LSST and AAVSO CCD photometry

Affiliation
American Association of Variable Star Observers (AAVSO)
Sun, 08/09/2015 - 02:46

This is a general question probably for for Arne,  but when LSST comes on line what might the effect be on AAVSO related photometry?  Put another way, how might the trajectory or scope of AAVSO CCD photometry be changed by mega-surveys like this?  What might the benefits be to someone doing AAVSO CCD photometry?

 

Thanks,

--John Ott

Affiliation
American Association of Variable Star Observers (AAVSO)
Probably not a big effect

I believe this issue has been discussed before on another thread. My take on LSST and its impact on AAVSO observing is this:

1. It is a single telescope at a single site in the southern hemisphere. Assuming it lives up to its promise, and surveys the entire sky visible to it every 3 days, that is nowhere near the coverage AAVSO observers can accomplish on a routine basis. Typical campaign objects get hourly coverage with numerous high cadence time series. The LSST cannot even come close to that sort of concentrated effort on any given object.

2. I am not sure of how close to the horizon its normal operating limits are, but at the latitude in Chile, I would suspect at best, only ~2/3 of the total sky  is accessible to it, with the gap around the N celestial pole area.

3. It has a limited funding objective of ten years. May or may not be extended.

4. System reliability and uptime is as yet to be determined.

5. It is a large telescope, and its targets will be the fainter variety, not the brighter objects which AAVSO usually concentrates on.

So, I believe LSST will be a very useful survey system that will uncover many new things about our universe, but will have minimal impact on what the AAVSO and its observers do.

Mike

 

Affiliation
American Association of Variable Star Observers (AAVSO)
impact of LSST

Stella is the one to give you details about the impact of LSST (and other surveys) with the AAVSO community.  However, as a member of the LSST consortium for many years, and a strong advocate of the variable-star community, let me give two examples.

First, nearly every star that has been observed by the AAVSO pro-am community over the past 100 years will be saturated in LSST and wil therefore not be observed by them.  There are other upcoming surveys that have more impact in that area.

Second, let's assume that LSST has discovered a new WZ Sge star, with quiescent magnitude 21,  as it goes into outburst.  As such a star would typically reach a peak magnitude of 13 or so, the outburst will be saturated in the LSST database and only identified as a transient object whose magnitude is unknown.  The amateur community gets all the fun data!  At the same time, 21st magnitude is the sweet spot for LSST, so it will have exquisite photometry of the WZ Sge star in quiescnece.  It may have even detected that star as a variable star in quiescence if the orbital signature is large, or if there was a precursor rise in brightness.  However, with the 3-4day cadence, it cannot obtain a good period for the star (way too much aliasing), and while it may have color information for the variable since return visits are often with a different filter, without knowledge of the true period the data cannot be phased properly.  Even phasing the data properly may not give good spectral information as the different-filter data were taken on different nights when the stellar activity is likely to be different.  All of those parameters require followup support, which is where your telescope and others will be important.

LSST will NOT be a competitor for the amateur community.  The harder part of LSST will be in sifting through its huge flood of transient objects to find the handful that are important to study.

Arne

Affiliation
American Association of Variable Star Observers (AAVSO)
Hello
Two very good answers.

Hello

Two very good answers.  I have talked to Stella about this, and Arne wrote

"The harder part of LSST will be in sifting through its huge flood of transient objects to find the handful that are important to study."  Yes, something like a hundred thousand transient objects per night.  LSST's original plan was to send out email alerts.  Do you want to get 100,000 email alerts per night--I think not.

So what Stella has proposed, and is currently spreading the word with the Professional Community, is to come to AAVSO with your requests for follow up.  We will observe in that mode.

I think this is very smart, as we now know which of these transients has caught the eye of a professional astronomer, and is important to her/him.  It also relieves AAVSO from sifting thru the data stream.  This may boil down to a dozen-ish campaigns per year, which we can handle.  

