J/A+A/341/163 MBM 7 and MBM 55 X-ray sources (Hearty+ 1999)
A search for star formation in the translucent clouds MBM 7 and MBM 55
Hearty T., Magnani L., Caillault J.-P., Neuhaeuser R., Schmitt J.H.M.M.,
Stauffer J.
<Astron. Astrophys. 341, 163 (1999)>
=1999A&A...341..163H 1999A&A...341..163H (SIMBAD/NED BibCode)
ADC_Keywords: X-ray sources
Keywords: ISM: clouds - stars: formation
Abstract:
The star formation capability of two molecular clouds at high galactic
latitude (|b|>30°) is investigated. Possible pre-main sequence
stars in and around the translucent clouds MBM7 and MBM55 have been
identified via their X-ray emission by inspecting ROSAT All-Sky Survey
observations of the clouds and environs and ROSAT pointed observations
of the high-density cores within the clouds. Follow-up optical
spectroscopy of the stellar X-ray sources with V≤15.5mag was
conducted with the 1.5-m Fred Lawrence Whipple Observatory telescope
to identify standard signatures of pre-main sequence stars (LiI
λ6708Å absorption and Hα emission). We found 11 stars
which have lithium equivalent widths, W(Li), above our detection
threshold. Three of the stars with lithium also have weak Hα
emission. Relative ages for the stars with lithium are estimated by
their position on an W(Li) vs. Teff diagram. A calibration derived
from data for several clusters with known ages indicates that the
stars are older than the translucent high-latitude clouds. This
conclusion is supported by a comparison with theoretical evolutionary
tracks of the stars from our sample for which we have distance
measurements from Hipparcos. We find it is unlikely that any of the
X-ray active, lithium-rich stars we identified have formed in the
clouds in question. Theoretical and observational arguments support
this conclusion and render unlikely the possibility that
low-extinction translucent clouds are the sites of star formation.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 131 180 X-ray identified sources with probable
stellar optical counterparts
notes.dat 79 28 Individual notes
table3.ps 72 1458 PostScript version of table3
table3.tex 230 273 LaTeX version of table3
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See also:
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1996)
IX/11 : ROSAT Source Catalog (Voges+ 1994)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1 A1 --- Note [ABCD] Source localisation (1)
3- 16 A14 --- RX RXJ name of the X-ray source
17 A1 --- m_RX [abcd] Multiplicity index on Name
18 A1 --- n_RX [*] *: This source was detected in both the
RASS and ROSAT pointed observations.
19- 20 I2 h RAh Right ascension (J2000)
22- 23 I2 min RAm Right ascension (J2000)
25- 28 F4.1 s RAs Right ascension (J2000)
30 A1 --- DE- Declination sign
31- 32 I2 deg DEd Declination (J2000)
34- 35 I2 arcmin DEm Declination (J2000)
37- 38 I2 arcsec DEs Declination (J2000)
40- 45 F6.1 --- ML Maximum likelihood of existence
47- 54 F8.5 ct/s CountRate Broad band (0.1-2.0 keV) count rate
56- 62 F7.5 ct/s e_CountRate rms uncertainty on CountRate
64 A1 --- l_HR1 limit flag on HR1
65- 69 F5.2 --- HR1 Hardness ratio 1
71- 74 F4.2 --- e_HR1 ? rms uncertainty on HR1
76 A1 --- l_HR2 Limit flag on HR2
77- 81 F5.2 --- HR2 ? Hardness ratio 2
83- 86 F4.2 --- e_HR2 ? rms uncertainty on HR2
88- 92 F5.2 mag Vmag V magnitude
93 A1 --- n_Vmag [:b] Uncertainty flag or note (2)
95- 99 F5.2 --- log(fx/fv) X-ray to optical flux ratio
101-105 A5 --- SpType Spectral type of the optical counterpart
107-111 F5.2 0.1nm EWHa ? Hα equivalent width (3)
112 A1 --- n_EWHa [-] When interval
113-116 F4.2 0.1nm EWHa2 ? Second Hα equivalent width value
when interval
117-121 F5.2 01.nm EWLi ? Li (6708Å) equivalent width (3)
124-131 A8 --- Com Comment (4)
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Note (1): A: MBM 7 RASS stars
B: MBM 7 ROSAT pointed observation stars
C: MBM 55 RASS stars
D: MBM 55 ROSAT pointed observation stars
Note (2): b: The optical source is just outside of the 40" error circle.
Note (3): Negative values of W(Hα) indicate emission lines.
The errors in equivalent width measurements are ∼0.06Å.
Note (4): 1: The Hα and lithium measurements listed in the table are
from Frasca & Catalano (1994A&A...284..883F 1994A&A...284..883F) and
Fekel & Balachandran (1993ApJ...403..708F 1993ApJ...403..708F), respectively.
2: This star is listed as a BY Dra candidate in the EEMSS
(Stocke et al., 1991ApJS...76..813S 1991ApJS...76..813S).
3: Cutispoto et al. (1996A&AS..115...41C 1996A&AS..115...41C) list this star as a binary
with K1/2 IV and F5 V components. It is listed as a G5 in SIMBAD.
*: Individual note in notes.dat file
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- RX RXJ name of the X-ray source
15- 16 A2 --- m_RX [ac] Multiplicity index on RXJ
18- 90 A73 --- Note Text of the note
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Acknowledgements: Thomas J. Hearty
(End) Patricia Bauer [CDS] 03-Dec-1998