J/ApJ/710/597 Accretion in disks in Cep OB2 (Sicilia-Aguilar+, 2010)
Accretion in evolved and transitional disks in Cep OB2: looking for the origin
of the inner holes.
Sicilia-Aguilar A., Henning T., Hartmann L.W.
<Astrophys. J., 710, 597-612 (2010)>
=2010ApJ...710..597S 2010ApJ...710..597S
ADC_Keywords: Photometry, UBVRI ; Mass loss ; Stars, pre-main sequence ; YSOs ;
Clusters, open
Keywords: accretion, accretion disks - protoplanetary disks -
stars: pre-main sequence
Abstract:
We present accretion rates for a large number of solar-type stars in
the Cep OB2 region, based on U-band observations. Our study comprises
95 members of the ∼4Myr old cluster Tr 37 (including 20 "transition"
objects (TOs)), as well as the only classical T Tauri star (CTTS) in
the ∼12Myr old cluster NGC 7160. The stars show different disk
morphologies, with the majority of them having evolved and flattened
disks. The typical accretion rates are about 1 order of magnitude
lower than in regions aged 1-2Myr, and we find no strong correlation
between disk morphology and accretion rates. Although half of the TOs
are not accreting, the median accretion rates of normal CTTS and
accreting "transition" disks are similar (∼3x10-9 and
2x10-9M☉/yr, respectively). Comparison with other regions
suggests that the TOs observed at different ages do not necessarily
represent the same type of objects, which is consistent with the fact
that the different processes that can lead to reduced IR excess/inner
disk clearing (e.g., binarity, dust coagulation/settling,
photoevaporation, giant planet formation) do not operate on the same
timescales.
Description:
The UVRI observations of Tr 37 were obtained during three nights
in 2007 June 9-11, using the Wide-Field Camera LAICA mounted on the
3.5m telescope in Calar Alto, Spain.
The observations of NGC 7160 were obtained in 2007 October 5, using
the 70cm King telescope of the Max-Planck-Institut fur Astronomie at
Koenigstuhl, Heidelberg, Germany.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 127 103 Optical data
table3.dat 114 103 Accretion and stellar properties
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See also:
J/AJ/132/2135 : High-resolution spectroscopy in Tr 37 (Sicilia-Aguilar+, 2006)
J/ApJ/638/897 : IR photometry in Trumpler 37 and NGC 7160 (Sicilia-Aguilar+,
2006)
J/AJ/130/188 : Young stars in Trumpler 37 and NGC 7160 (Sicilia-Aguilar+,
2005)
J/AJ/128/805 : Low-mass stars in the Cepheus OB2 region (Sicilia-Aguilar+
2004)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Cluster Target name (Tr 37 or NGC 7160)
9- 16 A8 --- [SHB2004] Source name (G1)
18- 33 A16 --- 2MASS 2MASS designation (HHMMSSss+DDMMSSs; J2000)
35- 38 A4 --- SpT MK spectral type
40- 44 A5 --- Ptg Pointing (1)
46- 51 F6.3 mag Umag U-band magnitude
53- 57 F5.3 mag e_Umag Umag uncertainty
58 A1 --- f_Umag [b] Probably non-member (2)
60- 65 F6.3 mag Vmag ? V-band magnitude
67- 71 F5.3 mag e_Vmag ? Vmag uncertainty
73- 78 F6.3 mag Rmag ? Johnson R-band magnitude
80- 84 F5.3 mag e_Rmag ? Rmag uncertainty
86- 91 F6.3 mag Imag ? Johnson I-band magnitude
93- 97 F5.3 mag e_Imag ? Imag uncertainty
99-102 F4.2 mag AV V-band extinction
104-107 F4.2 mag e_AV AV uncertainty
108 A1 --- f_AV [c] Anomalous extinction (2)
110-126 A17 --- Notes Notes (3)
127 A1 --- f_Notes [ab] excluded objects (2)
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Note (1): The pointing (1,2,3,4) and LAICA CCD ID (a,b,c,d) are indicated to
show whether all the UVRI measurements were simultaneous (see Table 1,
below). Two pointings are indicated (e.g., 3c+2b), when the U magnitude
was observed with pointing 3c, and the VRI data come from pointing 2.
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Date Telescope Pointing and filters Seeing
-----------------------------------------------------------
2007/06/09 LAICA/3.5m Tr 37-1(UVRI) 1.2"-1.3"
2007/06/10 LAICA/3.5m Tr 37-2(UVRI), Tr 37-3(U) 0.8"-1.0"
2007/06/11 LAICA/3.5m Tr 37-3(VRI), Tr 37-4(UVRI) 0.6"-0.8"
2007/10/05 70cm KING NGC 7160 (UVRI) 2"
-----------------------------------------------------------
Note (2): Flag as follows:
a = Objects that appeared merged with other stars/artifacts are excluded
from this study.
b = 21-895b is probably not a member and not a physical companion of
21-895a because of its position in the color-magnitude diagram.
c = The colors of 22-2651 are probably affected by non-standard
variability/anomalous extinction. Therefore, we adopt for this object
the cluster average extinction.
