P61-508: Electromagnetic transients associated with gravitational-wave signals

The advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) has detected gravitational waves (GWs) from coalescence of stellar-mass binary black holes and most recently from the merger of two inspiraling neutron stars in an event GW170817 which was followed by the discovery of an electromagnetic counterpart, i.e. kilonova AT2017gfo. Our aim is to spectroscopically classify optical transients discovered by large-scale sky surveys, which are plausibly associated with a GW detection, and carry out spectrophotometric follow-up of transients that are associated with a GW signal. The main science goals of the project are to probe the diversity of optical counterparts of GW events from LIGO/Virgo and to study the heavy element production of kilonovae.

ToO triggers

The OB generator will be used to request all ToO observations. Scripts to perform all the requested operations will be automatically created and placed in the directory ~/scripts/61-508/. An email will be sent automatically to the observer, which contains all the information about the requested observations, the names and locations of the scripts, instructions for observing and comments from the creator of the trigger.
To summarise:

Go to the directory
  cd ~/scripts/61-508
List the available scripts
  ls -lrt

and execute the OB generated scripts requested in the trigger email.

The information below is only given as additional support.

General information on the ALFOSC spectroscopy and photometry:

• Possible required setup:
• Filters: ugriz, (UBVRI)
• Grisms: #4, (#7, #8)
• Slits: 1.0", 1.3"


• If the seeing is better than ~1.2", the 1.0" slit should be used, otherwise the 1.3" one.


• Take 3 imaging flat fields in the required broadband filters using twilight sky, either in the evening or in the morning, using the alfosc.easyflat script.


• The exposure time of the spectrum depends on the magnitude of the target:
• If V < 17 mag the on-source exposure time is 1 x 900 sec
• If V = 17-18 mag the on-source exposure time is 1 x 1800 sec
• If V = 18-19 mag the on-source exposure time is 1 x 2400 sec
• If V > 19 mag the on-source exposure time is 1 x 3600 sec


• Standards will usually be selected by the triggering individual and OB scripts for observing these will also be present in ~/scripts/59-507. Typically one of the following spectroscopic standards is used (sorted in the order of preference):



ING ID	Name	RA (J2000.0)	DEC (J2000.0)	Exp. time	FC
SP1036+433	Feige 34	10:39:36.7	+43:06:10.1	100 sec	Feige34.gif
SP1234+254	Feige 66	12:37:23.6	+25:04:00.3	50 sec	Feige66.gif
SP0501+527	G191B2B	05:05:30.6	+52:49:56.0	120 sec	G191B2B.gif
SP1550+330	BD+33 2642	15:51:59.9	+32:56:53.0	60 sec	BD+33.2642.gif
SP2148+286	BD+28 4211	21:51:11.1	+28:51:52.0	60 sec	BD+28.4211.gif




• No blocking filter should be used in any of the spectroscopic observations.


• The ALFOSC specific Cookbook can be accessed here.

General information on the NOTCam photometry:

• Possible required setup:
• Filters: JHKs
• Camera: WF


• Take 2 sets (bright and faint with the same exposure time) of 8 imaging flat fields in the required broadband filters using twilight sky, either in the evening or in the morning, using the notcam.skyflat script.


• Please, make sure that the target counts (including sky background) remain linear, i.e. <25000 counts – check & adjust exposure times if necessary. This is particularly important in the Ks-band.


• Generally the targets are expected to be distant enough that off-source dithering for background subtraction will not be required and that the on-source exposures can be used also as sky frames. By default, the observing scripts are based on the 9point script which carries out a 9 point dither (3x3 grid) observation. However, if separate sky frames are required a beamswitch script will be used.


• The NOTCam specific Cookbook can be accessed here.

General information on the StanCam photometry:

• Possible required setup:
• Filters: UgRiz


• Take 3 imaging flat fields in the required broadband filters using twilight sky, either in the evening or in the morning.


• The StanCam specific Cookbook can be accessed here.


• The Cookbook describes the observing system switch to StanCam.

Should any of the observations have been carried out using the OB system, you will find additional information HERE