If anyone wishes to do data sifting, they certainly are welcome.  

Gary

Affiliation
American Association of Variable Star Observers (AAVSO)
LSST and AAVSO

Hello

Two very good answers.  I have talked to Stella about this, and Arne wrote

"The harder part of LSST will be in sifting through its huge flood of transient objects to find the handful that are important to study."  Yes, something like a hundred thousand transient objects per night.  LSST's original plan was to send out email alerts.  Do you want to get 100,000 email alerts per night--I think not.

So what Stella has proposed, and is currently spreading the word with the Professional Community, is to come to AAVSO with your requests for follow up.  We will observe in that mode.

I think this is very smart, as we now know which of these transients has caught the eye of a professional astronomer, and is important to her/him.  It also relieves AAVSO from sifting thru the data stream.  This may boil down to a dozen-ish campaigns per year, which we can handle.  

If anyone wishes to do data sifting, they certainly are welcome.  

Gary

Affiliation
American Association of Variable Star Observers (AAVSO)
0.1% of 100,000 per day is a lot of work.

Image the work load if only 0.1% of the newly discovered variables catch someone's eye. That amounts to a lot of VSX entries, sequence generations, and hopefully observations to accumulate and archive. As I said in another post in this thread imagine ASASSN but 1000-fold.there are a number of us observing regularly at 15th and 16th magnitude and some even deeper. 

Now if I can only convince my wife of the necessity of that 20" RC I have been eyeing, and of course that means a larger observatory building, and . . .

Brad Walter, WBY

Affiliation
American Association of Variable Star Observers (AAVSO)
PAN-STARRS

 

Is the PAN-STARRS project likely to be another source of variable-star data?  Looking at their web pages it's not clear to me.  They are primarily interested in moving targets, but it looks like their 3pi steradian survey might produce some general-purpose photometry.

Tom

Affiliation
American Association of Variable Star Observers (AAVSO)
PAN-STARRS

I seem to recall Arne commenting at the first photometry workshop at Tufts a few years ago that PAN-STARRS , could create a lot of follow up work for amateurs. It is interesting that I seem to see a lot of ASASSN object requests flowing through the sequence team. I don't seem to see a lot that are linked to PAN-STARRS. Howver, that may simply be due to naming conventions. 

PAN-STARRS is a much smaller telescope at 1.8 meters which may affect the need for follow up observations. Also, most of the area it surveys seems to be observed with a low cadence whcich may affect the rate at which new variables are discovered. However, with a low cadence, once a variable is discovered, follow up observations by others might be more important in classifying the type of variability.

"PS1 maps one-sixth of the sky at five wavelengths every month. Smaller programs complement the all-sky survey, including special fields that are visited nightly, a detailed survey of the solar system, a dedicated survey for planets around other stars, and a deep survey of the Andromeda Galaxy, the nearby twin to our own Milky Way."

Arne and Stella, what about PAN-STARRS? Has it generated much follow up work for the amateur community in general and AAVSO in particular? 

Brad Walter, WBY

Brad Walter

Affiliation
American Association of Variable Star Observers (AAVSO)
impact of LSST

I think the big thing with LSST is not how it impacts the AAVSO,  but how it impacts the professional community.  It overlaps with all of the 4m+ telescope astronomy, so what has been their exclusive domain will potentially disappear.  Its impact on crucial national funding (and for that matter, private funding) will be huge, and there will be a shake-out for a decade as observatories adjust to the change in priorities.  Plus, we're counting on it working as advertised.  Even little things like the unusually cloudy weather at CTIO for the past month will be important, as no photons means no science and missed opportunities.

We're in a transition period in astronomy, with surveys and big telescopes creating countless opportunities for pro-am collaborations.  I'm glad we have an active leader like Stella and a strong Council to sift through them to find the best matches for the AAVSO.

