How to observe a TRANSIENT: all the
practicalities of a follow-up program
Testo
Silvia Piranomonte+Enzo Brocato@OAR
and Marica Branchesi
Astro-­GR@Rome -­-­ 2014 July 16th
mercoledì 16 luglio 14
A restless Universe
Time domain provides the fourth dimension in astronomy
Castro-Tirado et al. 2007
(super)nova
QSO / blazar
Astro-­GR@Rome -­-­ 2014 July 16th
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The case of gamma-ray bursts
Why so much thrill for rapidity?
• For GRBs we have
the luxury of the
high-energy trigger
from satellites
(unlike novae,
supernovae, etc.)
• GRB luminosity
varies
logarithmically with
respect to the trigger
time:
a factor of 10 in time
implies a factor of
∼10 in faintness
Astro-­GR@Rome -­-­ 2014 July 16th
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• GRBs are the most
interesting objects in
the realm of
astronomy
A couple of examples
8-130 min
Vreeswijk et al. 2007
Line variability:
information
about the
absorbing
material
(particularly the
distance from
the GRB)
Astro-­GR@Rome -­-­ 2014 July 16th
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D’Elia et al. 2009
A couple of examples
8-130 min
D’Elia et al. 2009
GRB physics: earlytime light curves
allow probing the
emission
mechanism, jet
structure, especially
if carried out in
several wavebands
Bloom et al. 2009
Vreeswijk et al. 2007
Line variability:
information
about the
absorbing
material
(particularly the
distance from
the GRB)
Astro-­GR@Rome -­-­ 2014 July 16th
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Observations of the transient at ESO
First thing: we must have an
approved ToO-RRM proposal
at any Observatorywhateveritis
Observations of a newly
transient required interruption
of normal operations of the
telescope.
Broadly three types of
observations:
• “Soft” target-of-opportunity
(ToO) requiring modification of
the schedule on 1-3 days
timescale.
• “Hard” target-of-opportunity:
do it as soon as you can.
• Rapid-response mode (RRM):
Most used instruments at ESO: FORS,
do it NOW and don’t even try
UVES, ISAAC, and X-shooter
to say “but”. Conceived for
robotic execution.
Astro-­GR@Rome -­-­ 2014 July 16th
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How does it work?
Let’s start observing!
A new transient goes off!
✓ We can have the basic information of the object (position, significance,
…) from the large FoV analysis or from the high energy satellite (if we are
lucky!)
✓ First: check for low Galactic latitude, observability, significance
✓Is it visible NOW? If yes a robotic trigger is sent in RRM
✓If not visible now, evaluate a manual trigger whenever appropriate
✓Critical parameter 1: spatial position uncertainty and brightness of optical
afterglow gamma-rays (VST, PTF, Swift/BAT, Fermi/LAT, AGILE): if we have
still ∼arcminute errors we suggest waiting...
if X-rays: (Swift/XRT) few arcseconds, worth trying, need an imaging
sequence to start optical (e.g. from Swift/UVOT or robotic telescopes): will
be easier, but the optical counterpart and brightness are not really known
automatically
✓Critical parameter 2: time between the transient and the observation
✓Which instruments are available? RRM cannot change instrument
Astro-­GR@Rome -­-­ 2014 July 16th
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When can you trigger?
RRM can trigger (almost) always, interrupts ongoing integrations and
overrides visitors but cannot change instrument
ToOs cannot override visitors but you can always (politely) ask:
promise spectacular goals, ensure our Weltanschauung will change, and
offer authorship...!! :)
at ESO for example ToOs cannot override VLTI but usually they try to
accommodate reasonable requests
The telescope staff is usually competent and understanding
Astro-­GR@Rome -­-­ 2014 July 16th
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Phone calls from the sky
If you don’t have friends, GRBs allow to expand your network of
connections :)
GRB
Swift
GCN
GCN (Gamma-ray coordinate network) system at NASA receives triggers
from satellites and relies notices as
• email
• socket
• web content
Usually you set up a server receiving the notices and formatting according
to your needs
(e.g., the Covino® system or the system set up in Copenhagen for the Xshooter GTO)
Astro-­GR@Rome -­-­ 2014 July 16th
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GCN: The Gamma-ray Coordinates Network
(TAN: Transient Astronomy Network)
The GCN system distributes:
1. Locations of GRBs and other Transients (the Notices)
detected by spacecraft (most in real-time while the burst is
still bursting and others are that delayed due to telemetry
down-link delays).
2. Reports of follow-up observations (the Circulars and the
Reports) made by ground-based and space-based optical,
radio, x-ray, TeV, and other particle observers.
These two functions provide a one-stop shopping network for
follow-up sites and GRB and transient researchers.
The GCN system can be explored using the links above and below.
•
•
•
About GCN/TAN provides a number of 'Introductions' from
different points of view. 'Technical Details' (found on the
About GCN/TAN page) describes the various services and
products of GCN/TAN and how they are generated.
