Targets & Alerts

Target and Alert Team

Team Leaders: Kate Maguire (QUB ; from 1/9/2014)  
Team members - revised list : Andrea Pastorello (INAF-OAPd; was TAT leader until 1/9/2014), Joe Anderson (ESO Chile), Maria Teresa Botticella (INAF-Capodimonte), Regis Cartier (Southampton), (Janet) Ting-Wan Chen (MPE), Annalisa De Cia (ESO Garching), Michel Dennefeld (IAP, Paris), Nancy Elias-Rosa (INAF-OAPd), Morgan Fraser (University College Dublin), Lluís Galbany (Pittsburgh), Cosimo Inserra (QUB), Joe Lyman (Warwick), Stephen Smartt (QUB), Mark Sullivan (Southampton), Stefan Taubenberger (ESO Garching, MPA).

Information on selection of the Target and Alert Team for ePESSTO runs:
The dates of upcoming observing runs are available here:  Observing Runs A request email for volunteers will be sent by the TAT chair to alerts_@_pessto.org approx. one week prior to the start of the next observing run (generally made up of three subruns). Responses received by email within 24 hours will be included for consideration in the TAT schedule. Note: requests for inclusion in the TAT for future observing runs are also possible in advance of this email by emailing the TAT chair, Kate Maguire (kate.maguire_@_qub.ac.uk) with details of your availability. Preference will be given to people who haven't served in the TAT recently (if they so wish).


The Marshall is the interface through which targets are compiled from the feeder surveys, scheduled for classification, classifications are added and follow-up scheduling is overseen. 

Bugs & improvement/development requests can be reported via the 'bug' symbol on the right hand side of the top menu bar on the Marshall - this takes you to the github issues page)

Northern targets in the Marshall:

By default now these are still not visible. At the top of the page there is a button “NTT” which
you can use to turn on >+30deg northern targets. You can toggle on and off with this button.
The toggle should remain the the same when you move between lists (but let Dave know if not)
If you hover over that, it will display what you are turning on.

The reason for this is that we have northern targets from ATLAS and PS1 we want to keep track of,
and don’t really want to code up another marshall. Many of you have access to northern
facilities so feel free to take spectra of these, but please do put in a comment and/or classify them
with the usual marshall tool.

  • Do NOT archive something just because it is >+30deg. 
  • Feel free to comment and push them into the classification queue. 
  • Other Users can turn them on/off if they want to with the NTT button 

The Pan-STARRS data points you see are generally public (from PSST), so can be used freely.
ATLAS lightcurve data points you see (for the northern targets) are not public. You can
view the PNG plot to guide you if you want to classify things, but ask us if you want to use data
for any papers/analysis.

Information on classification and Target and Alert Team duties:


1. Target and Alert Team duty overview

The aim of the TAT is to identify suitable targets for spectroscopic classification with ePESSTO during an upcoming observing subrun.  Discovery information from feeder surveys is ingested by the Marshall and appears firstly in the 'Inbox'. The duty of the TAT is to prioritise the targets appearing in the inbox in the days leading up to an observing subrun.

Usually the TAT is most active in the days preceding observing nights and one to two days before the start of the subrun. Scheduling of targets for classification (adding them to the 'classification targets' queue) is best done no more than one to two days before the start of the observing subrun. This is because otherwise objects can be added for classification for which more data appears that makes them less interesting and then have to be downgraded but can sometimes be missed. Generally it is fine to 'snooze' objects (see below) well in advance of the subrun because these objects will reappear in the inbox if further information is obtained.

A general (but not-exhaustive) strategy for a TAT member on duty would be to go through the inbox and ask a number of initial questions about each target:
  1. Is the target bright enough for classification at NTT (brighter than approx. 20.5 mag)? Otherwise can be snoozed.
  2. Does the target appear to be real (not an artifact)?
  3. Is it centred on a point source i.e. likely variable star?
  4. Is it a target without a host galaxy that is close to the Galactic plane (see general tips below) i.e. likely variable star?
  5. Is the object currently visible from La Silla? Using e.g. http://catserver.ing.iac.es/staralt/

If it appears likely to be a true extragalactic transient then the criteria defined in Section 2 below can be applied to determine the priority.

The snooze button is there to be used for objects where their current light curve evolution is unclear or they are currently too faint for an NTT classification spectrum (>20.5 mag). Snoozing an object means that it is removed from the inbox and placed in the 'snoozed' list. When an additional light curve point becomes available that shows the transient to be rising, the object is automatically added back into the inbox for reevaluation by the TAT team on duty.

2. Criteria for selecting targets for classification

Light curve and discovery properties for approved ePESSTO science projects available here: Object properties   For nearly all transient events that fall into an ePESSTO science group, our aim is to observe as soon as possible after explosion. In most cases (with some notable exceptions), old declining transients are not of interest to us.

Targets that are suitable for classification are added to the 'classification queue' using the top button on the righthand side of the target. A comment should be included describing why it is of interest (or not) e.g 'Offset from z=0.005 galaxy. Deep non-detection three days ago and rising over past two nights. Currently -16 mag. High priority. ' The priority of the target is assigned on the 'classification queue using the 'flame' symbol dropdown menu on the righthand side of the target ('high', 'medium' or 'low'). 'High priority' for classifications should be reserved for the youngest, brightest, faintest, etc. transients to make it easier for the observers to prioritise during the night.

