# Presentation: 446286

## Pursuing Gamma Ray Bursts and Fast Optical Transients with Thinking Telescopes

**Pursuing Gamma Ray Bursts and Fast Optical Transients with Thinking Telescopes**

**Tom Vestrand, LANL**

## Definition

- The human brain, through a process we loosely call **thinking**, integrates data collection, pattern recognition, object classification, and memory to obtain a higher understanding of what action needs to be taken and promptly takes action ***to respond to a threat or an opportunity****.** *

## Why do Sky Monitoring Telescopes need to “think”?

**Threat**--- interference, telescope malfunction, etc.
**Opportunity**--- discovery of transients, new stuff not predicted. When you start looking at large fields (high etendue •A) you can find ephemeral thingstime domain astronomy, Space Situational Awareness

## We have reached the tipping point

- Time Domain Surveys (e.g. LSST) will generate 100 Petabytes of data (~2 Terabyte per hour) that must be mined in real time by the end of the decade.
- More than 10 Billion objects will be monitored for important variations in real time.
- Humans lack attention span, response time, and memory required to monitor the  data, recognize the important variations, and respond.

## How do we find important changes in persistent sources and respond in real time?

## Thinking Telescopes

**GENIE, **
**Unsupervised and**
**Supervised Classifiers,**
**Anomaly Detection,**
**SVMs, etc.**

**Advanced**
**Database Tech.**
- Context Knowledge
**Record of **
**Sky variability**
** ****(Virtual Observatory),**
**Massive Distributed**
** ****Disk Arrays**

**Robotic Hardware**
**Wide-Field Sky Monitoring Arrays,**
** ****Rapid Response Telescopes****,**
**Talons Distributed Network Technology**

**Thinking Telescopes**
**An Engine for Discovery**
**in the Time Domain**

**Need Integration of Three Components**

## Slide 7

##  Three Types of Machine Learning

** ****Automated Feature Extraction: **Real time identification of artifacts and transients in direct and difference images.
**Classifiers: **Automated classification of  celestial objects based on temporal and spectral properties.** **
**Anomaly Detection: **Real time recognition of important deviations from normal behavior for persistent sources.

## Supervised Machine Learning

**Easier to ****show**** a machine what to find...**
- Machine Learning derives classification algorithms directly from examples of data
**...than to ****tell**** a machine how to find it**
- Requires domain expertise
- Involves software development
- Demands careful attention to statistical characterization
- Entails substantial amount of *trial and error*

## Classification of Image Objects

##  What is an Anomaly?

- Dictionary Gives two Definitions—
- 1) Deviation or departure from the normal or common order, form, or rule
- 2) One that is peculiar, irregular, abnormal, or difficult to classify.

## Anomaly Detection

- Unsupervised machine learning
- Finds things that don’t fit in.
- Anomalies do not permit positive definition---***If I knew what they were, we wouldn’t call them anomalies.***

## http://skydot.lanl.gov

- http://skydot.lanl.gov

## Public SkyDOT website

- skydot.lanl.gov

## Slide 15

## RAPTOR response telescope....

**Deployed  RAPTOR-S in October/November 2004  for studying the optical emission from gamma ray bursts during the critical first few minutes after a GRB----slew speed >100 deg/second, acceleration >100 deg/sec****2****, can go anywhere in the sky and begin imaging in ~6 seconds.**

## RAPTOR Discovery of

** ****Prompt Optical Emission from GRBs**

**1) ****Prompt Optical Emission**** varying simultaneously with prompt gamma-rays.**
**2) ****Early Afterglow Emission**** that may start during prompt gamma-rays, but persists after gamma-rays fade.**
**3) ****Late Afterglow Emission**** that can last for hours to days.**

**A new taxonomy for optical emission from GRBs (Vestrand et al., Nature, 435,178, 2005).**

## In the Standard Theoretical Framework it makes physical sense to attribute the components to

**Prompt optical emission is generated by internal shocks in ejecta---driven by engine.**
**Early afterglow is generated by external shocks from interaction with surroundings.**
** ****Measuring the rise timescale of the early afterglow is a measure of the amount of “stuff” in the explosion environment.**

## RAPTOR discovery of the relationship between prompt and early optical afterglow emission.

## Afterglow is a Reverberation of the energy input measured by the prompt emission.

- Simple conjecture...

**Vestrand et al.  Nature, 442, 172—175 (2006)**

## Why is this important?

- The best tool for probing the structure of the circum-burst environment and evolution of jet/environment interaction.
- Since a significant number of GRBs are expected at very high redshifts (z>4), afterglow response can probe the nurseries of the first generations of stars.
- The observed response to late-time impulsive energy releases can reveal how earlier flaring episodes altered the environment.

