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J0501.6-7034
(RX J0501.6-7034, 2E 0501.8-7038, 1E 0501.8-7036,
HV
2289, CAL 9)
This Einstein and ROSAT variable source was identified with a Be star
by Schmidtke, Cowley, Frattare et al.
(1994). Later Schmidtke, Cowley,
Hauschildt et al. (1996) identified this star with
HV 2289, a known
variable
with a large amplitude of variability.
J0502.9-6626
(RX J0502.9-6626, CAL E)
The X-ray source RX J0502.9-6626 was originally detected by the
Einstein
observatory (Cowley, Crampton, Hutchings et
al. (1984)) at a flux of ~3 x 1036 erg s-1.
The source
was detected three times with the ROSAT PSPC at luminosities ~1035
- 1036 erg s-1
and once with the
HRI
during
a bright
outburst at 4 x 1037 erg s-1 (Schmidtke, Cowley, McGrath & Anderson
(1995)). During
the outburst, pulsations at
4.0635 s were detected. The identification of this source with the Be
star
[W63b] 564 = EQ 050246.6-663032.4 (Wooley
(1963)) was confirmed by Schmidtke,
Cowley, Frattare et al. (1994).
J0516.0-6916
(RX J0516.0-6916)
The identification of this source with a Be-star is unclear.
In several observations the source did not display any characteristics
of Be behaviour, however, Schmidtke,
Cowley, Crane
et al. (1999) classify it as a
Be-star.
J052016.0-692505
(XMMU J052016.0-692505)
This super-soft X-ray source was discovered with XMM-Newton (Kahabka, Haberl, Payne & Filipovic
(2006)). The likely optical counterpart of XMMU J052016.0−692505 is
the LMC variable star LMCV2135 (Kahabka, Haberl,
Payne & Filipovic (2006)). The infrared and optical colors and
magnitudes of this star are consistent with a hot star of likely
spectral type B. The long-term MACHO light curve shows variability with
a timescale of ~500 and ~1000 days (Kahabka, Haberl,
Payne & Filipovic (2006)). The optical spectra show strong Hα
and H
emission lines which indicate a B0–3e star. The radial velocities of
the Hα and H
emission lines show a variation from ~400-450 km s−1 to
~5-20 km s−1 which is consistent with the systemic velocity
of the LMC and an intrinsic variation most likely due to the rotation
of the Be disk. Kahabka,
Haberl, Payne & Filipovic (2006) discuss XMMU J052016.0−692505
as a Be/white dwarf binary system in the LMC. The super-soft X-ray
spectrum of the source could be due to a stable nuclear burning white
dwarf.
J0520.5-6932
(RX J0520.5-6932)
This X-ray source has been observed at a low X-ray luminosity
(5 x 1034 erg s-1)
in early 90-s by ROSAT (Schmidtke, Cowley,
Frattare et al. (1994)).
The light curve of the optical counterpart exhibits significant
modulation with a period of 24.5 d,
which is interpreted as the orbital period (Coe,
Negueruela, Buckley et
al. 2001)).
A spectral type O9V was proposed for the optical counterpart.
In a recent paper Edge, Coe, Galache
& Hill (2004) present new
optical and IR data
and archive BATSE data on the outburst.
J0529.8-6556
(RX J0529.8-6556, RX J0529.7-6556)
The transient X-ray source RX J0529.8-6556 was detected during one
single
outburst as a 69.5-s X-ray pulsar by Haberl,
Dennerl, Pietsch & Reinsch 1997),
who identified it with
a relatively bright blue star showing weak Hα
emission.
J0530.1-6551
(RX J0530.1-6551, XMMU J053011.2-655122)
This X-ray source was detected in ROSAT data (Haberl & Pietsch (1999)). Haberl, Dennerl & Pietsch (2003)
proposed this source as a new candidate HMXB based on its hard X-ray
spectrum and the presence of a likely optical counterpart. For this
X-ray source during the XMM-Newton observations probable pulsations
were found with a period of 271.97(5) s (Haberl,
Dennerl & Pietsch (2003)). Detection of a possible pulse period
for XMMU J053011.2-655122 leaves little doubt about the HMXB and most
likely Be/X-ray binary nature of this source (Haberl, Dennerl & Pietsch (2003)).
