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Register a new userConstraining axion-like particles using the white dwarf initial-final mass relation
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Axion-like particles (ALPs), a class of pseudoscalars common to many extensions of the Standard Model, have the capacity to drain energy from the interiors of stars. Consequently, stellar evolution can be used to derive many constraints on ALPs. We study the influence that keV-MeV scale ALPs which interact exclusively with photons can exert on the helium-burning shells of asymptotic giant branch stars, the late-life evolutionary phase of stars with initial masses less than $8M_{odot}$. We establish the sensitivity of the final stellar mass to such energy-loss for ALPs with masses currently permitted by stellar evolution bounds. A semi-empirical constraint on the white dwarf initial-final mass relation (IFMR) derived from observation of double white dwarf binaries is then used to exclude part of a currently unconstrained region of ALP parameter space, the cosmological triangle. The derived constraint relaxes when the ALP decay length becomes shorter than the width of the helium-burning shell. Other potential sources for stellar constraints on ALPs are also discussed.
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We calculate the production of ultra-light axion-like particles (ALPs) in a nearby supernova progenitor. Once produced, ALPs escape from the star and a part of them is converted into photons during propagation in the Galactic magnetic field. It is found that the MeV photon flux that reaches Earth may be detectable by gamma ray telescopes for ALPs lighter than ~1 neV when Betelgeuse undergoes oxygen and silicon burning. (Non-)detection of gamma rays from a supernova progenitor with next-generation gamma ray telescopes just after pre-supernova neutrino alerts would lead to an independent constraint on ALP parameters as stringent as a SN 1987A limit.
We present the first detailed photometric and spectroscopic study of the white dwarfs (WDs) in the field of the ~225 Myr old (log tau_cl = 8.35) open cluster NGC 1039 (M34) as part of the ongoing Lick-Arizona White Dwarf Survey. Using wide-field UBV imaging, we photometrically select 44 WD candidates in this field. We spectroscopically identify 19 of these objects as WDs; 17 are hydrogen-atmosphere DA WDs, one is a helium-atmosphere DB WD, and one is a cool DC WD that exhibits no detectable absorption lines. We find an effective temperature (T_eff) and surface gravity (log g) for each DA WD by fitting Balmer-line profiles from model atmospheres to the observed spectra. WD evolutionary models are then invoked to derive masses and cooling times for each DA WD. Of the 17 DAs, five are at the approximate distance modulus of the cluster. Another WD with a distance modulus 0.45 mag brighter than that of the cluster could be a double-degenerate binary cluster member, but is more likely to be a field WD. We place the five single cluster member WDs in the empirical initial-final mass relation and find that three of them lie very close to the previously derived linear relation; two have WD masses significantly below the relation. These outliers may have experienced some sort of enhanced mass loss or binary evolution; however, it is quite possible that these WDs are simply interlopers from the field WD population. Eight of the 17 DA WDs show significant CaII K absorption; comparison of the absorption strength with the WD distances suggests that the absorption is interstellar, though this cannot be confirmed with the current data.
It was recently pointed out that very energetic subclasses of supernovae (SNe), like hypernovae and superluminous SNe, might host ultra-strong magnetic fields in their core. Such fields may catalyze the production of feebly interacting particles, changing the predicted emission rates. Here we consider the case of axion-like particles (ALPs) and show that the predicted large scale magnetic fields in the core contribute significantly to the ALP production, via a coherent conversion of thermal photons. Using recent state-of-the-art SN simulations including magnetohydrodynamics, we find that if ALPs have masses $m_a sim {mathcal O}(10), rm MeV$, their emissivity via magnetic
The physics case for axions and axion-like particles is reviewed and an overview of ongoing and near-future laboratory searches is presented.
We present the preliminary results of a survey of the open clusters NGC3532 and NGC2287 for new white dwarf members which can help improve understanding of the form of the upper end of the stellar initial mass-final mass relation. We identify four objects with cooling times, distances and proper motions consistent with membership of these clusters. We find that despite a range in age of ~100Myr the masses of the four heaviest white dwarfs in NGC3532 span the narrow mass interval M~0.9-1.0Msolar suggesting that the initial mass-final mass relation is relatively flatter over 4.5Msolar <~ M_init <~ 6.5Msolar than at immediately lower masses. Additionally, we have unearthed WD J0646-203 which is possibly the most massive cluster white dwarf identified to date. With M~1.1Msolar it seems likely to be composed of ONe and has a cooling time consistent with it having evolved from a single star.
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