Observation of X-ray binaries with Skylark and Ariel 5

- some hits and some misses

Ken Pounds

University of Leicester

• 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

The Skylark research rocket

Priority in1960s remained in Solar X-ray studies

Ariel 1 (April 1962)

OSO-4 (October 1967)

ESRO-2 (May 1968)

OSO-5 (January 1969)

• 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

Sco X-1 discovery raised a new challenge, with Skylark from Woomera offering an unexplored part of the sky

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 into 500 km circular, equatorial orbit

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)

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

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)

Sky Survey Instrument

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

discovered with Ariel 5 RMC (expt A) identified as a Be star/ neutron star HMXRB in 110 day orbit

A0525+26 a Galactic transient of a quite different character

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 0 - majority were X-ray binaries

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 !