Arne

Affiliation
American Association of Variable Star Observers (AAVSO)
LSST and Amateur Astronomy

I think it is likely that LSST will create a huge amount of follow up work for amateurs getting details light curves of outburst events. It might not have a huge impact on those with very small telescopes, like the BSMs, but for amateurs with aopertures of 250 mm and larger, I suspect our biggest problem will be deciding which objects to follow on a frequent bases to cover the bright end of their variability range. Imaging ASASSN but a thousand fold or more. We might have to conscript people into the sequence team. and a small army to keep VSX up to date. I can envision something like the LSST superhump search brigade being formed. 

Of course I am being a bit facetious, but expect we will end up trying to drink not from a fire hose, but rather, a water main when LSST comes on-line. I would be very interested to read Stella's reflections on this subject. It could prove to be a challenging task master for what many observers think of as the "back-office" staff who do all of that database stuff we don't really understand but love the outputs and tools that it fuels. 

At any rate, it will be interesting to see what AAVSO does with the huge stream of variable data that will inevitably come out of LSST. If nothing else it may serve as a new justification for satisfying aperture fever!

 

Brad Walter, WBY

Affiliation
Vereniging Voor Sterrenkunde, Werkgroep Veranderlijke Sterren (Belgium) (VVS)
ASSASN survey

Hi,

an interesting disussion and I miss a statement of the new AAVSO director Stella.

For my observations ASSASN has had a large impact in the past two years. I observed so far 88 variables which are not Supernovae, the main interest of ASSASN. A couple of those were very interesting findings leading to special publications in refereed profressional astronomical journals (the last one being ASSASN14cc (http://arxiv.org/abs/1501.06659)).

So I think smaller telescope based surveys (like ASSASN) will have a larger impact on AAVSO based observations than giants like LSST or PAN-STARS.

I anyway look forward to new endevours.

Josch (HMB)

 

Affiliation
American Association of Variable Star Observers (AAVSO)
AAVSO observers in the LSST era

Hello all,

 

I just saw this thread, and most of the items are already very eloquently covered. In short, LSST will survey the entire night sky in 5 filters, with cadence of 4 days each. It will rotate between filters so it will take ~20 days for the telescope to go back at a specific part of the sky with a specific filter (think 20-day gaps between observations). Furthermore, LSST will saturate at g’~17. What will be of interest are the objects that do saturate at 17 magnitude: we will not know whether their peak magnitude will be 16 or 3 – and those are going to be the fun (and very special) LSST objects for our observers to follow-up.

 

I do expect an increase in our alert and notices activity in the LSST era. I hope activity will pick up soon with Gaia alerts (Gaia scientists are planning to increase their alert output by the end of the year – they are at target verification phase now). No doubt, there will be a huge number of targets of opportunity to follow-up at all magnitudes and amplitudes, so for those who worry, we will not be out of business. The professional astronomical community does not have infinite resources. With small professional astronomical telescopes (less than 3m aperture) closing, there is not much observing time available for the professional community to follow-up targets. At the same time, not all targets are of interest for discoveries. Quoting Brad “Image the work load if only 0.1% of the newly discovered variables catch someone's eye”. To add: imagine 1000 email alerts in your inbox, all requesting continuous monitoring on the same night! In principle, this is plausible but only the AAVSO can do it (after all, we do have ~1400 observers). At the same time, there aren’t enough professional astronomers who care about 1000 alerts a day. So far, our alerts and notices have been guided by the needs of the professional astronomical community. Looking forward, we will be an essential resource for professional astronomer’s  work -- we will be doing photometry when they are taking spectroscopic data/satellite data of the objects of interest. With our extensive network of observers, we can guarantee data (there is are always an AAVSO observer with clear skies). The professional community will be coming to us for data. And we will make sure to be well prepared to respond.

 

I would also like to encourage you to observe and study objects of your own interest. The sky is becoming available to all, and I am sure there are tons of discoveries to be made by all astronomers.

