Using X-ray Emission from Core-Collapse Supernova Shocks to Probe Circumstellar Environments

We have computed a spherically symmetric model for the interaction of matter ejected during the outburst of a classical nova with the stellar wind from its optical component. This model is used to describe the intense X-ray outburst (the peak 3–20 keV flux was ∼2 Crab) of the binary system CI Camelopardalis in 1998. According to our model, the stellar wind from the optical component heated by a strong shock wave produced when matter is ejected from the white dwarf as the result of a thermonuclear explosion on its surface is the emission source in the standard X-ray band. Comparison of the calculated and observed time dependences of the mean radiation temperature and luminosity of the binary system during its outburst has yielded very important characteristics of the explosion. We have been able to measure the velocity of the ejected matter immediately after the onset of the explosion for the first time: it follows from our model that the ejected matter had a velocity of ∼2700 km s−1 even on 0.1–0.5 day after the outburst onset and it flew with such a velocity for the first 1–1.5 day under an external force, possibly, the radiation pressure from the white dwarf. Subsequently, the matter probably became transparent and began to decelerate. The time dependence of the mean radiation temperature at late expansion phases has allowed us to estimate the mass of the ejected matter, ∼10−7–10−6 M ⊙. The mass loss rate in the stellar wind required to explain the observed peak luminosity of the binary system during its outburst has been estimated to be $$ \dot M $$ ∼ (1 − 2) × 10−6 M ⊙ yr−1.

We present panchromatic observations and modeling of calcium-strong supernovae (SNe) 2021gno in the star-forming host-galaxy NGC 4165 and 2021inl in the outskirts of elliptical galaxy NGC 4923, both monitored through the Young Supernova Experiment transient survey. The light curves of both, SNe show two peaks, the former peak being derived from shock cooling emission (SCE) and/or shock interaction with circumstellar material (CSM). The primary peak in SN 2021gno is coincident with luminous, rapidly decaying X-ray emission (L x = 5 × 1041 erg s−1) detected by Swift-XRT at δ t = 1 day after explosion, this observation being the second-ever detection of X-rays from a calcium-strong transient. We interpret the X-ray emission in the context of shock interaction with CSM that extends to r < 3 × 1014 cm. Based on X-ray modeling, we calculate a CSM mass M CSM = (0.3−1.6) × 10−3 M ⊙ and density n = (1−4) × 1010 cm−3. Radio nondetections indicate a low-density environment at larger radii (r > 1016 cm) and mass-loss rate of M ⊙ yr−1. SCE modeling of both primary light-curve peaks indicates an extended-progenitor envelope mass M e = 0.02−0.05 M ⊙ and radius R e = 30−230 R ⊙. The explosion properties suggest progenitor systems containing either a low-mass massive star or a white dwarf (WD), the former being unlikely given the lack of local star formation. Furthermore, the environments of both SNe are consistent with low-mass hybrid He/C/O WD + C/O WD mergers.

Type Ibn supernovae (SNe) are characterized by narrow helium ( ) lines from photons produced by the unshocked circumstellar material (CSM). About 80 SNe Ibn have been discovered to date and only a handful of them have extensive observational records. Thus, many open questions remain regarding the progenitor system and the origin of CSM. He i Here, we investigate potential correlations between the spectral features of the prominent łambda 5876 Å line and the optical and X-ray light curve properties of Type Ibn SNe (SNe Ibn). He i We compiled the largest sample of 61 SNe Ibn to date, of which 24 SNe have photometric and spectroscopic data available from the Young Supernova Experiment and 37 SNe benefit from archival datasets. We fit 24 SNe Ibn with sufficient photometric coverage (B to z bands) using semi-analytical models from . We demonstrate that the light curves of SNe Ibn are more diverse than previous analyses suggest, with absolute r-band peak magnitudes (r_̊m max) of -19.4± 0.6 mag, along with rise (from -10 days to peak, γ_-10) and decay rates (from peak to +10 days; γ_+10) of -0.08 ± 0.06 and 0.08± 0.03 mag/day, respectively. We find that the majority of SNe Ibn in the subsample are consistent with a low-energy explosion (&lt;10^51 erg) of a star with a compact envelope surrounded by ∼0.1 of helium-rich CSM. The inferred ejecta masses are small (M_ ej ∼ 1 lines, associated with the CSM, peaks at ∼ 1100 km/s. and expand with a velocity of ∼5000 km/s. Our spectroscopic analysis shows that the mean velocity of the narrow component of the The mean CSM and ejecta masses inferred for a subsample of SNe Ibn indicate that their progenitors are not massive (sim10 single stars at the moment of explosion; rather, they are likely to be binary systems. This finding is in agreement with detections of potential companion stars of SNe Ibn progenitors and inferred CSM properties from stellar evolution models.