'Burst Data Archives' are available under Burst & Transient
Information, which record the inputs and outputs of GCN/
TAN automatically and are updated in real-time.
You can also Search for past Bursts/Transients and
webtext.
Astro-­GR@Rome -­-­ 2014 July 16th
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Many many GCN notices
Astro-­GR@Rome -­-­ 2014 July 16th
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HOW DOES IT WORK? (1)
(after many many years of experience/human errors/sleep hours lost, we have
automatized as much as we could!)
Da: [email protected] (GRB Alert)
Oggetto: GRB 140710.428 (SWIFT_XRT)
Data: 10 luglio 2014 12:32:29 CEST
A: [email protected]
Packet-type: 67 (SWIFT_XRT), Notice-time: 10:31:51.00 UT
==============
GRB 140710.428 GRB-time: 10:16:40.04 UT (Jul 10.42824 UT)
==============
Time since trigger (notice-GRB): 00h15m10s
Sample:
ToO: [not OK] (A_V = 0.19; alt>30 @ never; t_start_XRT = 2 min)
RRM: [not OK] (A_V = 0.19; alt>23 @ 10:10-10:30 UT; t_pos_XRT = 15 min)
Swift (SWIFT_XRT) trigger number: 603954
Swift packet sequence number: 2
RA (J2000) = 02:44:16.25 (41.0677)
DEC(J2000) = +35:29:57.8 (35.4994)
Error radius: 2.2 arcsec
D(Moon) = 153.32 deg, D(Sun) = 59.25 deg
X-shooter finding chart and visibility plot:
http://too.dark-cosmology.dk/~grbtoo/trigger/infopageXS.php?grbid=GRB140710.428&grbtrignr=603954&grbseqnr=2&instrument=XSHOOTER
UVES finding chart and visibility plot: http://too.dark-cosmology.dk/~grbtoo/trigger/infopage.php?
grbid=GRB140710.428&grbtrignr=603954&grbseqnr=2&instrument=UVES
More finding charts: http://too.dark-cosmology.dk/~grbtoo/trigger/
X-shooter ToO info webpage: http://too.dark-cosmology.dk/~grbtoo/xsgrb/
(l, b) = (147.44, -21.95)
A_V = 0.19 mag
mercoledì 16 luglio 14
Astro-­GR@Rome -­-­ 2014 July 16th
HOW DOES IT WORK? (2)
At Paranal: now +1hr +2hr +4hr +8hr
GRB altitude: 24.82 29.01 29.66 21.44 -17.77
Sun altitude: -12.32 0.35 12.37 32.83 36.73
GRB-Moon distance: 153.32 142.55 141.89 140.52 137.88
Moon illumination: 0.87 0.94 0.94 0.95 0.96
Moon altitude: -26.79 -26.39 -35.81 -46.74 -24.15
Current time:
Thu Jul 10 10:31:52 UTC 2014
Thu Jul 10 12:31:52 CEST 2014
Thu Jul 10 06:31:52 CLT 2014 (Chile)
XRT flux = 100
XRT S/N = 10
Paranal meteo: http://archive.eso.org/asm/ambient-server?site=paranal
La Palma meteo: http://www.not.iac.es/weather/index.php
VLT/Melipal (UT3) schedule (starting 2 weeks ago): http://archive.eso.org/wdb/wdb/eso/sched_rep_arc/query?
tel=UT3&order=DATE_ASC&start=26-6-2014&tab_obs_mode=0&obs_mode=v&tab_title=1&tab_Dp_Id=0
GCN circulars: http://gcn.gsfc.nasa.gov/other/140710.gcn3
Swift GCN notices: http://www.swift.ac.uk/gcn/index.php?trig=00603954
UVOT blink image (may take a few min): http://heasarc.gsfc.nasa.gov/docs/swift/blink/
UVOT finding chart (permanent): http://heasarc.gsfc.nasa.gov/docs/swift/uvot_tdrss/603954/fc1_genie_combo.jpg
Enhanced XRT positions: http://www.swift.ac.uk/xrt_positions/index.php
SPER XRT positions: http://www.swift.ac.uk/sper/
SDSS data (if available): http://data.sdss3.org/fields/raDec?ra=41.0677&dec=35.4994&submit=Submit
SDSS field inspection tool (if field available): http://skyserver.sdss3.org/public/en/tools/chart/navi.aspx?ra=41.0677&dec=35.4994&opt=I
NED search (within 5 arcmin from position): http://ned.ipac.caltech.edu/cgi-bin/nph-objsearch?in_csys=Equatorial&in_equinox=J2000.0&lon=02:44:16.25&lat=
+35:29:57.8&radius=5.0&search_type=Near+Position+Search
ESO archive search (within 10 arcmin search box centered at position): http://archive.eso.org/wdb/wdb/eso/eso_archive_main/query?ra=02:44:16.25&dec=
+35:29:57.8&deg_or_hour=hours&box=00+10+00&max_rows_returned=500
Astro-­GR@Rome -­-­ 2014 July 16th
mercoledì 16 luglio 14
RRM trigger
The best thing is to have several ready-mostly automatized ways to trigger
• completely robotic;
triggers every GRB with “selected” properties which is immediately visible
currently sends a sequence of spectroscopic observations to look for line variability
• “easy” web page with a friendly button (see
http://too.dark-cosmology.dk/~grbtoo/trigger/infopageXS.php?
grbid=GRB140713.780&grbtrignr=604232&grbseqnr=2&instrument=XSHOOTER)
e.g. ESO rule for GRBs: can trigger RRM within 4 hours since trigger
But if there is enough time, consider triggering a ToO instead
Why
use manual RRM rather than a late-time ToO?