 

Thank you for your hard work!

Best wishes – clear skies,

Stella.

PS: Brad, perhaps now you have enough excuses for a larger observatory?  :)

 

Affiliation
American Association of Variable Star Observers (AAVSO)
Pan-STARRS

...I omitted to address this item: I see scattered papers from Pan-starrs, but nothing like the influx of publications I expected. They are really behind with data releases. At the recent IAU meeting, there were several papers (posters and oral papers) about data releases, and here's one of them: 

http://adsabs.harvard.edu/abs/2015IAUGA..2258174F

For transient follow-ups, this is old news. Pan-starrs will be good for data mining, though, and follow-up of interesting targets. Let's see how the professional astronomical community will react...

 

Best wishes - clear skies,

Stella.

 

Affiliation
American Association of Variable Star Observers (AAVSO)
Conversation With Stella Re LSST and Other Surveys

Stella, Gary Walker and I had a very informative conference call last Friday. Stella does intend that AAVSO will include in VSX stars that generate alerts from LSST and variables or suspected variables that generate interest in the professional community and require sequences and follow up observations.  These will generally be transients brighter than 17th magnitude that saturate LSST or are otherwise singled out as objects of interest by professional astronomers. In general these will be relatively bright compared to the magnitude range that LSST is designed to provide photometry.

AVSO will not try to create a catalog of all variable stars that LSST locates. The cadence of LSST is such that variability will not be classified for most of the new, dim variables discovered and there are likely to be positional uncertainties for many of the dim variables in other galaxies.  Since the primary purposes of the LSST are to investigate dark energy and dark matter many of the new variables will be outside our galaxy. Since these very dim stars will be beyond the reach of amateur telescopes and even most research telescopes used by professionals, including them in VSX would simply be a duplication of LSST catalog entries not bright enough to conduct follow up observations. They would essentially be “noise” in the AAVSO database. Therefore it makes sense not to include them.

Gaia and other future surveys aimed at brighter targets in our galaxy are another matter, however. It is expected that Gaia will generate a relatively large volume of alerts and variable star data that is important to AAVSO and may require additional volunteer and staff resources. AAVSO is keeping on top of the progress with Gaia as it is about to enter its period of “nominal” science operation. It has been taking positional, radial velocity and photometric data for that past year and according to their Press release earlier this month almost has its analysis pipeline up to speed.

 

I think AAVSO has a good approach and is maintaining its position as the primary repository of variable star information that is relevant for avocational astronomers and professionals astronomers using the great majority of research instruments in operation. We should also keep in mind that funding limitations threatening many of the smaller “work horse” research telescopes. Contributions by AAVSO astronomers in collaboration with professionals are likely to become increasingly important since available telescope time decreases as smaller instruments are mothballed or decommissioned.

 

This is a bit of an aside, but a question was raised in this thread about Pan-Starrs. Due to problems with the analysis pipeline handling the enormous amount of data, it has not produced a lot of alerts or other time critical information relevant to AAVSO as was initially speculated might happen. The Pan-Starrs website informs us that after the first Pan-Starrs telescope went into full scale observation in May 2010 after correction of some mechanical problems with the secondary mirror support, it has produced an average of around 500 images per night from which several hundred Supernovae and several thousand asteroids were detected. The word discovered was not used because problems in data reduction and analysis has inhibited the “rapid response” portion of the mission’s goal and the mission is producing mostly archival – catalog – data that will be very useful for data mining. The images are not kept, which is understandable since each image contains 1.4 billion pixels. Only measurements extracted from the images are retained. A modest 24 confirmed transient discovery alerts were made by PS1, in the first year of full operation (through May 2011) and less than 100 candidates alerts in the same period are listed on the Pan Starrs Science consortium website. All were approximately 19th magnitude and dimmer. None of these, therefore, were alerts in which AAVSO would be involved because of their magnitude range. The brightest single 1a SN shown in the 2014 paper  http://arxiv.org/abs/1310.3828 covering type 1a discoveries by Pan-Starrs 1 during the first 1.5 years of operation was approximately 17th magnitude. All others were 18th magnitude or dimmer with the great majority above 19th magnitude. 