view Abstract Citations (155) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-Rays from Colliding Stellar Winds Luo, Ding ; McCray, Richard ; Mac Low, Mordecai-Mark Abstract A stellar wind from a massive OB or Wolf-Rayet star in a binary system will strike the surface or stellar wind of its companion, forming shocked gas that can radiate X-rays. The X-ray spectrum from the shocked winds will vary in a predictable way with orbital phase, owing to photoelectric absorption by the stellar winds. Detailed models are calculated for the hydrodynamics and X-ray emission from two such systems. In one of these systems (HD 165052), the winds are nearly identical in strength. In the other (V444 Cygni), the wind of the Wolf-Rayet star overwhelms and crushes that of its companion. The calculated X-ray luminosities agree fairly well with the observed values for HD 165052 and for V444 Cygni. These results can be scaled to other such systems. Publication: The Astrophysical Journal Pub Date: October 1990 DOI: 10.1086/169263 Bibcode: 1990ApJ...362..267L Keywords: Companion Stars; Stellar Mass; Stellar Winds; Wolf-Rayet Stars; X Ray Binaries; Light Curve; Shock Waves; Signal To Noise Ratios; Stellar Luminosity; Astrophysics; STARS: BINARIES; STARS: INDIVIDUAL HENRY DRAPER NUMBER: HD 165052; STARS: INDIVIDUAL CONSTELLATION NAME: V444 CYGNI; STARS: WINDS; STARS: WOLF-RAYET; STARS: X-RAYS full text sources ADS | data products SIMBAD (2)

Another major US nuclear order for MHI

SN 2017hcc was remarkable for being a nearby and strongly polarized superluminous Type IIn supernova (SN). We obtained high-resolution Echelle spectra that we combine with other spectra to investigate its line-profile evolution. All epochs reveal narrow P Cygni components from pre-shock circumstellar material (CSM), indicating an axisymmetric outflow from the progenitor of 40–50 km s−1. Broad and intermediate-width components exhibit the classic evolution seen in luminous SNe IIn: symmetric Lorentzian profiles from pre-shock CSM lines broadened by electron scattering at early times, transitioning at late times to multicomponent, irregular profiles coming from the SN ejecta and post-shock shell. As in many SNe IIn, profiles show a progressively increasing blueshift, with a clear flux deficit in red wings of the intermediate and broad velocity components after day 200. This blueshift develops after the continuum luminosity fades, and in the intermediate-width component, persists at late times even after the SN ejecta fade. In SN 2017hcc, the blueshift cannot be explained as occultation by the SN photosphere, pre-shock acceleration of CSM, or a lopsided explosion of CSM. Instead, the blueshift arises from dust formation in the post-shock shell and in the SN ejecta. The effect has a wavelength dependence characteristic of dust, exhibiting an extinction law consistent with large grains. Thus, SN 2017hcc experienced post-shock dust formation and had a mildly bipolar CSM shell, similar to SN 2010jl. Like other superluminous SNe IIn, the progenitor lost around 10 M⊙ due to extreme eruptive mass-loss in the decade before exploding.

The recent discovery that the Fe-K line luminosities and energy centroids observed in nearby SNRs are a strong discriminant of both progenitor type and circumstellar environment has implications for our understanding of supernova progenitor evolution. Using models for the chemical composition of core-collapse supernova ejecta, we model the dynamics and thermal X-ray emission from shocked ejecta and circumstellar material, modeled as an $r^{-2}$ wind, to ages of 3000 years. We compare the X-ray spectra expected from these models to observations made with the Suzaku satellite. We also model the dynamics and X-ray emission from Type Ia progenitor models. We find a clear distinction in Fe-K line energy centroid between core-collapse and Type Ia models. The core-collapse supernova models predict higher Fe-K line centroid energies than the Type Ia models, in agreement with observations. We argue that the higher line centroids are a consequence of the increased densities found in the circumstellar environment created by the expansion of the slow-moving wind from the massive progenitors.

