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J/A+AS/146/323 RASS young sources around R CrA (Neuhaeuser+, 2000)
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Search for young stars among ROSAT All-Sky Survey X-ray sources in and around
the R CrA dark cloud
Neuhaeuser R., Walter F.M., Covino E., Alcala J.M., Wolk S.J., Frink S.,
Guillout P., Sterzik M.F., Comeron F.
<Astron. Astrophys. Suppl. Ser. 146, 323 (2000)>
=2000A&AS..146..323N
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ADC_Keywords: X-ray sources ; Stars, pre-main sequence ; Photometry, VRI ;
Photometry, infrared ; Radial velocities ; Rotational velocities
Mission_Name: ROSAT
Keywords: stars: formation - stars: luminosity function, mass function -
stars: pre-main sequence - X-rays: stars
Abstract:
We present the ROSAT All-Sky Survey data in a 126 deg^2^ area in and
around the CrA star forming region. With low-resolution spectroscopy
of unidentified ROSAT sources we could find 19 new pre-main sequence
stars, two of which are classical T Tauri stars, the others being
weak-lined. The spectral types of these new T Tauri stars range from
F7 to M6. The two new classical T Tauri stars are located towards two
small cloud-lets outside of the main CrA cloud. They appear to be ~10
Myrs old, by comparing their location in the H-R diagram with
isochrones for an assumed distance of 130 pc, the distance of the main
CrA dark cloud. The new off-cloud weak-line T Tauri stars may have
formed in similar cloudlets, which have dispersed recently.
High-resolution spectra of our new T Tauri stars show that they have
significantly more lithium absorption than zero-age main-sequence
stars of the same spectral type, so that they are indeed young. From
those spectra we also obtained rotational and radial velocities. For
some stars we found the proper motion in published catalogs. The
direction and velocity of the 3D space motion - south relative to the
galactic plane - of the CrA T Tauri stars is consistent with the dark
cloud being formed originally by a high-velocity cloud impact onto the
galactic plane, which triggered the star formation in CrA. We also
present VRIJHK photometry for most of the new T Tauri stars to derive
their luminosities, ages, and masses.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 98 206 *X-ray data for our sample.
table3.dat 99 93 *Optical counterparts
table4.dat 75 19 New T Tauri stars in CrA
table5.dat 94 20 Photometric data for new T Tauri stars in CrA.
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Note on table2.dat: Listed are all X-ray sources detected in the ROSAT All-Sky
Survey sorted by right ascension.
Note on table3.dat: For each X-ray source listed in Table 2, we list here the
optical counterpart from Simbad, GSC, or NED, unless no counterpart is found
within 40 arcsec around the X-ray position (in all but four cases, these
counterparts are the closest ones).
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See also:
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
IX/28 : ROSAT HRI Pointed Observations (1RXH) (ROSAT Team, 2000)
J/A+A/297/391 : T Tauri stars ROSAT survey (Neuhaeuser+, 1995)
J/A+A/341/L79 : Proper motions of faint ROSAT WTT stars (Terranegra+ 1999)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- [NWC2000] Sequential number
5- 18 A14 --- RXJ RXJ designation (based on J2000)
20- 21 I2 h RAh X-ray right ascension (J2000)
23- 24 I2 min RAm X-ray right ascension (J2000)
26- 29 F4.1 s RAs X-ray right ascension (J2000)
31 A1 --- DE- X-ray declination sign (J2000)
32- 33 I2 deg DEd X-ray declination sign (J2000)
35- 36 I2 arcmin DEm X-ray declination sign (J2000)
38- 41 F4.1 arcsec DEs X-ray declination sign (J2000)
43- 48 F6.1 ---- ML Maximum likelihood of existence
50- 51 A2 --- l_HR1 [=>< ] Limit flag on HR1
52- 56 F5.2 --- HR1 Hardness ratio 1 (1)
58- 61 F4.2 --- e_HR1 ? rms uncertainty on HR1
63- 64 A2 --- l_HR2 [=>< ] Limit flag on HR2
65- 69 F5.2 --- HR2 ? Hardness ratio 2 (1)
71- 74 F4.2 --- e_HR2 ? rms uncertainty on HR2
76- 80 F5.1 ct Counts Number of counts in the
broad band (0.1 to 2.4KeV)
82- 85 F4.1 ct e_Counts rms uncertainty on Counts
87- 91 F5.1 s Exp Exposition time
93- 98 F6.2 [10+7cm+2/J] logECF Energy conversion factor in counts
(in erg^-1^cm^2^)
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Note (1): Background subtracted and vignetting corrected)
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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- 3 I3 --- [NWC2000] Sequential number
5- 6 I2 h RAh Optical right ascension (J2000)
8- 9 I2 min RAm Optical right ascension (J2000)
11- 14 F4.1 s RAs Optical right ascension (J2000)
16 A1 --- DE- Optical declination sign (J2000)
17- 18 I2 deg DEd Optical declination (J2000)
20- 21 I2 arcmin DEm Optical declination (J2000)
23- 26 F4.1 arcsec DEs Optical declination (J2000)
28- 29 I2 arcsec Delta Offset between X-ray and optical position
31- 34 F4.1 mag Vmag ? V magnitude
35 A1 --- u_Vmag Uncertainty flag on Vmag
37- 41 F5.2 --- log(FX/FV) ? X-ray to optical flux ratio
43 A1 --- OptID [pyzend] Nature on the counterpart (1)
45- 97 A53 --- Rem Remarks (2)
99 I1 --- Note [1/2]? Notes (3)
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Note (1): Nature of the counterpart:
y for new young star listed in Table 4
z for zero-age main-sequence stars (i.e. low lithium)
d for dKe or dMe stars
e for extra-galactic
n for neither of the above (mostly old stars)
p for previously known TTS or non-TTS (not observed optically
except TY CrA)
counterparts without any entry have not been observed optically
Note (2): Finally, some remarks are given as found in Simbad (like proper
motion PM as [{mu}_{alpha}_*cos{delta},{mu}_{delta}_] in
milliarcseconds per year and radial velocity RV in [km/s] or from our
optical follow-up observations. Data on optical counterparts are taken
from Simbad or NED, if remarks are listed, otherwise from GSC. Some
GSC counterparts appear on several GSC plates which may have different
colors and different filters; we have always chosen the closest
counterpart. For stars with Vmag given with colons, positions and
magnitudes are estimated from the DSS charts, because the identified
counterpart is different from the relevant Simbad/GSC/NED counterpart
Note (3): The numbers indicate the following:
1: Maybe weak lithium (or noise), complex H{alpha},
maybe double-lined, could be ZAMS, RS CVn-type, dKe/dMe,
or a cool Algol.