Note (3): Notes as below:
var = variability (ΔV>0.5mag) observed;
n(x") = nearby star at x" projected distance, usually the photometry is not
affected. If the nearby star is bright and may affect the photometry.
SB1 = single-lined spectroscopic binary.
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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- 7 A7 --- Cluster Target name (Tr 37 or NGC 7160)
9- 16 A8 --- [SHB2004] Source name (G1)
18- 20 I3 0.1nm W(Ha)1 ? High-resolution equivalent width of
Hα (4)
22- 24 I3 0.1nm W(Ha)2 ? High-resolution EW of Hα (4)
26- 31 F6.1 0.1nm W(Ha)3 ? Low-resolution equivalent width of
Hα (4)
33- 35 I3 0.1nm W(Ha)4 ? Low-resolution EW of Hα (4)
37- 38 A2 --- Ha [BPN: ] Hα profile (5)
40- 43 A4 --- Disk Disk type (6)
45- 49 F5.2 Lsun Lum Photospheric luminosity in U-band (7)
51- 53 F3.1 Rsun Rad Stellar radius (8)
55- 58 F4.1 Myr Age Age (8)
60- 62 F3.1 Msun Mass Stellar mass (8)
64- 69 F6.3 10-8Msun/yr dMU/dt The accretion directly measured from the
U-band photometry (dMU/dt) (7)
71- 75 F5.3 10-8Msun/yr E_dMU/dt Positive error on dMU/dt
77- 81 F5.3 10-8Msun/yr e_dMU/dt Negative error on dMU/dt
83 A1 --- l_dM/dt Limit flag on dM/dt
84- 88 F5.2 10-8Msun/yr dM/dt The final value of the accretion rate (9)
90 A1 --- l_dM/dt2 Limit flag on dM/dt2
91- 94 F4.2 10-8Msun/yr dM/dt2 ? Second final value of the accretion
rate (9)
96-114 A19 --- Comm Comments (8)
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Note (4): The Hα EW has been compiled from Sicilia-Aguilar et al. (2005,
Cat. J/AJ/130/188, 2006, Cat. J/AJ/132/2135 and 2008ApJ...673..382S 2008ApJ...673..382S).
Note (5): The Hα profile is marked as follows:
B = broad,
P = probably broad
N = narrow (Sicilia-Aguilar et al. 2006, Cat. J/AJ/132/2135).
Note (6): The disk type is classified as follows:
CTTS = normal classical TTS,
TO = transition object,
TOe8 = transition object with only a small excess at 8um,
N = objects without a detectable excess.
Uncertain values are marked with ":". Objects that have no excess down
to 8um and have not been detected at 24um, but display some signs of
accretion, are marked with "*" and classified as potential TO with
large holes.
Note (7): Whenever the measured U-band luminosity was found to be below the
expected photospheric luminosity in U (LU is negative), we mark it
as a negative accretion rate (corresponding to the accretion rate
resulting from the absolute value of LU). The errors in the
luminosity are typically low (a few percent).
Note (8): Radii, masses, and ages are derived from the V versus V-I diagram
(or the HR diagram, see text, marked with HR in the "Comments"
column), using the Siess et al. (2000A&A...358..593S 2000A&A...358..593S) isochrones. For
K and M stars, the typical errors in these quantities are ∼10%,
although the age could be more affected by the presence of unresolved
binaries. The age of early K and G-type stars is far more uncertain
due to general problems establishing the birthline (Hartmann
2003ApJ...585..398H 2003ApJ...585..398H); such objects are marked as "G-age." Binary
information for spectroscopic binaries (unresolved, similar mass,
single-lined [SB1] or double-lined [SB2] spectroscopic binaries) is
taken from Sicilia-Aguilar et al. (2006, Cat. J/ApJ/638/897).
Note (9): dM/dt is the final value of the accretion rate after requiring a
detection probability >99% (based on 5000 simulations) and Hα
(see text). Accretion rates are marked as "0" when the simulated data
are consistent with zero and there is no further evidence of accretion
(see text). If the photometry is consistent with no accretion, but
Hα suggest that the object is accreting, we consider it as an
upper limit.
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Global notes:
Note (G1): Due to the small field overlap, some stars were observed more
than once. Stars are <[SHB2004] Trumpler 37 NN-NNNN> or <[SHB2004] NGC
7160 NN-NNNN> in Simbad; except for "21362507", "21383216", "21384350"
and "21400451" which have their corresponding 2MASS names.
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History:
From electronic version of the journal
References:
Sicilia-Aguilar et al. Paper I. 2004AJ....128..805S 2004AJ....128..805S Cat. J/AJ/128/805
Sicilia-Aguilar et al. Paper II. 2005AJ....130..188S 2005AJ....130..188S Cat. J/AJ/130/188
Sicilia-Aguilar et al. Paper III. 2006ApJ...638..897S 2006ApJ...638..897S Cat. J/ApJ/638/897
Sicilia-Aguilar et al. Paper IV. 2006AJ....132.2135S 2006AJ....132.2135S Cat. J/AJ/132/2135
(End) Emmanuelle Perret [CDS] 13-Mar-2012