J/PASJ/55/653 Chandra X-ray flares in rho Ophiuchi (Imanishi+, 2003)
A systematic study of X-ray flares from low-mass young stellar objects in the
rho Ophiuchi star-forming region with Chandra.
Imanishi K., Nakajima H., Tsujimoto M., Koyama K., Tsuboi Y.
<Publ. Astron. Soc. Jap., 55, 653 (2003)>
=2003PASJ...55..653I 2003PASJ...55..653I
ADC_Keywords: YSOs ; Stars, pre-main sequence ; Stars, flare ; X-ray sources
Keywords: ISM: clouds - ISM: individual (rho Ophiuchi cloud) - stars: flare -
stars: pre-main-sequence - X-rays: stars
Abstract:
We report on the results of a systematic study of X-ray flares from
low-mass young stellar objects, using two deep exposure Chandra
observations of the main region of the ρ Ophiuchi star-forming
cloud. From 195 X-ray sources, including class I-III sources and some
young brown dwarfs, we detected a total of 71 X-ray flares.
Description:
The Chandra X-ray Observatory (Weisskopf et al., 2002PASP..114....1W 2002PASP..114....1W)
observed the central region of Oph twice with a deep exposure of the
ACIS-I array, consisting of four abutted X-ray CCDs. The first
observation (here and after, obs. BF) covered the south-east
17.4'x17.4' area, including cores B, C, E, and F, while the second
observation (obs. A) covered the north-west area centered on core A
(Loren et al., 1990ApJ...365..269L 1990ApJ...365..269L). Although some of the ACIS-S chips
were simultaneously in operation, we do not use these data because
large off-axis angles cause a degeneration of the sensitivity and
position determination.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 150 306 Chandra X-ray sources in the rho Oph region
table3.dat 137 204 Identifications of the X-ray sources
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
J/A+A/359/113 : X-ray and IR study of Rho Oph dark cloud (Grosso+, 2000)
J/ApJ/438/813 : Stellar population in ρ Oph cloud core (Strom+, 1995)
J/ApJ/630/381 : Mid-IR imaging in ρ Oph (Barsony+, 2005)
J/ApJS/112/109 : Rho Oph Near IR Positions and Photometry (Barsony+, 1997)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- [INT2003] Source designation (G1) (1)
7- 8 A2 --- n_[INT2003] Note on [INT2003] (2)
10- 16 F7.1 ct Count Background-subtracted ACIS-I counts (3)
17- 19 A3 --- n_Count Note on Count (4)
21- 22 I2 h RAh Right ascension (J2000)
24- 25 I2 min RAm Right ascension (J2000)
27- 31 F5.2 s RAs Right ascension (J2000)
33 A1 --- DE- Declination sign (J2000)
34- 35 I2 deg DEd Declination (J2000)
37- 38 I2 arcmin DEm Declination (J2000)
40- 43 F4.1 arcsec DEs Declination (J2000)
45 A1 --- l_<kT> Limit flag on <kT>
46- 50 F5.2 keV <kT> ? Time-averaged temperature
52 A1 --- l_kTl Limit flag on kTl
53- 56 F4.2 keV kTl ? 90% confidence lower limit of kT
58- 62 F5.2 keV kTu ? 90% confidence upper limit of kT
63 A1 --- n_<kT> [f] f for fixed
65- 68 F4.1 [cm-3] log ? Mean emission measure
70 A1 --- l_logEMl Limit flag on logEMl
71- 74 F4.1 [cm-3] logEMl ? 90% confidence lower limit of logEM
76- 79 F4.1 [cm-3] logEMu ? 90% confidence upper limit of logEM
81- 86 F6.3 10+22cm-2 NH ? Absorption hydrogen column density
88 A1 --- l_NHl Limit flag on NHl
89- 95 F7.3 10+22cm-2 NHl ? 90% confidence lower limit of NH
97-102 F6.2 10+22cm-2 NHu ? 90% confidence upper limit of NH
103-109 F7.2 10-17W/m2 Flux ? Observed flux in 0.5-9.0keV
111-118 F8.3 10+22W ? Mean absorption-corrected X-ray luminosity
in 0.5-9.0keV
120-123 F4.2 --- Chi2 ? Reduced χ2 for the spectral fittings
125-127 I3 --- DOF ? Degree of freedom
129-150 A22 --- Com Comments
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Note (1): Different measurements are made for the same source (the name
and position of the source are repeated).
