X-RAY AND OPTICAL OBSERVATIONS OF A 0535+26

We present recent contemporaneous X-ray and optical observations of the Be/X-ray binary system A 0535+26 with the Fermi/Gamma-ray Burst Monitor (GBM) and several ground-based observatories. These new observations are put into the context of the rich historical data (since ~1978) and discussed in ter...

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Bibliographic Details
Published in:The Astrophysical journal 2012-07, Vol.754 (1), p.1-16
Main Authors: Camero-Arranz, A, Finger, M H, Wilson-Hodge, C A, Jenke, P, Steele, I, Coe, M J, Gutierrez-Soto, J, Kretschmar, P, Caballero, I, Yan, J
Format: Article
Language:English
Subjects:
ACCRETION DISKS
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BINARY STARS
BRIGHTNESS
CORRELATIONS
COSMIC GAMMA BURSTS
Disks
Equivalence
Evolution
GAMMA ASTRONOMY
Gamma ray bursts
KEV RANGE
MHZ RANGE
Monitors
NEUTRON STARS
OSCILLATIONS
Outbursts
PERIODICITY
PULSARS
PULSES
X RADIATION
X-rays
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Summary:We present recent contemporaneous X-ray and optical observations of the Be/X-ray binary system A 0535+26 with the Fermi/Gamma-ray Burst Monitor (GBM) and several ground-based observatories. These new observations are put into the context of the rich historical data (since ~1978) and discussed in terms of the neutron-star-Be-disk interaction. The Be circumstellar disk was exceptionally large just before the 2009 December giant outburst, which may explain the origin of the unusual recent X-ray activity of this source. We found a peculiar evolution of the pulse profile during this giant outburst, with the two main components evolving in opposite ways with energy. A hard 30-70 mHz X-ray quasi-periodic oscillation was detected with GBM during this 2009 December giant outburst. It becomes stronger with increasing energy and disappears at energies below 25 keV. In the long term a strong optical/X-ray correlation was found for this system, however in the medium term the H alpha equivalent width and the V-band brightness showed an anti-correlation after ~2002 August. Each giant X-ray outburst occurred during a decline phase of the optical brightness, while the H alpha showed a strong emission. In late 2010 and before the 2011 February outburst, rapid V/R variations are observed in the strength of the two peaks of the H alpha line. These had a period of ~25 days and we suggest the presence of a global one-armed oscillation to explain this scenario. A general pattern might be inferred, where the disk becomes weaker and shows V/R variability beginning ~6 months following a giant outburst.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/754/1/20