2023A&A...671A.120M


Query : 2023A&A...671A.120M

2023A&A...671A.120M - Astronomy and Astrophysics, volume 671A, 120 (2023/3-1)

Discovery of periodicities in two highly variable intermediate polars towards the Galactic centre.

MONDAL S., PONTI G., HABERL F., MORI K., REA N., MORRIS M.R., CAMPANA S. and ANASTASOPOULOU K.

Abstract (from CDS):

Aims. We performed a systematic analysis of X-ray point sources within 1$ \overset{\circ }{.} $5 of the Galactic centre using archival XMM-Newton data. While doing so, we discovered Fe Kα complex emission and pulsation in two highly variable sources, 4XMM J174917.7-283329 and 4XMM J174954.6-294336. In this work we report the findings of the X-ray spectral and timing studies.
Methods. We performed detailed spectral modelling of the sources and searched for pulsation in the light curves using Fourier timing analysis. We also searched for multi-wavelength counterparts for the characterization of the sources.
Results. The X-ray spectrum of 4XMM J174917.7-283329 shows the presence of complex Fe K emission in the 6-7 keV band. The equivalent widths of the 6.4 and 6.7 keV lines are $ 99^{+84}_{-72} $ and $ 220^{+160}_{-140} $ eV, respectively. The continuum is fitted by a partially absorbed apec model with a plasma temperature of $ kT=13^{+10}_{-2} $ keV. The inferred mass of the white dwarf (WD) is $ 0.9^{+0.3}_{-0.2}\,M_{\odot} $. We detected pulsations with a period of 1212 ± 3 s and a pulsed fraction of 26 ± 6%. The light curves of 4XMM J174954.6-294336 display an asymmetric eclipse and dipping behaviour. To date, this is only the second known intermediate polar to show a total eclipse in X-rays. The spectrum of the sources is characterized by a power-law model with photon index Γ = 0.4 ± 0.2. The equivalent widths of the iron fluorescent (6.4 keV) and Fe XXV (6.7 keV) lines are $ 171^{+99}_{-79} $ and $ 136^{+89}_{-81} $ eV, respectively. The continuum is described by emission from optically thin plasma with a temperature of kT ∼ 35 keV. The inferred mass of the WD is $ 1.1^{+0.2}_{-0.3}\,M_{\odot} $. We detect coherent pulsations from the source with a period of 1002 ± 2 s. The pulsed fraction is 66 ± 15%.
Conclusions. The spectral modelling indicates the presence of intervening clouds with a high absorbing column density in front of both sources. The detected periodic modulations in the light curves are likely associated with the spin period of WDs in magnetic cataclysmic variables. The measured spin period, hard photon index, and equivalent width of the fluorescent Fe Kα line are consistent with the values found in intermediate polars. 4XMM J174954.6-294336 has already been classified as an intermediate polar, and we suggest that 4XMM J174917.7-283329 is a new intermediate polar. The X-ray eclipses in 4XMM J174954.6-294336 are most likely caused by a low-mass companion star obscuring the central X-ray source. The asymmetry in the eclipse is likely caused by a thick bulge that intercepts the line of sight during the ingress phase but not during the egress phase located behind the WD along the line of sight.

Abstract Copyright: © The Authors 2023

Journal keyword(s): X-rays: binaries - Galaxy: center - Galaxy: disk - white dwarfs - novae - cataclysmic variables

Simbad objects: 17

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Number of rows : 17
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20     4.09     ~ 3922 0
2 V* XY Ari CV* 02 56 08.19048 +19 26 34.1844           ~ 157 1
3 V* GP Vel HXB 09 02 06.8608812864 -40 33 16.899168060 6.85 7.37 6.87 6.31 6.05 B0.5Ia 1505 0
4 HD 153919 HXB 17 03 56.7725629224 -37 50 38.913331452 6.06 6.78 6.51 6.08 5.90 O6Iafcp 814 1
5 4XMM J174033.8-301501 X 17 40 33.8 -30 15 01           ~ 2 0
6 NGC 6397 GlC 17 40 42.09 -53 40 27.6     5.17     ~ 1979 0
7 2CXO J174517.0-321356 CV* 17 45 17.01 -32 13 56.5           ~ 3 0
8 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 14463 0
9 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 4400 3
10 4XMM J174917.7-283329 V* 17 49 17.713 -28 33 29.44           ~ 1 0
11 [CHM2006] Candidate 1b LXB 17 49 38.039 -28 21 17.50           ~ 78 0
12 2MASS J17495452-2943358 LP* 17 49 54.5223002782 -29 43 35.872018999     21.606   15.668 ~ 10 0
13 IGR J18007-4146 CV? 18 00 42.7046057184 -41 46 50.251807200           ~ 6 0
14 NGC 6819 OpC 19 41 18.5 +40 11 24   8.21 7.3     ~ 635 0
15 V* HU Aqr CV* 21 07 58.1944529400 -05 17 40.557671916   16.198 15.814 14.891   D+M4V 274 1
16 NAME Galactic Ridge ? ~ ~           ~ 500 1
17 NAME Galactic Bulge reg ~ ~           ~ 4309 0

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