Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userNewly Determined Explosion Center of Tychos Supernova and the Implications for Proposed Ex-Companion Stars of the Progenitor
117
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
`Star G, near the center of the supernova remnant of Tychos SN1572, has been claimed to be the ex-companion star of the exploding white dwarf, thus pointing to the progenitor being like a recurrent nova. This claim has been controversial, but there have been no confident proofs or disproofs. Previously, no has seriously addressed the question as to the exact explosion site in 1572. We now provide accurate measures of the supernova position by two radically different methods. Our first method is to use the 42 measured angular distances between the supernova in 1572 and bright nearby stars, with individual measures being as good as 84 arc-seconds, and all resulting in a position with a 1-$sigma$ error radius of 39 arc-seconds (including systematic uncertainties). Our second method is to use a detailed and realistic expansion model for 19 positions around the edge of the remnant, where the swept-up material has measured densities, and we determine the center of expansion with a chi-square fit to the 19 measured radii and velocities. This method has a 1-$sigma$ error radius of 7.5 arc-seconds. Both measures are substantially offset from the geometric center, and both agree closely, proving that neither has any significant systematic errors. Our final combined position for the site of the 1572 explosion is J2000 $alpha$=0h 25m 15.36s, $delta=64^{circ} 8 40.2$, with a 7.3 arc-second 1-sigma uncertainty. Star G is rejected at the 8.2-$sigma$ confidence level. Our new position lies mostly outside the region previously searched for ex-companion stars.
rate research
Read More
We study the spatial correlations between the H$alpha$ emission and different types of massive stars in two local galaxies, the Large Magellanic Cloud (LMC) and Messier 33. We compare these to correlations derived for core-collapse supernovae (CCSNe) in the literature to connect CCSNe of different types with the initial masses of their progenitors and to test the validity of progenitor mass estimates which use the pixel statistics method. We obtain samples of evolved massive stars in both galaxies from catalogues with good spatial coverage and/or completeness, and combine them with coordinates of main-sequence stars in the LMC from the SIMBAD database. We calculate the spatial correlation of stars of different classes and spectral types with H$alpha$ emission. We also investigate the effects of distance, noise and positional errors on the pixel statistics method. A higher correlation with H$alpha$ emission is found to correspond to a shorter stellar lifespan, and we conclude that the method can be used as an indicator of the ages, and therefore initial masses, of SN progenitors. We find that the spatial distributions of type II-P SNe and red supergiants of appropriate initial mass ($gtrsim$9 $M_{odot}$) are consistent with each other. We also find the distributions of type Ic SNe and WN stars with initial masses $gtrsim$20 $M_{odot}$ consistent, while supergiants with initial masses around 15 $M_{odot}$ are a better match for type IIb and II-L SNe. The type Ib distribution corresponds to the same stellar types as type II-P, which suggests an origin in interacting binaries. On the other hand, we find that luminous blue variable stars show a much stronger correlation with H$alpha$ emission than do type IIn SNe.
In this paper we analyse the pre-explosion spectrum of SN2015bh by performing radiative transfer simulations using the CMFGEN code. This object has attracted significant attention due to its remarkable similarity to SN2009ip in both its pre- and post-explosion behaviour. They seem to belong to a class of events for which the fate as a genuine core-collapse supernova or a non-terminal explosion is still under debate. Our CMFGEN models suggest that the progenitor of SN2015bh had an effective temperature between 8700 and 10000 K, luminosity in the range ~ 1.8-4.74e6 Lsun, contained at least 25% H in mass at the surface, and half-solar Fe abundances. The results also show that the progenitor of SN 2015bh generated an extended wind with a mass-loss rate of ~ 6e-4 to 1.5e-3 Msun/yr and a velocity of 1000 km/s. We determined that the wind extended to at least 2.57e14 cm and lasted for at least 30 days prior to the observations, releasing 5e-5 Msun into the circumstellar medium. In analogy to 2009ip, we propose that this is the material that the explosive ejecta could interact at late epochs, perhaps producing observable signatures that can be probed with future observations. We conclude that the progenitor of SN 2015bh was most likely a warm luminous blue variable of at least 35 Msun before the explosion. Considering the high wind velocity, we cannot exclude the possibility that the progenitor was a Wolf-Rayet star that inflated just before the 2013 eruption, similar to HD5980 during its 1994 episode. If the star survived, late-time spectroscopy may reveal either a similar LBV or a Wolf-Rayet star, depending on the mass of the H envelope before the explosion. If the star exploded as a genuine SN, 2015bh would be a remarkable case of a successful explosion after black-hole formation in a star with a possible minimum mass 35 Msun at the pre-SN stage.
