BlackCAT A Catalog of Stellar-Mass Black Holes in X-ray Binaries

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ID# 30

SAX J1819.3-2525

V4641 Sgr

( Samus1999 )

RA     [J2000]     DEC

[]          []

18:19:21.58  -25:24:25.10

ℓ                      b

[deg]                            [deg]

006.7740023  -04.78873545

Year of discovery: 1999  
( intZand1999 )

# of outbursts after discovery: 3

Basic data

Distance [kpc] 6.2±0.7 MacDonald2014
Distance to the plane (z) [kpc] -0.52±0.06 MacDonald2014
Orbital period (Porb) [h] 67.6152±0.0002 Orosz2001
Peak X-ray flux [erg s-1 cm-2]
Outburst magnitude (AB) V=8.8 Orosz2001
Quiescent magnitude (AB) V=13.96±0.02 MacDonald2014 Orosz2001
E(B-V) [mag] 0.32 – 0.38 MacDonald2014

Dynamically confirmed BH


SAX J1819.3-2525 (V4641 Sgr) showed weak outbursts in 2002 ,2003 ( Bailyn2003 ), 2010 ( Yamaoka2010 ), 2014 ( Tachibana2014 ) and 2018 ( Negoro2018 ), and a complete outburst in 2015 ( Yoshii2015 ) and 2020 ( Shaw2020 ).
Gandhi2019 obtained a distance of 6.24+2.04-1.30 kpc from Gaia DR2.

Dynamical parameters

Orbital period [h] 67.6152±0.0002 Orosz2001
Star's spectral type B9III Orosz2001
Star's radial velocity amplitude (K2) [km/s] 211±3 Orosz2001
Mass function 'f(M1)' [M] 2.7±0.1 Orosz2001
BH mass (M1) [M] 6.4±0.6 MacDonald2014
Mass ratio (q=M2/M1) 0.63 – 0.70 MacDonald2014
Inclination angle (i) [deg] 72±4 MacDonald2014
Rot. broadening (v sini) [km/s] 100.9±0.8 MacDonald2014

Optical/NIR magnitudes

Mag. Outburst (AB)
Mag. Quiescent (AB)
MacDonald2014 Orosz2001
B∼13.91±0.04 V=13.96±0.02 R=13.73±0.02
J=14.86±0.05 H=14.23±0.05 K=12.83±0.05
Aladin finding chart
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SAX J1819.3-2525 in Simbad

Pan-STARRS1 finding chart

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PS1 Finding chart PS1 Finding chart

Finding charts

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Finding chart
Finding chart
Finding chart

This research has made use of NASA's Astrophysics Data System (ADS) and the SIMBAD database operated at CDS (Strasbourg, France)
Please acknowledge the use of this catalogue in any published work you derive from it.

Last modified: 27 August 2021.