XIAN: A large array of telescopes in Antarctica dedicated to transient science with “all-sky” imaging every 5 seconds

US: Donald G. York (Chicago), Lifan Wang (LBL), Carl Pennypacker

(SSL), Morley Blouke (Ball Aerospace), Don Lamb (Chicago), Doyal Harper(Chicago), Dale Sandford(Chicago), Julie Thorburn (Chicago)

China:Xiangqun Cui (NAIOT), Xu Zhou (CAS, Beijing), Jingyao Hu (CAS, Beijing),

Xiangyan Yuan (NAIOT)

Europe:Enrico Cappellaro, (INAF, Padova),

Roger Malina (LAM, France), Stephane Basa (LAM, France)

AustraliaJohn Storey (UNSW), J. Lawrence (UNSW), Michael Ashley

(UNSW),

XIAN Prime Science GoalGamma Ray Burst detection and follow up science

• 20th mag detections in 5-10 seconds (V, R)• Detect 25-50% GRBS in sky covered

– .3 GRB/day– > 100/day orphan afterglows/day– 0.1/day SN « blue flashes », 2000SN/yr

Follow up for GRB physics, use as cosmological probes, study high z host galaxy chemistry

• GLAST and SVOM space mission timeframes– SVOM is Sino-French Space Mission for GRB– Previously known as ECLAIRS

400, 50cm telescope array -Xian

Area for

Follow-up

Telescope(s)

SVOM

• Sino-French GRB satellite (ex ECLAIRS)• Currently in CNES Phase A study for 2011 launch.• Chinese: NAOC ( Beijing), IHEP (Beiking), XIOPM

(Xian)– Jianyan Wei (PI), Shuang Nan Zhang (Co-PI),

Jingyao Hu, Qiu Yulei, Shouchen Li• French: CEA ( J Paul PI), CESR D Barret.. J L

Atteia, ....Klotz,Casse, Daigne....• S.Basa (LAM) co-pi visible camera, ground based

follow up• CESR, LATT, IAP, APC• ISF Milan, TIFR Mumbai, MIT

XIAN Science Goals• Light curves from v short t (~5s) to 4 months --GRBs, with coincident optical/GRB (& X-ray)

for cosmic distance scale --Orphan afterglows (GRB opening angle) --Type II blue flash, early time Type Ia curves --Type II counts at low z --GRB and host physics (circumstellar lines,

clumpy?) • Deep optical survey (much deeper than SDSS)• “Calibration” of gravitational wave events

(shortest bursts) LIGO,LISA and neutrino bursts (ICE CUBE, ANTARES)

• Gravitational Lens planet searches

Xian Strawman under study• 8000 sq. deg., 400 scopes, each 5x5 deg• 0.5 meter, (clear aperture) Schmidts• • 16 K x 16 K pixels, segments 1 K x 4 K (so, 16x4

small devices per focal plane), 10 readouts per segment.

• Reduce sky coverage by x 2 , option under study– provide 2 Telescope coverage of each 5x5 deg area, – to minimize false positives – Redundancy

• Mag. Limit: 20 R effective, but broad band• Single filter, each year (to test trigger schemes)

The need for Xian as dedicated ground based array for transient

science• Once the flash is detected, follow-up is currently intermittent (less than 1%GRBS) owing to

--Lack of acceptable weather at a properly equipped site

--Lack of a system to allow overriding on-going programs

--Lack of a system into which all new observations are reported

--The impossibility of getting complete light curves.

.

The Need for Xian•Light curves are not well known --Some objects die out and recover

-- Short bursts (< 2 sec bursts) have a long tail with the same energy in it as the short spike.

--Physics of events as Zs are determined short bursts=merging, condensed matter stars long bursts =collapsing stars-SNe II)

-- GRB science drives need for dedicated facility ( cf early days of SN science)

XIAN Roadmap• Test-beds • T2 -- Test array at APO. Under development.

• T5-- Expanded array, 2+3 in SW-USA

• Deployment• T3 -- Test array of 3-5, identical telescopes.

Antarctica. Compelling stand alone science.

