MASS AND SPECTRAL TYPE OF THE COMPANION STARMASS AND SPECTRAL TYPE OF THE COMPANION STARObservations of LMC X-3 in its low state allowed us to determine the Observations of LMC X-3 in its low state allowed us to determine the mass and spectral type of the companion. The system was observed mass and spectral type of the companion. The system was observed with XMM/OM on 2000 April 19, in a low state. From the U,B,V with XMM/OM on 2000 April 19, in a low state. From the U,B,V brightness and colours we infer that the companion is a subgiant of brightness and colours we infer that the companion is a subgiant of mass 4.5 < mass 4.5 < MM < 5.0 M < 5.0 Msunsun and temperature 15500 < and temperature 15500 < TTeffeff < 16500 < 16500 (spectral type B5 IV). No significant wind is expected from such a (spectral type B5 IV). No significant wind is expected from such a star, in agreement with the low column density star, in agreement with the low column density

inferred from the X-ray data. The companion was inferred from the X-ray data. The companion was previously thought to be a main sequence B3 star previously thought to be a main sequence B3 star ((MM ~~ 7 M 7 Msunsun).).

MASS TRANSFER VIA ROCHE LOBE OVERFLOW MASS TRANSFER VIA ROCHE LOBE OVERFLOW The mean mass density in the Roche lobe (RL) of the companion star The mean mass density in the Roche lobe (RL) of the companion star is uniquely determined by the binary period. We plot here the is uniquely determined by the binary period. We plot here the evolutionary tracks in the (evolutionary tracks in the (MMVV plane (for Z=0.008), compared with plane (for Z=0.008), compared with the mean density inside the RL. Stars with mass the mean density inside the RL. Stars with mass MM ~~ 4.5 M 4.5 Msunsun would would be very close to filling their RL. Mass transfer would occur mainly be very close to filling their RL. Mass transfer would occur mainly via RL overflow, in agreement with our X-ray observations. A more via RL overflow, in agreement with our X-ray observations. A more massive companion would not fill its RL, and the mechanism of mass massive companion would not fill its RL, and the mechanism of mass transfer would have to be a stellar wind. This is ruled out by the transfer would have to be a stellar wind. This is ruled out by the UV/optical colours and by the RGS data.UV/optical colours and by the RGS data.

STATE TRANSITIONS IN LMC X-3STATE TRANSITIONS IN LMC X-3Roberto Soria, Mat Page, Kinwah Wu (MSSL/UCL)

LLxx ~~ 6 x 106 x 103838 erg/s erg/s

LLxx ~~ 5 x 105 x 103535 erg/s erg/s

LLxx ~~ 3 x 103 x 103737 erg/s erg/s

X-RAY SPECTRAL STATE TRANSITIONSX-RAY SPECTRAL STATE TRANSITIONS Most Most black-hole candidates (BHC) show transitions between soft and hard X-black-hole candidates (BHC) show transitions between soft and hard X-ray spectral states. In the soft state, the X-ray spectrum consists of a ray spectral states. In the soft state, the X-ray spectrum consists of a thermal component (disk blackbody) and a power-law component thermal component (disk blackbody) and a power-law component (Comptonised emission); in the hard state, the thermal component is (Comptonised emission); in the hard state, the thermal component is insignificant and the power law is harder. The BHC LMC X-3 (insignificant and the power law is harder. The BHC LMC X-3 (MM > > 5 5 MMsunsun) is normally found in the soft state; a rare transition to the hard ) is normally found in the soft state; a rare transition to the hard state occurred in 2000 April. We used XMM to study its spectral state occurred in 2000 April. We used XMM to study its spectral behaviour over this transition. The thermal disk component behaviour over this transition. The thermal disk component disappeared in the low-hard state, but became dominant again as the disappeared in the low-hard state, but became dominant again as the system returned to the high-soft state. The inner-disk temperature system returned to the high-soft state. The inner-disk temperature changed as shown in the figures below. The emitted luminosity in the changed as shown in the figures below. The emitted luminosity in the 0.3-10 keV band varied by 3 orders of magnitude. The optical/UV 0.3-10 keV band varied by 3 orders of magnitude. The optical/UV luminosity increased by a factor of 2 (0.8 mag) in the high-soft state.luminosity increased by a factor of 2 (0.8 mag) in the high-soft state. WIND ACCRETION RULED WIND ACCRETION RULED

OUTOUT High-resolution RGS High-resolution RGS spectra allowed us to spectra allowed us to determine the absorbing determine the absorbing column density for the X-ray column density for the X-ray emitting region. From the emitting region. From the depth of the Odepth of the O I I absorption absorption edge, weedge, we infer an intrinsicinfer an intrinsic nnHH <<~~ 10 102020 cm cm-2-2 (figure above). (figure above). This rules out wind accretion This rules out wind accretion as the main mechanism of as the main mechanism of mass transfer, and suggests mass transfer, and suggests that accretion is instead due to that accretion is instead due to Roche-lobe overflow.Roche-lobe overflow.

TTinin ~~ 1.3 keV1.3 keV

TTinin ~~ 0.2 keV0.2 keV

disk not detecteddisk not detected

XMM/PN data XMM/RGS data

2000 Feb 02 2000 Mar 07

2000 Jun 09 2000 Nov 24

Confidence contours: 68%, 95%, 99%

nH ~ 4 1020 cm-2 nH ~ 4 1020 cm-2

nH ~ 4 1020 cm-2 nH ~ 4 1020 cm-2

Feb 02Feb 02

Mar 07Mar 07

Nov 24Nov 24

Apr 19Apr 19

Jun 09Jun 09

Apr 19Apr 19

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