This is a special venue for me!
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Time Domain Astronomy: The
Next Decade
S. R. Kulkarni
Caltech Optical Observatories
MAJOR DIVISION: VARIABLE
OBJECTS & TRANSIENTS
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Variable Objects
• Key measurement: Light Curves
– Photometric Precision
• Low: RR Lyrae, Cepheids, AGN, Type Ia
• Moderate: Eclipsing Binaries, Gravitational Lensing
• High: Planetary Transits, Asteroseismology
• What is of value?
– Total number of visits usually matters more than
cadence
• Spectroscopy (followup)
– In most cases rapid follow up is not essential
– In many cases spectroscopy helps but is not crucial
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Transient Objects
• Imaging surveys provide the starting point for investigation
– Supernova investigations are triggered by detection of a rising object
– For many studies the follow up is decoupled from the initial detection
of a GRB (at high energies)
• Cadence control is critical
– On the first night of an imaging survey the detected transients are
dominated by old supernovae
– Conversely lack of cadence control presents significant opportunity
costs (negative)
• Cadence directly determines the phase space that is being
explored
– “Universal” cadence simply means that everyone is equally unhappy
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This Talk
• Focused entirely on transient object astronomy
• Main thesis:
– Transient object astronomy is served best by sharply focused time
domain surveys
– Conversely, the returns from a generic time domain survey are likely to
be quite poor (and wasteful of follow up resources)
• Transient Object Astronomy has a bright future in this decade and
likely to continue into the next decade (when TMT will become
operational)
– However, TMT time is precious
– Transient object astronomy has its own learning curve
– The TMT collaboration must start preparing now
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AN EXEMPLAR
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The Intermediate
Palomar Transient Facility (iPTF)
The Palomar Observatory
P60
P48
P200
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P60
Confirmation
P48
Discovery
P200
Spectroscopy
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Kasliwal 2011 (PhDT)
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Super-luminous Supernovae
(no Hydrogen)
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Death Omen!
PTF10tel
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Double degenerates: The new frontier
Source: LISA Mission, NASA
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ON TO LOW LATENCY
(SAME NIGHT)
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Progenitor of a Ib Supernova!
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What next?
S. R. Kulkarni
Short timescale is terra incognito
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PTF11agg: Dirty Fireball?
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Same night arcsecond localization of
error region of 72 square degrees!
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As we go to press! GRB131011A
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M. Kasliwal
L. Singer 22
•
TITLE: GCN CIRCULAR
NUMBER: 15324
SUBJECT: Fermi403206457: iPTF detection of a possible optical afterglow
DATE: 13/10/12 12:09:55 GMT
FROM: Mansi M. Kasliwal at Caltech/Carnegie <mansikasliwal@gmail.com>
M. M. Kasliwal (Carnegie Observatories/Princeton), L. P. Singer (Caltech) and S. B. Cenko
(NASA/GSFC) report on behalf of the intermediate Palomar
Transient Factory (iPTF) collaboration:
Starting 2013-10-12 05:26 UT, we imaged about 70 deg^2 in the vicinity of the localization of
the Fermi-GBM trigger 403206457 with the Palomar 48-inch Oschin telescope (P48). Sifting
through 10,816 candidate variable sources in the GBM error circle using standard iPTF vetting
procedures including Palomar 60-inch follow-up, we identify iPTF13dsw as a possible
optical afterglow candidate:
RA(J2000) = 02h 10m 06.38s
DEC(J2000) = -04d 24' 40.3"
Light Curve: R=19.7mag @ 05:26 UT (P48), R=20.2mag @ 08:07 UT (P60)
iPTF13dsw is 3.4 deg away from the center of the final GBM localization
(68% statistical confidence radius of 2.75 deg). Nothing was detected at
this location to a limiting magnitude of 20.6 mag on 2013 Sep 25.
At 08:56 UT, we obtained a Gemini-South/GMOS spectrum in twilight. The
spectrum is mostly featureless, with no prominent emission or absorption
lines between 5100-9300A.
.
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WHAT IS THE METRIC OF SYNOPTIC
SURVEYS?
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Proposed Metrics
• The “Reach” Etendue, AΔΩ
• Point source sensitivity, AΔΩ/θ2
• These metrics make sense only for static surveys.
• Not relevant for transient surveys
• For transients mere detection in itself is limited
value
• Classification and follow up is the key
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Fundamental Parameters of a Time
Domain Survey (Transients)
•
•
•
•
Field-of-view (FOV), ΔΣ
Sensitivity (6σ), Sl
Time to move one FOV, τm
Cadence: typical time separation between revisit to the same FOV
• Basic Integration time, τs (frame time)
– Assume 60-s for all surveys
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Areal Rate
• Short Duration Transients (T<τs)
• Long Duration Transients (T>τs)
• If follow up is essential then all that matters is Sl (set by
follow up) and the parameters shown above. For 21mag ZTF is 250 times faster than say HSC.
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Zwicky Transient Facility
47-sq degree camera for P48
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The SED Machine for P60
30 arcsec
7 arcminute
PI: Nick Konidaris, PS: Robert Quimby
In collaboration with
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A Proposal: TMT Community based
Transient Object Facilities
• Recognizing that transient object astronomy is a
growing field with great promise the TMT
community should ensure that it has access to
quality transients
• Transient searches have three fundamental
parameters and as such the idea that a single
facility (equipped with “Universal Cadence”) can
provide the transient stream is incorrect
• The preparation for this should start now so that
the event streams will be ready by 2022.
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ZTF Annual Workshops
• The ZTF consortium will be holding yearly
meetings (along the lines of the very
successful iPTF 2013 Workshop)
– We plan to invite key players from TMT
consortium to attend these meetings
• http://ptf.caltech.edu/iptf/iptf_workshop/
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