المؤلفون: Blanchard, Peter, Villar, V, Chornock, Ryan, Laskar, Tanmoy, Li, Yijia, Leja, Joel, Pierel, Justin, Berger, Edo, Margutti, Raffaella, Alexander, Kate, Barnes, Jennifer, Cendes, Yvette, Eftekhari, Tarraneh, Kasen, Daniel, LeBaron, Natalie, Metzger, Brian, Muzerolle Page, James, Rest, Armin, Sears, Huei, Siegel, Daniel, Yadavalli, S

المصدر: Nature Astronomy. 8(6)

مصطلحات موضوعية: High-energy astrophysics, Time-domain astronomy, Transient astrophysical phenomena

الوصف: Identifying the sites of r-process nucleosynthesis, a primary mechanism of heavy element production, is a key goal of astrophysics. The discovery of the brightest gamma-ray burst (GRB) to date, GRB 221009A, presented an opportunity to spectroscopically test the idea that r-process elements are produced following the collapse of rapidly rotating massive stars. Here we present James Webb Space Telescope observations of GRB 221009A obtained +168 and +170 rest-frame days after the gamma-ray trigger, and demonstrate that they are well described by a SN 1998bw-like supernova (SN) and power-law afterglow, with no evidence for a component from r-process emission. The SN, with a nickel mass of approximately 0.09 M ⊙, is only slightly fainter than the brightness of SN 1998bw at this phase, which indicates that the SN is not an unusual GRB-SN. This demonstrates that the GRB and SN mechanisms are decoupled and that highly energetic GRBs are not likely to produce significant quantities of r-process material, which leaves open the question of whether explosions of massive stars are key sources of r-process elements. Moreover, the host galaxy of GRB 221009A has a very low metallicity of approximately 0.12 Z ⊙ and strong H2 emission at the explosion site, which is consistent with recent star formation, hinting that environmental factors are responsible for its extreme energetics.

وصف الملف: application/pdf

الوصول الحر: https://escholarship.org/uc/item/1qc9k917Test
https://escholarship.org/content/qt1qc9k917/qt1qc9k917.pdfTest

المؤلفون: Blanchard, Peter K., Villar, V. Ashley, Chornock, Ryan, Laskar, Tanmoy, Li, Yijia, Leja, Joel, Pierel, Justin, Berger, Edo, Margutti, Raffaella, Alexander, Kate D., Barnes, Jennifer, Cendes, Yvette, Eftekhari, Tarraneh, Kasen, Daniel, LeBaron, Natalie, Metzger, Brian D., Page, James Muzerolle, Rest, Armin, Sears, Huei, Siegel, Daniel M., Yadavalli, S. Karthik

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Identifying the astrophysical sites of the $r$-process, one of the primary mechanisms by which heavy elements are formed, is a key goal of modern astrophysics. The discovery of the brightest gamma-ray burst of all time, GRB 221009A, at a relatively nearby redshift, presented the first opportunity to spectroscopically test the idea that $r$-process elements are produced following the collapse of rapidly rotating massive stars. Here we present spectroscopic and photometric $\textit{James Webb Space Telescope}$ (JWST) observations of GRB 221009A obtained $+168$ and $+170$ rest-frame days after the initial gamma-ray trigger, and demonstrate they are well-described by a supernova (SN) and power-law afterglow, with no evidence for an additional component from $r$-process emission, and that the SN component strongly resembles the near-infrared spectra of previous SNe, including SN 1998bw. We further find that the SN associated with GRB 221009A is slightly fainter than the expected brightness of SN 1998bw at this phase, concluding that the SN is therefore not an unusual GRB-SN. We infer a nickel mass of $\approx0.09$ M$_{\odot}$, consistent with the lack of an obvious SN detection in the early-time data. We find that the host galaxy of GRB 221009A has a very low metallicity of $\approx0.12$ Z$_{\odot}$ and our resolved host spectrum shows that GRB 221009A occurred in a unique environment in its host characterized by strong H$_2$ emission lines consistent with recent star formation, which may hint at environmental factors being responsible for its extreme energetics.
Comment: 32 pages, 14 Figures, Submitted to Nature Astronomy