* Readiness (e.g. if there is little time before the GRB becomes observable)
* Override visitors
* On the other hand, a ToO is more flexible and manageable (e.g., change parameters).
The RRM robot sends finding charts and a message to the observatory. These are set up for a
“generic” situation – get immediately in touch with the telescope.
Astro-­GR@Rome -­-­ 2014 July 16th
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ToO trigger
Most of the times triggers are late-time ToOs
Triggers must be sent by filling a ToO form:
http://www.eso.org/sci/facilities/paranal/sciops/ToO/ToOForm_cgi.php
Finding chart: important thing is that it is clear
indicate whether it is an archival (DSS, SDSS) image or it is an afterglow
image
indicate the wavelength (R, NIR, etc.)
for shallow finding charts (e.g. from UVOT) ensure scale and depth are
indicated
ESO guidelines: http://www.eso.org/sci/observing/phase2/
FindingCharts.html
Sky, seeing, airmass conditions: usually “whatever”, but depends a bit on
the case
Additional strategy comments: place here special requests, modifications
to the OB,
longer/shorter exptimes, different slits, different acquisition filters,
Vogon poetry…
Communication: email [email protected] or telephone +56 5543 5322
Astro-­GR@Rome -­-­ 2014 July 16th
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Politics and data release
ToO data are made immediately available on an FTP account
(proprietary)
RRM data are usually made immediately available to all PIs of GRB
proposals
however with the advent of GTO ToO this has changed a bit:
• RRM GTO data are proprietary to the GTO
• RRM non-GTO data are shared only among non-GTO GRB PIs
The RRM/ToO bottleneck is the data release 
• problems with calibration files (missing, promised, unreleased,
corrupted…)
• if some data conflict arises, often the data are blocked and nobody
has them
Conflicts with other similar programs
In general: expect troubles :)
Astro-­GR@Rome -­-­ 2014 July 16th
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What to do with the data?
(well, this is quite a silly question)
Try
> pipeline_instrument_command do_writepaper --author=me <file.dat>

If it doesn’t work, then try getting yourself a quick-look redshift. You
can use archival/old calibration data (perhaps check lambda with
skylines). No flux calibration is really needed at quick-look stage.
If you get z, send out a GCN circular reporting your quick-look
analysis – no coauthorship policy has been defined, in general who works
is in, who doesn’t is out (funny?).
However, always add to the coauthor list the statement
e.g.“on behalf of the “e.g. GW-EM” team”
Astro-­GR@Rome -­-­ 2014 July 16th
mercoledì 16 luglio 14
… when you do things properly …
Arricchimento Chimico
22-mar-12
mercoledì 16 luglio 14
OAR Fellow Day - S. Piranomonte
… when you do things properly …
Arricchimento Chimico
GRB
GRB 030323 z=3.372 (Vreeswijk et al. 2004)
GRB damped Lyman α (DLA)
Intestellar Medium (T<1000 K)
Chemical Enrichment
Dust Extinction
Molecular Hydrogen
22-mar-12
mercoledì 16 luglio 14
OAR Fellow Day - S. Piranomonte
… when you do things properly …
Arricchimento Chimico
GRB host
Interstellar medium T=104 K
Chemical enrichment
Dust Extinction
Star Formation Rate
Electron Density
GRB 030329 z=0.168 (Gorosabel et al. 2005)
22-mar-12
mercoledì 16 luglio 14
OAR Fellow Day - S. Piranomonte
GRB 080319B : the brightest
Astro-­GR@Rome -­-­ 2014 July 16th
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Racusin et al. 2008, Nature, 455, 183
GRB 080319B : the brightest
Astro-­GR@Rome -­-­ 2014 July 16th
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Racusin et al. 2008, Nature, 455, 183
GRB 090423 : the more distant, z=8.2
Astro-­GR@Rome -­-­ 2014 July 16th
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Free discussion
How we can transfer the follow-up GRBexperience into GW-EM science?
(Of course we have “some” more difficulties to
take into account...)
What information we quickly need in order to
characterize the GW-object?
..........
...........
Astro-­GR@Rome -­-­ 2014 July 16th
mercoledì 16 luglio 14
Thank you for
your attention !

mercoledì 16 luglio 14