J/ApJ/885/105 Chandra X-ray sources in AE Aur region (Rangelov+, 2019)
Runaway O-star bow shocks as particle accelerators? The case of AE Aur
revisited.
Rangelov B., Montmerle T., Federman S.R., Boisse P., Gabici S.
<Astrophys. J., 885, 105 (2019)>
=2019ApJ...885..105R 2019ApJ...885..105R
ADC_Keywords: X-ray sources; Photometry, infrared; Radio sources;
Stars, O; Active gal. nuclei
Keywords: Runaway stars ; Stellar bow shocks ; Particle astrophysics ;
Massive stars ; X-ray astronomy
Abstract:
We present results of our Chandra/ACIS observations of the field
centered on the fast, runaway O star AE Aur and its bow shock.
Previous XMM-Newton observations revealed an X-ray "blob" near the IR
arc tracing the bow shock, possibly a nonthermal source consistent
with models of Inverse Compton scattering of dust IR photons by
electrons accelerated at the shock. The new, subarcsecond-resolution
Chandra data, while confirming the presence of the XMM-Newton source,
clearly indicate that the latter is neither extended nor coincident
with the IR arc and strongly suggest it is a background active
galactic nucleus. Motivated by results published for the bow shock of
BD+43°3654, we extended our study to the radio domain by analyzing
archival EVLA data. We find no radio emission from the AE Aur bow
shock either. The corresponding upper limits for the absorbed
(unabsorbed) X-ray flux of 5.9(7.8)x10-15erg/cm2/s (3σ) and,
in the radio range of 2mJy (1.4GHz) and 0.4mJy (5.0GHz), are used to
put constraints on model predictions for particle acceleration within
the bow shock. In the "classical" framework of diffusive shock
acceleration, we find that the predicted X-ray and radio emission by
the bow shock is at least two orders of magnitude below the current
upper limits, consistent with the systematic nondetections of up to 60
stellar bow shocks. The only exception so far remains that of
BD+43°3654, which is probably the result of its very large
mass-loss rate among runaway O stars.
Description:
We carried out a campaign to observe the region of AE Aur with
Chandra. The program (PI: B. Rangelov) was split into five
observations totaling 140.53 ks exposure over a two-month period. The
first data set was taken on 2016 December 16 (ObsID 19943; 14.88 ks),
followed by 2016 December 17 (ObsID 19445; 44.49 ks), 2017 January 3
(ObsID 19979; 26.72 ks), 2017 January 4 (ObsID 19941; 26.72 ks), and
2017 January 6 (ObsID 19951; 27.72 ks). All data were taken with the
ACIS-I instrument operated in "VeryFaint" Timed exposure mode.
The data have been restricted to the energy range between 0.3 and 7keV
and filtered in three energy bands: 0.3-1.2keV (soft), 1.2-2keV
(medium), and 2-7keV (hard).
We detected a total of 114 X-ray sources in the merged data.
We used archival data from XMM-Newton (PI: F. Damiani,
ObsID 0206360101) with a total exposure time of 58.9ks.
See Section 2.2.
The region of AE Aur has been observed with the EVLA in the C band in
2013 (B configuration; project 13B-212; PI C. Peri), as well as in the
L band in 2016 (C configuration; project 16A-152; PI C. Peri).
See Section 3.5.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
05 16 18.14 +34 18 44.3 AE Aur = V* AE Aur
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 91 114 X-ray sources (ObsID 19445)
table3.dat 60 5 Selected radio sources in the C- and L-band
archival EVLA fields centered on AE Aur
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
B/xmm : XMM-Newton Obs. Log (XMM-Newton Science Operation Center, 2012-)
B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-)
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/328 : AllWISE Data Release (Cutri+ 2013)
J/A+A/331/949 : Wolf-Rayet and O-star runaways kinematics (Moffat+ 1998)
J/ApJS/117/361 : PNe in NRAO VLA Sky Survey (Condon+ 1998)
J/ApJS/169/401 : ChaMP X-ray point source catalog (Kim+, 2007)
J/A+A/493/339 : XMM-Newton serendipitous Survey. V. (Watson+, 2009)
J/MNRAS/410/190 : Young runaway stars within 3kpc (Tetzlaff+, 2011)
J/A+A/578/A45 : E-BOSS. II. Catalogue second release (Peri+, 2015)
J/ApJ/827/96 : WISE census of YSOs in Canis Major (Fischer+, 2016)
J/A+A/594/A116 : HI4PI spectra and column density maps (HI4PI team+, 2016)
J/A+A/612/A3 : HESS Galactic supernova remnants (Hess+, 2018)
J/AJ/157/176 : X-ray emission from Gal. stellar bow shocks (Binder+, 2019)
J/AN/341/645 : AE Aur and iota Ori runaway stars RV curves (Heyne+, 2020)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- CAX [1/114] CAX Sequential running identifier
6- 16 F11.8 deg RAdeg [78.87/79.3] Right Ascension (J2000)
18- 28 F11.8 deg DEdeg [34.15/34.5] Declination (J2000)
30- 43 F14.9 --- Net [4/3397]? Background subtracted net counts,
ObsID 19445 only
45- 52 E8.2 mW/m2 Fx [4.6e-16/2.4e-12]? X-ray flux in the 0.5-7keV
band, erg/s/cm2
54- 61 E8.2 mW/m2 e_Fx [4.7e-16/7.8e-14]? Uncertainty in Fx
63- 67 F5.2 mag Imag [5.8/17.42]? USNO-B1 I band magnitude
69- 74 F6.3 mag Jmag [5.3/16.1]? 2MASS J band magnitude
76- 81 F6.3 mag W1mag [5.3/15.2]? WISE W1 band magnitude
83- 86 A4 --- Class Machine-learning based Class ("AGN",
3 occurrences; or "STAR", 5 occurrences)
88- 89 I2 % Prob [71/92]? Classification confidence
91 A1 --- Flag Source Flags (1)
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Note (1): Source flags as follows:
f = This source is unidentified, but has a radio counterpart, EVS-2;
g = This source is AE Aur;
h = This source is the "LS blob".
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- EVS EVLA source sequential running identifier
(<[RMF2019] EVS-N> in Simbad)
7- 16 F10.7 deg RAdeg [78.94/79.2] Right Ascension (J2000)
18- 27 F10.7 deg DEdeg [34.2/34.4] Declination (J2000)
29- 33 F5.2 mJy Lflux [1.47/13.1] L-band (tuned at 1.52GHz) flux (1)
35- 38 F4.2 mJy Cflux [0.8/1.6]? C-band (tuned at 5.5GHz) flux (2)
40- 44 F5.2 --- alpha [-1.63/-0.36]? Spectral index α from L to
C frequency
46- 58 A13 --- Ident Identification
60 A1 --- Flag Source flag (3)
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Note (1): L band = tuned at 1.52 GHz (config. C: beamsize 11").
Note (2): C band = tuned at 5.5 GHz (config. B: beamsize 1.1"). Sources
EVS-1 and EVS-5 lie outside the C-band FOV (see Figure 7).
Note (3): EVS-2 coincides with CAX-51 to better than 0.1", but has no other
counterpart. Note that AE Aur itself is not detected.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Jan-2025