Optical+Transient+Surveys

=**Optical / NIR Transient Surveys**= The aim of this workshop is to address some of the key issues facing the current and forthcoming, ground-based, optical/NIR, synoptic sky surveys. The coverage will include: key lessons learned from the current surveys, what are the principal bottlenecks, especially regarding the follow-up observations, the scientific opportunities, technological challenges, coordination between different surveys at all wavelengths, etc.

Our workshop has been split into two sessions on Monday afternoon, one of 90 minutes and one of 60 minutes. In the first session we will initiate discussions by having 5 short talks of 15 min each. This first session will highlight some of the current or imminent transient surveys, their scientific goals, and the key outstanding challenges that they are encountering. The second session will be a panel led discussion that will focus on the issues of effective follow-up and coordination between different surveys, community engagement, and the cyber-infrastructure needs.

=Main Concerns raised in the workshop=

1) There is not enough awareness in the community of all of the tools and facilities available, such as SkyAlerts, so follow up of transients is not as efficient as it should be.

2) The main bottleneck in extracting science from the existing synoptic surveys is the follow-up spectroscopy. This problem will get worse by orders of magnitude as we move towards the LSST. Dedicated spectroscopic facilities may be necessary. A lot of spectrographs developed for large telescopes are designed for many faint objects over a small FOV, whereas transients are observed one at a time.

3) There should be more coordination between surveys at different wavelengths to maximise the science return. The cadences and pointings need to be coordinated, sometimes with offsets as emission at some wavelengths (e.g. radio) can occur later. Given such a variety of different technologies and science requirements this is an extremely complex task.

=Short Talks= Nicholas Cross (Current and upcoming near IR variability surveys),

Andrew Drake (The Catalina Real-Time Transient Survey),



Stephen Smartt (PanSTARRS)



Matt Lehner (TAOS & TAOS2)



Lukasz Wyrzykowski (Gaia satellite as a transient survey) - replaced at last minute by Simon Hodgkin

=Panel Discussion=

Minutes of Optical Transient Survey Panel Discussion 19/09/2011
Panel consisted of George Djorgovski, Peter Nugent, Neil Gehrels, Joseph Lazio and Nicholas Cross

GD introduced the session which is about the multi-wavelength transient programmes: surveys and followup. Each panelist apart from GD and NC (the organisers) gave a short introduction before discussion was opened up.

PN: The expensive parts are the computing and followup. People try to get the most out of their own pipelines, but there is a lot of useful historical data: "historical followup".

JL: A range of radio data from sub-mm to decametre. Radio wavelengths are important for astrometry in X-ray/GR followup and provide constraints on the physics.

NG: The good: Gamma Ray transients get followup, especially with telescopes with NIR spectroscopy for high-z events. The bad: everyone does the interesting GRBs and ignores the rest. X-ray follow up: Swift started with 100 TOO requests per year and now receives 1000. It cannot handle any more. Also, it will not last forever: what will replace it.

Bob Hanisch: We can now do 1000000 row crossmatch in a couple of seconds, but the difficulty is getting the data to the server. Real time follow up is constrained by X-matching to external data. We still need humans.

Carole Mundell: The Liverpool GRB team have GRBs to 24 mag but no redshifts. The support amongst TACs for followup to GRB detections is dropping just as the physics is getting better defined.

Brian Schmidt: We have the wrong hardware for follow up. Multi-object spectrographs are not useful for following up a single bright object. Long slit spectrographs are not useful for most transients either. We need dedicated hardware.

Shri Kulkarni: The Palomar Transient Factory has follow up telescopes too. A generous time allocation to collaboration investigators is not enough. Any idiot can discover a supernova, but follow up is more difficult and the followup telescope has to be bigger than the survey telescope.

Carole Mundell: The Liverpool Telescope has spectroscopy and polarimity and a 10s changeover time between instruments.

GD: Large surveys should be designed or organised to compliment each other by simultaneously following each other up.

Joseph Lazio: There is also the need for robust archives since the radio often turns on much later.

GD: We use layers of followup, gradually reducing the candidates until we have the ones that are interesting enough for spectra.

SK and GD: This is the golden age of transient astronomy. It will be over by LSST.

BS: The main phase space of transients will be covered soon, perhaps the next 12 months and then we will move into a dour regime. But we cannot do the high redshift universe well. We have the wrong hardware.

GD: QSOs were spotted in the optical in the 1920s, but they were thought to be variable stars. They were only noticed as something special when they were matched to the radio.

BS: Gravity waves will open up new studies.

??: With GRBs detected by EXIST we will need NIR photometric follow up from space to answer the dedicated science questions. This will not be possible in the present funding climate, but a 2 to 3 m class telescope in Antartica would cover half the sky for 5 months of the year.

Stephen Ridgway: What can we expect from LSST followup? No one is doing the simulations to test this, they are too busy.

GD: On the contrary, we have the opposite problem. Too many good people are wasting their time doing this.

SK: We cannot extrapolate 10 years. This is the decade of discovery: PTF/PanSTARRS/SWIFT/HST/Chandra. Dark Energy Camera will also be around soon. LSST will be like Kepler: people will use time series analyse on the light curves rather than following up detections. It will be a physics machine, not a discovery machine. Lots of chi-squared tests.

JL: The precursors to the SKA will be interesting and the metre and cm wavelengths. There will be new incoherent and coherent sources, and fast transients. We are still exploring the discovery space. What about high-speed optical surveys? There is TAOS, but it is not wide field.

GD: Have to think about the cadences as well as the wide field.

Tom Vestrand: We need to understand the whole system and have real time knowledge of what is available. Sometimes it is like "2nd graders playing soccer: everyone kicks at the ball". Everyone observes the same GRB at the same time and doesn't know that it is already being observed.

GD: VOEvent was designed with problems like this in mind.

NG: Lots of small telescopes that are useful for followup are getting closed down.

SK: Lots of small telescopes need to be refurbished.

GD: We need to use computers to observe archives as a historical followup.

GD: This will be the first and last meeting dedicated to time domain astronomy. The field will be too big for one meeting and there will be more specialised meetings.