Owing to its extremely high luminosity and long duration, supernova (SN) 2006gy radiated more energy in visual light than any other known SN. Two hypotheses to explain its high luminosity at early times - that it was powered by shock interaction with circumstellar material (CSM) as implied by its Type IIn spectrum, or that it was fueled by radioactive decay from a large mass of 56Ni synthesized in a pair-instability SN-predicted different late-time properties. Here we present observations of SN 2006gy obtained more than a year after discovery. We were unable to detect it at visual wavelengths, but clear near-infrared (IR) K′ and H-band detections show that it is still at least as luminous as the peak of a normal Type II SN. We also present spectra giving an upper limit to the late-time Ha luminosity of ≲S10 39 erg s-1. Based on the weak late-time Ha, X-ray, and radio emission, combined with the difficulty of explaining the shift to IR wavelengths, we can rule out ongoing CSM interaction as the primary late-time power source of SN 2006gy. Instead, we propose that the evolution of SN 2006gy is consistent with one of two possible scenarios: (1)apairinstability SN plus modest CSM interaction, where the radioactive decay luminosity shifts to the IR because of dust formation; or (2) an IR echo, where radiation emitted during peak luminosity heats a pre-existing dust shell at radii near 1 light year, requiring the progenitor star to have ejected another shell of ∼10 M ⊙ about 1500 yr before the SN. © 2008. The American Astronomical Society. All rights reserved.

When a star dies, it leaves a mark on its surrounding environment. The energy from the supernova explosion forms an expanding shock wave that interacts with interstellar and circumstellar material, creating what we know as a supernova remnant (SNR). If the original star has a mass that is greater than or equal to 8 solar masses, this can also lead to the formation of a rapidly rotating neutron star called a pulsar. As these objects evolve, they interact with the surrounding environment, producing non-thermal and thermal emission. For an SNR, its non-thermal emission arises from a population of relativistic particles being accelerated at the shock front of the SNR, while its thermal emission arises from the shock front heating ejecta and and swept-up interstellar medium to X-ray emitting temperatures. For pulsars, their non-thermal emission arises from relativistic particles being accelerated at the termination shock of a pulsar wind. These particles interact with surrounding magnetic fields and ambient photon fields producing synchrotron and inverse Compton emission which we observe as a pulsar wind nebula (PWN), while its thermal emission arises from the surface of the neutron star. These properties of SNRs and pulsars provide a unique window into studying the acceleration, injection, propagation and interaction of highly energetic particles called cosmic rays with the interstellar medium. In addition, they providing information about the evolution, and dynamics of these objects; properties of the shock fronts; details about the original progenitor star; and the impact that these objects have on their surroundings. The research presented here focuses on analysing the intimate connection between cosmic rays, the non-thermal emission arising from SNRs interacting with molecular clouds, and pulsar wind nebulae; as well as analysing the observational and evolutionary properties of these objects. In this thesis we model the propagation of cosmic rays through the Galaxy in an attempt to characterise a standard cosmic ray background with uncertainties, to reveal the origin of the cosmic ray electron positron anomaly. Furthermore, we analyse the gamma-ray emission from SNRs Kes 79 and MSH 11-61A, which are known to be interacting with molecular clouds, as well as the non-thermal X-ray emission arising from the PWN of PSR J1741-2054. We find that the emission from both SNRs most likely arises from the decay of neutral pions that resulted from the interaction of relativistic ions which are accelerated at the shock-front of a SNR, with ambient material. For PSR J1741-2054, we characterise the properties, minimum magnetic field and minimum energy of the particle population that produces the observed diffuse synchrotron emission that surrounds and trails the pulsar. In addition, we characterise the X-ray emission arising from Kes 79, MSH 11-61A and PSR J1741-2054, in an attempt to shed light on the origin and nature of these objects and their emission. Using X-ray data from XMM-Newton and Suzaku respectively, we probe the temperature, ionisation state, and elemental abundance of the shocked gas of each SNR. This allows us to determine their evolutionary properties, properties of the shock, and mass of the original progenitor; and constrain the density of the X-ray emitting plasma. Using Chandra, we determined the temperature of PSR J1741-2054, as well as characterised its proper motion, velocity, direction of motion, and presence of small scale structure immediately surrounding the pulsar.

The stellar winds of hot early-type stars are characterised spectroscopically by the presence of P-Cygni profiles, which are most marked for resonance transitions of common ions and generally occur in the UV, and typical resonance lines of SiIV, CIV, NV and OVI are well known P-Cygni signatures of stellar winds in luminous OB stars. Analyses of these profiles can lead to important information concerning the velocity, density and temperature structure of such winds. The WR stars have more developed stellar winds than OB stars, supporting higher particle densities at larger distances from the stellar “photosphere”. Recently Barlow, Smith &amp; Willis, hereinafter BSW, (1980), have derived reliable mass loss rates for 21 WR stars. The mean value is 4x10-5 M0 /y and the rates are considerably larger than can be accomodated by soley radiative models. The, as yet unidentified, mechanism initiating the WR mass loss may also be important for Of stars ( Lamers 1980 ).

