The Cow: Discovery of a Luminous, Hot, and Rapidly Evolving Transient

By S. Prentice, K. Maguire, S. Smartt, M. Magee, P. Schady, S. Sim, Ting-Wan Chen, P. Clark, C. Colin, M. Fulton and 20 more. Astrophysical Journal, 2018

174 citations recorded by the source corpus.

We present the ATLAS discovery and initial analysis of the first 18 days of the unusual transient event, ATLAS18qqn/AT2018cow. It is characterized by a high peak luminosity (∼1.7 × 1044 erg s−1), rapidly evolving light curves (>5 mag rise to peak in ∼3.5 days), and hot blackbody spectra, peaking at ∼27,000 K that are relatively featureless and unchanging over the first two weeks. The bolometric light curve cannot be powered by radioactive decay under realistic assumptions. The detection of high-energy emission may suggest a central engine as the powering source. Using a magnetar model, we estimated an ejected mass of 0.1–0.4 M , which lies between that of low-energy core-collapse events and the kilonova, AT2017gfo. The spectra cooled rapidly from 27,000 to 15,000 K in just over two weeks but remained smooth and featureless. Broad and shallow emission lines appear after about 20 days, and we tentatively identify them as He i although they would be redshifted from their rest wavelengths. We rule out that there are any features in the spectra due to intermediate mass elements up to and including the Fe group. The presence of r-process elements cannot be ruled out. If these lines are due to He, then we suggest a low-mass star with residual He as a potential progenitor. Alternatively, models of magnetars formed in neutron star mergers, or accretion onto a central compact object, give plausible matches to the data.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a69ec28c807fcc43a6e81b627c9d82063f64388e

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Citations in the corpus

The fast, luminous ultraviolet transient AT2018cow: extreme supernova, or disruption of a star by an intermediate-mass black hole? (2018, methodology): “The ASAS-SN non-detection reported by Prentice et al. 2018 (g > 18.9 at 58284.13) provides an even tighter constraint: a rise of > 4.2 magnitudes over <1.3 days.”
An Embedded X-Ray Source Shines through the Aspherical AT 2018cow: Revealing the Inner Workings of the Most Luminous Fast-evolving Optical Transients (2018, methodology): “AT 2018cow was discovered on 2018 June 16 by the ATLAS survey as a rapidly evolving transient located within a spiral arm of the dwarf star-forming galaxy CGCG 137-068 at 60Mpc (Prentice et al. 2018; Smartt et al. 2018).”