| 1. |
- Bellm, Eric C., et al.
(författare)
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The Zwicky Transient Facility : System Overview, Performance, and First Results
- 2019
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Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:995
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Tidskriftsartikel (refereegranskat)abstract
- The Zwicky Transient Facility (ZTF) is a new optical time-domain survey that uses the Palomar 48 inch Schmidt telescope. A custom-built wide-field camera provides a 47 deg(2) field of view and 8 s readout time, yielding more than an order of magnitude improvement in survey speed relative to its predecessor survey, the Palomar Transient Factory. We describe the design and implementation of the camera and observing system. The ZTF data system at the Infrared Processing and Analysis Center provides near-real-time reduction to identify moving and varying objects. We outline the analysis pipelines, data products, and associated archive. Finally, we present on-sky performance analysis and first scientific results from commissioning and the early survey. ZTF's public alert stream will serve as a useful precursor for that of the Large Synoptic Survey Telescope.
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| 2. |
- Ho, Anna Y. Q., et al.
(författare)
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ZTF20aajnksq (AT 2020blt) : A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 905:2
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Tidskriftsartikel (refereegranskat)abstract
- We present ZTF20aajnksq (AT 2020blt), a fast-fading (Delta r = 2.3 mag in Delta t = 1.3 days) red (g - r 0.6 mag) and luminous (M-1626 A = -25.9 mag) optical transient at z = 2.9 discovered by the Zwicky Transient Facility (ZTF). AT 2020blt shares several features in common with afterglows to long-duration gamma-ray bursts (GRBs): (1) an optical light curve well-described by a broken power law with a break at t(j) = 1 d (observer frame); (2) a luminous (L0.3-10 KeV = 10(46) erg s(-1)) X-ray counterpart; and (3) luminous (L-10 GHz = 4 x 10(31) erg s(-1) Hz(-1)) radio emission. However, no GRB was detected in the 0.74 days between the last ZTF nondetection (r > 21.36 mag) and the first ZTF detection (r = 19.60 mag), with an upper limit on the isotropic-equivalent gamma-ray energy release of E-gamma,E-iso < 7 x 10(52) erg. AT 2020blt is thus the third afterglow-like transient discovered without a detected GRB counterpart (after PTF11agg and ZTF19abvizsw) and the second (after ZTF19abvizsw) with a redshift measurement. We conclude that the properties of AT 2020blt are consistent with a classical (initial Lorentz factor Gamma(0) greater than or similar to 100) on-axis GRB that was missed by high-energy satellites. Furthermore, by estimating the rate of transients with light curves similar to that of AT 2020blt in ZTF high-cadence data, we agree with previous results that there is no evidence for an afterglow-like phenomenon that is significantly more common than classical GRBs, such as dirty fireballs. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.
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| 3. |
- Kupfer, Thomas, et al.
(författare)
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Year 1 of the ZTF high-cadence Galactic plane survey : strategy, goals, and early results on new single-mode hot subdwarf B-star pulsatos
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 505:1, s. 1254-1267
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Tidskriftsartikel (refereegranskat)abstract
- We present the goals, strategy, and first results of the high-cadence Galactic plane survey using the Zwicky Transient Facility (ZTF). The goal of the survey is to unveil the Galactic population of short-period variable stars, including short-period binaries, and stellar pulsators with periods less than a few hours. Between 2018 June and 2019 January, we observed 64 ZTF fields resulting in 2990 deg2 of high stellar density in the ZTF-r band along the Galactic plane. Each field was observed continuously for 1.5 to 6 h with a cadence of 40 sec. Most fields have between 200 and 400 observations obtained over 2–3 continuous nights. As part of this survey, we extract a total of ≈230 million individual objects with at least 80 epochs obtained during the high-cadence Galactic plane survey reaching an average depth of ZTF–r ≈ 20.5 mag. For four selected fields with 2–10 million individual objects per field, we calculate different variability statistics and find that ≈1–2 per cent of the objects are astrophysically variable over the observed period. We present a progress report on recent discoveries, including a new class of compact pulsators, the first members of a new class of Roche lobe filling hot subdwarf binaries as well as new ultracompact double white dwarfs and flaring stars. Finally, we present a sample of 12 new single-mode hot subdwarf B-star pulsators with pulsation amplitudes between ZTF–r = 20–76 mmag and pulsation periods between P = 5.8–16 min with a strong cluster of systems with periods ≈6 min. All of the data have now been released in either ZTF Data Release 3 or Data Release 4.
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| 4. |
- Soumagnac, Maayane T., et al.
(författare)
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SN 2018fif : The Explosion of a Large Red Supergiant Discovered in Its Infancy by the Zwicky Transient Facility
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 902:1
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Tidskriftsartikel (refereegranskat)abstract
- High-cadence transient surveys are able to capture supernovae closer to their first light than ever before. Applying analytical models to such early emission, we can constrain the progenitor stars' properties. In this paper, we present observations of SN 2018fif (ZTF 18abokyfk). The supernova was discovered close to first light and monitored by the Zwicky Transient Facility (ZTF) and the Neil Gehrels Swift Observatory. Early spectroscopic observations suggest that the progenitor of SN 2018fif was surrounded by relatively small amounts of circumstellar material compared to all previous cases. This particularity, coupled with the high-cadence multiple-band coverage, makes it a good candidate to investigate using shock-cooling models. We employ the SOPRANOS code, an implementation of the model by Sapir & Waxman and its extension to early times by Morag et al. Compared with previous implementations, SOPRANOS has the advantage of including a careful account of the limited temporal validity domain of the shock-cooling model as well as allowing usage of the entirety of the early UV data. We find that the progenitor of SN 2018fif was a large red supergiant with a radius of R = 744.0(-128.0)(+183.0) R-circle dot and an ejected mass of M-ej = 9.3(-5.8)(+0.4) M-circle dot. Our model also gives information on the explosion epoch, the progenitor's inner structure, the shock velocity, and the extinction. The distribution of radii is double-peaked, with smaller radii corresponding to lower values of the extinction, earlier recombination times, and a better match to the early UV data. If these correlations persist in future objects, denser spectroscopic monitoring constraining the time of recombination, as well as accurate UV observations (e.g., with ULTRASAT), will help break the extinction/radius degeneracy and independently determine both.
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