Constraining Axions with ZTF J1901+1458

The axion-nucleon coupling enables the production of axions through the decay of excited ${}^{57}\textrm{Fe}$ isotopes, and axions produced in the Sun through this process are often a target of helioscope searches. We show for the first time that hot, highly magnetic white dwarfs such as ZTF J1901+1458 are a viable target to search for the X-ray signature of axions that were produced by the ${}^{57}\textrm{Fe}$ transition in the core and then converted to photons in the magnetosphere. We calculate that a 100 ks observation of ZTF J1901+1458 with NuSTAR would constrain the coupling of axions to nucleons and photons at a level below the bounds of both current and future planned helioscopes.Comment: 6 pages, 2 figure

The origin of ultramassive white dwarfs: hints from Gaia EDR3

Gaia Data Release 2 revealed a population of ultramassive white dwarfs on the Q branch that are moving anomalously fast for a local disc population with their young photometric ages. As the velocity dispersion of stars in the local disc increases with age, a proposed explanation of these white dwarfs is that they experience a cooling delay that causes current cooling models to infer photometric ages much younger than their true ages. To explore this explanation, we investigate the kinematics of ultramassive white dwarfs within 200 pc of the Sun using the improved Gaia Early Data Release 3 observations. We analyse the transverse motions of 0.95 - 1.25 $M_\odot$ white dwarfs, subdivided by mass and age, and determine the distributions of the three-dimensional components of the transverse velocities. The results are compared to expectations based on observed kinematics of local main-sequence stars. We find a population of photometrically young ($\sim$ 0.5 - 1.5 Gyr) ultramassive ($\sim$ 1.15 - 1.25 $M_\odot$) white dwarfs for which the transverse velocity component in the direction of Galactic rotation is more dispersed than for local disc stars of any age; thus, it is too dispersed to be explained by any cooling delay in white dwarfs originating from the local disc. Furthermore, the dispersion ratio of the velocity components in the Galactic plane for this population is also inconsistent with a local disc origin. We discuss some possible explanations of this kinematically anomalous population, such as a halo origin or production through dynamical effects of stellar triple systems.Comment: 11 pages, 3 figures, published in MNRA

The Onset of Convective Coupling and Freezing in the White Dwarfs of 47 Tucanae

Using images from the Hubble Space Telescope Advanced Camera for Surveys, we measure the rate of cooling of white dwarfs in the globular cluster 47 Tucanae and compare it to modelled cooling curves. We examine the effects of the outer convective envelope reaching the nearly isothermal degenerate core and the release of latent heat during core crystallisation on the white dwarf cooling rates. For white dwarfs typical of 47 Tuc, the onset of these effects occur at similar times. The latent heat released during crystallisation is a small heat source. In contrast, the heat reservoir of the degenerate core is substantially larger. When the convective envelope reaches the nearly isothermal interior of the white dwarf, the star becomes brighter than it would be in the absence of this effect. Our modelled cooling curves that include this convective coupling closely match the observed luminosity function of the white dwarfs in 47 Tuc.Comment: 6 pages, 5 figures. Submitted to MNRA

Optimal Summary Statistics for X-ray Polarization

We develop two new highly efficient estimators to measure the polarization (Stokes parameters) in experiments that constrain the position angle of individual photons such as scattering and gas-pixel-detector polarimeters, and analyse in detail a previously proposed estimator. All three of these estimators are at least fifty percent more efficient on typical datasets than the standard estimator used in the field. We present analytic estimates of the variance of these estimators and numerical experiments to verify these estimates. Two of the three estimators can be calculated quickly and directly through summations over the measurements of individual photons

Clinical benefit of adding oxaliplatin to standard neoadjuvant chemoradiotherapy in locally advanced rectal cancer: a meta-analysis : Oxaliplatin in neoadjuvant treatment for rectal cancer

Abstract. Background: To evaluate the treatment tolerance and clinical outcomes in patients aged 70 years and older with locally advanced oropharyngeal cancer treated by definitive intensity-modulated radiation therapy (IMRT). Patients and Methods: We retrospectively analyzed 15 consecutive elderly patients, with histologically-proven squamous cell carcinoma of the oropharynx, staged T3-4 with or without involved lymph nodes at diagnosis, who received definitive sequential IMRT (70 Gy; 2 Gy/fraction). Adult Comorbidity Evaluation-27 (ACE-27) score was calculated and its influence on treatment tolerance and clinical outcomes was analyzed. Results: A total of 15 patients were included with a median age of 77 years (range=70-88 years). At baseline, 8 patients (53.3%) had an ACE-27 score of 1, and the remainder (n=7, 46.7%) had a comorbidity index of 0. All patients completed programmed IMRT treatment, without any reduction of total dose. Oral pain and mucositis were the most common acute side-effects, classified as grade 3 in 6 patients (40%) only. Xerostomia was reported in 13 patients (86.7%), without severe manifestation. There was no hematological toxicity. ACE-27 score was not related to higher severe acute toxicity. No patients experienced grade 3 or more late toxicity. Five-year overall survival and disease-free survival rates were 63.6% (95% confidence interval=32.7-83.3%) and 55% (95% confidence interval=24.4-77.6%), respectively. Comorbidity score did not influence survival outcomes, both overall survival (p=0.46) and disease-free survival (p=0.55). Conclusion: Treatment tolerance, as well as survival outcomes were good in elderly oropharyngeal cancer patients treated with definitive sequential IMRT. Due to age and comorbidity, no dose or volume reduction for IMRT should be considered in this setting of patients. A prospective randomized trial with a large sample size should be conducted to confirm our result

The Colibrì: taking the pulse of black holes and neutron stars

We propose a high-time-resolution, high-spectral-resolution X-ray telescope that uses transition-edge sensors (TES) as detectors and collector optics to direct the X-rays onto the focal plane, providing a large effective area in a small satellite. The key science driver of the instrument is to study neutron stars and accreting black holes. The proposed instrument is built upon two technologies that are already at high TRL: TES X-ray detectors and collector optics

The Colibrì: taking the pulse of black holes and neutron stars

We propose a high-time-resolution, high-spectral-resolution X-ray telescope that uses transition-edge sensors (TES) as detectors and collector optics to direct the X-rays onto the focal plane, providing a large effective area in a small satellite. The key science driver of the instrument is to study neutron stars and accreting black holes. The proposed instrument is built upon two technologies that are already at high TRL: TES X-ray detectors and collector optics