053109-6609.2
(EXO 053109-6609.2, RX J0531.2-6609, RX
J0531.2-6607,
EXO 0531.1-6609)
This source was discovered by EXOSAT during deep observations of the
LMC
X-4
region in 1983 (Pakull, Brunner, Pietsch et
al.
(1985)). It was detected
again in 1985 by the
SL2
XRT experiment.
The lack of detection in EXOSAT observations made between these dates
demonstrates the
transient nature of the source. The companion is optically identified
with
a Be star (Haberl, Dennerl & Pietsch
(1995)). Burderi, di Salvo, Robba et
al. (1998) reported a timing analysis of the
Be transient X-ray binary
EXO 053109-6609.2 in outburst
observed with BeppoSAX. The pulsed fraction is nearly constant in the
whole
energy range.
The source shows pulsations from 0.1 up to 60 keV.
In the MECS (Medium Energy Concentrator Spectrometer) pulse profile in
the
1.8-10.5 keV band the pulsed fraction
is 0.54±0.05. In the LECS (Low Energy
Concentrator Spectrometer)
pulse profile (the 0.1-1.8 keV band), the
main pulse is still evident, while the interpulse is more broadened,
and
pulsed fraction is 0.78±0.28. The PDS (Phoswich Detection
System) pulse
profile (15-60
keV energy band)
still shows a double-peaked structure (pulsed fraction is
0.64±0.16)
in phase with the previous ones.
Although the statistics is poor, the pulsed fraction does not seem to
decrease with energy (Burderi, di Salvo,
Robba, et
al. (1998)).
J053115.4-705350
(XMMU J053115.4-705350)
This
source is considered likely HMXB candidate (Shtykovskiy & Gilfanov
(2005)). Luminocity was calculated using the archival data of the
XMM-Newton observatory (2-10 keV) (Shtykovskiy
& Gilfanov
(2005)).
J0532.4-6535
(RX J0532.4-6535)
This source was observed by the ROSAT PSPC (Haberl
& Pietsch (1999)). The hardness ratios of this source suggest
an X-ray binary or background AGN. The fact that it is one of three
sources from the catalogue of Reid, Glass
& Catchpole (1988) which are X-ray emitters, with one of them
the known Be/X-ray transient A0538-66, favour an HMXB nature of RX
J0532.4-6535. For a Be/X-ray binary in the LMC the X-ray luminosity is
between 3 and 7 x 1034 erg s-1 (0.1-2.4 keV) (Haberl & Pietsch (1999)). The
relatively low variability suggests a system like X Per or RX
J0146.9-6121 detected during the persistent quiescent state.
J0531.5-6518
(RX J0531.5-6518)
This source was detected with the ROSAT PSPC in June 1990
(Haberl & Pietsch (1999)). The
source is probably variable,
since other pointings
failed to detect
it. The optical counterpart is probably a Be star coming back from an
extended disk-less phase
(Negueruela & Coe (2002)).
J0535.0-6700
(RX J0535.0-6700)
This source was observed by the ROSAT PSPC at a luminosity ~3 x 1035
erg s-1 (Haberl & Pietsch
(1999)). Its
positional coincidence with an optically variable star in the LMC
(RGC28
in paper by Reid, Glass & Catchpole
(1988)) is very good.
RGC28 is an early-type Be star and likely it is the optical counterpart
to
RX J0535.0-6700 (Negueruela & Coe
(2002)). The star
displays periodic variability
in its I-band lightcurve at 241 d, which Reid,
Glass & Catchpole
(1988)
originally believed
to be the period of a Mira variable. Haberl
& Pietsch (1999)
suggested that this
variability
can be related to the orbital period.
