Fermi Gamma-ray Space Telescope

Fermi ToO 100600-1-1

A ToO observation to observe ASAS-SN 17HX at RA, Dec = 277.9413, -14.3154 (J2000) was approved at 2017-09-12 18:51:51 UTC.

The justification for the ToO is: We request target-of-opportunity observations of the Galactic nova ASASSN-17hx, which was discovered on 2017 June 23 (ATel #10523) and originally peaked at 8.5 mag. During this first rise to maximum, ASAS-SN 17hx was observed for 500 ksec by Fermi/LAT, and we achieved a marginal gamma-ray detection with TS = 14. The marginal gamma-ray detections continued (even after return to normal LAT operations) at TS ~ 10, for the next 3 weeks. We thought this nova then would fade into obscurity, until... A rebrightening of ASAS-SN 17hx is now being observed in the optical (ATel #10735). Its optical light curve is still on the rise, at ~9.2 mag. Intriguingly, the nova now shows substantially faster expansion velocities than it did in July (ATel #10736). Therefore, we expect this later ejection of m

The planned duration is 500.00 ks.

The autonomous request threshold during this ToO is LOW.

The ToO observation should begin between 2017-09-12 18:51:50 UTC and 2017-09-19 18:51:50 UTC.

The ToO observation was requested by PROF. LAURA CHOMIUK.

Exposure Map for Week 484

Exposure Map
  • Energy Band: 100.00 MeV to 200000.00 MeV

Exposure Map for Week 485

Exposure Map
  • Energy Band: 100.00 MeV to 200000.00 MeV
  • The ToO is inserted in the Mission Week 485 timeline from 2017-257-00:00:00 to 2017-261-12:44:00.
  • Exposure is 1.5847e+09 cm^2 s^1 at the ToO location (RA=277.9413, dec=-14.3154)
  • Orbit latitude of the pointing is -29.9612 degrees