• Xian -- Large array of small telescopes. Antarctica

• Big Telescope (BT)--Dedicated, on site , 2.5m NIR robotic telescope for spectroscopy,photometry

Close view of Xian

Slide 19

Triggers for Transients

--Short frame comparisons for triggers (little changes in sky, CCD artifacts, etc. over 5-10 sec)

--Mask known stars and asteroids (masking depends on brightness)

--Use SDSS (T2, T5 in the North) or Mt Stromlo Survey (T3, Xian in the South) for quiescent sources until we have our own from averaging one season’s worth of data.

--Co-add in, e.g., 100s, 3000s, 10 hr, 100hr., 1000 hr., images to look for triggers for longer time scales (orphan afterglows, SN Ia or AGNs).Full reductions for these.

Data (per telescope)

--52 megabtyes/sec for the triggers

--2 Terabytes per night, short term storage

--4 Terabytes long term storage (will increase as storage becomes cheaper)

source sec) Vlim

GRB(>2s) 2-200 0.02 -rays

GRB a. glow 200-105 0.01 20-23

Orphan 104-105 >2 23

Blue flash-r 600 0.0005 18 ( z=0.03)

Blue flash-b 60 0.0005 21.6

Type Ia SNe 106 2.2 23 (z=0.3)

Type II SNe 106 0.1 23 (z=0.1)

Strong Grav.

Lens (QSO)

105.6 0.01 22

AGN 106 20 21

AM CVn 600 0.001 19

Cataclysmic Variables

1800 0.05 17.5

Planet eclipse 3600 0.01 13 (rocky

Planets)

*No. per Sq. degreePer year

365 per year, all-sky,==> = 0.01

VARIABLESOF INTEREST

Figures of merit

System FOV sec h* Vlim

SDSS-SNe 4 1.5 ~106 0.2 22Deep Lens 4 0.5 1300 0.16 24ROTSE III 3.5 4 1800 1.7 17.5

T2 20 2 30 2 20.4T3 60 2 10 6 20

Xian 4000 2 10 1200 20Tombo 10000 4 60 4000 17

10000 60 60 5000 12

*[h] = sq.deg.- yr, the no. of sq. deg. constantly covered for timescales, , in a year

KS-Technical Desiderata-1

• Maximum coverage at Dome C/A --Circumpolar sky is large, excellent

observing efficiency, cold• No moving parts: natural focus, one filter, no telescope motion, no(?) CCD Dewars• Trade off CCD block size design (t min) with

acceptable yield on amplifiers• Single pixel triggers, drift scan• Magnitude limit in selected time• Low power because fuel is expensive

For better image quality, adopt two correcting Schmidt plates (achromatic Schmidt)

Fig.3 Layout of the achromatic Schmidt telescope

Spot diagram

for Antarctica

The above simulation shows the focal length changed 0.02mm from 20°C to

–50.8 °C; the best image plane changed 3microns.

The image quality only slightly changed in geo diameter (encircled energy 100%).

Design of the telescopes

FOV 5x5 degrees, 20 sq. degrees

0.5 meter Schmidt

1 arcsec per pixel (9 micron pixel)

80% encircled energy in 1 pixel

3860A to 9000A

26% obscuration

f/3.28

Focus independent of temperature

dx 2000+/-2000

dy 0+/-100

8 modules8k pixels

4 modules across, 16,000 pixels across

10, 100x4000 TDI arrays per module dx 2000+/-2000

dy 0+/-100

8 modules8k pixels

4 modules across, 16,000 pixels across

10, 100x4000 TDI arrays per module

CCD layout (16,000 x 8,000 pixels)--x and y scales differ

CCD Design

QE > 50% (red favored?)Read noise < 2 electrons, rms (on chip, variable gain)Integration time 5-10s, drift scanPixel size 9-10 micronsWell capacity <0.99995 electronsDark current < 0.1 electrons per secSerial registers per unit: up to 131 unit: 1000x4000 pixels 64 units per focal plane16K x 16K pixelsPower dissipation per focal plane 16W

KS-Technical Desiderata-2• Minimize computing goals, evolve as

technology evolves -- t(short) to t(short) comparisons -- Send triggers to separate pipeline for evaluation, pull out that track of triggered object to get long timescale information -- Co add and compare for longer time scales -- Discard most frames after co-add’s are done (consider look-back requirements)

KS-Technical Desiderata-3• Follow-up maximal number of selected

classes of bursts with on-site, conventional, well equipped telescope, sized to science:

• 2.5m class, rapid response (IRAIT .8m)• --spectra, IR, optical (for redshifts to 10) --photometry (optical, IR) --polarimetry --autoalert, fast tracking• This is called BT (Big Telescope).

