Time Domain Astronomy at Caltech (ZTF) S. R. Kulkarni Director, Caltech Optical Observatories Principal Investigator, Zwicky Transient Facility (ZTF)

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1 Time Domain Astronomy at Caltech (ZTF) S. R. Kulkarni Director, Caltech Optical Observatories Principal Investigator, Zwicky Transient Facility (ZTF)

2 Time Domain Astronomy (TDA) has emerged! TDA is now widely recognized to be a frontier field for this decade TDA is a major goal of LSST TDA is a major area of research at Caltech Optical: Zwicky Transient Facility (successor to the Palomar Transient Factory or PTF) Gravitational Wave: LIGO (& VIRGO) Radio: Owens Valley Radio Observatory (& JVLA)

3 Owens Valley Radio Observatory

4 OVRO: One of the largest university radio observatories in the world Suite of experiments ranging from 10 MHz 35 GHz

6 Palomar Observatory

8 Fritz Zwicky ( )

9 A phased program for optical time domain astronomy Phase I: Palomar Transient Factory ( ) Systematic exploration of sky on timescales of week Integrated approach: P48->P60->P200 Phase II: intermediate Palomar Transient Factory ( ) Systematic exploration of sky on timescales of one night Robotic Spectroscopy on demand (SEDM on P60) Phase III: Zwicky Transient Factory ( ) pre-cursor TDA survey to LSST (Z. Ivezic, LSST) stepping stone to LSST in the area of TDA (A. Tyson, LSST)

10 A Thermonuclear SN only hours old! (Double Degenerate Model) Nugent et al Li et at al. 2011

11 LETTER doi: /nature14440 A strong ultraviolet pulse from a newborn type Ia supernova Yi Cao 1, S. R. Kulkarni 1,2, D. Andrew Howell 3,4, Avishay Gal-Yam 5, Mansi M. Kasliwal 6, Stefano Valenti 3,4, J. Johansson 7, R. Amanullah 7, A. Goobar 7, J. Sollerman 8, F. Taddia 8, Assaf Horesh 5, Ilan Sagiv 5, S. Bradley Cenko 9, Peter E. Nugent 10,11, Iair Arcavi 3,12, Jason Surace 13, P. R. Woźniak 14, Daniela I. Moody 14, Umaa D. Rebbapragada 15, Brian D. Bue 15 & Neil Gehrels 9 Type Ia supernovae 1 are destructive explosions of carbon-oxygen white dwarfs 2,3. Although they are used empirically to measure cosmological distances 4 6, the nature of their progenitors remains mysterious 3. One of the leading progenitor models, called the single degenerate channel, hypothesizes that a white dwarf accretes matter from a companion star and the resulting increase in its central pressure and temperature ignites thermonuclear explosion 3,7,8. Here we report observations with the Swift Space Telescope of strong but declining ultraviolet emission from a type Ia supernova within four days of its explosion. This emission is consistent with theoretical expectations of collision between material ejected by the supernova and a companion star 9, and therefore provides evidence that some type Ia supernovae arise from the single degenerate channel. On UTC (Coordinated Universal Time) 2014 May 3.29 the intersion. As detailed in Methods subsection Spherical models for the early ultraviolet pulse, we explored models in which the ultraviolet emission is spherically symmetric with the supernova explosion (such as shock cooling and circumstellar interaction). These models are unable to explain the observed ultraviolet pulse. Therefore we turn to asymmetric models in which the ultraviolet emission comes from particular directions. A reasonable physical model is ultraviolet emission arising in the ejecta as the ejecta encounters a companion 9,14. When the rapidly moving ejecta slams into the companion, a strong reverse shock is generated in the ejecta that heats up the surrounding material. Thermal radiation from the hot material, which peaks in the ultraviolet part of the spectrum, can then be seen for a few days until the fastmoving ejecta engulfs the companion and hides the reverse shock region. We compare a semi-analytical model 9 to the Swift/UVOT

