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J/MNRAS/287/293 BR photometry of EUVE sources (Maoz+ 1997)
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Evidence for a new class of extreme ultraviolet sources
Maoz D., Ofek E.O., Shemi A.
<Mon. Not. R. Astron. Soc. 287, 293 (1997)>
=1997MNRAS.287..293M (SIMBAD/NED BibCode)
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ADC_Keywords: X-ray sources; Ultraviolet ; Photometry
Keywords: stars: activity - stars: neutron - novae, cataclysmic variables -
white dwarfs - X-rays: stars.
Abstract:
Most of the sources detected in the extreme ultraviolet
(EUV; 100-600{AA}) by the ROSAT/WFC and EUVE all-sky surveys have been
identified with active late-type stars and hot white dwarfs that are
near enough to the Earth to escape absorption by interstellar gas.
However, about 15 per cent of EUV sources are as yet unidentified with
any optical counterparts. We examine whether the unidentified EUV
sources may consist of the same population of late-type stars and
white dwarfs. We present B and R photometry of stars in the fields of
seven of the unidentified EUV sources. We detect in the optical the
entire main-sequence and white dwarf population out to the greatest
distances where they could still avoid absorption. We use
colour-magnitude diagrams to demonstrate that, in most of the fields,
none of the observed stars has the colours and magnitudes of late-type
dwarfs at distances less than 100pc. Similarly, none of the observed
stars is a white dwarf within 500pc that is hot enough to be a EUV
emitter. The unidentified EUV sources we study are not detected in
X-rays, while cataclysmic variables, X-ray binaries, and active
galactic nuclei generally are. We conclude that some of the EUV
sources may be a new class of nearby objects, which are either very
faint at optical bands or which mimic the colours and magnitudes of
distant late-type stars or cool white dwarfs. One candidate for
optically faint objects is isolated old neutron stars, slowly
accreting interstellar matter. Such neutron stars are expected to be
abundant in the Galaxy, and have not been unambiguously detected.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1 81 7 Unidentified EUV sources
tab2-8 75 446 BR photometry for unidentified EUV sources
table9 76 23 X-ray visibility of EUV-detected CVs
tables.tex 120 622 LaTeX version of the tables
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See also:
J/ApJS/93/569 : First EUVE source catalogue (Bowyer+, 1994)
II/203 : Second Extreme Ultra-Violet Explorer Catalog (2EUVE, 1996)
J/MNRAS/274/1165 : The 2RE Source Catalogue (Pye+ 1995)
Byte-by-byte Description of file: table1
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Bytes Format Units Label Explanations
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1- 13 A13 --- EUVE EUV source name (EUVE or RE)
16- 29 A14 --- Band EUV band
32- 33 I2 h RAh Right ascension (J2000)
35- 36 I2 min RAm Right ascension (J2000)
38- 39 I2 s RAs Right ascension (J2000)
42 A1 --- DE- Declination sign
43- 44 I2 deg DEd Declination (J2000)
46- 47 I2 arcmin DEm Declination (J2000)
49- 50 I2 arcsec DEs Declination (J2000)
54- 56 I3 deg GLON Galactic longitude
59- 61 I3 deg GLAT Galactic latitude
64- 71 A8 "DD/MM/YY" Date Observation date
73- 76 I4 s Bexp Time of B exposition
78- 81 I4 s Rexp Time of R exposition
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Byte-by-byte Description of file: tab2-8
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Bytes Format Units Label Explanations
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1- 13 A13 --- EUVE EUV source name
15- 17 I3 --- Star Star number in the EUVE field
19- 23 F5.1 arcsec Sep Separation
25- 30 F6.1 arcsec oRA Offset in right ascension (1)
32- 37 F6.1 arcsec oDE Offset in declination (1)
39- 44 F6.3 mag Bmag B magnitude
46- 50 F5.3 mag e_Bmag rms uncertainty on Bmag
52- 57 F6.3 mag Rmag R magnitude
59- 63 F5.3 mag e_Rmag rms uncertainty on Rmag
65- 69 F5.3 mag B-R B-R colour
71- 75 F5.3 mag e_B-R rms uncertainty on B-R
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Note (1): Positions (J2000) are relative to:
RA=07h15m50s, DE=+14{deg}10'18" for EUVE 0715+141
RA=08h07m59s, DE=+21{deg}04'12" for EUVE 0807+210
RA=08h47m13s, DE=+59{deg}47'00" for RE 0847+594
RA=09h22m29s, DE=+71{deg}10'06" for EUVE 9022+711
RA=16h36m34s, DE=-28{deg}32'00" for EUVE 1636-285
RA=20h53m35s, DE=-17{deg}33'54" for EUVE 2053-175
RA=21h14m41s, DE=+50{deg}18'12" for EUVE 2114+503
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Byte-by-byte Description of file: table9
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Star name
15- 23 A9 --- Type Stellar type
25- 30 F6.1 ct/ks EUVE100 ? EUVE survey at 100{AA} counts
31 A1 --- n_EUVE100 [*] *: EUVE observations with the
Deep Survey Telescope
32- 34 I3 ct/ks e_EUVE100 ? rms uncertainty on EUVE100
36- 37 I2 ct/ks EUVE200 ? EUVE survey at 200{AA} counts
39- 40 I2 ct/ks e_EUVE200 ? rms uncertainty on EUVE200
42- 43 I2 ct/ks EUVE400 ? EUVE survey at 400{AA} counts
45- 46 I2 ct/ks e_EUVE400 ? rms uncertainty on EUVE400
48- 49 I2 ct/ks EUVE600 ? EUVE survey at 600{AA} counts
51- 52 I2 ct/ks e_EUVE600 ? rms uncertainty on EUVE600
54- 56 I3 ct/ks WFC100 ? ROSAT WFC survey at 100{AA} counts
58- 59 I2 ct/ks e_WFC100 ? rms uncertainty on WFC100
61- 63 I3 ct/ks WFC150 ? ROSAT WFC survey at 150{AA} counts
65- 66 I2 ct/ks e_WFC150 ? rms uncertainty on WFC150
68- 72 I5 ct/ks XRT ? ROSAT XRT survey at 0.1-2.4keV counts
74- 76 I3 ct/ks e_XRT ? rms uncertainty on XRT
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Acknowledgements: Dan Maoz <dani@wise.tau.ac.il>
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(End) James Marcout, Patricia Bauer [CDS] 24-Oct-1997