IGR J17544-2619

Type/Spectral Type Orb. Per. / Spin Per. Radio Counterpart Infrared Counterpart
R.A. (J2000) Dec. (J2000) References (position) R.A. (J2000) Dec. (J2000) References (position)
probable neutron star
Supergiant Fast X-ray Transient / O 9Ib		 4.927 d / 71.49 s 2MASS J17542527-2619526 (2 Mass -J image here )

Rodriguez et al. 2003 Atel 194
17h 54m 25.28s -26° 19' 52.6"
Published Papers
Miscellaneous :
Gonzalez-Riestra et al. 2004
  • NH=~1-2 x 1022 cm-2
  • Candidate IR counterpart confirmed
  • Companion is an early O-type star (?)
  • Oscillation-like behaviour on a time scale of 1.5-2 hours
Smith 2004 Atel 338:
  • Optical magnitudes (USNO B1.0): B2=13.9, R2=11.9, possible distance=8.5kpc
in't Zand 2005:
  • confirms the association of IGR J17544-2619 with 2MASS J17542527-2619526
  • Identified as a blue supergiant located at 3-4 kpc
  • Quiescent spectrum is very soft and suggests the compact object in this source is a neutron star rather than a black hole
  • Column density shows no variations and remains at a level compatible with the Galactic absorption ( NH=~1.4 +/- 0.2 x 1022 cm-2) during flare as compared to quiescence
  • Origin of flares related to donor star
Sguera et al. 2006 :
    20-60 keV peak flux of 240 mCrab
Pelliza et al. 2006:
  • Counterpart is a O9Ib star of 25-28 Msol at 2.1-4.2 kpc
  • Magnitudes estimates => variations in J H, possibly related to X-ray activity
  • Compact object more likely to be a NS
Rahoui et al. 2008:
  • Medium infrared observations
  • SED fitting => AV=6.1, Tstar=31000 K
  • Obscuring material contributes little to MIR spectrum
  • Suggested distance 3.6 kpc
Sidoli et al. 2008: ATel 1454
  • New outburst seen with Swift BAT and XRT
  • BAT light curve is a plateau from ~T-107 s to T+553 s including ~8 s long peak
  • BAT plateau spectrum is simple power-law with Γ=4.7
  • Decrease of the flux of a factor 400 in ~1.5 hours
  • XRT spectrum is hard during peak and significantly softer after
Sidoli et al. 2008:
  • Swift study of the "out-of-outburst" periods
  • Absorbed pl or bbody fits the data well
  • Γ= 2.1 and NH=3.2x1022cm-2 or kT=1.1 keV and NH=1.5x1022cm-2
Bozzo et al. 2008:
  • Theoretical consideration about the accretion in Supergiant High Mass X-ray binaries+expansion to SFXTs.
  • Large factor of luminosity variations <=>Transition between different regimes of accretion (eg sub and super sonic propeller, sub and super Keplerian regimes)
  • No direct accretion
  • =>SFXTs showing large variations and low spin for the pulsar must have magnetic fields of the same order as magnetars.
  • Test on IGR J17544-2619 =>lowest level of emission is compatible with the emission from the supergiant companion
  • In case of magnetic barrier and low spin vs. centrifugal barrier and higher spin=>BIGR J17544-2619 inferred are in the magnetar range
Sidoli et al. 2008:
  • Swift monitoring => observation of 1 flare
  • Spectrum is hard (Γ=0.75) and not so absorbed (NH=1.1 x1022 cm-2).
  • Compared to the out-of-outburst periods, the spectrum is much harder but shows a similar absorption.
  • Broad band spectrum <=> Comptonization model with a plasma temperature of 4 keV and τ=19
  • B comptible with 2-3 x1012 G => difficut to reconcile with high B required by Bozzo et al.'s model
Romano et al. 2008 ATel 1697:
  • Bright flaring activity seen with Swift in observations starting on Sept 4, 2008.
  • Follows observation of intense activity seen with INTEGRAL
  • IBIS 18-40 keV peak is ~50 mCrab
  • XRT light curve shows a peak exceeding 20 counts/s
  • XRT spectrum can be fitted with an absorbed power law with Γ=1.3 and NH=1.8 x1022cm-2. The average unabs. 2-10 keV flux~8 x10-10 erg/cm2/s.
  • Fainter X-ray emission: absorbed power law with NH=1.4 x1022 cm-2, Γ=0.8; average unabs. 2-10 keV flux~2x 10-10 erg/cm2/s .
Sidoli et al. 2009 (MNRAS):
  • Flare of Sept 4, 2008 (as seen with Swift) seems softer than the ones previously observed
  • Spectrum well fitted by either an absorbed power law or an absorbed black body