Note (2): Notes as follows:
a = We determine spectral parameters with fixed temperatures of 1keV
and 5keV (see text). For sources which only show the parameters
for kT=1 or 5keV, no good fitting is obtained for the other
temperature.
b = We assume the same abundances as the ``F2'' phase in Imanishi et
al. (2002ApJ...572..300I 2002ApJ...572..300I). The quiescent spectrum is not obtained
because the decay phases of the two flares occupy all of the
light curve.
d = No spectral fit is done due to the limited statistics
e = Abundances are free parameters (see sub-subsection 4.8.1 in
Paper I, Imanishi et al., 2001ApJ...557..747I 2001ApJ...557..747I and Imanishi, 2003,
PhD Thesis, Kyoto University)
f = We make the flare spectra with a bit larger time scale in order to
obtain as good statistics as possible. Errors of for A-29 in
the quiescent are not determined because of the limited statistics
g = The spectra show possible edge absorption of neutral Ca or warm Ar.
The non-thermal model also well reproduces the spectra (Hamaguchi,
Imanishi, 2002, PASJ, submitted)
h = We assume the same temperature because of the limited statistics.
i = These show non-thermal spectra (Imanishi, 2003, PhD Thesis,
Kyoto University)
k = Imanishi et al. (2002ApJ...572..300I 2002ApJ...572..300I) proposed
two-temperature model with an unusual abundance pattern
l = Foreground star. The distance is 60pc (Festin, 1998A&A...336..883F 1998A&A...336..883F)
m = The best-fit value of <kT> is not determined (larger than 10keV),
hence we assume 10keV temperature for the estimation of the other
parameters.
n = NH and reduced-chi2 are estimated by the simultaneous fittings
with the identical sources in obs. A.
Note (3): X-ray counts in 0.5-2.0keV, 2.0-9.0keV, and 0.5-9.0keV for
soft-band, hard-band, and the other sources, respectively. The
soft-band and hard-band sources are indicated by the prefixes "S" and "H".
Note (4): Note on Count as follows:
(m) = denotes sources with marginal detections (the confidence level
<99.9%, see subsection 3). Although the confidence levels of
A-48 and A-H2 are significant enough, we regard them as marginal
sources because of the larger source size (A-48) and severe
contamination from A-2 (A-H2).
++ = The pile-up effect is not corrected
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- [INT2003] Source designation (G1)
7- 10 F4.2 arcsec o2MASS ? Offset between the Chandra and nearest
2MASS sources (Cat. II/246)
11- 13 A3 --- n_o2MASS [(R)# ] Note on o2MASS (2)
15- 25 A11 --- RNames Radio source names, separated by comma (3)
27- 33 A7 --- PSPC X-ray source detected by ROSAT/PSPC
(Casanova et al., 1995ApJ...439..752C 1995ApJ...439..752C,
ROXR1 NN or ROXR1 CNN)
35- 37 A3 --- HRI X-ray source detected by ROSAT/HRI
(Grosso et al., 2000, Cat. J/A+A/359/113,
ROXRA NN or ROXRF NN)
38 A1 --- n_HRI [*] From Grosso (2001A&A...370L..22G 2001A&A...370L..22G)
40- 41 A2 --- ASCA X-ray source detected by ASCA
(Katama et al., 1997PASJ...49..461K 1997PASJ...49..461K,
ROXA NNA or ROXA CN)
42 A1 --- n_ASCA [+] +: From Tsuboi et al., 2000ApJ...532.1089T 2000ApJ...532.1089T
44- 45 I2 --- [IKT2001] ? Chandra sources already listed in Paper I,
Imanishi et al., 2001ApJ...557..747I 2001ApJ...557..747I
47-121 A75 --- ONames Other names (4)
122 A1 --- n_ONames [+S] Note on ONames (5)
124-136 A13 --- Class Classification of the source (6)
137 A1 --- n_Class [a] a: From NIR spectroscopy (7)
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Note (2): Note on o2MASS as follows:
(R) = for sources having a radio counterpart only, the offset between
the Chandra and radio sources (Andre et al., 1987AJ.....93.1182A 1987AJ.....93.1182A)
are shown.
