11 research outputs found
Seven years of coordinated ChandraâNuSTAR observations of SN 2014C unfold the extreme mass-loss history of its stellar progenitor
We present the results from our 7 yr long broadband X-ray observing campaign of SN 2014C with Chandra and NuSTAR. These coordinated observations represent the first look at the evolution of a young extragalactic SN in the 0.3â80 keV energy range in the years after core collapse. We find that the spectroscopic metamorphosis of SN 2014C from an ordinary type Ib SN into an interacting SN with copious hydrogen emission is accompanied by luminous X-rays reaching L x â 5.6 Ă 1040 erg sâ1 (0.3â100 keV) at âŒ1000 days post-explosion and declining as L x â t â1 afterwards. The broadband X-ray spectrum is of thermal origin and shows clear evidence for cooling after peak, with T(t)â20keV(t/tpk)â0.5 . Soft X-rays of sub-keV energy suffer from large photoelectric absorption originating from the local SN environment with NHint(t)â3Ă1022(t/400days)â1.4cmâ2 . We interpret these findings as the result of the interaction of the SN shock with a dense (n â 105 â 106 cmâ3), H-rich disk-like circumstellar medium (CSM) with inner radius âŒ2 Ă 1016 cm and extending to âŒ1017 cm. Based on the declining NHint(t) and X-ray luminosity evolution, we infer a CSM mass of âŒ(1.2 fâ2.0 f)Mâ , where f is the volume filling factor. We place SN 2014C in the context of 121 core-collapse SNe with evidence for strong shock interaction with a thick circumstellar medium. Finally, we highlight the challenges that the current mass-loss theories (including wave-driven mass loss, binary interaction, and line-driven winds) face when interpreting the wide dynamic ranges of CSM parameters inferred from observations
Multi-Messenger Astronomy with Extremely Large Telescopes
The field of time-domain astrophysics has entered the era of Multi-messenger
Astronomy (MMA). One key science goal for the next decade (and beyond) will be
to characterize gravitational wave (GW) and neutrino sources using the next
generation of Extremely Large Telescopes (ELTs). These studies will have a
broad impact across astrophysics, informing our knowledge of the production and
enrichment history of the heaviest chemical elements, constrain the dense
matter equation of state, provide independent constraints on cosmology,
increase our understanding of particle acceleration in shocks and jets, and
study the lives of black holes in the universe. Future GW detectors will
greatly improve their sensitivity during the coming decade, as will
near-infrared telescopes capable of independently finding kilonovae from
neutron star mergers. However, the electromagnetic counterparts to
high-frequency (LIGO/Virgo band) GW sources will be distant and faint and thus
demand ELT capabilities for characterization. ELTs will be important and
necessary contributors to an advanced and complete multi-messenger network.Comment: White paper submitted to the Astro2020 Decadal Surve
SN 2019ehk: A Double-peaked Ca-rich Transient with Luminous X-Ray Emission and Shock-ionized Spectral Features
We present panchromatic observations and modeling of the Calcium-rich supernova (SN) 2019ehk in the star-forming galaxy M100 (d â 16.2 Mpc) starting 10 hr after explosion and continuing for ~300 days. SN 2019ehk shows a double-peaked optical light curve peaking at t = 3 and 15 days. The first peak is coincident with luminous, rapidly decaying Swift-XRTâdiscovered X-ray emission (L_x â 10âŽÂč erg sâ»Âč at 3 days; L_x â tâ»Âł), and a Shane/Kast spectral detection of narrow Hα and He II emission lines (v â 500 km sâ»Âč) originating from pre-existent circumstellar material (CSM). We attribute this phenomenology to radiation from shock interaction with extended, dense material surrounding the progenitor star at r (0.1â1) Ă 10Âčâ· cm. The photometric and spectroscopic properties during the second light-curve peak are consistent with those of Ca-rich transients (rise-time of t_r = 13.4 ± 0.210 days and a peak B-band magnitude of M_B = â15.1 ± 0.200 mag). We find that SN 2019ehk synthesized (3.1 ± 0.11) Ă 10â»ÂČ M_â of â”â¶Ni and ejected M_(ej) = (0.72 ± 0.040) Mâ total with a kinetic energy E_k = (1.8 ± 0.10) Ă 10â”â° erg. Finally, deep HST pre-explosion imaging at the SN site constrains the parameter space of viable stellar progenitors to massive stars in the lowest mass bin (~10 M_â) in binaries that lost most of their He envelope or white dwarfs (WDs). The explosion and environment properties of SN 2019ehk further restrict the potential WD progenitor systems to low-mass hybrid HeCO WD+CO WD binaries