الوصول الحر: http://arxiv.org/abs/2308.14197Test

المؤلفون: Gottlieb, Ore, Issa, Danat, Jacquemin-Ide, Jonatan, Liska, Matthew, Foucart, Francois, Tchekhovskoy, Alexander, Metzger, Brian D., Quataert, Eliot, Perna, Rosalba, Kasen, Daniel, Duez, Matthew D., Kidder, Lawrence E., Pfeiffer, Harald P., Scheel, Mark A.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: We present the first numerical simulations that track the evolution of a black hole-neutron star (BH-NS) merger from pre-merger to $r\gtrsim10^{11}\,{\rm cm}$. The disk that forms after a merger of mass ratio $q=2$ ejects massive disk winds ($3-5\times10^{-2}\,M_{\odot}$). We introduce various post-merger magnetic configurations and find that initial poloidal fields lead to jet launching shortly after the merger. The jet maintains a constant power due to the constancy of the large-scale BH magnetic flux until the disk becomes magnetically arrested (MAD), where the jet power falls off as $L_j\sim t^{-2}$. All jets inevitably exhibit either excessive luminosity due to rapid MAD activation when the accretion rate is high or excessive duration due to delayed MAD activation compared to typical short gamma-ray bursts (sGRBs). This provides a natural explanation for long sGRBs such as GRB 211211A but also raises a fundamental challenge to our understanding of jet formation in binary mergers. One possible implication is the necessity of higher binary mass ratios or moderate BH spins to launch typical sGRB jets. For post-merger disks with a toroidal magnetic field, dynamo processes delay jet launching such that the jets break out of the disk winds after several seconds. We show for the first time that sGRB jets with initial magnetization $\sigma_0>100$ retain significant magnetization ($\sigma\gg1$) at $r>10^{10}\,{\rm cm}$, emphasizing the importance of magnetic processes in the prompt emission. The jet-wind interaction leads to a power-law angular energy distribution by inflating an energetic cocoon whose emission is studied in a companion paper.
Comment: For movies of the simulations, see https://oregottlieb.com/bhns.htmlTest

الوصول الحر: http://arxiv.org/abs/2306.14947Test

المؤلفون: Gottlieb, Ore, Issa, Danat, Jacquemin-Ide, Jonatan, Liska, Matthew, Tchekhovskoy, Alexander, Foucart, Francois, Kasen, Daniel, Perna, Rosalba, Quataert, Eliot, Metzger, Brian D.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: The ongoing LIGO-Virgo-KAGRA observing run O4 provides an opportunity to discover new multi-messenger events, including binary neutron star (BNS) mergers such as GW170817, and the highly anticipated first detection of a multi-messenger black hole-neutron star (BH-NS) merger. While BNS mergers were predicted to exhibit early optical emission from mildly relativistic outflows, it has remained uncertain whether the BH-NS merger ejecta provides the conditions for similar signals to emerge. We present the first modeling of early near-ultraviolet/optical emission from mildly relativistic outflows in BH-NS mergers. Adopting optimal binary properties: a mass ratio of $q=2$ and a rapidly rotating BH, we utilize numerical relativity and general relativistic magnetohydrodynamic (GRMHD) simulations to follow the binary's evolution from pre-merger to homologous expansion. We use an M1 neutrino transport GRMHD simulation to self-consistently estimate the opacity distribution in the outflows and find a bright near-ultraviolet/optical signal that emerges due to jet-powered cocoon cooling emission, outshining the kilonova emission at early time. The signal peaks at an absolute magnitude of $\sim -15$ a few hours after the merger, longer than previous estimates, which did not consider the first principles-based jet launching. By late 2024, the Rubin Observatory will have the capability to track the entire signal evolution or detect its peak up to distances of $\gtrsim1$ Gpc. In 2026, ULTRASAT will conduct all-sky surveys within minutes, detecting some of these events within $\sim 200$ Mpc. The BH-NS mergers with higher mass ratios or lower BH spins would produce shorter and fainter signals.
Comment: For movies of the simulations, see https://oregottlieb.com/bhns.htmlTest

