| 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. |
- Coughlin, Michael W., et al.
(författare)
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GROWTH on S190425z : Searching Thousands of Square Degrees to Identify an Optical or Infrared Counterpart to a Binary Neutron Star Merger with the Zwicky Transient Facility and Palomar Gattini-IR
- 2019
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 885:1
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Tidskriftsartikel (refereegranskat)abstract
- The third observing run by LVC has brought the discovery of many compact binary coalescences. Following the detection of the first binary neutron star merger in this run (LIGO/Virgo S190425z), we performed a dedicated follow-up campaign with the Zwicky Transient Facility (ZTF) and Palomar Gattini-IR telescopes. The initial skymap of this single-detector gravitational wave (GW) trigger spanned most of the sky observable from Palomar Observatory. Covering 8000 deg(2) of the initial skymap over the next two nights, corresponding to 46% integrated probability, ZTF system achieved a depth of 21 m(AB) in g- and r-bands. Palomar Gattini-IR covered 2200 square degrees in J-band to a depth of 15.5 mag, including 32% integrated probability based on the initial skymap. The revised skymap issued the following day reduced these numbers to 21% for the ZTF and 19% for Palomar Gattini-IR. We narrowed 338,646 ZTF transient ?alerts? over the first two nights of observations to 15 candidate counterparts. Two candidates, ZTF19aarykkb and ZTF19aarzaod, were particularly compelling given that their location, distance, and age were consistent with the GW event, and their early optical light curves were photometrically consistent with that of kilonovae. These two candidates were spectroscopically classified as young core-collapse supernovae. The remaining candidates were ruled out as supernovae. Palomar Gattini-IR did not identify any viable candidates with multiple detections only after merger time. We demonstrate that even with single-detector GW events localized to thousands of square degrees, systematic kilonova discovery is feasible.
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| 3. |
- Ho, Anna Y. Q., et al.
(författare)
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Evidence for Late-stage Eruptive Mass Loss in the Progenitor to SN2018gep, a Broad-lined Ic Supernova : Pre-explosion Emission and a Rapidly Rising Luminous Transient
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 887:2
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Tidskriftsartikel (refereegranskat)abstract
- We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 +/- 0.1 mag hr(-1)) and luminous (M-g,M- peak = -20 mag) transient. It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity (L-bol greater than or similar to 3 x 10(44) erg s(-1)), the short rise time (t(rise) = 3 days in g band), and the blue colors at peak (g-r similar to -0.4) all resemble the high-redshift Ic-BL iPTF16asu, as well as several other unclassified fast transients. The early discovery of SN2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature (T-eff greater than or similar to 40,000 K) spectra of a stripped-envelope SN. A retrospective search revealed luminous (M-g similar to M-r approximate to -14 mag) emission in the days to weeks before explosion, the first definitive detection of precursor emission for a Ic-BL. We find a limit on the isotropic gamma-ray energy release E-gamma,E- iso < 4.9 x 10(48) erg, a limit on X-ray emission L-X < 10(40) erg s(-1), and a limit on radio emission nu L-v less than or similar to 10(37) erg s(-1). Taken together, we find that the early (< 10 days) data are best explained by shock breakout in a massive shell of dense circumstellar material (0.02 M-circle dot) at large radii (3 x 10(14) cm) that was ejected in eruptive pre-explosion mass-loss episodes. The late-time (> 10 days) light curve requires an additional energy source, which could be the radioactive decay of Ni-56.
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| 4. |
- Perley, Daniel A., et al.
(författare)
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The fast, luminous ultraviolet transient AT2018cow : extreme supernova, or disruption of a star by an intermediate-mass black hole?
