Elsevier

New Astronomy

Volume 84, April 2021, 101548
New Astronomy

Possible post-kick jets in SN 1987A

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Abstract

I suggest that the recently observed hot-dust elongated structure that likely engulfs the neutron star (NS) remnant of supernova (SN) 1987A was shaped by jets that the NS launched shortly after it acquired its natal kick velocity. I take the axis of the two post-kick jets to be along the long dimension of the hot-dust elongated structure, which I term the bipolar lobe. The jittering jets explosion mechanism accounts for the misalignment of the post-kick jets axis and the main-jets axis of the ejecta. For post-kick jets to shape the bipolar lobe their energy should have been about equal to the energy of the ejecta inner to the outer edge of the lobe, E2jEej(Rlobe)4.6×1048erg. For an efficiency of ζ=0.010.1 to convert accretion energy to post-kick jets’ energy I estimate that the post-kick accreted mass was Macc,pk2×1040.002M. The negative jets feedback mechanism, where jets remove some of the mass that could have been accreted, accounts for the limited amount of accreted mass. This study adds to the growing recognition of the importance of jets in core collapse supernovae, including post-explosion jets.

Introduction

The expansion of the supernova (SN) remnant of SN 1987A (SNR 1987A) allows observations in recent years to better resolve the geometrical structure of the ejecta (e.g., Frank, Zhekov, Park, McCray, Dwek, Burrows, 2016, Larsson, Fransson, Alp, et al., 2019, Miceli, Orlando, Burrows, et al., 2019, Arendt, Dwek, Bouchet, John Danziger, Gehrz, Park, Woodward, 2020), as well as to establish the properties of dust (e.g., Dwek, Arendt, 2015, Matsuura, De Buizer, Arendt, et al., 2019). These observations reveal a complicated non-spherical morphology of the ejecta. It is accepted that a binary companion to the progenitor of SN 1987A might account for the non-spherical explosion itself (Chevalier and Soker, 1989), for the progenitor being a blue supergiant (e.g., Podsiadlowski, Joss, Rappaport, 1990, Menon, Heger, 2017, Urushibata, Takahashi, Umeda, Yoshida, 2018), and for the formation of the three rings (e.g., Soker, 1999, Morris, Podsiadlowski, 2009). However, unlike the three circumstellar rings that have a general axisymetrical morphology (e.g., Wampler, Wang, Baade, Banse, D’Odorico, Gouiffes, Tarenghi, 1990, Burrows, Krist, Hester, et al., 1995), the structure of the ejecta is much more complicated than just being axi-symmetrical (e.g., Abellán, Indebetouw, Marcaide, et al., 2017, Matsuura, Indebetouw, Woosley, et al., 2017).

A recent addition to the observations that show the non-spherical SNR 1987A inner structure is the detection of a hot-dust blob (Cigan et al., 2019) that might reveal the location of the NS remnant of SN 1987A (Cigan, Matsuura, Gomez, et al., 2019, Page, Beznogov, Garibay, et al., 2020), solving the earlier puzzling non-detection of the remnant (e.g., Haberl, Geppert, Aschenbach, Hasinger, 2006, Indebetouw, Matsuura, Dwek, et al., 2014). The hot-dust blob is surrounded by a larger hot-dust region that I term the bipolar lobe. The study of possible implications of this bipolar lobe is the focus of the present paper.

