Forbidden hugs in pandemic times

Pastorello, A.; Valerin, G.; Fraser, M.; Elias‐Rosa, N.; Valenti, S.; Reguitti, A.; Mazzali, Paolo A.; Amaro, R.; Andrews, Jennifer E.; Dong, Yize; Jencson, J.; Lundquist, M.; Reichart, D.; Sand, David J.; Wyatt, S.; Smartt, S. J.; Smith, K.; Srivastav, Shubham; Cai, Yongzhi; Holmbo, S.; Fiore, A.; Jones, David; Kankare, E.; Karamehmetoglu, E.; Lundqvist, Peter; Morales-Garoffolo, A.; Reynolds, T.; Stritzinger, M. D.; Williams, S. C.; Chambers, K.; Boer, T. J. L. de; Huber, M. E.; Rest, A.; Wainscoat, R. J.

doi:10.1051/0004-6361/202039953

Cited by 20 publications

(33 citation statements)

References 90 publications

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“…We used the same interstellar extinction and distance values as in Pastorello et al (2019a, see their Table 3). The data of AT 2018hso and AT 2014ej are from Cai et al (2019) and Stritzinger et al (2020), respectively, while those of AT 2020kog and AT 2020hat are from Pastorello et al (2021). In all panels, the curves for the different objects are identified with the symbols labelled in the right panel.…”

Section: Comparison With Other Lrnementioning

confidence: 99%

“…The follow-up campaign of AT 2019zhd has been carried out during the pandemic period in part, and has been affected by a limited access to the observational facilities. Despite these restrictions, the past few months have been prolific in terms of LRN discoveries as AT 2020hat and AT 2020kog (Pastorello et al 2021) were announced soon after AT 2019zhd.…”

Section: Introductionmentioning

confidence: 99%

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Forbidden hugs in pandemic times

Pastorello

Fraser

Valerin

et al. 2021

A&A

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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 Mr = −2.8 ± 0.2 mag to Mr = −5.6 ± 0.1 mag. Then, over a four to five day period, AT 2019zhd experienced a major brightening, reaching a peak of Mr = −9.61 ± 0.08 mag and an optical luminosity of 1.4 × 1039 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 post-plateau decline, show a very red continuum (Teff ≈ 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 (MF555W = 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: Comparison With Other Lrnementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Forbidden hugs in pandemic times

Pastorello

Fraser

Valerin

et al. 2021

A&A

Self Cite

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“…There are several different names to the heterogeneous group of transients with typical luminosities between those of classical novae and supernovae and their subclasses (e.g., Mould et al 1990;Bond et al 2003;Rau et al 2007;Ofek et al 2008;Mason et al 2010;Kasliwal 2013;Tylenda et al 2013;Kaminski et al 2018;Pastorello et al 2018;Boian & Groh 2019;Cai et al 2019;Jencson et al 2019;Kashi et al 2019;Howitt et al 2020;Jones 2020;Kamiński et al 2020;Pastorello et al 2021aPastorello et al , 2021bAndrews et al 2021;Blagorodnova et al 2021;Kamiński et al 2021;Klencki et al 2021). These names include intermediate luminosity (red) transients, red novae, luminous red novae (e.g., Jencson et al 2019;Blagorodnova et al 2021), and gap transients (e.g., Kasliwal 2011;Blagorodnova et al 2017;.…”

Section: Introductionmentioning

confidence: 99%

A Rapidly Fading Star as a Type II Obscuring Intermediate Luminosity Optical Transient (ILOT) in a Triple-star System

Bear

Soker

Kashi

2022

ApJ

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We propose a triple-star scenario where the merger of two pre-main-sequence low-mass stars, ≲0.5 M ⊙, ejects a dusty equatorial outflow that obscures and temporarily causes the disappearance of a massive star, ≳8 M ⊙. The merger of the low-mass inner binary powers a faint outburst, i.e., a faint intermediate luminosity optical transient (ILOT), but its main effect that can last for decades is to (almost) disappear the luminous massive star of the triple system. The typical orbital period of the triple system is about 1 yr. The merger process proceeds as the more-massive star of the two low-mass pre-main-sequence stars starts to transfer mass to the least-massive star in the triple system and as a result of that expands. This type II obscuring ILOT scenario in a triple-star system might account for the fading, rebrightening, and then refading of the massive post-main-sequence star M101-OC1. It might recover in about 20–100 yr. Our study strengthens the claim that there are alternative scenarios to account for the (almost) disappearing of massive stars, removing the need for failed supernovae. In these scenarios the disappearing is temporary, lasting from months to decades, and therefore at a later time the massive star explodes as a core collapse supernova, even if it forms a black hole.

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“…We make use of the modeled progenitor masses, radii, luminosities, and effective temperatures reported in the literature for eight transients: V4332 Sgr (Martini et al 1999), V838 Mon (Munari et al 2002;Bond et al 2003;Tylenda 2005;Tylenda et al 2005b), V1309 Sco (Mason et al 2010;Tylenda et al 2011), NGC4490-OT2011 (Smith et al 2016), M31 LRN 2015 (Williams et al 2015;Kurtenkov et al 2015;MacLeod et al 2017;Blagorodnova et al 2020), M101 LRN 2015(Blagorodnova et al 2017, SN Hunt 248 (Mauerhan et al 2015), and AT2018 bwo (Blagorodnova et al 2021). The extragalactic transients AT 2018hso (Cai et al 2019), AT 2019zhd (Pastorello et al 2021a), AT 2020hat and AT 2020kog (Pastorello et al 2021b) also have pre-outburst absolute magnitudes and colors, but no comparisons to stellar model tracks have been made.…”

Section: Luminous Red Nova Samplementioning

confidence: 99%

Dusty, Self-Obscured Transients from Stellar Mergers and Common Envelope Phases

MacLeod¹,

De²,

Loeb³

2022

Preprint

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We discuss the central role that dust condensation plays in shaping the observational appearance of outflows from coalescing binary systems. As binaries enter into a common envelope phase or merger, they shock-heat and expel material into their surroundings. Depending on the properties of the merging system, this material can expand to the point where molecules and dust form, dramatically increasing the gas opacity. We use the existing population of Luminous Red Novae (LRNe) to constrain the thermodynamics of these ejecta, then apply our findings to the progressive obscuration of merging systems in the lead in to their coalescence. Compact progenitor stars near the main sequence or in the Hertzsprung gap along with massive progenitor stars have sufficiently hot circumstellar material to remain unobscured by dust. By contrast, more extended, low-mass giants should become completely optically obscured by dust formation in the circumbinary environment. We predict that approximately half of stellar merger and common envelope transients for solar-mass stars will be dusty, infraredluminous sources. The dusty, infrared transients will selectively trace the population of systems that may successfully eject their common envelopes, while the unobscured, optical transients correspond to the LRNe population of stellar mergers.

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Forbidden hugs in pandemic times

Cited by 20 publications

References 90 publications

Forbidden hugs in pandemic times

Forbidden hugs in pandemic times

A Rapidly Fading Star as a Type II Obscuring Intermediate Luminosity Optical Transient (ILOT) in a Triple-star System

Dusty, Self-Obscured Transients from Stellar Mergers and Common Envelope Phases

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