الوصول الحر: http://arxiv.org/abs/2306.14946Test

المؤلفون: Khatami, David, Kasen, Daniel

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics

الوصف: The interaction of supernova ejecta with a surrounding circumstellar medium (CSM) generates a strong shock which can convert the ejecta kinetic energy into observable radiation. Given the diversity of potential CSM structures (arising from diverse mass loss processes such as late-stage stellar outbursts, binary interaction, and winds), the resulting transients can display a wide range of light curve morphologies. We provide a framework for classifying the transients arising from interaction with a spherical CSM shell. The light curves are decomposed into five consecutive phases, starting from the onset of interaction and extending through shock breakout and subsequent shock cooling. The relative prominence of each phase in the light curve is determined by two dimensionless quantities representing the CSM-to-ejecta mass ratio $\eta$, and a breakout parameter $\xi$. These two parameters define four light curve morphology classes, where each class is characterized by the location of shock breakout and the degree of deceleration as the shock sweeps up the CSM. We compile analytic scaling relations connecting the luminosity and duration of each light curve phase to the physical parameters. We then run a grid of radiation hydrodynamics simulations for a wide range of ejecta and CSM parameters to numerically explore the landscape of interaction light curves, and to calibrate and confirm the analytic scalings. We connect our theoretical framework to several case studies of observed transients, highlighting the relevance in explaining slow-rising and superluminous supernovae, fast blue optical transients, and double-peaked light curves.
Comment: 30 pages, 18 figures, submitted to ApJ

الوصول الحر: http://arxiv.org/abs/2304.03360Test

المؤلفون: Blondin, Stéphane, Blinnikov, Sergei, Callan, Fionntan P., Collins, Christine E., Dessart, Luc, Even, Wesley, Flörs, Andreas, Fullard, Andrew G., Hillier, D. John, Jerkstrand, Anders, Kasen, Daniel, Katz, Boaz, Kerzendorf, Wolfgang, Kozyreva, Alexandra, O'Brien, Jack, Pássaro, Ezequiel A., Roth, Nathaniel, Shen, Ken J., Shingles, Luke, Sim, Stuart A., Singhal, Jaladh, Smith, Isaac G., Sorokina, Elena, Utrobin, Victor P., Vogl, Christian, Williamson, Marc, Wollaeger, Ryan, Woosley, Stan E., Wygoda, Nahliel

المصدر: A&A 668, A163 (2022)

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - High Energy Astrophysical Phenomena

الوصف: We present the first results of a comprehensive supernova (SN) radiative-transfer (RT) code-comparison initiative (StaNdaRT), where the emission from the same set of standardized test models is simulated by currently-used RT codes. A total of ten codes have been run on a set of four benchmark ejecta models of Type Ia supernovae. We consider two sub-Chandrasekhar-mass ($M_\mathrm{tot} = 1.0$ M$_\odot$) toy models with analytic density and composition profiles and two Chandrasekhar-mass delayed-detonation models that are outcomes of hydrodynamical simulations. We adopt spherical symmetry for all four models. The results of the different codes, including the light curves, spectra, and the evolution of several physical properties as a function of radius and time, are provided in electronic form in a standard format via a public repository. We also include the detailed test model profiles and several python scripts for accessing and presenting the input and output files. We also provide the code used to generate the toy models studied here. In this paper, we describe in detail the test models, radiative-transfer codes and output formats and provide access to the repository. We present example results of several key diagnostic features.
Comment: Accepted for publication in A&A. 27 pages, 12 figures (v4: updated to match published version). The ejecta models and output files from the simulations are available at https://github.com/sn-rad-trans/data1Test

