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J/A+A/341/163 MBM 7 and MBM 55 X-ray sources (Hearty+ 1999)
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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 (SIMBAD/NED BibCode)
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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{deg}) 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
{lambda}6708{AA} absorption and H{alpha} 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 H{alpha}
emission. Relative ages for the stars with lithium are estimated by
their position on an W(Li) vs. T_eff_ 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 (2000)
22- 23 I2 min RAm Right ascension (2000)
25- 28 F4.1 s RAs Right ascension (2000)
30 A1 --- DE- Declination sign
31- 32 I2 deg DEd Declination (2000)
34- 35 I2 arcmin DEm Declination (2000)
37- 38 I2 arcsec DEs Declination (2000)
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 ? H{alpha} equivalent width (3)
112 A1 --- n_EWHa [-] When interval
113-116 F4.2 0.1nm EWHa2 ? Second H{alpha} equivalent width value
when interval
117-121 F5.2 01.nm EWLi ? Li (6708{AA}) 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(H{alpha}) indicate emission lines.
The errors in equivalent width measurements are ~0.06{AA}.
Note (4): 1: The H{alpha} and lithium measurements listed in the table are
from Frasca & Catalano (1994A&A...284..883F) and
Fekel & Balachandran (1993ApJ...403..708F), respectively.
2: This star is listed as a BY Dra candidate in the EEMSS
(Stocke et al., 1991ApJS...76..813S).
3: Cutispoto et al. (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 <thearty@xray.mpe.mpg.de>
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(End) Patricia Bauer [CDS] 03-Dec-1998