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Observation of X-ray binaries with Skylark and Ariel 5
- some hits and some misses
Ken Pounds
University of Leicester
The Skylark research rocket
• first test flight at Woomera in
February 1957
• payload of 150 kg to 300 km
• Sun, Moon and star-pointing
versions from 1964
• Leicester group set up in 1960
with £13k grant to `study solar
and stellar X-ray emission’
• PC on Sun in September 1961
(Sco X-1 also in view !)
• Stellar X-ray instrument selected
for OAO-C (Copernicus) in 1961
Priority in1960s remained in Solar X-ray studies
ESRO-2 (May 1968)
Ariel 1 (April 1962)
OSO-4 (October 1967)
OSO-5 (January 1969)
Sco X-1 discovery raised a new challenge, with Skylark
from Woomera offering an unexplored part of the sky
• SL 118 (10 April 1967)
295 cm2 PC. FOV 30x30 deg.
First use of rtd/psd background reduction
• Cen X-2 brighter and softer than Sco X-1.
Tau X-1 also detected. (Cen X-3 not seen)
• SL 723 (July 1968) and 724 (April 1969) with
largest PCS to date, 2 x 1380 cm2
• spectra of brightest sources
Skylarks 723/724 in 1968/69
Attitude controlled Skylark allowed more sophisticated experiments
• Bragg polarimetry of Sco X-1 (P<17%)
• cooled Si-LiF spectrometer to measure ISM Oxygen absorption edge
• grazing incidence slat telescope mapping of the Vela SNR
and 2 flights to obtain precise source positions:
• concertina-type modulation collimator (Centaurus field)
• lunar occultations of GX 3+1 and GX 5-1
GX 3+1 (September/October 1971)
Sun-pointing vehicle, with Sco X-1 detector to
fix roll angle
Launch timing for occultation to occur when
rocket at apogee
A sub-arc-sec position
but no optical counterpart found !
due to heavy dust obscuration in GC region
it was time to move into orbit!
Ariel 5 Scout B-1 launch 15 October 1974
500 km circular, equatorial orbit
129 kg S/C into equatorial LEO
10 rpm spin with axis control by gas
jets, later by magnetorquer
operated for 5.5 years to re-entry in
March 1980
A. Rotation modulation collimator (UCL/MSSL)
B. Sky survey Instrument (Leicester)
C. Proportional counter spectrometer (UCL/MSSL)
D. Bragg Polarimeter (Leicester)
F. Hard X-ray scintillation counter (Imperial)
G. All sky monitor (Goddard)
into
Sky Survey Instrument
6 quick-look orbits data in near real-time - adding to the excitement –
and to the effective science exploitation
bulk data within 24 hours
• SSI data (sector, time, energy) stored in
1024 (16 bit) words over each orbit
(15 tweets in 2012 currency)
• data reduction by PDP-8 computer
on to strip chart, labelled with known
X-ray sources and candidate objects
• revised commands sent if required
• data to main frame computer
together with S/C housekeeping etc
Analysis automated – but quick-look data monitored by duty scientist team
(Cooke, Elvis, Griffiths, Lawrence, McHardy, Seward, Turner, Watson, Villa)
Sky Survey Instrument
PC of 145 cm2 (LE) and 290 cm2 (HE)
0.75 x 10.5 0 FOV, inclined at 65 0 to spin plane
74 orbits data with
the spin axis to the
Galactic pole
strong sources in
Galactic bulge
Several new
detections from long
exposure
many variable from
day to day (Tra X-1)
Observing Cen X-3 over 8
binary cycles
Strong support for
stellar wind model
and first detection of
accretion wake
transient or highly variable sources were surprisingly
common in the X-ray sky
SSI study with 1 orbit time resolution revealed 27 fast transients in 3 A catalogue,
mostly Galactic but also a BL Lac and a GRB.
Low mass and high mass binary systems looked very different
A0620-00 (nova Mon)
• new X-ray source seen in SSI
over weekend 2/3 August
• European Astronomy Society
meeting 3 days later – in
Leicester
• brightest ever cosmic X-ray
source after 2 weeks
• attracting alarming headlines
• but priority target for radio and
optical telescopes worldwide
Short exposure
with UK Schmidt
telescope at
Siding Springs
Palomar Sky
Survey red plate
V616Mon
K5V star (mv 22>11)
A0620-00
Ariel 5 monitoring continued for 6
months as X-ray flux fell back
exponentially
• optical counterpart identified by 7 mag
increase, spectroscopy showed a 7.8 hr
binary system with unseen companion
• high orbital velocity shows companion
too massive for neutron star
• now confirmed as a 11 (+/- 2) solar
mass black hole
• predicted to flare again in 2033
A0525+26 a Galactic transient of a quite different character
discovered with Ariel 5 RMC (expt A)
identified as a Be star/ neutron star HMXRB
in 110 day orbit
further giant outbursts seen by GINGA, EXOSAT and RXTE. Lx > 1037
smaller outbursts at regular periastron passage
GX301+02
discovery of long period X-ray pulsars
on-axis PCS (expt C) found
11.6 min X-ray pulse period of
GX301-2
period found to vary by up to
0.5 s in a sinusoidal manner
extended observations
revealed 41 day orbit about a
B2 supergiant star
3A catalogue contained 109 sources at |b| < 10
- majority were X-ray binaries
0
highlighting A1909+04 = SS433
a super-luminous black hole binary star
Observation of X-ray binaries with Skylark and Ariel 5
a few misses, but enough hits to finally give up
Solar Physics !