4.6 Article

The transitional gap transient AT 2018hso: new insights into the luminous red nova phenomenon

期刊

ASTRONOMY & ASTROPHYSICS
卷 632, 期 -, 页码 -

出版社

EDP SCIENCES S A
DOI: 10.1051/0004-6361/201936749

关键词

binaries: close; stars: winds, outflows; stars: massive; supernovae: individual: AT 2018hso; supernovae: individual: AT 2017jfs supernovae; individual: NGC4490-2011OT1

资金

  1. China Scholarship Council [201606040170]
  2. H2020 ERC grant [758638]
  3. Royal Society - Science Foundation Ireland University Research Fellowship
  4. PRIN-INAF 2017 of Toward the SKA and CTA era: discovery, localization, and physics of transient sources
  5. Jenny and Antti Wihuri foundation
  6. Vilho, Yrjo and Kalle Vaisala foundation
  7. Millennium Institute of Astrophysics (MAS)of the Iniciativa Cientifica Milenio
  8. VILLUM FONDEN [00025501, 16599]
  9. Polish NCN MAESTRO grant [2014/14/A/ST9/00121]
  10. H2020 Hemera program [730970]
  11. Instrument Centre for Danish Astrophysics (IDA)
  12. UK Science and Technology Facilities Council
  13. UKRI Science and Technology Facilities Council
  14. University of Edinburgh within the LSST:UK Science Consortium [ST/N002512/1]
  15. Queen's University Belfast within the LSST:UK Science Consortium [ST/N002520/1]
  16. National Optical Astronomy Observatories (NOAO) in Tucson, Arizona
  17. STFC [ST/P006892/1, ST/S006176/1] Funding Source: UKRI

向作者/读者索取更多资源

Context. The absolute magnitudes of luminous red novae (LRNe) are intermediate between those of novae and supernovae (SNe), and show a relatively homogeneous spectro-photometric evolution. Although they were thought to derive from core instabilities in single stars, there is growing support for the idea that they are triggered by binary interaction that possibly ends with the merging of the two stars. Aims. AT 2018hso is a new transient showing transitional properties between those of LRNe and the class of intermediate-luminosity red transients (ILRTs) similar to SN 2008S. Through the detailed analysis of the observed parameters, our study supports that it actually belongs to the LRN class and was likely produced by the coalescence of two massive stars. Methods. We obtained ten months of optical and near-infrared photometric monitoring, and 11 epochs of low-resolution optical spectroscopy of AT 2018hso. We compared its observed properties with those of other ILRTs and LRNe. We also inspected the archival Hubble Space Telescope (HST) images obtained about 15 years ago to constrain the progenitor properties. Results. The light curves of AT 2018hso show a first sharp peak (reddening-corrected M-r = -13.93 mag), followed by a broader and shallower second peak that resembles a plateau in the optical bands. The spectra dramatically change with time. Early-time spectra show prominent Balmer emission lines and a weak [Ca II] doublet, which is usually observed in ILRTs. However, the strong decrease in the continuum temperature, the appearance of narrow metal absorption lines, the great change in the H alpha strength and profile, and the emergence of molecular bands support an LRN classification. The possible detection of a M-I similar to -8 mag source at the position of AT 2018hso in HST archive images is consistent with expectations for a pre-merger massive binary, similar to the precursor of the 2015 LRN in M101. Conclusions. We provide reasonable arguments to support an LRN classification for AT 2018hso. This study reveals growing heterogeneity in the observables of LRNe than has been thought previously, which is a challenge for distinguishing between LRNe and ILRTs. This suggests that the entire evolution of gap transients needs to be monitored to avoid misclassifications.

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