We present panchromatic observations and modeling of the Calcium-rich supernova (SN) 2019ehk in the star-forming galaxy M100 (d ≈ 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-XRT–discovered X-ray emission ( at 3 days; L x ∝ t −3), and a Shane/Kast spectral detection of narrow Hα and He ii emission lines (v ≈ 500 ) 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 &lt; 1015 cm and the resulting cooling emission. We calculate a total CSM mass of ∼7 × 10−3 (M He/M H ≈6) with particle density n ≈ 109 cm−3. Radio observations indicate a significantly lower density n &lt; 104 cm−3 at larger radii r &gt; (0.1–1) × 1017 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 = −15.1 ± 0.200 mag). We find that SN 2019ehk synthesized (3.1 ± 0.11) × 10−2 of and ejected M ej = (0.72 ± 0.040) total with a kinetic energy E k = (1.8 ± 0.10) × 1050 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 ) 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.

view Abstract Citations (56) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Massive Star Formation and Superwinds in IRAS 19254-7245 (The ``Superantennae'') Colina, Luis ; Lipari, Sebastian ; Macchetto, F. Abstract The ultraluminous IRAS galaxy IRAS 19254 - 7245 is investigated by means of aperture spectroscopy and it shows the spectral characteristics of a Seyfert 2-type galaxy with the emission lines split into four images independent kinematical components separated by a velocity of 1491 km s^-1^. A heavy internal obscuration corresponding to E(B -V) = 1.40 and a total amount of ionized gas equal to M_g_ = 1.1 x 10^8^ M_sun_ have been measured in the circumnuclear emission-line regions. The upper limit to the total dust mass is M_d_ = 1.5 x 10^7^ M_sun_ and the corresponding cold gas mass is M_cg_= 3.0 x 10^9^ M_sun_, while the total amount of molecular gas detected in the whole system is M_H2_= 3.0x10^10^ M_sun_ . The optical morphology shows a distorted main body composed of two differentiated nuclei separated by about 10 kpc while two long tails extending over a total size of 305 kpc in projection are also detected. The measured amounts of cold gas and dust together with the extraordinarily large size of the tails indicate that IRAS 19254-7245 is the merger of two almost equally massive gas-rich spiral galaxies and that the merging process did start 10^9^ yr ago. The line splitting is interpreted as produced in a biconical outflow characterized by an opening angle of around 800, an inclination of the symmetry axis with respect to our line-of-sight of 73^deg^, and flow velocity of 800 km s^-1^. The total kinetic energy of this outflow amounts to E_K_ = 0.5 M_g_V_flow_ = 1.4 x 10^57^ ergs and is explained as produced by supernova explosions and stellar mass loss winds generated during a process of steady star formation with SFR=150 M_sun_ yr^-1^ over a time scale of t_SFR_ = 2 x 10^7^ yr. The amount and energy distribution of the ionizing photons generated in the star formation process are sufficient to account for the large infrared and Hα luminosities, while the shape of the spectrum is not hard enough to explain the Seyfert 2-type excitation conditions. These properties are interpreted under the scenario of a quasar-type central nucleus obscured by a huge amount of gas/dust clouds where the massive star formation is taking place. Publication: The Astrophysical Journal Pub Date: September 1991 DOI: 10.1086/170489 Bibcode: 1991ApJ...379..113C Keywords: Infrared Sources (Astronomy); Interacting Galaxies; Massive Stars; Quasars; Seyfert Galaxies; Star Formation; Stellar Winds; Astronomical Spectroscopy; Cosmic Dust; Emission Spectra; Gas Ionization; Infrared Astronomy Satellite; Line Spectra; Molecular Gases; Astrophysics; GALAXIES: INDIVIDUAL ALPHANUMERIC: IRAS 19254-7245; GALAXIES: INTERACTIONS; GALAXIES: INTERNAL MOTIONS; GALAXIES: SEYFERT; INFRARED: SOURCES; STARS: FORMATION; QUASARS full text sources ADS | data products NED (3) SIMBAD (2)

