The Carnegie Supernova Project II

Stritzinger, Maximilian; Taddia, F.; Fraser, M.; Tauris, T. M.; Contreras, C.; Drybye, S; Galbany, L.; Holmbo, S.; Morrell, N.; Pastorello, A.; Phillips, M. M.; Pignata, G.; Tartaglia, L.; Suntzeff, Nicholas B.; Anais, J.; Ashall, C.; Baron, Edward; Burns, Christopher R.; Hoêflich, P.; Hsiao, E. Y.; Karamehmetoglu, E.; Moriya, Takashi J.; Bock, G.; Campillay, A.; Castellón, S.; Inserra, C.; González, C.; Marples, P.; Parker, Stu; Reichart, D.; Torres-Robledo, S.; Young, D. R.

doi:10.1051/0004-6361/202038019

Cited by 18 publications

(27 citation statements)

References 68 publications

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“…Following Pastorello et al (2019a, see their figure 10), we identify the prominent Fe II multiplets in absorption, along with Sc II, Ba II, Ti II, Na I doublet, Ca II and O I. This transitional spectrum is typical of LRNe during the second, redder peak (Smith et al 2016;Blagorodnova et al 2017;Pastorello et al 2019b;Cai et al 2019;Stritzinger et al 2020), although here the transition is much more rapid, in agreement with the rapid light curve evolution.…”

Section: Datesupporting

confidence: 85%

“…We note that in AT 2019zhd and M31-LRN2015 the evolution of T bb and R ph follows a similar trend as more luminous LRNe, such as AT 2020kog (Pastorello et al 2020), AT 2018hso (Cai et al 2019), AT 2017jfs (Pastorello et al 2019b), and AT 2014ej (Stritzinger et al 2020), that have higher temperature (T bb > 7000 K) and a more compact radius at the early maximum. In contrast, M31-RV is much redder (the temper-ature is lower by a factor of two) and has a larger radius at maximum.…”

Section: Bolometric Light Curve and Evolution Of The Temperature And ...supporting

confidence: 55%

“…We used the same interstellar extinction and distance values as in Pastorello et al (2019a, see their Table3). The data of AT 2018hso and AT 2014ej are fromCai et al (2019) andStritzinger et al (2020), respectively, while those of AT 2020kog and AT 2020hat are fromPastorello et al (2020). In all panels, the curves for the different objects are identified with the symbols labelled in the right panel.…”

mentioning

confidence: 99%

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Luminous Red Nova AT 2019zhd, a new merger in M 31

Pastorello,

Fraser,

Valerin

et al. 2020

Preprint

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We present the follow-up campaign of the luminous red nova (LRN) AT 2019zhd, the third event of this class observed in M 31. The object was followed by several sky surveys for about five months before the outburst, during which it showed a slow luminosity rise. In this phase, the absolute magnitude ranged from M r = −2.8 ± 0.2 mag to M r = −5.6 ± 0.1 mag. Then, over a four to five day period, AT 2019zhd experienced a major brightening, reaching a peak of M r = −9.61 ± 0.08 mag and an optical luminosity of 1.4 × 10 39 erg s −1 . After a fast decline, the light curve settled onto a short-duration plateau in the red bands. Although less pronounced, this feature is reminiscent of the second red maximum observed in other LRNe. This phase was followed by a rapid linear decline in all bands. At maximum, the spectra show a blue continuum with prominent Balmer emission lines. The post-maximum spectra show a much redder continuum, resembling that of an intermediate-type star. In this phase, Hα becomes very weak, Hβ is no longer detectable, and a forest of narrow absorption metal lines now dominate the spectrum. The latest spectra, obtained during the postplateau decline, show a very red continuum (T e f f ≈ 3000 K) with broad molecular bands of TiO, similar to those of M-type stars. The long-lasting, slow photometric rise observed before the peak resembles that of LRN V1309 Sco, which was interpreted as the signature of the common-envelope ejection. The subsequent outburst is likely due to the gas outflow following a stellar merging event. The inspection of archival HST images taken 22 years before the LRN discovery reveals a faint red source (M F555W = 0.21 ± 0.14 mag, with F555W − F814W = 2.96 ± 0.12 mag) at the position of AT 2019zhd, which is the most likely quiescent precursor. The source is consistent with expectations for a binary system including a predominant M5-type star.