الوصول الحر: http://arxiv.org/abs/2209.11671Test

المؤلفون: Tsang, Benny T. -H., Kasen, Daniel, Bildsten, Lars

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - High Energy Astrophysical Phenomena

الوصف: Eruptive mass loss likely produces the energetic outbursts observed from some massive stars before they undergo core-collapse supernovae (CCSNe). The resulting dense circumstellar medium (CSM) may also cause the subsequent SNe to be observed as Type IIn events. The leading hypothesis of the cause of these outbursts is the response of the envelope of the red supergiant (RSG) progenitor to energy deposition in the months to years prior to collapse. Early theoretical studies of this phenomena were limited to 1D, leaving the 3D convective RSG structure unaddressed. Using FLASH's hydrodynamic capabilities, we explore the 3D outcomes by constructing convective RSG envelope models and depositing energies less than the envelope binding energies on timescales shorter than the envelope dynamical time deep within them. We confirm the 1D prediction of an outward moving acoustic pulse steepening into a shock, unbinding the outermost parts of the envelope. However, we find that the initial 2-4 km/s convective motions seed the intrinsic convective instability associated with the high entropy material deep in the envelope, enabling gas from deep within the envelope to escape, increasing the amount of ejected mass compared to an initially "quiescent" envelope. The 3D models reveal a rich density structure, with column densities varying by 10x along different lines of sight. Our work highlights that the 3D convective nature of RSG envelopes impacts our ability to reliably predict the outburst dynamics, the amount, and the spatial distribution of the ejected mass associated with deep energy deposition.
Comment: 19 pages, 14 figures, accepted for publication in ApJ

الوصول الحر: http://arxiv.org/abs/2207.13090Test

المؤلفون: Tsang, Benny T-H, Kasen, Daniel, Bildsten, Lars

المصدر: The Astrophysical Journal. 936(1)

مصطلحات موضوعية: Affordable and Clean Energy, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics

الوصف: Abstract: Eruptive mass loss likely produces the energetic outbursts observed from some massive stars before they become core-collapse supernovae (SNe). The resulting dense circumstellar medium may also cause the subsequent SNe to be observed as Type IIn events. The leading hypothesis of the cause of these outbursts is the response of the envelope of the red supergiant (RSG) progenitor to energy deposition in the months to years prior to collapse. Early theoretical studies of this phenomenon were limited to 1D, leaving the 3D convective RSG structure unaddressed. Using FLASH's hydrodynamic capabilities, we explore the 3D outcomes by constructing convective RSG envelope models and depositing energies less than the envelope binding energies on timescales shorter than the envelope dynamical time deep within them. We confirm the 1D prediction of an outward-moving acoustic pulse steepening into a shock, unbinding the outermost parts of the envelope. However, we find that the initial 2–4 km s−1 convective motions seed the intrinsic convective instability associated with the high-entropy material deep in the envelope, enabling gas from deep within the envelope to escape and increasing the amount of ejected mass compared to an initially “quiescent” envelope. The 3D models reveal a rich density structure, with column densities varying by ≈10× along different lines of sight. Our work highlights that the 3D convective nature of RSG envelopes impacts our ability to reliably predict the outburst dynamics, the amount, and the spatial distribution of the ejected mass associated with deep energy deposition.