Multi-Messenger Astronomy with Extremely Large Telescopes
The field of time-domain astrophysics has entered the era of Multi-messenger Astronomy (MMA). One key science goal for the next decade (and beyond) will be to characterize gravitational wave (GW) and neutrino sources using the next generation of Extremely Large Telescopes (ELTs). These studies will have a broad impact across astrophysics, informing our knowledge of the production and enrichment history of the heaviest chemical elements, constrain the dense matter equation of state, provide independent constraints on cosmology, increase our understanding of particle acceleration in shocks and jets, and study the lives of black holes in the universe. Future GW detectors will greatly improve their sensitivity during the coming decade, as will near-infrared telescopes capable of independently finding kilonovae from neutron star mergers. However, the electromagnetic counterparts to high-frequency (LIGO/Virgo band) GW sources will be distant and faint and thus demand ELT capabilities for characterization. ELTs will be important and necessary contributors to an advanced and complete multi-messenger network
Target-of-opportunity observations of gravitational-wave events with Vera C. Rubin Observatory
The discovery of the electromagnetic counterpart to the binary neutron star (NS) merger GW170817 has opened the era of gravitational-wave multimessenger astronomy. Rapid identification of the optical/infrared kilonova enabled a precise localization of the source, which paved the way to deep multiwavelength follow-up and its myriad of related science results. Fully exploiting this new territory of exploration requires the acquisition of electromagnetic data from samples of NS mergers and other gravitational-wave sources. After GW170817, the frontier is now to map the diversity of kilonova properties and provide more stringent constraints on the Hubble constant, and enable new tests of fundamental physics. The Vera C. Rubin Observatory's Legacy Survey of Space and Time can play a key role in this field in the 2020s, when an improved network of gravitational-wave detectors is expected to reach a sensitivity that will enable the discovery of a high rate of merger events involving NSs (âŒtens per year) out to distances of several hundred megaparsecs. We design comprehensive target-of-opportunity observing strategies for follow-up of gravitational-wave triggers that will make the Rubin Observatory the premier instrument for discovery and early characterization of NS and other compact-object mergers, and yet unknown classes of gravitational-wave events
SN 2019ehk: A Double-peaked Ca-rich Transient with Luminous X-Ray Emission and Shock-ionized Spectral Features
We present panchromatic observations and modeling of the Calcium-rich
supernova 2019ehk in the star-forming galaxy M100 (d16.2 Mpc) starting
10 hours after explosion and continuing for ~300 days. SN 2019ehk shows a
double-peaked optical light curve peaking at and days. The first
peak is coincident with luminous, rapidly decaying -XRT
discovered X-ray emission ( at 3 days; ), and a Shane/Kast spectral detection of narrow H and
He II emission lines ( km/s) originating from pre-existent
circumstellar material. We attribute this phenomenology to radiation from shock
interaction with extended, dense material surrounding the progenitor star at
cm and the resulting cooling emission. We calculate a total CSM
mass of with particle density
. Radio observations indicate a significantly
lower density at larger radii. The photometric and
spectroscopic properties during the second light curve peak are consistent with
those of Ca-rich transients (rise-time of days and a peak
B-band magnitude of mag). We find that SN 2019ehk
synthesized of
and ejected
total with a kinetic energy .
Finally, deep pre-explosion imaging at the SN site constrains
the parameter space of viable stellar progenitors to massive stars in the
lowest mass bin (~10 ) in binaries that lost most of their He
envelope or white dwarfs. The explosion and environment properties of SN
2019ehk further restrict the potential WD progenitor systems to low-mass hybrid
HeCO WD + CO WD binaries.Comment: 51 pages, 27 figures. Accepted for publication in Ap