0535-668
(RX
J0535.6-6651, 1A 0538-66, 1A 0535-66)
This source was discovered by the Ariel 5 satellite in June 1977,
during
outburst in which the flux peaked at ~9 x 1038 erg s-1
(White & Carpenter (1978)). When
active, 1A 0535-66 displays
very bright
short
X-ray outbursts separated by 16.6 days, which is believed to be the
orbital period. The optical counterpart experiences drastic changes in
the
spectrum, with the
appearance of strong P-Cygni-like emission lines, and brightening by
more
than 2 mag in the V band (Charles, Booth, Densham et
al. (1983)).
The Be star has a V magnitude
of ~14.8
during the X-ray quiescent
periods. The magnitude reaches a peak of 12.5 mag during the X-ray
outbursts.
Detection of a 69-ms pulsation in the X-ray signal has been reported
only
once (Skinner, Bedford, Elsner et al. (1982)).
Further X-ray observations of outbursts were made by Skinner, Shulman, Share et
al. (1980) using
the HEAO 1 satellite. The X-ray outbursts were found to last up to at
least
14
days or to be as short as a few hours. 1A 0535-66 in its largest
outbursts (Skinner, Shulman, Share et
al. (1980)) has luminosity around 1039 erg s-1.
ROSAT (Mavromatakis & Haberl (1993))
and ASCA observations (Corbet, Smale,
Charles & Southwell (1995))
have
revealed low-level outbursts with luminosities of 4 x 1037
erg s-1
and 2 x 1037 erg s-1
in the two ROSAT
observations
and ~5.5 x 1036 erg s-1
in the ASCA
observation.
Due to the low count rate and sampling frequency it was not possible to
determine whether the 69 ms pulsations were present in the data.
The ratio of Lmax to Lmin
in soft X-rays is >1000. Alcock,
Allsman, Alves et
al. (2001)
reported the discovery of 421 day periodicity.
J054134.7-682550
(XMMU J054134.7-682550)
This
source is considered likely HMXB candidate (Shtykovskiy & Gilfanov
(2005)). The pulse period is 61.601 ± 0.017 seconds, with a
pulsed
semi-amplitude of about 40% (Markwardt,
Swank & Corbet (2007)). There are no obvious signs of orbital
Doppler modulation. Assuming this source is a Be star system having a
giant, "Type II" outburst, the estimated orbital period is about 80
days (within a factor of ~2) based on a fit to the Pspin vs.
Porb for other similar systems (Markwardt, Swank
& Corbet (2007)). For a distance of 52 kpc, the mean 2-40 keV
luminosity is 2.0 x 38 erg s-1 (Markwardt, Swank
& Corbet (2007)).
0544-665
(H 0544-665, H 0544-66)
This source was discovered with the HEAO-1 scanning modulation
collimator
by Johnston, Bradt & Doxsey
(1979).
The brightest object within the X-ray error circle was found to be a
variable B0-1 V star (van der Klis, Tuohy,
Elso et
al. (1983)) but no
emission lines have been
observed in its
spectrum to identify it as a Be star. van
der Klis, Tuohy, Elso et
al. (1983) published photometry
which showed a
negative correlation between optical magnitudes and color indices,
typical
of Be stars whose
variability is due to variations in the circumstellar disc. Stevens, Coe & Buckley
(1999)
suggested that
the object may be a Be star in the state of low activity.
J0544.1-7100
(RX J0544.1-7100, AX J0544.1-7100, AX J0548-704,
1WGA J0544.1-7100, 1SAX J0544.1-7100)
This source is a transient X-ray pulsar (P = 96 s) with
hard
X-ray spectrum observed by BeppoSAX (Cusumano,
Israel, Mannucci et al. (1998))
and by ROSAT in the LMC (Haberl &
Pietsch (1999)). The
observations of the optical
counterpart were presented by Coe,
Negueruela, Buckley et
al. (2001), who
found it to display large
variability in
the I-band lightcurve and Hα
in
emission. An approximate spectral
type of B0 Ve was
proposed.