# = Offset from a nearest NIR source in Greene and Young
(1992ApJ...395..516G 1992ApJ...395..516G).
Note (3): S, R, and L indicate sources listed as follows in:
R = Andre et al. (1987AJ.....93.1182A 1987AJ.....93.1182A) (ROC NN)
S = Stine et al. (1988AJ.....96.1394S 1988AJ.....96.1394S) (SFAM NN)
L = Leous et al. (1991ApJ...379..683L 1991ApJ...379..683L) (LFAM NN)
Lp denotes possible radio sources in LFAM.
Note (4): Source names used in the literature; abbreviations for names are:
SR: Struve, Rudkjobing, 1949ApJ...109...92S 1949ApJ...109...92S
DoAr: Dolidze, Arakelyan, 1959AZh....36..444D 1959AZh....36..444D
ROXs: Bouvier, Appenzeller, 1992A&AS...92..481B 1992A&AS...92..481B
S: Grasdalen et al., 1973ApJ...184L..53G 1973ApJ...184L..53G
YLW: Young et al., 1986ApJ...304L..45Y 1986ApJ...304L..45Y
GY: Greene, Young, 1992ApJ...395..516G 1992ApJ...395..516G
WL: Wilking, Lada, 1983ApJ...274..698W 1983ApJ...274..698W
VSSG: Vrba et al., 1975ApJ...197...77V 1975ApJ...197...77V
GSS: Grasdalen et al., 1973ApJ...184L..53G 1973ApJ...184L..53G
Elias: Elias, 1978ApJ...224..453E 1978ApJ...224..453E
BBRCG: Barsony et al., 1989ApJ...346L..93B 1989ApJ...346L..93B
CRBR: Comeron et al., 1993ApJ...416..185C 1993ApJ...416..185C
SKS: Strom et al., 1995, Cat. J/ApJ/438/813
IRS: Wilking et al., 1989ApJ...340..823W 1989ApJ...340..823W
ISO: Bontemps et al., 2001, Cat. J/A+A/372/173
For sources having NIR counterpart only in the 2MASS catalog, we
alternatively show the 2MASS source names.
Note (5): Note on ONames as follows:
+ = The position of GY5 (Greene, Young, 1992ApJ...395..516G 1992ApJ...395..516G) is
slightly shifted (∼2.3") from the 2MASS source.
S = A candidate of HH object (Gomez et al., 1998AJ....115.2018G 1998AJ....115.2018G).
Note (6): Source classifications as follows:
I = class I YSO (infall envelope and accretion disk)
II = class II YSO (accretion disk)
III = class III YSO (remnant or absent accretion disk)
IIIc = class III candidate (table 5 in Bontemps et al., 2001,
Cat. J/A+A/372/173)
BD = brown dwarf
BDc = brown dwarf candidate (Imanishi et al., 2001ApJ...563..361I 2001ApJ...563..361I)
F = foreground star (Festin, 1998A&A...336..883F 1998A&A...336..883F).
Unclassified NIR sources are indicated by "?", and sources with no NIR
counterpart are called "unidentified sources", and have a blank field.
For BD/BD_cs, we show the available IR classification in Bontemps et
al. (2001, Cat. J/A+A/372/173) in the parentheses.
Note (7): Wilking et al. (1999AJ....117..469W 1999AJ....117..469W) derived for these M dwarfs masses
higher than the hydrogen burning limit.
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Global notes:
Note (G1): The sources of the first observation are labelled A-NN (NN=1 to 84),
A-HN (N=-1-5) for the hard (2.0-9.0keV) band,
A-SN (N=-1-5) for the soft (0.5-2.0keV) band.
The sources of the second observation are labelled BF-NN (1-98),
BF-HN (N=1-4) for the hard (2.0-9.0keV) band,
BF-SN (N=1-8) for the soft (0.5-2.0keV) band.
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History:
From electronic version of the journal
(End) James Marcout, Patricia Bauer [CDS] 21-Nov-2003