There are two explosion mechanisms that researchers use to account for the non-spherical structure of SNR 1987A. In the neutrino-driven explosion mechanism instabilities of different kinds alone account for all aspects of the the non-spherical structure (e.g., Wongwathanarat, Janka, Müller, Pllumbi, Wanajo, 2017, Utrobin, Wongwathanarat, Janka, Müller, Ertl, Woosley, 2019, Jerkstrand, Wongwathanarat, Janka, et al., 2020). On the other hand, some studies argue that in addition to the role of instabilities a global bipolar outflow (Orlando et al., 2020), or several jets that the newly born NS launched at and shortly after the explosion and in varying directions (Soker, 2017, Bear, Soker, 2018b) play the major role in determining the large scale departure from spherical symmetry. The jittering jets explosion mechanism (e.g., Papish, Soker, 2011, Gilkis, Soker, 2014, Gilkis, Soker, 2016) is behind the varying directions of jets’ axes. Earlier studies attributed some morphological features, e.g., two opposite protrusions (‘Eras’), in several SNRs to jittering jets during the explosion (e.g., Bear, Soker, 2017, Bear, Grichener, Soker, 2017, Grichener, Soker, 2017, Akashi, Bear, Soker, 2018). The neutrino-driven explosion mechanism and the jittering jets explosion mechanism might overlap, at least in some cases (Soker, Obergaulinger, Aloy). I note that (Wang et al., 2002) already suggested that jets powered the explosion of SN 1987A, but their predicted jets’ axis is not compatible with new observations by, e.g., Abellán et al. (2017). More generally, there are many earlier studies related to CCSN explosions in the frame of the classical jet-driven magnetorotational mechanism, where the jets are stable and do not jitter (e.g., Khokhlov, Höflich, Oran, et al., 1999, Aloy, Muller, Ibanez, Marti, MacFadyen, 2000, Maeda, Moriya, Kawabata, et al., 2012, López-Cámara, Morsony, Begelman, Lazzati, 2013, Bromberg, Tchekhovskoy, 2016, Nishimura, Sawai, Takiwaki, Yamada, Thielemann, 2017).

The jittering jets explosion mechanism has many challenges to overcome. Regarding the kick velocity of the NS that is relevant to this study, the jittering jets explosion mechanism attributes the kick to the same mechanism as that of the neutrino driven mechanism, the tug-boat mechanism (Scheck, Plewa, Janka, Kifonidis, Müller, 2004, Scheck, Kifonidis, Janka, Müller, 2006, Nordhaus, Brandt, Burrows, Livne, Ott, 2010, Wongwathanarat, Janka, Müller, 2010, Wongwathanarat, Janka, Müller, 2013, Janka, 2017). In this mechanism one or more dense clumps that are expelled by the explosion gravitationally attract the NS and accelerate it. The jittering jets explosion mechanism predicts that the kick velocity direction tends to avoid the close angles with the main jets axis (Bear and Soker, 2018a).

I here raise the possibility that the newly detected hot-dust bipolar lobe was shaped by post-kick jets, i.e., jets that the NS launched after it acquired its natal kick velocity (section 3). I summarise the main results in section 4. I open by discussing the natal kick direction in relation to the main axis of the ejecta (section 2)

Section snippets

Natal kick direction

In Fig. 1 I mark the relevant morphological features for this study, the main-jet axis, the blob, and the bipolar lobe (hereafter the lobe). I use four panels from figure 3 of Cigan et al. (2019). Bear and Soker (2018b) identify the jet-like feature (lower-right panel of Fig. 1) in the molecular emission image from Abellán et al. (2017). I take the line more or less along this jet-like feature to be the main-jet axis (dashed-white line), as it also defines a general symmetry line of the ejecta.

The ejecta

Although the ejecta is not spherical, to allow an analytical calculation I take the density profile to be that of a spherical explosion according to Chevalier and Soker (1989) as in Eqs. (1)–(6) of Suzuki and Maeda (2019) with δ=1 and m=10ρ(r,t)={ρ0(rtvbr)1rtvbrρ0(rtvbr)10r>tvbr,where Mej is the ejecta mass, ESN is its kinetic energy,vbr=(207)1/2(ESNMej)1/2=3.92×103×(ESN1.5×1051erg)1/2(Mej14M)1/2kms1,andρ0=7Mej18πvbr3t3.I scale the ejecta mass and energy with values from Jerkstrand

Summary

I studied the recently observed hot-dust region in SNR 1987A (Cigan et al., 2019), which I term the bipolar-lobe (Fig. 1), in the frame of the jittering jets explosion mechanism. I assumed that the radiation from the NS remnant of SN 1987A heats the bipolar lobe (Cigan, Matsuura, Gomez, et al., 2019, Page, Beznogov, Garibay, et al., 2020), and therefore that the dust in the lobe has a clear path to radiation from the NS remnant.

I proposed that post-kick jets that the NS remnant of SN 1987A

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

I thank Avishai Gilkis, Amit Kashi and an anonymous referee for useful comments. This research was supported by a grant from the Israel Science Foundation (420/16 and 769/20) and a grant from the Asher Space Research Fund at the Technion.

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