Therefore, from an AAVSO perspective, Pan-Starrs didn’t produce a lot of actionable results. More may develop as time progresses and more astronomers mine data it generates.

Brad Walter, WBY

Affiliation
American Association of Variable Star Observers (AAVSO)
EVRYSCOPE Issue

I am fairly concerned, more about the UNC Evryscope http://evryscope.astro.unc.edu/

This is a very high cadence system that covers everything brighter than mag 16. Exactly our territory! Understand its only in the southern hemisphere right now, but isn't a similar one planned for the north? That would cover the entire sky down to mag 16.5, more than nightly!

This could seriously impact AAVSO observers' surveying modes , creating redundancy and waste of time?

Mike

 

Affiliation
American Association of Variable Star Observers (AAVSO)
Evryscope

Hi Mike,

Yes, Evryscope and ASAS-SN are two of the three current systems that overlap the AAVSO generic magnitude range (the other is CRTS).  I know that Stella is aware of these.  The Evryscope-south system is undergoing commissioning in one of the PROMPT clamshells at CTIO; at dusk/dawn, you can see it in their webcam:

http://skynet.unc.edu/promptcam/

You can't mistake Evryscope for any other telescope system.  There are lots of systems that have taken data covering large swaths of the sky, but for some reason, the data never seem to get released, or only last for small periods of time.  Examples are the original ROTSE system, from which one year of data was extracted to build NSVS; ASAS, which has not publicly released data since 2009; MOTESS, all of the exoplanet survey systems, etc.

Arne

Affiliation
American Association of Variable Star Observers (AAVSO)
EVRYSCOPE

This is an extremely interesting system and the data pipeline is also interesting since they are processing essentially real time and saving all of the images. I expect this is going to create a lot of alerts and discover a whole bunch of new variables and characterize them. Some things that the system in it's presently planned operation isn't doing. 

1. multi-filter observation. EVRYSCOPE has the capability but the planned operation is single filter.

2. Continuous coverage campaigns of an object "WET style" using observers positioned around the globe. Of course, once it has proven itself, these telescopes would not be terribly expensive to duplicate and distribute around the globe. There does not seem to be a plan to do that at present.  

3. Crowding. These small telescopes have a pretty wide field of view and large plate scales (large angle per pixel). Larger, longer focal length telescope will be able to obtain photometry on objects that will suffer from crowding in these 61 mm aperture telescopes with 85 mm f/1.4 lenses. Take a look at the image here to see what I mean: http://evryscope.astro.unc.edu/2015/07/02/evryscope-collects-first-100000-images-5-5tb-of-data/ 

4. High speed photometry and better SNR on a short time scale. The long baseline of observations mitigates high speed photometry to some extent. Pulsating white dwarfs and other types of pulsating sub dwarfs (extreme horizontal branch stars pulsators and some ELM stars) pulsate with periods of around 100 seconds to around 10 minutes. The WET network observe these with telescopes ranging from around 0.6 meters to 2 meter class continuously for a week or two at a time  with cadences of, say 10 seconds to 30 seconds.  high speed photometry is probably less applicable to many amateurs with smaller telescopes and tends to be hard on shuttered cameras.  However, going deeper requires stacking multiple EVRYSCOPE images and larger amateur scopes can get better SNR with shorter exposures. 

So EVRYSCOPE may do a lot of things we do, but not everything and not with the geographic and plate scale diversity AAVSO can brings to the party. I suspect it may end up generating a whole bunch of requests for multi-filter and smaller plate scale follow up observations.  It may make us very, very busy - ASASSN many times over. 

Brad Walter, WBY