12 Publications of the Astronomical Society of the Pacific, 128: (7pp), 2016 November The Astronomical Society of the Pacific. All rights reserved. Printed in the U.S.A. doi: / /128/969/ Intermediate Palomar Transient Factory: Realtime Image Subtraction Pipeline Yi Cao 1, Peter E. Nugent 2,3, and Mansi M. Kasliwal 1 1 Astronomy Department, California Institute of Technology, Pasadena, CA 91125, USA 2 Department of Astronomy, University of California, Berkeley, CA , USA 3 Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50B-4206, Berkeley, CA 94720, USA Received 2016 June 6; accepted 2016 August 2; published 2016 September 30 Abstract A fast-turnaround pipeline for realtime data reduction plays an essential role in discovering and permitting followup observations to young supernovae and fast-evolving transients in modern time-domain surveys. In this paper, we present the realtime image subtraction pipeline in the intermediate Palomar Transient Factory. By using highperformance computing, efficient databases, and machine-learning algorithms, this pipeline manages to reliably deliver transient candidates within 10 minutes of images being taken. Our experience in using high-performance computing resources to process big data in astronomy serves as a trailblazer to dealing with data from large-scale time-domain facilities in the near future. Key words: surveys methods: observational (stars:) supernovae: general Online material: color figures

13 The Astrophysical Journal Letters,767:L23(5pp),2013April20 C The American Astronomical Society. All rights reserved. Printed in the U.S.A. doi: / /767/2/l23 RCORONAEBOREALISSTARSINM31FROMTHEPALOMARTRANSIENTFACTORY Sumin Tang 1,2,YiCao 2,LarsBildsten 1,PeterNugent 3,4,EricBellm 2,ShrinivasR.Kulkarni 2,RussLaher 5, David Levitan 2,FrankMasci 6,EranO.Ofek 7,ThomasA.Prince 2,BranimirSesar 2,andJasonSurace 5 1 Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA 2 Division of Physics, Mathematics, & Astronomy, California Institute of Technology, Pasadena, CA 91125, USA 3 Computational Cosmology Center, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, USA 4 Department of Astronomy, University of California, Berkeley, California , USA 5 Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA 6 Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA 7 Benoziyo Center for Astrophysics and the Helen Kimmel Center for Planetary Science, Weizmann Institute of Science, Rehovot, Israel Received 2013 March 7; accepted 2013 March 15; published 2013 April 1 ABSTRACT We report the discovery of R Coronae Borealis (RCB) stars in the Andromeda galaxy (M31) using the Palomar Transient Factory (PTF). RCB stars are rare hydrogen-deficient, carbon-rich supergiant variables, most likely the merger products of two white dwarfs. These new RCBs, including two confirmed ones and two candidates, are the first to be found beyond the Milky Way and the Magellanic Clouds. All of M31 RCBs showed >1.5magirregular declines over timescales of weeks to months. Due to the limiting magnitude of our data (R mag), these RCB stars have R mag at maximum light, corresponding to M R = 4 to 5, making them some of the most luminous RCBs known. Spectra of two objects show that they are warm RCBs, similar to the Milky Way RCBs RY Sgr and V854 Cen. We consider these results, derived from a pilot study of M31 variables, as an important proof-of-concept for the study of rare bright variables in nearby galaxies with the PTF or other synoptic surveys. Key words: galaxies: individual (M31) stars: AGB and post-agb stars: carbon stars: variables: general supergiants Online-only material: color figure

