Search Publications
X-ray bounds on cooling, composition, and magnetic field of the Cassiopeia A neutron star and young central compact objects
Ho, Wynn C. G.; Kaplan, D. L.; Heinke, Craig O. +3 more
We present analysis of multiple Chandra and XMM-Newton spectra, separated by 9-19 yr, of four of the youngest central compact objects (CCOs) with ages <2500 yr: CXOU J232327.9+584842 (Cassiopeia A), CXOU J160103.1-513353 (G330.2+1.0), 1WGA J1713.4-3949 (G347.3-0.5), and XMMU J172054.5-372652 (G350.1-0.3). By fitting these spectra with thermal m…
Constraining planetesimal stirring: how sharp are debris disc edges?
Marino, Sebastian
The dust production in debris discs by grinding collisions of planetesimals requires their orbits to be stirred. However, stirring levels remain largely unconstrained, and consequently the stirring mechanisms as well. This work shows how the sharpness of the outer edge of discs can be used to constrain the stirring levels. Namely, the sharper the …
The effects of surface fossil magnetic fields on massive star evolution - III. The case of τ Sco
Martins, F.; Meynet, G.; de Koter, A. +2 more
τ Sco, a well-studied magnetic B-type star in the Upper Sco association, has a number of surprising characteristics. It rotates very slowly and shows nitrogen excess. Its surface magnetic field is much more complex than a purely dipolar configuration which is unusual for a magnetic massive star. We employ the CMFGEN radiative transfer code to dete…
Swift/UVOT follow-up of gravitational wave alerts in the O3 era
Troja, E.; Cenko, S. B.; Sakamoto, T. +41 more
In this paper, we report on the observational performance of the Swift Ultra-violet/Optical Telescope (UVOT) in response to the gravitational wave (GW) alerts announced by the Advanced Laser Interferometer Gravitational Wave Observatory and the Advanced Virgo detector during the O3 period. We provide the observational strategy for follow-up of GW …
Effective temperatures of red supergiants estimated from line-depth ratios of iron lines in the YJ bands, 0.97-1.32µm
Kobayashi, Naoto; Matsunaga, Noriyuki; Kawakita, Hideyo +10 more
Determining the effective temperatures (Teff) of red supergiants (RSGs) observationally is important in many fields of stellar physics and galactic astronomy, yet some significant difficulties remain as a result of the model uncertainty, which originates mainly in the extended atmospheres of RSGs. Here we propose a line-depth ratio (LDR…
Solo dwarfs II: the stellar structure of isolated Local Group dwarf galaxies
Côté, P.; Battaglia, G.; Lewis, G. F. +5 more
The Solo (Solitary Local) Dwarf Galaxy survey is a volume-limited, wide-field g- and i-band survey of all known nearby (<3 Mpc) and isolated (>300 kpc from the Milky Way or M31) dwarf galaxies. This set of 44 dwarfs is homogeneously analysed for quantitative comparisons to the satellite dwarf populations of the Milky Way and M31. In this pap…
Press-Schechter primordial black hole mass functions and their observational constraints
Padilla, Nelson D.; Magaña, Juan; Sureda, Joaquín +1 more
We present a modification of the Press-Schechter (PS) formalism to derive general mass functions for primordial black holes (PBHs), considering their formation as being associated with the amplitude of linear energy density fluctuations. To accommodate a wide range of physical relations between the linear and non-linear conditions for collapse, we…
Highly r-process enhanced stars in ultra-faint dwarf galaxies
Bromm, Volker; Besla, Gurtina; Jeon, Myoungwon
Highly r-process enhanced metal-poor stars (MP r-II; $\rm [Eu/Fe]\gt 1$ and $\rm [Fe/H]\lesssim -1.5$) have been observed in ultra-faint dwarf (UFD) galaxy, specifically in Reticulum II (Ret II). The fact that only a few UFDs contain such stars implies that the r-process site may reflect very rare but individually prolific events, such as neutron …
Most of the cool CGM of star-forming galaxies is not produced by supernova feedback
Afruni, Andrea; Fraternali, Filippo; Pezzulli, Gabriele
The characterization of the large amount of gas residing in the galaxy haloes, the so-called circumgalactic medium (CGM), is crucial to understand galaxy evolution across cosmic time. We focus here on the cool (T ~ 104 K) phase of this medium around star-forming galaxies in the local Universe, whose properties and dynamics are poorly un…
The flaring X-ray corona in the quasar PDS 456
Porquet, D.; Reeves, J. N.; Braito, V. +3 more
New Swift monitoring observations of the variable, radio-quiet quasar, PDS 456, are presented. A bright X-ray flare was captured in 2018 September, the flux increasing by a factor of 4 and with a doubling time-scale of 2 d. From the light crossing argument, the coronal size is inferred to be ≲30 gravitational radii for a black hole mass of 10…