Old version of selection criteria for targets can be found here: (Criteria for selecting targets for classification up to mag 20.5)

3. Tips and tricks (including understanding the feeder survey webpages)

General tips:

  1. Beware of Galactic transients e.g. variable stars that are generally located near the Galactic plane. They usually appear like orphan candidates without a visible host galaxy. The Galactic coordinates are available on the ATLAS and PS webpages for their transients. For a quick check of the sky position, an image like this can be useful (Credit: D. Coe (STScI), D. Schlegel (LBNL), D. P. Finkbeiner (Harvard), M. Davis (Berkeley))



Survey specific tips:
  1. Pan-STARRS (Example: https://star.pst.qub.ac.uk/sne/ps13pi/psdb/candidate/1142016661152029700/):
    1.  Due to the large chips gaps in PS images, non-detections do not mean what you typically might think. They are calculated from the limiting magnitude for each particular skycell for that night. However, they are also displayed for objects that fall on a chip gap or are masked for some reason so a non-detection arrow does not necessarily mean that a true non-detection occurred on that night.
    2.  Galactic coordinates are given on the right-hand side in the top info panel.
    3.  Objects that Ken Smith is confident are real transients and likely SNe are added to the TNS. If a PS1 object has no ‘AT’ designation, treat it with more suspicion.
  2. ATLAS  (Example: http://psweb.mp.qub.ac.uk/sne/atlas3/candidate/1105336031064310400/):
    1. The ATLAS filters are non-standard. Broadly cyan corresponds to ‘g+r’ and orange to ‘r+i’. More details on the ATLAS filters can be found here: ATLAS filters
    2. The second light curve plot on ATLAS pages is from forced photometry so should be more accurate.
    3. Galactic coordinates are given on the right-hand side in the top info panel.
    4. Comments (added mainly by Ken Smith) are available in the top box. Objects that Ken is confident are real transients and likely SNe are added to the TNS. If an ATLAS object has no ‘AT’ designation, treat it with more suspicion.
  3. Gaia (Example: http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia17ayc/):
    1. Underneath the image, there is generally a comment detailing the Gaia scanner’s impression of the target. ‘GS-TEC predicts’ relates to the Gaia spectrophotometry transient events classifier of Blagorodnova et al. (2014, MNRAS, 442, 327). It uses the blue and red grism spectra to estimate the most likely type.
    2. A low-res spectrum is obtained for each epoch. You can scroll through by clicking on the arrows to the right and left of the spectrum.
    3. The spectra are not flux calibrated. For details on interpreting Gaia spectra, see https://gaia.ac.uk/alerts/what-and-why/gaia-spectra
    4. Gaia is not a SN survey - there will be CVs, YSOs and other transients there too! Checking the galactic latitude of a candidate is probably a good idea!

Information on follow-up target requests:

When a classification spectrum identifies an interesting target for follow-up, the science lead of the relevant science group as first refusal on this target. If they are not interested or able to lead a full follow-up campaign, others may take the lead with the approval of the Survey P.I., the Science Board chair and the TAT chair. For each science target, a science P.I. is assigned (and their contact details are listed on the Marshall).

Once approved, science targets can be added to the 'follow-up targets' list on the Marshall. The P.I. is responsible for scheduling follow-up observations. All requests and their details should be entered via the Marshall (not via email!) including a recent estimate of the magnitude of the target. Details on typical exposure times are available at: OBs information  Since SOFI spectroscopy is very time-consuming, requests for follow-up SOFI spectra must be made to the Survey P.I., the Science Board chair and the TAT chair with justification of the science case.

There are three classes of priority for follow-up: (i) CRITICAL, (ii) IMPORTANT, and (iii) USEFUL. There has been an overuse of 'critical' in the past, this should only be used when the resulting publication is expected to significantly suffer for the lack of these data. Once the data have been obtained or the time period of the request expires, the priority will be reset to 'NONE'.
 
PriorityMeaningUsageExample
CRITICALEssentialObjects that are disappearing, or phase is critical, or fast rising/rapid decliningCRITICAL (3rd December) ; CRITICAL (first sub-run in December)

IMPORTANTImportant but not criticalto target a phase or expected changeIMPORTANT (third sub-run in December) ; IMPORTANT (during December)
USEFULData useful additiongood coverage already, data would be useful supplementUSEFUL (1st subrun in December) ;USEFUL (once in December, date not important)

Optical light curves of follow-up targets:

It is PESSTO policy that optical light curves should not be obtained with the NTT unless the target is too faint for smaller facilities (e.g. fainter than >21 mag). It is the responsibility of the Science PI of each follow-up target to organise the light curve coverage, which should be in place (at least in principle) before PESSTO spectroscopic follow-up commences.

2. GROND (2.2m, g'r'i'z'JHK simultaneously, unusual SNe, PI: Ting-Wan Chen)