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Section: Datesupporting

confidence: 85%

Section: Bolometric Light Curve and Evolution Of The Temperature And ...supporting

confidence: 55%

mentioning

confidence: 99%

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Luminous Red Nova AT 2019zhd, a new merger in M 31

Pastorello,

Fraser,

Valerin

et al. 2020

Preprint

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“…The dynamical merger event may generate a shortlived transient powered by the ejection of mass, primarily from the donor's envelope (Soker & Tylenda 2006). "Luminous red novae" (LRN) are the class of optical transients with typical durations of weeks to months and peak luminosities ∼ 10 38 −10 41 erg s −1 between those of classical novae and supernovae (SNe) and characteristically red colors (e.g., Martini et al 1999;Munari et al 2002;Bond et al 2003;Kulkarni et al 2007;Tylenda et al 2011;Kurtenkov et al 2015;Smith et al 2016;Blagorodnova et al 2017;Cai et al 2019;Stritzinger et al 2020; see Pastorello et al 2019a for a recent review and Fig. 1 for a sample of LRNe).…”

Section: Introductionmentioning

confidence: 99%

Light Curve Model for Luminous Red Novae and Inferences about the Ejecta of Stellar Mergers

Matsumoto¹,

Metzger²

2022

Preprint

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The process of unstable mass transfer in a stellar binary can result in either a complete merger of the stars or successful removal of the donor envelope leaving a surviving more compact binary. "Luminous red nova" (LRN) are the class of optical transients believed to accompany such merger/common envelope events. Past works typically model LRNe using analytic formulae for supernova light curves which make assumptions (e.g., radiation dominated ejecta, neglect of hydrogen recombination energy) not justified in stellar mergers due to the lower velocities and specific thermal energy of the ejecta. We present a one-dimensional model of LRN light curves, which accounts for these effects. Consistent with observations, we find that LRNe typically possess two light curve peaks, an early phase powered by initial thermal energy of the hot, fastest ejecta layers and a later peak powered by hydrogen recombination from the bulk of the ejecta. We apply our model to a sample of LRNe to infer their ejecta properties (mass, velocity, and launching radius) and compare them to the progenitor donor star properties from pre-transient imaging. We define a maximum luminosity achievable for a given donor star in the limit that the entire envelope is ejected, finding that several LRNe violate this limit. Shock interaction between the ejecta and pre-dynamical mass-loss, may provide an additional luminosity source to alleviate this tension. Our model can also be applied to the merger of planets with stars or stars with compact objects.

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“…Their colours become progressively redder; for example, the intrinsic B − V colour of an LRN can even reach 1.8 mag at late phases (see Figure 4 of Pastorello et al 2019b). The evolution of the SED and the radius of LRNe is markedly different from that of ILRTs (Cai et al 2019;Stritzinger et al 2020a). LRNe are likely produced by the coalescence of two stars, however we disfavour such a merging scenario for ILRTs.…”

Section: Plausible Scenarios For Ilrts and Conclusionmentioning

confidence: 55%

Intermediate-luminosity red transients: Spectrophotometric properties and connection to electron-capture supernova explosions

Cai,

Pastorello,

Fraser

et al. 2021

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We present the spectroscopic and photometric study of five intermediate-luminosity red transients (ILRTs), namely AT 2010dn, AT 2012jc, AT 2013la, AT 2013lb, and AT 2018aes. They share common observational properties and belong to a family of objects similar to the prototypical ILRT SN 2008S. These events have a rise time that is less than 15 days and absolute peak magnitudes of between −11.5 and −14.5 mag. Their pseudo-bolometric light curves peak in the range 0.5 -9.0 × 10 40 erg s −1 and their total radiated energies are on the order of (0.3 -3) × 10 47 erg. After maximum brightness, the light curves show a monotonic decline or a plateau, resembling those of faint supernovae IIL or IIP, respectively. At late phases, the light curves flatten, roughly following the slope of the 56 Co decay. If the late-time power source is indeed radioactive decay, these transients produce 56 Ni masses on the order of 10 −4 to 10 −3 M . The spectral energy distribution of our ILRT sample, extending from the optical to the mid-infrared (MIR) domain, reveals a clear IR excess soon after explosion and non-negligible MIR emission at very late phases. The spectra show prominent H lines in emission with a typical velocity of a few hundred km s −1 , along with Ca II features. In particular, the [Ca ii] λ7291,7324 doublet is visible at all times, which is a characteristic feature for this family of transients. The identified progenitor of SN 2008S, which is luminous in archival Spitzer MIR images, suggests an intermediate-mass precursor star embedded in a dusty cocoon. We propose the explosion of a super-asymptotic giant branch star forming an electron-capture supernova as a plausible explanation for these events.

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The Carnegie Supernova Project II

Cited by 18 publications

References 68 publications

Luminous Red Nova AT 2019zhd, a new merger in M 31

Luminous Red Nova AT 2019zhd, a new merger in M 31

Light Curve Model for Luminous Red Novae and Inferences about the Ejecta of Stellar Mergers

Intermediate-luminosity red transients: Spectrophotometric properties and connection to electron-capture supernova explosions

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