The rapid X-ray variability of V4641 Sagittarii (SAX J1819.3-2525 = XTE J1819-254)

Abstract

We report on the rapid X-ray variability of the variable star and X-ray transient V4641 Sagittarii (SAX J1819.3-2525; XTE J1819-254) as observed on 15 Sept. 1999 by the proportional counter array (PCA) on board the Rossi X-ray Timing Explorer (RXTE). During the first ~900 s of the first PCA observation, V4641 Sgr showed very strong X-ray fluctuations by a factor of 4 on time scales of seconds to about 500 on time scales of minutes. The spectrum of the source during this flaring episode became harder when the count rate decreased. After this flaring episode, V4641 Sgr entered a quiescent state in which it remained for the rest of this, and the subsequent PCA observations. The X-ray spectrum was considerably softer in this quiescent state than during the flaring episode. The intrinsic X-ray luminosity (both during the flaring episode and the quiescent state) and the rapid X-ray variability do not strongly constrain the nature of the compact object (neutron star or black hole) in the system, although a black hole seems to be more likely. The very short duration of the bright X-ray phase of V4641 Sgr and its likely close distance suggest that many similar objects could be present in our galaxy, most of which are not noticed when they are in X-ray outburst due to the short duration of these outbursts. A considerable number of the black holes present in our galaxy might be contained in systems similar to V4641 Sgr.

Accepted for publication in ApJ Letters, 12 Nov 1999

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Cited by in corpus (29)

• WATCHDOG: A Comprehensive All-Sky Database of Galactic Black Hole X-ray Binaries
• A Black Hole in the Superluminal source SAX J1819.3-2525 (V4641 Sgr)
• On the Misalignment of Jets in Microquasars
• Super-Eddington outburst of V4641 Sgr
• Inclination Effects and Beaming in Black Hole X-ray Binaries
• The obscured X-ray binaries V404 Cyg, Cyg X-3, V4641 Sgr, and GRS 1915+105
• The low-luminosity accretion disc wind of the black hole transient V4641 Sagittarii
• X-Ray Flares and Oscillations from the Black Hole Candidate X-Ray Transient XTE J1650-500 at Low Luminosity
• Black Holes in Short Period X-ray Binaries and the Transition to Radiatively Inefficient Accretion
• M74 X-1 (CXOU J013651.1+154547): An Extremely Variable Ultraluminous X-Ray Source
• X-Ray Observations of V4641 SGR (= SAX J1819.3-2525) During the Brief and Violent Outburst of 2003
• Luminous X-ray Flares from Low Mass X-ray Binary Candidates in the Early-Type Galaxy NGC 4697
• Optical and near-infrared observations of the microquasar V4641 Sagittarii during the 1999 September outburst
• Discovery of thermonuclear (Type I) X-ray bursts in the X-ray binary Swift J1858.6-0814 observed with NICER and NuSTAR
• NuSTAR observations of the Transient Galactic Black Hole Binary Candidate Swift J1858.6-0814: A New Sibling of V404 Cyg and V4641 Sgr?
• Fast X-ray Transients and Their Connection to Gamma-Ray Bursts
• Origin of Spin-Orbit Misalignments: The Microblazar V4641 Sgr
• Dips and eclipses in the X-ray binary Swift J1858.6-0814 observed with NICER
• New clues on outburst mechanisms and improved spectroscopic elements of the black-hole binary V4641 Sagittarii
• The variable radio counterpart of Swift J1858.6-0814
• A search for very high-energy flares from the microquasars GRS 1915+105, Circinus X-1, and V4641 Sgr using contemporaneous H.E.S.S. and RXTE observations
• Soft X-ray emission lines in the X-ray binary Swift J1858.6-0814 observed with XMM-Newton-RGS: disc atmosphere or wind?
• MAXI and NuSTAR observations of the faint X-ray transient MAXI J1848-015 in the GLIMPSE-C01 Cluster
• The $\text{False Widow}$ Link Between Neutron Star X-ray Binaries and Spider Pulsars
• X-ray Eclipse Mapping Constrains the Binary Inclination and Mass Ratio of Swift J1858.6-0814
• X-ray flashes from the low-mass X-ray binary IGR J17407-2808
• Timing Analysis of V404 Cyg during Its Brightest Outburst with INTEGRAL/SPI
• Accretion Geometry of Black Hole X-ray Binaries: Insights from X-ray Observations
• The complex spectral behavior of the newly discovered neutron star X-ray binary Swift J1858.6-0814