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AT 2016dah and AT 2017fyp: the first classical novae discovered within a tidal stream

Darnley, M. J. and Newsam, A. M. and Chinetti, K. and Hawkins, I. D. W. and Jannetta, A. L. and Kasliwal, M. M. and McGarry, J. C. and Shara, M. M. and Sitaram, M. and Williams, S. C. (2020) AT 2016dah and AT 2017fyp: the first classical novae discovered within a tidal stream. Monthly Notices of the Royal Astronomical Society, 495 (1). pp. 1073-1092. ISSN 0035-8711.

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AT 2016dah and AT 2017fyp are fairly typical Andromeda galaxy (M 31) classical novae. AT 2016dah is an almost text book example of a ‘very fast’ declining, yet uncommon, Fe II‘b’ (broad-lined) nova, discovered during the rise to peak optical luminosity, and decaying with a smooth broken power-law light curve. AT 2017fyp is classed as a ‘fast’ nova, unusually for M 31, its early decline spectrum simultaneously shows properties of both Fe II and He/N spectral types – a ‘hybrid’. Similarly, the light curve of AT 2017fyp has a broken power-law decline but exhibits an extended flat-topped maximum. Both novae were followed in the UV and X-ray by the Neil Gehrels Swift Observatory, but no X-ray source was detected for either nova. The pair were followed photometrically and spectroscopically into their nebular phases. The progenitor systems were not visible in archival optical data, implying that the mass donors are main-sequence stars. What makes AT 2016dah and AT 2017fyp particularly interesting is their position with respect to M 31. The pair are close on the sky but are located far from the centre of M 31, lying almost along the semiminor axis of their host. Radial velocity measurements and simulations of the M 31 nova population leads to the conclusion that both novae are members of the Andromeda Giant Stellar Stream (GSS). We find the probability of at least two M 31 novae appearing coincident with the GSS by chance is ∼1 per cent⁠. Therefore, we claim that these novae arose from the GSS progenitor, not M 31 – the first confirmed novae discovered in a tidal steam.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Darnley, M. J.0000-0003-0156-3377
Kasliwal, M. M.0000-0002-5619-4938
Williams, S. C.0000-0001-8178-0202
Additional Information:© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Supplementary data. Accepted 2020 April 20. Received 2020 April 20; in original form 2020 March 10. We would like to express our gratitude to Massimo Della Valle for his helpful and thoughtful comments when refereeing the original manuscript. The authors would like to thank Conor Ransome (and collaborators) for advanced access to the extended M 31 nova spectroscopic catalogue. MJD would like to thank Kim Page for guidance with respect to reduction and analysis of Swift UVOT and XRT data, and Andreea Font for discussion regarding the Giant Stellar Stream. MJD and AMN also acknowledge funding from the UK Science and Technology Facilities Council (STFC) consolidated grant ST/R000484/1. ALJ acknowledges funding from INTO Newcastle University. IDWH acknowledges funding from Student Finance England. This work was supported in part by the GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by the National Science Foundation Partnership in International Research and Education program under Grant No 1545949. GROWTH is a collaborative project between California Institute of Technology (USA), Pomona College (USA), San Diego State University (USA), Los Alamos National Laboratory (USA), University of Maryland College Park (USA), University of Wisconsin Milwaukee (USA), University of Washington Seattle (USA), Texas Tech University (USA), Tokyo Institute of Technology (Japan), National Central University (Taiwan), Indian Institute of Astrophysics (India), Inter-University Center for Astronomy and Astrophysics (India), Weizmann Institute of Science (Israel), The Oskar Klein Centre at Stockholm University (Sweden), Humboldt University (Germany), Liverpool John Moores University (LJMU; UK), University of Sydney (Australia). The Liverpool Telescope is operated on the island of La Palma by LJMU in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias with financial support from STFC. IRAF is distributed by the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. This research has made use of data and software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.
Group:Astronomy Department
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)ST/R000484/1
Newcastle UniversityUNSPECIFIED
Student Finance EnglandUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Participating InstitutionsUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:stars: individual: (AT 2016dah, AT 2017fyp), novae, cataclysmic variables, galaxies: haloes, galaxies: individual: M31, ultraviolet: stars
Issue or Number:1
Record Number:CaltechAUTHORS:20200608-115354566
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Official Citation:M J Darnley, A M Newsam, K Chinetti, I D W Hawkins, A L Jannetta, M M Kasliwal, J C McGarry, M M Shara, M Sitaram, S C Williams, AT 2016dah and AT 2017fyp: the first classical novae discovered within a tidal stream, Monthly Notices of the Royal Astronomical Society, Volume 495, Issue 1, June 2020, Pages 1073–1092,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103766
Deposited By: George Porter
Deposited On:08 Jun 2020 19:55
Last Modified:08 Jun 2020 19:55

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