations and isotopic compositions were measured with
the Nancy ims 1270 and 1280 ion microprobes according to procedures
previously described (Chaussidon et al. 2006GeCoA..70..224C 2006GeCoA..70..224C). Primary
intensities of ∼5nA were used, with beam sizes of up to 25um in
diameter. The Be-B concentrations were directly determined from the
secondary beam intensities normalized to the primary beam intensity.
The Be/B elemental ratio was determined using a hibonite (Madagascar)
standard.
Isotopic ratios were calculated following the approach of Ogliore et
al. (2011NIMPB.269.1910O 2011NIMPB.269.1910O), i.e., ratioing the total number of counts.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 79 74 Elemental ratios and isotopic compositions of
21 Isheyevo (CH/CB) calcium-aluminum-rich
inclusions (CAIs)
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See also:
J/ApJ/748/L25 : Li-Be-B measurements using SIMS (Wielandt+, 2012)
J/ApJ/733/L31 : Distribution of 26Al in the solar system (Makide+, 2011)
J/ApJ/728/70 : The abundance of boron in diffuse clouds (Ritchey+, 2011)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- CAI [405/2012] CAI number (1)
6- 10 F5.2 --- 9Be/11B [0.03/20.2]? 9Be/11B ratio
12- 17 F6.1 10-3 d11B ? Isotopic ratio δ11B (2)
19- 22 F4.1 10-3 e_d11B ? 1σ uncertainty in d11B (3)
24- 30 F7.2 10-9 [B] ? Boron concentration (in ppb)
32- 37 F6.2 10-3 d18O ? Isotopic ratio δ18O (4)
39- 42 F4.2 10-3 e_d18O ? 1σ uncertainty in d18O (3)
44- 49 F6.2 10-3 d17O ? Isotopic ratio δ17O (4)
51- 55 F5.3 10-3 e_d17O ? 1σ uncertainty in d17O (3)
57- 62 F6.1 --- 27Al/24Mg ? 27Al/24Mg ratio
64- 69 F6.2 --- e_27Al/24Mg ? 1σ uncertainty in 27Al/24Mg (3)
71- 74 F4.1 10-3 D26Mg [-6/14]? Δ26Mg anomaly
76- 79 F4.2 10-3 e_D26Mg ? 1σ uncertainty in d26Mg (3)
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Note (1): All three systems were measured on different spots; in other words
the placement on a same line for different isotopic systems has no
meaning. For the Al-Mg system, only 9 CAIs were measured due to the
limited size of the samples which were heavily cratered after the
first two sets (Be-B and oxygen isotopic composition) of measurements.
Note (2): δ11B=((11B/10B)sample/(11B/10B)std-1)*1000,
where the standard is the NIST SRM 951 boric acid.
Note (3): Based on counting statistics, but for 9Be/11B and [B] which
are estimated to be respectively of 10 and 20% relative
(Chaussidon et al. 2006GeCoA..70..224C 2006GeCoA..70..224C).
Note (4): δxO= (xO/16O)sample/(xO/16O)SMOW-1)x1000
(SMOW = Standard Mean Ocean Water).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 21-Oct-2014