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 484:1, s. 1031-1049
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Tidskriftsartikel (refereegranskat)abstract
- Wide-field optical surveys have begun to uncover large samples of fast (t(rise) less than or similar to 5 d), luminous (M-peak < 18), blue transients. While commonly attributed to the breakout of a supernova shock into a dense wind, the great distances to the transients of this class found so far have hampered detailed investigation of their properties. We present photometry and spectroscopy from a comprehensive worldwide campaign to observe AT 2018cow (ATLAS 18qqn), the first fast-luminous optical transient to be found in real time at low redshift. Our first spectra (<2 days after discovery) are entirely featureless. A very broad absorption feature suggestive of near-relativistic velocities develops between 3 and 8 days, then disappears. Broad emission features of H and He develop after >10 days. The spectrum remains extremely hot throughout its evolution, and the photospheric radius contracts with time (receding below R < 10 (14) cm after 1 month). This behaviour does not match that of any known supernova, although a relativistic jet within a fallback supernova could explain some of the observed features. Alternatively, the transient could originate from the disruption of a star by an intermediate-mass black hole, although this would require long-lasting emission of highly super-Eddington thermal radiation. In either case, AT 2018cow suggests that the population of fast luminous transients represents a new class of astrophysical event. Intensive follow-up of this event in its late phases, and of any future events found at comparable distance, will be essential to better constrain their origins.
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| 5. |
- Collett-Solberg, Paulo F., et al.
(författare)
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Diagnosis, Genetics, and Therapy of Short Stature in Children : A Growth Hormone Research Society International Perspective
- 2019
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Ingår i: Hormone Research in Paediatrics. - : S. Karger. - 1663-2818 .- 1663-2826. ; 92:1, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- The Growth Hormone Research Society (GRS) convened a Workshop in March 2019 to evaluate the diagnosis and therapy of short stature in children. Forty-six international experts participated at the invitation of GRS including clinicians, basic scientists, and representatives from regulatory agencies and the pharmaceutical industry. Following plenary presentations addressing the current diagnosis and therapy of short stature in children, breakout groups discussed questions produced in advance by the planning committee and reconvened to share the group reports. A writing team assembled one document that was subsequently discussed and revised by participants. Participants from regulatory agencies and pharmaceutical companies were not part of the writing process. Short stature is the most common reason for referral to the pediatric endocrinologist. History, physical examination, and auxology remain the most important methods for understanding the reasons for the short stature. While some long-standing topics of controversy continue to generate debate, including in whom, and how, to perform and interpret growth hormone stimulation tests, new research areas are changing the clinical landscape, such as the genetics of short stature, selection of patients for genetic testing, and interpretation of genetic tests in the clinical setting. What dose of growth hormone to start, how to adjust the dose, and how to identify and manage a suboptimal response are still topics to debate. Additional areas that are expected to transform the growth field include the development of long-acting growth hormone preparations and other new therapeutics and diagnostics that may increase adult height or aid in the diagnosis of growth hormone deficiency.
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| 6. |
- Frederick, Sara, et al.
(författare)
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A New Class of Changing-look LINERs
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 883:1
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of six active galactic nuclei (AGNs) caught turning on during the first nine months of the Zwicky Transient Facility (ZTF) survey. The host galaxies were classified as low-ionization nuclear emissionline region galaxies (LINERs) by weak narrow forbidden line emission in their archival SDSS spectra, and detected by ZTF as nuclear transients. In five of the cases, we found via follow-up spectroscopy that they had transformed into broad-line AGNs, reminiscent of the changing-look LINER iPTF16bco. In one case, ZTF18aajupnt/ AT2018dyk, follow-up Hubble Space Telescope ultraviolet and ground-based optical spectra revealed the transformation into a narrow-line Seyfert 1 with strong [Fe VII, X, XIV] and He II lambda 4686 coronal lines. Swift monitoring observations of this source reveal bright UV emission that tracks the optical flare, accompanied by a luminous soft X-ray flare that peaks similar to 60 days later. Spitzer follow-up observations also detect a luminous midinfrared flare, implying a large covering fraction of dust. Archival light curves of the entire sample from CRTS, ATLAS, and ASAS-SN constrain the onset of the optical nuclear flaring from a prolonged quiescent state. Here we present the systematic selection and follow-up of this new class of changing-look LINERs, compare their properties to previously reported changing-look Seyfert galaxies, and conclude that they are a unique class of transients well-suited to test the uncertain physical processes associated with the LINER accretion state.
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