J/MNRAS/449/268 Type II bursts in the Rapid Burster (Bagnoli+, 2015)
A population study of Type II bursts in the Rapid Burster.
Bagnoli T., In't Zand J.J.M., D'angelo C.R., Galloway D.K.
<Mon. Not. R. Astron. Soc., 449, 268-287 (2015)>
=2015MNRAS.449..268B 2015MNRAS.449..268B (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, X-ray ; Gamma rays
Keywords: stars: neutron - X-rays: binaries - X-rays: bursts -
X-rays: individual: MXB 1730-335
Abstract:
Type II bursts are thought to arise from instabilities in the
accretion flow on to a neutron star in an X-ray binary. Despite having
been known for almost 40 years, no model can yet satisfactorily
account for all their properties. To shed light on the nature of this
phenomenon and provide a reference for future theoretical work, we
study the entire sample of Rossi X-ray Timing Explorer data of
type II bursts from the Rapid Burster (MXB 1730-335). We find that
type II bursts are Eddington-limited in flux, that a larger amount of
energy goes in the bursts than in the persistent emission, that type
II bursts can be as short as 0.130s, and that the distribution of
recurrence times drops abruptly below 15-18s. We highlight the
complicated feedback between type II bursts and the NS surface
thermonuclear explosions known as type I bursts, and between type II
bursts and the persistent emission. We review a number of models for
type II bursts. While no model can reproduce all the observed burst
properties and explain the source uniqueness, models involving a
gating role for the magnetic field come closest to matching the
properties of our sample. The uniqueness of the source may be
explained by a special combination of magnetic field strength, stellar
spin period and alignment between the magnetic field and the spin
axis.
Description:
This study is about measurements with the Proportional Counter Array
(PCA) onboard RXTE.
Nearly all RXTE observations of the RB (exposure time 2.4Ms) were
carried out in one of three configurations. For 553ks, the PCA was
directly pointed at the source. These observations are contaminated by
the presence of the persistently bright 4U 1728-34 at an angular
distance of 0.56°. For 612ks, the pointing was offset by just this
amount, thus avoiding the contamination at the expense of roughly half
the effective area. Finally, for 1.3Ms the PCA was pointed at
4U 1728-34, serendipitously encompassing the RB. We have investigated all
of the 2.4Ms of data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 156 5547 Burst properties for the entire sample
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Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1 I1 --- Flag [0/1] Contamination flag (1)
3- 17 A15 --- ObsID Observation ID
19- 22 A4 --- Mode Burst mode
24- 30 F7.2 ct/s Fpersmin Minima of persistent flux measured in a 8-s
long interval before the burst
32- 39 F8.2 --- Ftot ? Total average flux (persistent+burst)
within a recurrence time
40 A1 --- n_Ftot [i] i for infinity
41- 50 F10.2 --- EpersP Total persistent fluence before a burst (2)
52- 61 F10.2 --- EperN Total persistent fluence after a burst (3)
63- 71 F9.2 --- EpersPs Total persistent fluence before a burst, after
subtracting Fpersmin*Delta_t (4)
73- 81 F9.2 --- EpersNs Total persistent fluence after a burst, after
subtracting Fpersmin*Delta_t (4)
83- 94 F12.2 s Tstart Burst start time, MET
96-101 F6.2 s Dur Duration
103-109 F7.2 ct/s Fpeak Net peak flux [c/s/pcu] (after subtracting
persistent and background counts)
111-119 F9.2 ct Eb Net burst energy [c/PCU] (after subtracting
persistent and background counts)
121-127 F7.2 s DtP Duration of the previous burst,
if =0: no continuous data to the prev burst
129-136 F8.3 s DtN Duration of the next burst,
if =0: no continuous data to the next burst
138 A1 --- l_alphaP Upper limit flag (eg if data gap) on alphaP
139-145 F7.3 --- alphaP Backward-defined alpha value (5)
147 A1 --- l_alphaN Upper limit flag (eg if data gap) on alphaN
148-156 F9.3 --- alphaN forward-defined alpha value (6)
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Note (1): Contamination flag:
if =0 4U1728-34 is in FOV -> Do NOT use columns 4 through 9, 16 through 19
Note (2): Divide by (DtP, duration of the previous burst) to get
<Fpers>prev, i.e., the burst average flux previous a burst.
Note (3): Divide by (DtN, duration of the next burst) to get <Fpers>next,
i.e., the burst average flux after a burst.
Note (4): basically, it indicates if there's a surplus of fluence, i.e. a hump,
before/after the burst.
Note (5): Backward-defined alpha value is the parameter that is normally
employed in studies of type I bursts.
Note (6): Forward-defined alpha value shows a more significant relationship for
type II bursts.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 10-Nov-2015