166 research outputs found
Distance and Reddening of the Enigmatic Gamma-ray-Detected Nova V1324 Sco
It has recently been discovered that some, if not all, classical novae emit
GeV gamma-rays during outburst. Despite using an unreliable method to determine
its distance, previous work showed that nova V1324 Sco was the most gamma-ray
luminous of all gamma-ray-detected novae. We present here a different, more
robust, method to determine the reddening and distance to V1324 Sco using
high-resolution optical spectroscopy. Using two independent methods we derived
a reddening of E(B-V) = 1.16 +/- 0.12 and a distance rD > 6.5 kpc. This
distance is >40% greater than previously estimated, meaning that V1324 Sco has
an even higher gamma-ray luminosity than previously calculated. We also use
periodic modulations in the brightness, interpreted as the orbital period, in
conjunction with pre-outburst photometric limits to show that a main-sequence
companion is strongly favored.Comment: Submitted to ApJ. 6 pages, 5 figure
Thirty Years of Radio Observations of Type Ia SN 1972E and SN 1895B: Constraints on Circumstellar Shells
We have imaged over 35 years of archival Very Large Array (VLA) observations
of the nearby (d 3.15 Mpc) Type Ia supernovae SN\,1972E and
SN\,1895B between 9 and 121 years post-explosion. No radio emission is
detected, constraining the 8.5 GHz luminosities of SN\,1972E and SN\,1895B to
be L 6.0 10 erg s Hz 45
years post-explosion and L 8.9 10 erg
s Hz 121 years post-explosion, respectively. These limits imply a
clean circumstellar medium (CSM), with 0.9 cm out to radii of a
few 10 cm, if the SN blastwave is expanding into uniform
density material. Due to the extensive time coverage of our observations, we
also constrain the presence of CSM shells surrounding the progenitor of
SN\,1972E. We rule out essentially all medium and thick shells with masses of
0.050.3 M at radii between 10 and 10 cm, and
thin shells at specific radii with masses down to 0.01 M.
These constraints rule out swaths of parameter space for a range of single and
double degenerate progenitor scenarios, including recurrent nova,
core-degenerate objects, ultra-prompt explosions and white dwarf (WD) mergers
with delays of a few hundred years between the onset of merger and explosion.
Allowed progenitors include WD-WD systems with a significant ( 10
years) delay from the last episode of common envelope evolution and single
degenerate systems undergoing recurrent nova, provided that the recurrence
timescale i short and the system has been in the nova phase for
10 yr, such that a large ( 10 cm) cavity has been
evacuated. Future multi-epoch observations of additional intermediate-aged Type
Ia SNe will provide a comprehensive view of the large-scale CSM environments
around these explosions.Comment: Accepted for publication in the Astrophysical Journa
X-ray Emission from an Asymmetric Blast Wave and a Massive White Dwarf in the Gamma-ray Emitting Nova V407 Cyg
Classical nova events in symbiotic stars, although rare, offer a unique
opportunity to probe the interaction between ejecta and a dense environment in
stellar explosions. In this work, we use X-ray data obtained with Swift and
Suzaku during the recent classical nova outburst in V407 Cyg to explore such an
interaction. We find evidence of both equilibrium and non-equilibrium
ionization plasmas at the time of peak X-ray brightness, indicating a strong
asymmetry in the density of the emitting region. Comparing a simple model to
the data, we find that the X-ray evolution is broadly consistent with nova
ejecta driving a forward shock into the dense wind of the Mira companion. We
detect a highly absorbed soft X-ray component in the spectrum during the first
50 days of the outburst that is consistent with supersoft emission from the
nuclear burning white dwarf. The high temperature and short turn off time of
this emission component, in addition to the observed breaks in the optical and
UV lightcurves, indicate that the white dwarf in the binary is extremely
massive. Finally, we explore the connections between the X-ray and GeV
gamma-ray evolution, and propose that the gamma ray turn-off is due to the
stalling of the forward shock as the ejecta reach the red giant surface.Comment: Accepted for publication in ApJ. 17 pages, 9 figure
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