We report the results of our follow-up campaign of the supernova impostor PSN J09132750+7627410, based on optical data covering $sim250,rm{d}$. From the beginning, the transient shows prominent narrow Balmer lines with P-Cygni profiles, with a blue-shifted absorption component becoming more prominent with time. Along the $sim3,rm{months}$ of the spectroscopic monitoring, broad components are never detected in the hydrogen lines, suggesting that these features are produced in slowly expanding material. The transient reaches an absolute magnitude $M_r=-13.60pm0.19,rm{mag}$ at maximum, a typical luminosity for supernova impostors. Amateur astronomers provided $sim4,rm{years}$ of archival observations of the host galaxy, NGC 2748. The detection of the quiescent progenitor star in archival images obtained with the Hubble Space Telescope suggests it to be an $18-20$msun white-yellow supergiant.
1E 0102.2--7219 (hereafter E0102) is a young supernova remnant (SNR) in the Small Magellanic Cloud (SMC). It contains oxygen-rich SN ejecta, a possible neutron star (NS), and a small amount of fast-moving H-rich ejecta material. These properties are also seen in Cas A, it has thus been suggested that E0102 is also a Type IIb SNR, whose SN progenitors hydrogen envelope was stripped off possibly via interactions with a companion star. To search for a surviving companion of E0102s SN progenitor, we have used archival Hubble Space Telescope (HST) continuum images to make photometric measurements of stars projected in the SNR to construct color-magnitude diagrams and compare the stars with those expected from surviving companions of Type IIb SNe. We have also used the Multi-Unit Spectroscopic Explorer observations taken with the Very Large Telescope to perform spectroscopic analyses of stars and search for peculiar radial velocities as diagnostics of surviving companions. We further use the HST and Gaia data to inspect proper motions of stars for complementary kinetic studies. No plausible companion candidates are found if the SN explosion site was near the NS, while the B3 V star 34a may be a plausible companion candidate if the SN explosion site is near the SN ejectas expansion center. If the NS is real and associated with E0102, it needs a ~1000 km/s runaway velocity, which has been observed in other SNRs and can be acquired from an asymmetric SN explosion or a kick by the SN explosion of a massive companion.
We present an analysis of late-time Hubble Space Telescope Wide Field Camera 3 and Wide Field Planetary Camera 2 observations of the site of the Type Ic SN 2007gr in NGC 1058. The SN is barely recovered in the late-time WFPC2 observations, while a possible detection in the later WFC3 data is debatable. These observations were used to conduct a multiwavelength study of the surrounding stellar population. We fit spatial profiles to a nearby bright source that was previously proposed to be a host cluster. We find that, rather than being an extended cluster, it is consistent with a single point-like object. Fitting stellar models to the observed spectral energy distribution of this source, we conclude it is A1-A3 Yellow Supergiant, possibly corresponding to a star with $M_{ZAMS} = 40M_{odot}$. SN 2007gr is situated in a massive star association, with diameter of $approx 300,mathrm{pc}$. We present a Bayesian scheme to determine the properties of the surrounding massive star population, in conjunction with the Padova isochrones. We find that the stellar population, as observed in either the WFC3 and WFPC2 observations, can be well fit by two age distributions with mean ages: ~6.3 Myr and ~50 Myr. The stellar population is clearly dominated by the younger age solution (by factors of 3.5 and 5.7 from the WFPC2 and WFC3 observations, respectively), which corresponds to the lifetime of a star with $M_{ZAMS} sim 30M_{odot}$. This is strong evidence in favour of the hypothesis that SN 2007gr arose from a massive progenitor star, possibly capable of becoming a Wolf-Rayet star.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
