Imaging the Crab nebula when it is flaring in gamma-rays

0 Assigned ID: 523 ----- Attempting Submission 1 (Fri Apr 11 15:18:24 GMT 2014) ----- 0 ----- Attempting Submission 1 (Thu Jul 24 08:48:26 GMT 2014) ----- Imaging the Crab nebula when it is flaring in gamma-rays One of the most intriguing results of the gamma-ray instruments currently in orbit has been the detection of powerful flares from the Crab Nebula. Such events, with a recurrence time of about once per year, can be so dramatic to make the system the brightest source in the gamma-ray sky, as it occurred in April 2011. Such a discovery challenges our understanding of how pulsar wind nebulae work and defies current astrophysical models for particle acceleration. With the aim of locating the site(s) of the flares, an ad hoc HST strategy have been put in place to be prepared and react promptly in case of a new brightening in gamma rays. We ask here for a triggered TOO observation of the Crab Nebula with ACS/WFC in case a gamma-ray flare is announced by the Agile and/or the Fermi missions. This TOO is crucial part of a multiwavelength program that we have organized, based on lessons learnt from our follow-up observations of previous flares, including a regular (quarterly) monitoring of the source both in X-rays and optical through a joint Chandra-HST proposal. We ask to perform four-epoch imaging of the Crab Pulsar and Nebula, reacting with the fastest possible response time to a trigger provided by the detection of a new gamma-ray flare from the Crab by Fermi-LAT and/or AGILE. The first-epoch observation should be performed as soon as possible after the trigger, the second-epoch observation one week after the first observation, the third one week after the second and the fourth one week after the third. We will use the HST/ACS instrument in its WFC configuration, with the large-band F550M filter, well suited to sample the continuum emission from the system, with almost no contamination from line emission from the SNR filaments. For each epoch, a box dithering pattern will be implemented to fill the inter-chip gap as well as to reject cosmic ray hits. Setting an exposure of 500 s for each position of the dithering pattern results in 2000 s exposure time per visit, which is well suited to achieve our goals and allows for an optimal use of the orbital visibility window. The images collected under this ToO will be completed and compared with images acquired with an identical instrument setup by the quarterly HST monitoring campaign that we have successfully proposed as a joint Chandra-HST program. HOT STARS 12 false false 0.0 0.0 false false false SUPPORTED STAR NEUTRON STAR PULSAR J2000 J2000 ACS/WFC Imaging No No F550M ACS/WFC Imaging No No F550M ACS/WFC Imaging No No F550M ACS/WFC Imaging No No F550M POS-TARG DITHER 3.5 LINE 0.5 false false 85.28 4 85.28 ACS-WFC-DITHER-BOX 1

false

1406020159364 Timing link suitability includes constraints ([02 After 01 by 7.0 to 8.0 days]) The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. 1408585634000 266.8673043042915 (Tic-Visit :proposal-id 13751 :visit-id "01" :proposal-version -1 :trans-version "20140605" :date "22-Jul-2014 11:09:19.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13751 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13751 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2704 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3070 :pcs-gap 0 ) true 1 0 This is a target of opportunity observation. The trigger will be provided by the detection of a new gamma-ray flare from the Crab nebula by Fermi-LAT and/or AGILE. 1406020164632 Timing link suitability includes constraints ([02 After 01 by 7.0 to 8.0 days] [03 After 02 by 7.0 to 8.0 days]) The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13751 :visit-id "02" :proposal-version -1 :trans-version "20140605" :date "22-Jul-2014 11:09:24.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13751 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13751 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2704 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3070 :pcs-gap 0 ) true 1 0 1406020168405 Timing link suitability includes constraints ([03 After 02 by 7.0 to 8.0 days] [04 After 03 by 7.0 to 8.0 days]) The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13751 :visit-id "03" :proposal-version -1 :trans-version "20140605" :date "22-Jul-2014 11:09:28.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13751 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13751 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2704 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3070 :pcs-gap 0 ) true 1 0 1406020171270 Timing link suitability includes constraints ([04 After 03 by 7.0 to 8.0 days]) The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13751 :visit-id "04" :proposal-version -1 :trans-version "20140605" :date "22-Jul-2014 11:09:31.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13751 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13751 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2704 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3070 :pcs-gap 0 ) true 1 0