The Zwicky Transient Facility: Surveys and Scheduler

Bellm, Eric C.; Kulkarni, S. R.; Barlow, Tom A.; Feindt, U.; Graham, M. J.; Goobar, A.; Kupfer, Thomas; Ngeow, Chow-Choong; Nugent, P.; Ofek, E. O.; Prince, Thomas A.; Riddle, Reed; Walters, Richard; Ye, Quanzhi

doi:10.1088/1538-3873/ab0c2a

Cited by 478 publications

(440 citation statements)

References 46 publications

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“…As part of the Zwicky Transient Facility (ZTF), the Palomar 48-inch (P48) telescope images the sky every clear night (Bellm et al 2019a;Graham et al 2019). ZTF J2130+4420 was first discovered in a dedicated high-cadence survey at low Galactic latitudes performed in the ZTF-r band (Bellm et al 2019b). The high-cadence data was complemented by data from the ZTF public survey obtained in 2018 which was made available after data release 1 on May 8, 2018.…”

Section: Observationsmentioning

confidence: 99%

The First Ultracompact Roche Lobe–Filling Hot Subdwarf Binary

Kupfer

Bauer

Marsh

et al. 2020

ApJ

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We report the discovery of the first short period binary in which a hot subdwarf star (sdOB) fills its Roche lobe and started mass transfer to its companion. The object was discovered as part of a dedicated high-cadence survey of the Galactic Plane named the Zwicky Transient Facility and exhibits a period of P = 39.3401(1) min, making it the most compact hot subdwarf binary currently known. Spectroscopic observations are consistent with an intermediate He-sdOB star with an effective temperature of T eff = 42, 400 ± 300 K and a surface gravity of log(g)= 5.77 ± 0.05. A high-signal-to noise GTC+HiPERCAM light curve is dominated by the ellipsoidal deformation of the sdOB star and an eclipse of the sdOB by an accretion disk. We infer a low-mass hot subdwarf donor with a mass M sdOB = 0.337 ± 0.015 M and a white dwarf accretor with a mass M WD = 0.545 ± 0.020 M .Theoretical binary modeling indicates the hot subdwarf formed during a common envelope phase when a 2.5 − 2.8 M star lost its envelope when crossing the Hertzsprung Gap. To match its current P orb , T eff , log(g), and masses, we estimate a post-common envelope period of P orb ≈ 150 min, and find the sdOB star is currently undergoing hydrogen shell burning. We estimate that the hot subdwarf will become a white dwarf with a thick helium layer of ≈ 0.1 M and will merge with its carbon/oxygen white dwarf companion after ≈ 17 Myr and presumably explode as a thermonuclear supernova or form an R CrB star.

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Section: Observationsmentioning

confidence: 99%

The First Ultracompact Roche Lobe–Filling Hot Subdwarf Binary

Kupfer

Bauer

Marsh

et al. 2020

ApJ

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“…Our four objects were discovered as part of a dedicated high-cadence survey at low Galactic latitudes with ZTF (Bellm et al 2019a;Graham et al 2019). During that dedicated survey we either observed one field or alternated between two adjacent fields continuously for ≈1.5-3 hours on two to three consecutive nights in the ZTF-r band (Bellm et al 2019b). Image processing of ZTF data is described in full detail in Masci et al (2019).…”

Section: Observationsmentioning

confidence: 99%

A New Class of Large-amplitude Radial-mode Hot Subdwarf Pulsators

Kupfer

Bauer

Burdge

et al. 2019

ApJL

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Using high-cadence observations from the Zwicky Transient Facility at low Galactic latitudes, we have discovered a new class of pulsating, hot, compact stars. We have found four candidates, exhibiting blue colors (g −r ≤ −0.1 mag), pulsation amplitudes of > 5%, and pulsation periods of 200−475 sec. Fourier transforms of the lightcurves show only one dominant frequency. Phase-resolved spectroscopy for three objects reveals significant radial velocity, T eff and log(g) variations over the pulsation cycle, consistent with large amplitude radial oscillations. The mean T eff and log(g) for these stars are consistent with hot subdwarf B (sdB) effective temperatures and surface gravities. We calculate evolutionary tracks using MESA and adiabatic pulsations using GYRE for low-mass helium-core pre-white dwarfs and low mass helium-burning stars. Comparison of low-order radial oscillation mode periods with the observed pulsation periods show better agreement with the pre-white dwarf models. Therefore, we suggest that these new pulsators and Blue Large-Amplitude Pulsators (BLAPs) could be members of the same class of pulsators, composed of young ≈ 0.25 − 0.35 M ⊙ helium-core pre-white dwarfs.

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“…Up to now there has not been a large (> 100 objects) uniform dataset of SN Ia light curves with both multiband photometry and dense early-time sampling. With the Zwicky Transient Facility (ZTF, Bellm et al 2019b;Graham et al 2019), we are undertaking a high-cadence survey with six epochs per night (3g + 3r; Bellm et al 2019a). This experiment is conducted over a large area of the sky (∼2500 deg 2 ) and thus enables large-number statistics.…”

Section: Introductionmentioning

confidence: 99%

ZTF Early Observations of Type Ia Supernovae. I. Properties of the 2018 Sample

Yao

Miller

Kulkarni

et al. 2019

ApJ

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Early-time observations of Type Ia supernovae (SNe Ia) are essential to constrain their progenitor properties. In this paper, we present high-quality light curves of 127 SNe Ia discovered by the Zwicky Transient Facility (ZTF) in 2018. We describe our method to perform forced point spread function (PSF) photometry, which can be applied to other types of extragalactic transients. With a planned cadence of six observations per night (3g + 3r), all of the 127 SNe Ia are detected in both g and r band more than 10 d (in the rest frame) prior to the epoch of g-band maximum light. The redshifts of these objects range from z = 0.0181 to 0.165; the median redshift is 0.074. Among the 127 SNe, 50 are detected at least 14 d prior to maximum light (in the rest frame), with a subset of 9 objects being detected more than 17 d before g-band peak. This is the largest sample of young SNe Ia collected to date; it can be used to study the shape and color evolution of the rising light curves in unprecedented detail. We discuss six peculiar events in this sample, including one 02cx-like event ZTF18abclfee (SN 2018crl), one Ia-CSM SN ZTF18aaykjei (SN 2018cxk), and four objects with possible super-Chandrasekhar mass

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The Zwicky Transient Facility: Surveys and Scheduler

Cited by 478 publications

References 46 publications

The First Ultracompact Roche Lobe–Filling Hot Subdwarf Binary

The First Ultracompact Roche Lobe–Filling Hot Subdwarf Binary

A New Class of Large-amplitude Radial-mode Hot Subdwarf Pulsators

ZTF Early Observations of Type Ia Supernovae. I. Properties of the 2018 Sample

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