J/ApJ/923/191 RXTE, Swift & NICER obs. of WR 140 (Pollock+, 2021)
Competitive X-ray and optical cooling in the collisionless shocks of WR 140.
Pollock A.M.T., Corcoran M.F., Stevens I.R., Russell C.M.P., Hamaguchi K.,
Williams P.M., Moffat A.F.J., Weigelt G., Shenavrin V., Richardson N.D.,
Espinoza D., Drake S.A.
<Astrophys. J., 923, 191 (2021)>
=2021ApJ...923..191P 2021ApJ...923..191P
ADC_Keywords: Stars, Wolf-Rayet; Stars, double and multiple; X-ray sources
Keywords: Wolf-Rayet stars ; Binary stars ; X-ray stars ; Stellar bow shocks ;
Plasma astrophysics
Abstract:
The long-period, highly eccentric Wolf-Rayet star binary system WR140
has exceptionally well-determined orbital and stellar parameters.
Bright, variable X-ray emission is generated in shocks produced by the
collision of the winds of the WC7pd+O5.5fc component stars. We discuss
the variations in the context of the colliding-wind model using
broadband spectrometry from the RXTE, Swift, and NICER observatories
obtained over 20yr and nearly 1000 observations through three
consecutive 7.94yr orbits, including three periastron passages. The
X-ray luminosity varies as expected with the inverse of the stellar
separation over most of the orbit; departures near periastron are
produced when cooling shifts to excess optical emission in
CIIIλ5696 in particular. We use X-ray absorption to estimate
mass-loss rates for both stars and to constrain the system morphology.
The absorption maximum coincides closely with the inferior conjunction
of the WC star and provides evidence of the ion-reflection mechanism
that underlies the formation of collisionless shocks governed by
magnetic fields probably generated by the Weibel instability.
Comparisons with K-band emission and HeIλ10830 absorption show
that both are correlated after periastron with the asymmetric X-ray
absorption. Dust appears within a few days of periastron, suggesting
formation within shocked gas near the stagnation point. The X-ray
flares seen in η Car have not occurred in WR 140, suggesting the
absence of large-scale wind inhomogeneities. Relatively constant soft
emission revealed during the X-ray minimum is probably not from
recombining plasma entrained in outflowing shocked gas.
Description:
In total there are 940 observations of WR 140 by the Rossi X-ray
Timing Explorer (RXTE), Swift, and the Neutron star Interior
Composition ExploreR (NICER), for a total exposure of 1342ks, included
here.
The first observation of WR 140 by RXTE was obtained on 2000-December-9,
63 days before WR140's periastron passage which occurred on
2001-February-10, after which RXTE observed the system approximately
once per week for just over 2yr. After a 2yr hiatus starting in
2003-March, observations resumed on 2005 March 8, 39 days after
apastron (φ=0.513), and continued for 6yr until 2011 December 23,
just before end of mission, at a variable cadence of a few
observations per month to one per day during the periastron passage
and X-ray minimum in 2009 January. See Section 2.1.
We used the X-ray Telescope (XRT) on the Neil Gehrels Swift
Observatory (Swift) to monitor changes in the X-ray spectrum.
The Swift-XRT observations of WR 140 started on 2008 August 11 with
sporadic phase coverage. The last observation we analyze here was
taken on 2018 April 5.
See Section 2.2
NICER is an X-ray astronomy facility that was installed on the
International Space Station (ISS) in 2017 June. NICER's primary
mission is to obtain high time resolved X-ray spectrometry in the
0.2-12keV band with moderate spectral resolution of cosmic X-ray
sources. See Section 2.3.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
20 20 27.97 +43 51 16.2 WR 140 = WDS J20205+4351A
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tableb1.dat 59 533 Log of RXTE / Proportional Counter Array (PCA)
observations and fluxes
tableb2.dat 65 316 Log of SWIFT/XRT observations and fluxes
tableb3.dat 58 89 Log of NICER / X-ray Timing Instrument (XTI)
observations and fluxes
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See also:
B/sb9 : SB9: 9th Catalogue of Spectroscopic Binary Orbits (Pourbaix+ 2004-2014)
B/xmm : XMM-Newton Observation Log (XMM-Newton Science Operation Center, 2012)
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
J/PAZh/37/34 : JHKLM light curves of WR 140 (Taranova+, 2011)
J/AJ/141/129 : Chandra Transmission Grating Data (Huenemoerder+, 2011)
J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)
J/ApJ/838/45 : eta Carinae obs. around 2014 X-ray minimum (Corcoran+, 2017)
J/MNRAS/465/2432 : MiMeS magnetic analysis of O-type stars (Grunhut+, 2017)
J/AJ/156/144 : The very high-eccentricity binary HR7345 (Farrington+, 2018)
J/A+A/625/A122 : CIELO-RGS, soft X-ray ionized emission lines (Mao+, 2019)
Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 I10 --- obsID [2000120902/2011122315] RXTE observation
identifier
12- 20 F9.3 d MJD [51887.1/55918.7] Modified Julian Date
at mid-point (JD-2400000.5)
22- 26 F5.3 --- Phase [1.97/3.37] Orbital Phase
28- 33 F6.1 s Exp [16/2192] Exposure Time
35- 38 F4.2 ct/s Rate [0.79/7.11] Net Count Rate
40- 43 F4.2 ct/s e_Rate [0.08/1.2] Error in Net Count Rate
45- 49 F5.2 ct/s Bkg [10.65/15.74] Background Count Rate
51- 54 F4.2 10-11mW/m2 Flux [0.2/6.1] Flux 2-10keV
56- 59 F4.2 10-11mW/m2 e_Flux [0.1/2.3] Uncertainty in Flux 2-10keV
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 I8 --- obsID [10120001/91396015] SWIFT observation
identifier
10- 18 F9.3 d MJD [54689.2/58587.5] Modified Julian Date
at mid-point (JD-2400000.5)
20- 24 F5.3 --- Phase [2.94/4.3] Orbital Phase
26- 32 F7.1 s Exp [79/19760] Exposure Time
34- 38 F5.3 ct/s Rate [0.029/2.427] Net Count Rate
40- 44 F5.3 ct/s e_Rate [0.003/0.2] Error in Net Count Rate
46- 50 F5.3 ct/s Bkg [0/0.32] Background Count Rate
52- 56 F5.3 10-11mW/m2 Flux [0.15/6.93] Flux 2-10keV
58- 62 F5.3 10-11mW/m2 e_Flux [0.02/1.2] Uncertainty in Flux 2-10keV
64- 65 A2 --- Mode SWIFT mode
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 I10 --- obsID [1120010102/3591010701] NICER observation
identifier
12- 20 F9.3 d MJD [58073.8/59002.2] Modified Julian Date
at mid-point (JD-2400000.5)
22- 26 F5.3 --- Phase [4.1/4.5] Orbital Phase
28- 33 F6.1 s Exp [57.4/4501.1] Exposure Time
35- 38 F4.2 ct/s Rate [7.2/9.4] Net Count Rate
40- 43 F4.2 ct/s e_Rate [0.04/0.5] Error in Net Count Rate
45- 48 F4.2 ct/s Bkg [0.3/3.31] Background Count Rate
50- 53 F4.2 10-11mW/m2 Flux [0.85/1.95] Flux 2-10keV
55- 58 F4.2 10-11mW/m2 e_Flux [0.01/0.2] Uncertainty in Flux 2-10keV
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-May-2023