2: Our detection of weak lithium with
W_{lambda}_(Li)=0.19~=W_{lambda}_(Ca) confirms the classification
of HR 7330 as member of the ~200Myr old nearby Castor moving group
by Barrado y Navascues (1998A&A...339..831B).
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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- 3 I3 --- [NWC2000] Sequential number
5- 18 A14 --- RXJ RXJ designation
19- 20 A2 --- m_RXJ [NE SW] Multiplicity index in RXJ
22- 25 A4 --- PMS PMS type (wTTS or cTTS)
27- 28 A2 --- SpType Spectral type
30- 34 F5.1 0.1nm EWHa H{alpha} equivalent width (1)
35 A1 --- u_EWHa [:] : when EWHa not from high-resolution spectra
37- 40 F4.2 0.1nm EWLi Lithium equivalent width (1)
41 A1 --- u_EWLi [:] : when EWLi not from high-resolution spectra
43- 46 F4.1 km/s vsini ? Rotational velocity
48- 51 F4.1 km/s HRV ? Heliocentric radial velocity
53- 57 F5.2 [10-7W] logLX X-ray luminosity (2)
58- 73 A16 --- Rem Remarks
75 I1 --- Note [1/5]? Notes (3)
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Note (1): Negative when in emission
Note (2): X-ray luminosity in 130 pc distance, calculated from counts,
exposure and ECF listed in Table 2, 65 pc for TTS No. 82
Note (3): Notes:
1: Complex H{alpha} profile.
2: Given the relatively early spectral type and relatively small
lithium strength, this star could be either pre- or zero-age MS
stars (see also Sect. 6.3). Its Hipparcos distance is 65 pc,
L_X_ given for 65 pc.
3: Also observed with low resolution in 1995 and twice in 1996, when
EWH{alpha} varied from -53.6{AA} to -88.7{AA} from night to
night. Double-peaked H{alpha} emission, also HeI and [OII]
emission.
4: Visual pair; position given in Table 3 is for the primary, i.e.
the slightly brighter star; not resolved spatially with ROSAT
(the combined L_X_ is given).
5: Observed once in 1995 with low resolution and about the same
H{alpha} as given above for high-resolution spectrum, and five
times with low resolution in 1996 with EWH{alpha} from
-5.22{AA} to -8.97{AA}.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- [NWC2000] Sequential number (1)
4 A1 --- --- [-]
5- 6 A2 --- m_[NWC2000] [NE SW] Multiplicity index on Seq
8- 11 F4.1 mag Bmag ? B magnitude
12 A1 --- u_Bmag Uncertainty flag on Bmag (2)
14- 18 F5.2 mag Vmag V magnitude
19 A1 --- u_Vmag Uncertainty flag on Vmag (2)
21- 24 F4.2 mag e_Bmag ? rms uncertainty on Bmag
26- 29 F4.2 mag V-R ? V-R colour index
31- 34 F4.2 mag e_V-R ? rms uncertainty on V-R
36- 39 F4.2 mag R-I ? R-I colour index
41- 44 F4.2 mag e_R-I ? rms uncertainty on R-I
46- 50 F5.2 mag Kmag ? K magnitude
52- 55 F4.2 mag e_Kmag ? rms uncertainty on Kmag
57- 60 F4.2 mag J-K ? J-K colour index (3)
62- 65 F4.2 mag e_J-K ? rms uncertainty on J-K
67- 70 F4.2 mag H-K ? H-K colour index (3)
72- 75 F4.2 mag e_H-K ? rms uncertainty on H-K
77- 79 F3.1 mag AVmag Absorption in V band
81- 85 F5.2 [solLum] LogLbol Bolometric luminosity (4)
87- 90 F4.1 Myr Age Age (5)
92- 94 F3.1 solMass Mass Mass (5)
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Note (1): Additional data:
207 = RXJ1855.1-3754, not in table2, numbered by CDS
Position: RA = 18 55 11.7, DE = -37 53 45 (J2000).
This object, RXJ1855.1-3754, is the TTS found in Neuhauser et al.
(1997A&A...318L..43N), a ROSAT HRI source, not a RASS source.
Note (2): When no error is given, data are taken from Simbad, GS C, or USNO,
which are more uncertain.(indicated by colons).
Note (3): For TTS No. 64, the JHK data are from the 2nd 2 MASS data release.
Note (4): Bolometric luminosity are estimated for a distance of 130 pc
(65 pc for TTS no. 82).
Note (5): Ages and masses are estimated by comparison with isochrones and tracks
from D'Antona & Mazzitelli (1994ApJS...90..467D).
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History:
From A&AS electronic version
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(End) Patricia Bauer [CDS] 13-Nov-2000