2017A&A...606A..89F


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.13CEST07:17:22

2017A&A...606A..89F - Astronomy and Astrophysics, volume 606A, 89-89 (2017/10-1)

Studying the accretion geometry of EXO 2030+375 at luminosities close to the propeller regime.

FURST F., KRETSCHMAR P., KAJAVA J.J.E., ALFONSO-GARZON J., KUHNEL M., SANCHEZ-FERNANDEZ C., BLAY P., WILSON-HODGE C.A., JENKE P., KREYKENBOHM I., POTTSCHMIDT K., WILMS J. and ROTHSCHILD R.E.

Abstract (from CDS):

The Be X-ray binary EXO 2030+375was in an extended low-luminosity state during most of 2016. We observed this state with NuSTARand Swift, supported by INTEGRALobservations and optical spectroscopy with the Nordic Optical Telescope (NOT). We present a comprehensive spectral and timing analysis of these data here to study the accretion geometry and investigate a possible onset of the propeller effect. The Hα data show that the circumstellar disk of the Be-star is still present. We measure equivalent widths similar to values found during more active phases in the past, indicating that the low-luminosity state is not simply triggered by a smaller Be disk. The NuSTARdata, taken at a 3-78keV luminosity of ∼6.8x1035erg/s (for a distance of 7.1kpc), are nicely described by standard accreting pulsar models such as an absorbed power law with a high-energy cutoff. We find that pulsations are still clearly visible at these luminosities, indicating that accretion is continuing despite the very low mass transfer rate. In phase-resolved spectroscopy we find a peculiar variation of the photon index from ∼1.5 to ∼2.5 over only about 3% of the rotational period. This variation is similar to that observed with XMM-Newtonat much higher luminosities. It may be connected to the accretion column passing through our line of sight. With Swift/XRT we observe luminosities as low as 1034erg/s where the data quality did not allow us to search for pulsations, but the spectrum is much softer and well described by either a blackbody or soft power-law continuum. This softer spectrum might be due to the accretion being stopped by the propeller effect and we only observe the neutron star surface cooling.

Abstract Copyright: © ESO, 2017

Journal keyword(s): X-rays: binaries - stars: neutron - accretion, accretion disks - magnetic fields - magnetic fields

Simbad objects: 8

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Number of rows : 8

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 V* V635 Cas HXB 01 18 31.9704429246 +63 44 33.071137750 17.05 16.64 15.19 14.34 13.22 B0.2Ve 661 0
2 V* BQ Cam HXB 03 34 59.9116460415 +53 10 23.296351781   17.16 15.42 14.26 13.04 O8.5Ve 398 1
3 HD 245770 HXB 05 38 54.5749436467 +26 18 56.839215267 9.30 9.84 9.39 8.77 8.30 O9/B0III/Ve 870 0
4 V* GP Vel HXB 09 02 06.8610736194 -40 33 16.896402010 6.85 7.37 6.87 6.31 6.05 B0.5Ia 1373 0
5 V* V850 Cen HXB 13 01 17.0966951298 -61 36 06.636402972   15.6       B2Vne 273 0
6 HD 226868 HXB 19 58 21.6758193269 +35 12 05.782512305 9.38 9.72 8.91 8.42   O9.7Iabpvar 3925 0
7 V* V2246 Cyg HXB 20 32 15.2744631713 +37 38 14.839930326   22.16 19.41 17.32 15.18 B0Ve 376 0
8 GSC 03588-00834 HXB 21 03 35.7101268891 +45 45 05.568943629   15.34 14.20 13.49 12.75 B0Ve 147 0

    Equat.    Gal    SGal    Ecl

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2020.07.13-07:17:22

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