SSM onboard ASTROSAT Calibration and First Results SAG

SSM onboard ASTROSAT Calibration and First Results SAG, SMG, CSG @ ISRO Satellite Centre, Bangalore IUCAA, Pune VSSC, Trivandrum M. C. Ramadevi IACHEC, IUCAA, Mar. , 1 st, 2016

● ● ● scan almost 50% of the sky in one full rotation of the platform in 6 hours Step and Stare mode (10 min at every 10 deg) Sensitivity of ~30 m. Crab in 10 min

Instrument Details Detector 1 D position sensitive gas proportional counter Coded Mask 1 D coded mask Gas mixture (75% P-10 + 25% Xe) @ 800 torr Anode Carbon coated Quartz (25 mic dia) Cathode Gold coated Tungsten (75 mic dia) Anode High Voltage 1500 Volts 5

Science Objectives ● Detect and locate transient sources ● Long-term time variability ● Transient Alert generation ● Catalog ● ● ● scan almost 50% of the sky in one full rotation of the platform once in every 6 hours Step and Stare mode (10 min at every 10 deg) Sensitivity of 30 m. Crab in 10 min

SSM – Crab observations – Imaging aspects – Sensitivity – Collimator response – Spectral – Timing

Xray sky SSM Powered ON Oct 12, 2015 Earth occult SAA

Crab in SSM FOV (First orbit of SSM observations onboard – Oct 12, 2015) Angular resolution – expected 12 arcmin - Observed - Confined within a pixel (12 arcmin X 2. 5 deg) ➢sub-pixel imaging – aiming at finer resolution

Sub-pixel imaging (First orbit of SSM observations onboard – Oct 12, 2015) ● ● ● . Sub-pixel imaging for localising the source better additional peaks – probably due to statistics of the data from single orbit. Need to co-add many orbits for sub-pixel imaging in order to get rid of the spurious peaks

Crab in SSM 1, 2, 3 FOV - Crab at the expected locations in all three units - Observed at various positions in FOVs of each unit - spurious peaks are observed - fine tuning of calibration constants - Careful data selection

PV Phase : Second slot Crab observations (Nov, 2015) PV Phase : First slot Crab observations (Oct 2015) Crab counts extracted from Sky Image

SSM Crab Obs Collimator Response Crab at different positions in SSM's Field of View + + + + +

Crab at different positions in SSM's FOV - analysis is underway.

Crab spectrum ● ● ● SSM observations with Crab as the strong source in FOV Large FOV (100 X 22 sq-deg) and background is significantly high Other source contributions Position of the Crab in the FOV also to be considered - collimator response An Optimistic attempt. . .

Anode spectra

Ground calibration

Crab spectra in first three PV phases observations Black – Oct. 12 Th , 2015 Red – Nov 6 th, 2015 Green – Jan 15 th, 2016

Crab in FOV and Faint field spectra In Black - Crab spectrum with other unresolved sources + bkgd - FOV: 100 X 22 sq deg In Red – Faint field observations – considered bkgd

Crab in FOV along with other sources (one of the FOVs) RA Dec 52. 7972 43. 9031 53. 7498 53. 1734 64. 9252 55. 9996 65. 4281 32. 9075 83. 6332 22. 0145 84. 7272 26. 3158 94. 2092 22. 4708 94. 2805 9. 1371 95. 6852 -0. 3457 104. 61 -7. 2638 cnt/s src-name (theta_x, theta_y) in SSM 2. 19 gkper -11. 62383 -43. 82445 0. 225 v 0332+53 -2. 23588 -49. 95809 2. 19 xtej 0421+560 7. 90293 -47. 91637 0. 225 groj 0422+32 -8. 99822 -28. 92295 30 crab 0. 72754 -11. 44549 0. 9 x 0535+262 3. 56415 -14. 91754 2. 19 ic 443 snr 9. 96182 -7. 93732 3. 3 x 0614+091 4. 82040 4. 50453 0. 225 x 0620 -003 2. 36662 13. 77493 0. 6 x 0656 -072 8. 24969 23. 78644

Crab-FOV spectrum (black) and simulated Crab spectrum

● Observed Crab spectrum – other source contributions and background to be removed (100 X 22 sq-deg) – ● ● Choice of orbits with common FOVs with sources present in FOVs of Crab obs Diffuse X-ray Background spectra needs to be known Band-wise imaging – source flux extraction in different energy bands - spectral fitting for the source needs to be done

SSM – GRS 1915+105 Black Hole source Observations; Oct 15, 2015 Astronomer's Telegram ATel#8185 generated on the above detection of variability in GRS 1915+105

β-Class variability

SSM Observations of a binary pulsar 4 U 0115+63 Observed on October 26, 2015

Pulsations from binary pulsars Vela X 1 241+/-0. 8 s Cen X 3 4. 8+/- 0. 25 s

From Oct 12, 2015 to Dec 10, 2015

Current status ➢ Operational since Oct 12 th, 2015 ➢ Instrument in PV phase ➢ Initial results are very encouraging ➢ More detailed analysis for every calibration aspect of the instrument is underway ➢Looking forward to interesting discoveries and dedicated Xray sky survey with SSM

To. O Observations with ASTROSAT -> Optimal planning required – being worked out -> How fast we can do it -> And make the best use of ASTROSAT capabilities to study these sources

Thank you

PV Phase : First slot Crab observations PV Phase : Second slot Crab observations

SSM Observations of GRS 1915+105 – orbit 00248 Spectral Variability

SSM – Indication of a M - class S olar Flare SSM light curve on 16 th October 2015

Nov. 4, 2015 3: 25 UT Oct. 16, 2015 6: 10 UT

Performance Specs Parameter Expected Specs Observed Specs Remarks Angular Resolution 12 arcmin X 2. 5 deg FWZM of per pixel: 10 arcmin X 2. 5 deg Will definitely be better with sub-pixel imaging Hardness Ratio (Gain indicator and Spectral parameter) 0. 9 +/- 0. 05 (for Crab) (Can vary with other sources in FOV) 0. 5 to 0. 8 (With all sources in FOV + Sky background) Extracting events with respect to different sources needs to be done. Removal of background needs to be done Sensitivity 25 m. Crab at 10 min integration time Yet to be estimated. However, imaging at finer timebins with 1 Crab source was tried. Yet to be estimated from faint fields Effective Area 11 sq cm at 2. 5 ke. V 53 sq cm at 5 ke. V First order estimate of counts from Crab indicate the expected value Yet to be estimated

Xray sky SSM Powered ON Oct 12, 2015 Earth occult SAA

Spectrum

SSM – GRS 1915+105 Black Hole source Observations Oct 15, 2015 GRS 1915+105 at (theta_x, theta_y): (1, 20) in SSM 3 FOV

SSM – GRS 1915+105; Black Hole source Observations; Oct 15, 2015 – SSM Sky Image GRS 1915+105 at (-1, -25) in SSM 1 FOV along with other sources

SSM as an indicator of SAA entry ✔ SSM detectors show signatures of SAA entry promptly with an increase in veto count rates. This has been used by LAXPC team to set/optimize the timings for SAA entry/exit accordingly with the existing time-tagged mode of operation. ✔ It is being planned to use this parameter of SSM for indication of SAA entry, as a back-up plan for the existing time-tagged mode of SAA entry-exit operations by mission. ✔ In this context SSM team is working out the procedure for Event-Based-Command for SAA entry with SSM parameter along with Controls and Mission team.