## Why we need simultaneous 4-color photometry.

- The prompt optical is not a low-frequency tail of the gamma-rays, the variability of the optical spectrum is the key to understanding the physics.
- Most GRBs occur in dusty, star forming regions. The intense radiation field destroys the grains during the first minutesvariable extinction

## Simultaneous Multi-color Measurements during the first minute

- Color measurements slope of continuum, that plus time evolution yields basic parameters of flow : *the Lorentz factor, the ambient density, the fraction of the energy in mass of the particles, and the fraction of the energy in the magnetic field*

## New Generation of RAPTOR response telescopes(Observations starting ~6 seconds after alert)

- RAPTOR-Z : Ultra-fast imaging cadence (EMCCD) for studying prompt emission
- RAPTOR-T: Simultaneous Multicolor Imaging of prompt and early afterglow

## GRBs as Cosmological Beacons:  Finding the most distant objects through multi-color observations  

- Most important GRBs are at redshifts larger than z=5 when the Universe was <10% of its current age.
- Can act as beacons to map diffuse material that never condensed into stars (4% of the Universe is in baryons—1/10 of that is in visible stars and dust) This diffuse matter is in filaments that can be seen in absorption, if the GRB can be recognized when they are bright.
- RAPTOR can find them using a very simple technique---look for the cutoff at 912 Angstroms due to absorption by neutral hydrogen.
- This cutoff is redshifted to wavelengths longer than 5000 Angstroms for Z=5 or more (out of Swift band-pass). So look for optical counterparts only visible in the red.
*Simultaneous multicolor observations during the first minute are the best way to quickly identify these distant GRBs and enable high-resolution spectroscopic observations while they are still bright.*

## Identification of a Salient Class of Optical Afterglows from GRBs

- All GRB afterglows with measured redshifts transformed to z=2.
***(From Panaitescu & Vestrand, MNRAS, 387, 497 (2008))***

## Discovery of relationship between peak time and peak flux of early rising afterglows

- Crude “Standard Candles”---but potentially usable out to z~10 . We are currently exploring other properties that may refine the correlation.
***From Panaitescu & Vestrand 2008***

## Toward continuous sky monitoringThe next generation untriggered optical searchand why it matters

- Motivation stronger than ever
- Transients are there (GRB 060206, DLS, radio etc.)
- Incredibly productive interplay between Swift and ground based robotic instruments
- Pre-Swift OT concepts completely revised
- Guaranteed result down to ~16.0 mag
- We are looking one step ahead
- Orphans, on-axis “optical GRBs”, TGBNs, etc.
- Thinking Telescopes: distributed aperture

## Precursors, Short GRBs, Optically-Rich Fast Transients

- Monitor 1000 sq-degrees simultaneously
- Sensitivity ~16th magnitude in 30 second exposure
- Carried on fast slewing mount--- can cover the full sky on ~5-10 minute circuit.

## RAPTOR Network Detection of a “Naked Eye” GRB  in March 2008 (Mv=-38.6!)

- Persistent Monitoring

- Follow-up Observations

## Discoveries from GRB 080319b

- Synchrotron Self-Compton is the emission process in GRBs
- Synchrotron Self-Absorption cut-off moved through optical band
- Large Angle off-axis emission in optical
- Strongest limits on precursor activity
***(from Wozniak, Vestrand, Panaitescu, et al. , 2008)***

## First Simultaneous Multi-color Optical Observations---Mixture of two different color components

## GRB 060206: existence proofbright, high redshift, explosion with few gamma-rays

- Low fluence, high redshift (z=4.05) gamma-ray burst.
- Flared to R~16.4 mag. at ~1 hour without producing significant gamma-ray emission.
- Important implications for untriggered searches for fast optical transients and studies of GRB environments at high redshifts. (Wozniak et al. ApJ, 642, L99, 2006)

## Other exciting possibilities

- Off-axis orphan GRBs
- Strange fast transients (~100-1000) are showing up in other surveys: Deep Lens Survey, Quest, etc.
- On-axis orphans

## Other Optical Transients: Outburst of Comet 17P Holmes

## Conclusions GRBs

- We are now able to measure the relationship between the prompt optical emission and the early optical afterglow.
- The early afterglow can be understood as a response of the energy input measured by the prompt emission.
- Early afterglow structure is a new tool for probing the nature of the circumburst environment and the evolution of the jet/environment
- The observed response to late time impulsive energy releases can reveal how earlier flaring episodes have altered the jet/environment parameters
- Since a significant number of GRBs are expected to occur at high redshifts, afterglow response can probe the nurseries of the first generations of stars.

## Conclusions

-  Fast optical transients are a powerful cosmological probes, but Time Domain Astronomy is too important to be left to the Astronomers.
-   To be effective it requires real-time follow-up observations.
-  We do not have the attention span, response time, or memory required to monitor the huge volume of data, recognize important variations, and respond.
- Autonomous Robotic Telescopes with “smarts” and the ability to learn will be essential for exploring the Time Domain in astronomy.