• Test of engineering and of science goals• 10-100 sq. deg. (2-5 telescopes, underfill focal plane with CCDs if need be.)• Self-reliant science goals (does not depend on KS): --Minimum set of orphan afterglows --Minimum set of blue bursts, SN II --Confirmation of SN II /SN Ia rate at low z (z~0.3). --Deep co-added survey (SDSS imaging equivalent)

T2,T3, T5

T2,T3, T5 -Engineering

--software for triggers (identify sources of false positives)

--test triggering schemes (different filters each year)

--recognition of triggers early enough to get correct follow-up (spectra photometry)

--Dewarless CCDs, focus by design

Examples of false positives

--variable detector artifacts--solar system, atmospheric events--saturated stars --stars that make “dipoles” because of variable PSFs when comparing frames-- radiation hits (cosmic rays or gamma rays from equipment near the CCDs)--ghosts from Schmidt systems (which move as strip scans) (need AR coatings)--true variable sources (CVs, etc.)--slow moving asteroids (put half of telescopes at different sites and use triangulation of asteroids in co-pointed fields.)--Earth orbiting satellites

ConclusionsThe 16Kx 16K CCDs are feasible to build. Low power electronics is a major development.

The minimum-moving-parts goal is attainable on paper

Previous experience to build on, but a large step is needed.

Fast algorithms will be a major challenge

T2, T3, T5 are logical first steps

Xian is feasible and should be built

Xian will impact the study of cosmology, supernova physics, variable stars, gravitational waves and neutrino astronomy

SVOM • Sino-French GRB satellite• Currently in CNES Phase A study for 2011

launch.• Chinese: NAOC ( Beijing), IHEP (Beiking),

XIOPM (Xian)– Jianyan Wei (PI), Shuang Nan Zhang

(Co-PI)• French: CEA ( J Paul PI), • S.Basa (LAM) co-pi visible camera, ground

based follow up• CESR, LATT, IAP, APC• ISF Milan, TIFR Mumbai, MIT

SVOM High Energy Instruments

FOV Energy Range Pos

CXG 2 sr 4-300 kev 10 arcmin

SXC 2 sr 1-12 kev 30 arcsec

GRM 6.2 sr .02 -5 Mev NA

Expected GRB rate: 100/yr

SVOM• Trigger on 200GRB’s per year• X, Gamma, Visible on satellite• Location in <10 sec to <10 arc min

– 50% of the cases <1 arc min for ground follow up

• Allow for 75% cases red shift and spectroscopy follow up

• On board visible cameras under study– WAC V 40 degx 40 deg 15 mag in 10 sec– VIRT K 10arc min x 10 20 mag in 300 sec– Observe « prompt » emission before and after GRB

Requirements for SVOM Ground Based Follow up

Telescope• Provide link to 8m class telescopes

• Visible to NIR for high z GRB

• Positions to 1 arc sec within 5 min

• Lightcurve

• Photometric redshifts

• Transient sorting for 8m follow up

• Current Strawman: 1.5 m class, R I J H

AcknowledgementsWhile our designs developed independently, many of the ideas here were also arrived at, in connection with the TOMBO* project, by Y. Ohno, T. Ebisuzaki, K. Sunouchi, R. Susukita, C. Otani, H. M. Shimizu, A. Yoshida, No. Kawai, M. Matsuoka, M. Euno, T. Wada, M. Yamauchi and N. Takeyama, Riken Review No. 47, July 2002. We acknowledge discussions with C. Akerlof.

*TOMBO stands for Tombo Observing for Microlensing and Bursting Objects.