arXiv subjects
Publications and source records attributed to Feng Ma.
The spin-down power of an isolated neutron star can drive its central density increase and overall structural changes, and trigger a quark-hadron phase transition. A series of observational signatures may be seen as a result of the phase transition, including pulsar spin-down and glitch behaviors, Soft Gamma Repeaters or Gamma-Ray Bursts.
Assuming there is a blazar type continuum in every radio-loud quasar, we find that the free-free heating due to the beamed infrared continuum can greatly enhance collisionally excited lines, and thus explain the stronger CIV $λ$1549 line emission observed in radio loud quasars. We further predict that the CIV line should show variability {\it not} associated with observed continuum or Ly$α$ variability.
This is a comment on a paper by Glendenning, Pei, and Weber (Phys. Rev. Lett., 79, 1603, 1997), where the authors gave an incorrect estimate of the event rate and neglected the important gravitational energy release. Previous work on the same subject is reviewed, and a new suggestion is made to link quark-hadron phase transitions with soft gamma-ray repeaters.
The edge-on, nearby spiral galaxy NGC5907 has long been used as the prototype of a ``non-interacting'' warped galaxy. We report here the discovery of two interactions with companion dwarf galaxies that substantially change this picture. First, a faint ring structure is discovered around this galaxy that is likely due to the tidal disruption of a companion dwarf spheroidal galaxy. The ring is elliptical in shape with the center of NGC5907 close to one of the ring's foci. This suggests the ring material is in orbit around NGC5907. No gaseous component to the ring has been detected either with deep H$α$ images or in Very Large Array (VLA) HI 21-cm line maps. The visible material in the ring has an integrated luminosity <= 10^8 L_sun and its brightest part has a color R-I ~ 0.9. All of these properties are consistent with the ring being a tidally-disrupted dwarf spheroidal galaxy. Second, we find that NGC5907 has a dwarf companion galaxy, PGC54419, projected to be only 36.9 kpc from the center of NGC5907, close in radial velocity (ΔV = 45 km s^{-1}) to the giant spiral galaxy. This dwarf is seen at the tip of the HI warp and in the direction of the warp. Hence, NGC5907 can no longer be considered ``non-interacting,'' but is obviously interacting with its dwarf companions much as the Milky Way interacts with its dwarf galaxies. These results, coupled with the finding by others that dwarf galaxies tend to be found around giant galaxies, suggest that tidal interaction with companions, even if containing a mere 1% of the mass of the parent galaxy, might be sufficient to excite the warps found in the disks of many large spiral galaxies.
When a spinning-down neutron star undergoes a phase transition that produces quark matter in its core, a Super-Giant Glitch of the order $Δ Ω/Ω\sim 0.3$ occurs on time scales from 0.05 seconds to a few minutes. The energy released is about $10^{52}$ ergs and can account for Gamma Ray Bursts at cosmological distances. The estimated burst frequency, $10^{-6}$ per year per galaxy, is in very good agreement with observations. We also discuss the possibility of distinguishing these even ts from neutron star mergers by observing the different temporal behavior of gravitational waves.