TY - JOUR
T1 - Where is the Engine Hiding Its Missing Energy? Constraints from a Deep X-Ray Non-detection of the Superluminous SN 2015bn
AU - Bhirombhakdi, Kornpob
AU - Chornock, Ryan
AU - Margutti, Raffaella
AU - Nicholl, Matt
AU - Metzger, Brian D.
AU - Berger, Edo
AU - Margalit, Ben
AU - Milisavljevic, Dan
N1 - Funding Information:
We thank G. Migliori for sharing expertise with XMM-SAS. K.B. and R.C. acknowledge support from National Aeronautics and Space Administration (NASA) XMM-Newton grant No. 80NSSC18K0665. Facility: XMM. software: BOXFIT (van Eerten et al. 2012), MOSFiT (Guillochon et al. 2018), SAS (https://www.cosmos.esa.int/ web/xmm-newton/sas-news).
Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved.
PY - 2018/12/1
Y1 - 2018/12/1
N2 - SN 2015bn is a nearby hydrogen-poor superluminous supernova (SLSN-I) that has been intensively observed in X-rays with the goal to detect the spindown powered emission from a magnetar engine. The early-time ultraviolet/optical/infrared (UVOIR) data fit well to the magnetar model, but require leakage of energy at late times of ≲1043 erg s-1, which is expected to be partially emitted in X-rays. Deep X-ray limits until ∼300 days after explosion revealed no X-ray emission. Here, we present the latest deep 0.3-10 keV X-ray limit at 805 days obtained with XMM-Newton. We find L X < 1041 erg s-1, with no direct evidence for central-engine powered emission. While the late-time optical data still follow the prediction of the magnetar model, the best-fit model to the bolometric light curve predicts that ∼97% of the total input luminosity of the magnetar is escaping outside of the UVOIR bandpass at the time of observation. Our X-ray upper limit is <1.5% of the input luminosity, strongly constraining the high-energy leakage, unless non-radiative losses are important. These deep X-ray observations identify a missing energy problem in SLSNe-I, and we suggest future observations in hard X-rays and γ-rays for better constraints. Also, independent of the optical data, we constrain the parameter spaces of various X-ray emission scenarios, including ionization breakout by magnetar spindown, shock interaction between the ejecta and external circumstellar medium, off-axis γ-ray burst afterglow, and black hole fallback accretion.
AB - SN 2015bn is a nearby hydrogen-poor superluminous supernova (SLSN-I) that has been intensively observed in X-rays with the goal to detect the spindown powered emission from a magnetar engine. The early-time ultraviolet/optical/infrared (UVOIR) data fit well to the magnetar model, but require leakage of energy at late times of ≲1043 erg s-1, which is expected to be partially emitted in X-rays. Deep X-ray limits until ∼300 days after explosion revealed no X-ray emission. Here, we present the latest deep 0.3-10 keV X-ray limit at 805 days obtained with XMM-Newton. We find L X < 1041 erg s-1, with no direct evidence for central-engine powered emission. While the late-time optical data still follow the prediction of the magnetar model, the best-fit model to the bolometric light curve predicts that ∼97% of the total input luminosity of the magnetar is escaping outside of the UVOIR bandpass at the time of observation. Our X-ray upper limit is <1.5% of the input luminosity, strongly constraining the high-energy leakage, unless non-radiative losses are important. These deep X-ray observations identify a missing energy problem in SLSNe-I, and we suggest future observations in hard X-rays and γ-rays for better constraints. Also, independent of the optical data, we constrain the parameter spaces of various X-ray emission scenarios, including ionization breakout by magnetar spindown, shock interaction between the ejecta and external circumstellar medium, off-axis γ-ray burst afterglow, and black hole fallback accretion.
KW - X-rays: individual (SN 2015bn)
KW - supernovae: individual (SN 2015bn)
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U2 - 10.3847/2041-8213/aaee83
DO - 10.3847/2041-8213/aaee83
M3 - Article
AN - SCOPUS:85057805315
VL - 868
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
SN - 2041-8205
IS - 2
M1 - L32
ER -