  • Black body model provides a better representation of the spectrum with kTbb found between 1.5 and 1.8 keV, and a radius of 1.3 km
  • Size of BBody compatible with the size of the polar cap
Romano et al. 2009 (MNRAS):
  • Swift analysis of the first year of monitoring
  • Complete spectral analysis of the data => spectra well fitted with either an absorbed power law or an absorbed black body
  • duty cycle of inactivity = 55% => true quiescence is a rare state
Clark et al. 2009 (MNRAS):
  • Analysis of archival data from INTEGRAL/ISGRI
  • 11 outbursts identified => a period of 4.926 d is identified
  • Period interpreted as orbital period of the system
  • Large outbursts occasionally occur outside periastron
  • Rstar <23 Rsol
Rampy et al. 2009 (ApJ):
  • > 60 hours Suzaku observation: different states of activity
  • Intense flare is seen with flux 9000 times greater than first hours of observations.
  • Separation of observation in several time intervals => On long time scale the (averaged) photon index hardens with increasing flux + absorption roughly constant.
  • Shorter time intervals =>significant variation of Nh is seen.
  • Sudden increase of Nh <=> evidence for the presence of a dense clump in the wind of the companion
Romano et al. 2011a,b:
  • 2 years of Swift monitoring
  • duty cycle of inactivity ~ 55%
  • X-ray spectroscopy in different luminosity phases of activity
  • Analysis of 2010 March outburst
  • Multi-peaked outburst=>could be a defining characteristic of the class and is probably due to inhomogeneities in the companion's wind.
Drave et al. 2012:
  • Discovery of X-ray pulsations in RXTE observations of the region
  • Pulsation at 71.49s
  • Favour IGR 17544-2619 as the origin of this pulsation
Farinelli et al. 2012 (MNRAS):
  • Swift observations
  • Spectral fits and interpretation within framework of comptonisation
Wang & Chang 2012 (A&A):
  • Study retrograde wind accretion scenario
  • => spin and orbital period => R corrotation ~ 1.7e9 cm and source is a retrograde propeller
Drave et al. 2014 (MNRAS):
  • XMM newton observations and archival INTEGRAL data analysis
  • refined estimate of the orbital period to 4.9272 d
  • Analysis of possible orbital geometry and accretion mechanisms => accretion under the quasi spherical accretion model provides a good description of the behaviour of the source`
Mao et al. 2014 (ApJ):
  • Chandra observations of scattered halo
  • Halo produced by 2 interstellar clouds
  • Assuming dsource= 3.6 kpc closest cloud @ d~ 1.8kpc farthest @`d~ 3.4 kpc
Smith 2014 ATel 6227:
  • Ephemeris based on 69 bright outbursts seen with INTEGRAL, RXTE, Swift & Suzaku
  • Period derived = 4.92693 +/- 0.00036 day
  • Periastron at MJD = 53732.65 +/- 0.23
  • Excluding some of the events lead to 4.92646 +/- 0.00040 day and periastron MJD = 53733.11 +/- 0.27.
Bhalerao et al. 2015 (MNRAS):
  • Nustar Observations
  • Spectrum = 1 keV blac body plus power law + cyclotron line @ 17 keV
  • => confirms the source hosts a neutron star, with B~ 1.45 x 1012 G
  • No pulsation detected between 1 and 2000s
Romano et al. 2015 (A&A):
  • Swift observations of a giant outburst on 2014 October 10
  • Reached 2.1 Crab (0.3-10 keV) unabsorbed or L~3e38 erg/s => dynamica range of variations > 1e6
  • Suggest that giant outburst due to the formation of a transient accretion disc
  • Tentative detection of pulsation at 11.6 s (4σ significance)
Sidoli et al. 2016 (MNRAS):
  • Correlation between total energy emitted during outburst and total duration of outburst (valid for 3 SFXTs)
Gimenez-Garcia et al. 2016 (A&A):
  • Spectroscopuc analysis of the optical companion
  • Stellar parameters in good agreement with the O9I spectral type
  • Distance refined to 3.0 ±0.2 kpc
  • eccentricity of the system <0.25
  • Wind terminal velocity =1500 km/s, in combination with the NS spin, might explain the difference with classical sgHMXB

Last updated March 7 2016

Jerome Rodriguez