Luminous fast blue optical transients (LFBOTs) such as AT2018cow form a rare class of engine-powered explosions of uncertain origin. A hallmark feature of these events is radio/millimeter synchrotron emission powered by the interaction of fast ≳0.1c ejecta and dense circumstellar material (CSM) extending to large radii ≳1016 cm surrounding the progenitor. Assuming this CSM to be an outflow from the progenitor, we show that dust grains up to ∼1 μm in size can form in the outflow in the years before the explosion. This dusty CSM would attenuate the transient’s ultraviolet emission prior to peak light, before being destroyed by the rising luminosity, reddening the premaximum colors (consistent with the premaximum red-to-blue color evolution of the LFBOT candidate MUSSES2020J). Reradiation by the dust before being destroyed generates a near-infrared (NIR) “echo” of luminosity ∼1041–1042 erg s−1 lasting weeks, which is detectable over the transient’s rapidly fading blue continuum. We show that this dust echo is compatible with the previously unexplained NIR excess observed in AT2018cow. The gradual decay of the early NIR light curve can result from CSM, which is concentrated in a wide-angle equatorial outflow or torus, consistent with the highly aspherical geometry of AT2018cow’s ejecta. Premaximum optical/UV and NIR follow-up of LFBOTs provide a new probe of their CSM environments and place additional constraints on their progenitors.

The winds of hot stars are generally understood to be driven by the absorption of momentum from the intense stellar radiation field by line transitions in the ultraviolet and farultraviolet regions of the spectrum. Observational diagnostics of these dense winds can be reproduced quite well for most early-type stars within the context of a “standard model,” in which the outflow is spherically symmetric, smooth, and steady. This model serves as a useful starting point for estimating global properties such as mass-loss rates and for investigating the various ways that winds interact with their local interstellar environments. However, there is abundant evidence that essentially all hot-star winds contain time-dependent structure on a variety of spatial scales. Observations of anisotropy, clumpiness, and variability contradict the assumptions of the standard model and imply that our understanding of mass loss via stellar winds is still incomplete. IAU Colloquium 169 was convened to review the observational evidence for variability and asphericity in hotstar winds; to discuss the physical processes that might cause such behavior; and to look for evolutionary consequences. The meeting was hosted by the Landessternwarte HeidelbergKonigstuhl, a venue that was fitting not only because 1998 marked the centennial of its founding, but also because of its enviable history as a center for hot-star research. The meeting attracted nearly 150 researchers from 26 countries. Over the course of four and one-half days, 62 oral review and contributed papers and approximately 70 poster papers were presented. The topics of these papers included both garden-variety OBA stars and their more exotic cousins: Be stars, Wolf-Rayet stars, and the rare B[e] stars and luminous blue variables (LBVs). The role played by rotation in shaping the emergence of the stellar wind was a recurrent theme in these presentations and also provides a framework for this brief report on the meeting. The proceedings contain comprehensive discussions of these and other highlights, which included reports of impressive progress in modeling disk winds; analysis and simulations of the nebulae ejected by hot stars in episodic mass-loss events; and distance determination from quantitative spectral analysis of the photospheres and winds of hot stars. Rotation is the most obvious, universal process that can induce large-scale asphericity in the stellar winds of single stars, and it is therefore not surprising that it was a focus for this

The majority of young, low-mass stars are surrounded by optically thick accretion disks. These circumstellar disks provide large reservoirs of gas and dust that will eventually be transformed into planetary systems. Theory and observations suggest that the earliest stage toward planet formation in a protoplanetary disk is the growth of particles, from sub-micron-sized grains to centimeter- sized pebbles. Theory indicates that small interstellar grains are well coupled into the gas and are incorporated to the disk during the proto-stellar collapse. These dust particles settle toward the disk mid-plane and simultaneously grow through collisional coagulation in a very short timescale. Observationally, grain growth can be inferred by measuring the spectral energy distribution at long wavelengths, which traces the continuum dust emission spectrum and hence the dust opacity. Several observational studies have indicated that the dust component in protoplanetary disks has evolved as compared to interstellar medium dust particles, suggesting at least 4 orders of magnitude in particle- size growth. However, the limited angular resolution and poor sensitivity of previous observations has not allowed for further exploration of this astrophysical process. As part of my thesis, I embarked in an observational program to search for evidence of radial variations in the dust properties across a protoplanetary disk, which may be indicative of grain growth. By making use of high angular resolution observations obtained with CARMA, VLA, and SMA, I searched for radial variations in the dust opacity inside protoplanetary disks. These observations span more than an order of magnitude in wavelength (from sub-millimeter to centimeter wavelengths) and attain spatial resolutions down to 20 AU. I characterized the radial distribution of the circumstellar material and constrained radial variations of the dust opacity spectral index, which may originate from particle growth in these circumstellar disks. Furthermore, I compared these observational constraints with simple physical models of grain evolution that include collisional coagulation, fragmentation, and the interaction of these grains with the gaseous disk (the radial drift problem). For the parameters explored, these observational constraints are in agreement with a population of grains limited in size by radial drift. Finally, I also discuss future endeavors with forthcoming ALMA observations.