TCrB Instructions

[It's Happening]

PI & COIs

Gamma-ray:
PI: David Green (+49 151 57636472)
COIs: Rubén Lopez Coto, Julian Sitarek (phone in here, during the night call me from shift leader mobile phone)

Stellar Intensity Interferometry:
PI: Tarek Hassan (+34 680 26 02 66)
COIs: Alejo Cifuentes (+34 629 52 31 95) Juan Cortina (+34 646 357 376)

Source

Source: T CrB
Coordinates: RA = 15h 59m 30.16s, DEC = +25º 55' 12.61"
Wobble: Standard
Zenith angle: < 70 deg
HV settings: Standard / Interferometry / Reduced HV (if around full moon)
DT settings: Extragalactic / Moon
Stereo observations with LST-1

Instructions

This section describes the instructions for the first night of observations of T CrB. Unless otherwise stated by the PIs, these observations are broken into two parts: Gamma-ray and Stellar Intensity Interferometry (SII). After the first night, only gamma-ray observations are planned, except if you are told otherwise by the PIs.

If you receive an alert regarding the T CrB eruption during the night, please call the PIs as soon as possible (their phone numbers are listed at the top of this page). In the case that gamma-ray observations of T CrB are started due to the automatic (GRB) procedure, stop these observations and switch to SII as described below. Also, if the PIs are not available, please begin the SII observations and keep trying to contact them. Once the PIs are aware of the eruption, communication with them should go through the following Zoom room: https://mppmu.zoom-x.de/j/65181605135?pwd=eW9lQjhyd25yK3ovU1paQTY2ZG9OZz09.

Important: The automatic GRB procedure should be disabled when observing T CrB to prevent the automatic repointing to another eventual transient event.

Coordination with MAGIC

T CrB observations should be done together with MAGIC. For this purpose, the Shift Leader phone is in a Telegram group with the PIs and the MAGIC Shift Leader phone. Use this group and the aforementioned Zoom room to coordinate the wobble positions with MAGIC and communicate with the PIs.

Cadence of Observations

The cadence of observations for the first night will go as described below unless otherwise stated. Wobble positions should be coordinated with MAGIC.

• SII: First 40 minutes (ON mode)
  
• Gamma-ray: Next 40 minutes (standard W1 + W2)
  
• SII: Next 20 minutes (ON mode)
  
• Gamma-ray: Next 40 minutes (standard W3 + W4)
  
• SII: Next 20 minutes (ON mode)
  
• Gamma-ray: Next 40 minutes (standard W1 + W2)
  
• Repeat the 20/40 minute cycle until T CrB goes above a zenith angle of 70 deg or the night ends.

It may be the case that LST only does gamma-ray observations and, if so, they will follow the standard wobble scheme. In this case, the procedure described above should be slightly changed so that the wobbles used by MAGIC match those used by LST, as shown in the following table:

If LST only takes

gamma-ray data

LST	MAGIC
W0.40+000	ON
W0.40+180	ON
W0.40+090	W0.40+090
W0.40+270	W0.40+270
W0.40+000	ON
W0.40+180	W0.40+180
W0.40+090	W0.40+090
W0.40+270	ON
W0.40+000	W0.40+000
W0.40+180	W0.40+180
...	...

There is also the chance that the initial 40-min SII observations will be shortened if T CrB is not detectable by SII. In that case, the 40-min gamma-ray observations will begin and the 20/40 cycle will follow. Instructions on how to determine whether T CrB has been detected by SII are given below, as well as the detailed steps to swap from SII to gamma-ray observations and the other way around.

Gamma-ray observations

Gamma-ray observations are straightforward, since the source should already be included in the Current Period catalog of TCU. Observations should take place jointly with MAGIC, so please be in contact with the MAGIC shifters to ensure that the wobbles match and the observations begin at the same time.

If we are lucky, we will observe the optical rise of the nova, which is expected to happen very quickly, at several magnitudes per hour. Be aware that T CrB will become very bright in the optical, with an expected peak V-band magnitude of ~ 2. This will cause pixels around the source go into reduced HV and may cause oscillations in the rates. If this is the case, continue observations normally and report in the ELOG any issues that you see.

From gamma-ray to SII observations

Below are the detailed steps to follow in order to swap from gamma-ray to SII observations. A more in-depth description of the SII observations can be found [here].

1. [eGUI]: -> TCU tab -> In the AutoOpertator section click on "Disable GCN follow up"
2. [eGUI]: -> TCU tab -> In the SM section -> Configure: click on new source and a drop down menu will appear -> select T CrB, select ON mode. -> Click on "Star observing" and enter the observing time in seconds.
3. Open a CIC terminal if not done already and send the following commands.
4. Check in CIC that camera state is READY.
5. Check in CIC that shutter is closed.
6. [CIC]: -> cbox.set_laser_status off
7. [CIC]: -> clus.disable_hv
8. [CIC]: -> set_hv_interferometry_80
9. [CIC]: -> clus.enable_hv 1
10. Check in camera monitor 0 that only m133p4 and m134p4 pixels have HV on (it takes a few seconds to update, you might need to refresh the webpage).
11. [CIC]: -> movetotpoint
12. Wait until camera reaches TPOINT state in CIC.
13. [CIC]: -> ecc.sis_move_xy 1110 1291
14. Wait 10s for the SIS to move.
15. [CIC]: -> ecc.shutter_move 1
16. Check in camera monitor 0 that DC is higher in m133p4 (signal pixel) than in m134p4 (background pixel).
17. Contact MAGIC shifters and tell them you are ready, they should have started the interferometry DAQ once MAGIC is ready.

SII observations

The SII DAQ is controlled from the MAGIC CH. Once started it will take a run every 5 min, MAGIC shifters will check the joint data.

During the observations monitor check that SM is tracking. If it stops tracking before the observation ends, do not change the camera state and track again T CrB in ON mode.

You can also check the DC and HV values from the camera monitor 0.

Stop SII observations earlier only if MAGIC decides to stop (because of a very faint DC signal).

From SII to gamma-ray observations

Below are the detailed steps to follow in order to swap from SII to gamma-ray observations.

1. If you are still tracking, stop tacking from SM.
2. Using CIC terminal use the following commands:
3. [CIC] -> ecc.shutter_move 0'
4. [CIC] -> backfromtpoint
5. Check that camera reaches READY state in CIC. You might need to sync CM in TCU.
6. Check that there are no pixels in error in camera monitor 6. In the Pixel error state plot (all the pixels should be in blue).
7. Now that Camera and SM are in READY you can schedule a gamma-ray observation using AutoOperator.