14 Research in Astronomy and Astrophysics manuscript no. (L A TEX: agn.tex; printed on August 21, 2017; 20:28) Quasars behind M31 from PTF survey Yu-Han Yao 1, Shrinivas R. Kulkarni 2, Thomas Kupfer 2 and Kevin Burdge 2 1 Kavli Institute for Astronomy & Astrophysics and Department of Astronomy, Peking University, Yi He Yuan Lu 5, Hai Dian District, Beijing , China; yaoyuhan2014@pku.edu.cn 2 Division of Physics, Mathematics, & Astronomy, California Institute of Technology, Pasadena, CA 91125, USA Abstract This paper reports the discovery of quasars in the vicinity of the Andromeda galaxy (M31) with light curves from the Palomar Transient Factory (PTF). Identifying quasars behind M31 is challenging due to the high stellar surface density, yet they are powerful beacons to probe the interstellar medium (ISM) via absorption-line analysis. We use the optical variability data spanning 7 years to identify quasar candidates in the 7.2 deg 2 PTF M31 field. Based on Machine Learning (ML) algorithms, we build our star-quasar separation filter with 59 known quasars and 2000 known stars as a training set, which then select 122 candidates. Follow-up spectroscopy for 56 candidates reveals that at least 45 of them are bona fide quasars, which suggests that over 88% of the remaining candidates are likely real quasars. Among the 45 newly discovered quasars, 5 are in the background sky of the bright disk with a radius of 27 kpc. Key words: galaxies: individual (M31) quasars: general

15 S. Kulkarni Principal Investigator M. J. Graham Project Scientist E. C. Bellm Survey Scientist

16 Wide field Imagers HSC, 1.7 deg 2 DES, 2.5 deg 2 PS1, 7 deg 2 PTF/iPTF, 7.3 deg 2 ZTF, 47 deg 2 LSST, 9.6 deg 2 1 deg

17 ZTF 3-year survey begins January 2018 ZTF is not one but several surveys 3-day wide & shallow survey (10,000 sq degree covered in 3 nights) (PUBLIC) 1-day Galactic Plane patrol (PUBLIC) Partnership survey for high cadence TOO response to LIGO events

18 ZTF Data Release Framework IPAC is the data center for ZTF Real time alerts four months after survey starts (managed by UW) There is more to ZTF than transient object astronomy! Astronomy based on light curves (variable stars, quasars, NEOs) The first major release is 12 months after survey starts Raw and reduced images Photometric extractions Thereafter semester releases Includes light curves Goal: database queries for light curves

20 First light from ZTF is expected to be this week!

Dream with ZTF: dirty fireballs & orphans (Anna HO s thesis topic) The Astrophysical Journal, 769:130(16pp),2013June1 PTF11agg Cenko et al.

The P48 discovery (R-band) image is shown in the left panel.

The location of PTF11agg, as determined from our P48 imaging, is indicated with a solid circle (1 radius; note that this is significantly larger than the

21 Dream with ZTF: dirty fireballs & orphans (Anna HO s thesis topic) The Astrophysical Journal, 769:130(16pp),2013June1 PTF11agg Cenko et al. P48 R band 2011 Jan Keck/LRIS g band 2011 Sep Keck/LRIS g band 2011 Sep " 5" Figure 1. Optical imaging of the field of PTF11agg. The P48 discovery (R-band) image is shown in the left panel. Follow-up Keck/LRIS g-band observations, obtained on 2011 September 26, are displayed in the center (wider field) and right (zoomed in) panels. The location of PTF11agg, as determined from our P48 imaging, is indicated with a solid circle (1 radius; note that this is significantly larger than the astrometric uncertainty in our alignment between the Keck/LRIS and P48 images, which is 50 mas in each coordinate). A faint, unresolved source consistent with the location of PTF11agg is detected in both our g-band and R-band (not shown) images. All images are oriented with north facing up and east to the left.

22 Next Show in 2022: Ultimate Celestial Cinematography

Bumps, Burps & Booms in the Skies. Source: APOD, NASA

Bumps, Burps & Booms in the Skies Source: APOD, NASA 48 0 The Palomar Observatory 48 1 Fritz Zwicky (1889-1974) 48 2 A Star Dies: A Supernova is born Astronomy Picture of the Day (NASA) 48 3 Metals =Stellar