وصف الملف: application/pdf

الوصول الحر: https://escholarship.org/uc/item/5x88x19zTest

المؤلفون: Dimitriadis, Georgios, Foley, Ryan J., Arendse, Nikki, Coulter, David A., Jacobson-Galán, Wynn V., Siebert, Matthew R., Izzo, Luca, Jones, David O., Kilpatrick, Charles D., Pan, Yen-Chen, Taggart, Kirsty, Auchettl, Katie, Gall, Christa, Hjorth, Jens, Kasen, Daniel, Piro, Anthony L., Raimundo, Sandra I., Ramirez-Ruiz, Enrico, Rest, Armin, Swift, Jonathan J., Woosley, Stan E.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Seeing pristine material from the donor star in a Type Ia supernova (SN Ia) explosion can reveal the nature of the binary system. In this paper, we present photometric and spectroscopic observations of SN 2020esm, one of the best-studied SNe of the class of "super-Chandrasekhar" SNe Ia (SC SNe Ia), with data obtained $-12$ to +360 days relative to peak brightness, obtained from a variety of ground- and space-based telescopes. Initially misclassified as a Type II supernova, SN 2020esm peaked at $M_{B} = -19.9$ mag, declined slowly ($\Delta m_{15}(B) = 0.92$ mag), and had particularly blue UV and optical colors at early times. Photometrically and spectroscopically, SN 2020esm evolved similarly to other SC SNe Ia, showing the usual low ejecta velocities, weak intermediate mass elements (IMEs), and the enhanced fading at late times, but its early spectra are unique. Our first few spectra (corresponding to a phase of $\gtrsim$10~days before peak) reveal a nearly-pure carbon/oxygen atmosphere during the first days after explosion. This composition can only be produced by pristine material, relatively unaffected by nuclear burning. The lack of H and He may further indicate that SN 2020esm is the outcome of the merger of two carbon/oxygen white dwarfs (WDs). Modeling its bolometric light curve, we find a $^{56}$Ni mass of $1.23^{+0.14}_{-0.14}$ M$_{\odot}$ and an ejecta mass of $1.75^{+0.32}_{-0.20}$ M$_{\odot}$, in excess of the Chandrasekhar mass. Finally, we discuss possible progenitor systems and explosion mechanisms of SN 2020esm and, in general, the SC SNe Ia class.
Comment: 21 pages, 15 figures, accepted for publication in APJ

الوصول الحر: http://arxiv.org/abs/2112.09930Test

المؤلفون: Patra, Kishore C., Yang, Yi, Brink, Thomas G., Höflich, Peter, Wang, Lifan, Filippenko, Alexei V., Kasen, Daniel, Baade, Dietrich, Foley, Ryan J., Maund, Justyn R., Zheng, WeiKang, Hung, Tiara, Cikota, Aleksandar, Wheeler, J. Craig, Bulla, Mattia

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics

الوصف: Detailed spectropolarimetric studies may hold the key to probing the explosion mechanisms and the progenitor scenarios of Type Ia supernovae (SNe Ia). We present multi-epoch spectropolarimetry and imaging polarimetry of SN 2019ein, an SN Ia showing high expansion velocities at early phases. The spectropolarimetry sequence spans from $\sim -11$ to $+$10 days relative to peak brightness in the $B$-band. We find that the level of the continuum polarization of SN 2019ein, after subtracting estimated interstellar polarization, is in the range $0.0-0.3\%$, typical for SNe Ia. The polarization position angle remains roughly constant before and after the SN light-curve peak, implying that the inner regions share the same axisymmetry as the outer layers. We observe high polarization ($\sim 1\%$) across both the Si II $\lambda6355$ and Ca II near-infrared triplet features. These two lines also display complex polarization modulations. The spectropolarimetric properties of SN 2019ein rule out a significant departure from spherical symmetry of the ejecta for up to a month after the explosion. These observations disfavour merger-induced and double-detonation models for SN 2019ein. The imaging polarimetry shows weak evidence for a modest increase in polarization after $\sim 20$ days since the $B$-band maximum. If this rise is real and is observed in other SNe Ia at similar phases, we may have seen, for the first time, an aspherical interior similar to what has been previously observed for SNe IIP. Future polarization observations of SNe Ia extending to post-peak epochs will help to examine the inner structure of the explosion.
Comment: Accepted by MNRAS. 13 pages, 7 figures. Updated Figure 6

الوصول الحر: http://arxiv.org/abs/2110.07980Test