593 research outputs found
The mysterious eruption of V838 Mon
V838 Mon is marking one of the most mysterious stellar outbursts on record.
The spectral energy distribution of the progenitor resembles an under-luminous
F main sequence star (at V=15.6 mag), that erupted into a cool supergiant
following a complex and multi-maxima lightcurve (peaking at V=6.7 mag). The
outburst spectrum show BaII, LiI and lines of several s-elements, with wide
P-Cyg profiles and a moderate and retracing emission in the Balmer lines. A
light-echo discovered expanding around the object helped to constrain the
distance (d=790+/-30 pc), providing M_V=+4.45 in quiescence and M_V=-4.35 at
optical maximum (somewhat dependent on the still uncertain E(B-V)=0.5
reddening). The general outburst trend is toward lower temperatures and larger
luminosities, and continuing so at the time of writing. The object properties
conflict with a classification within already existing categories: the
progenitor was not on a post-AGB track and thus the similarities with the
born-again AGB stars FG Sge, V605 Aql and Sakurai's object are limited to the
cool giant spectrum at maximum; the cool spectrum, the moderate wind velocity
(500 km/sec and progressively reducing) and the monotonic decreasing of the low
ionization condition argues against a classical nova scenario. The closest
similarity is with a star that erupted into an M-type supergiant discovered in
M31 by Rich et al. (1989), that became however much brighter by peaking at
M_V=-9.95, and with V4332 Sgr that too erupted into an M-type giant (Martini et
al. 1999) and that attained a lower luminosity, closer to that of V838 Mon.
M31-RedVar, V4332 Sgr and V838 Mon could be manifestations of the same and new
class of astronomical objects.Comment: A&A, in pres
Helium Nova on a Very Massive White Dwarf -- A Light Curve Model of V445 Puppis (2000) Revised
V445 Pup (2000) is a unique object identified as a helium nova. Color indexes
during the outburst are consistent with those of free-free emission. We present
a free-free emission dominated light curve model of V445 Pup on the basis of
the optically thick wind theory. Our light curve fitting shows that (1) the
white dwarf (WD) mass is very massive (M_WD \gtrsim 1.35 M_\sun), and (2) a
half of the accreted matter remains on the WD, both of which suggest that the
increasing WD mass. Therefore, V445 Pup is a strong candidate of Type Ia
supernova progenitor. The estimated distance to V445 Pup is now consistent with
the recent observational suggestions, 3.5 < d < 6.5 kpc. A helium star
companion is consistent with the brightness of m_v=14.5 mag just before the
outburst, if it is a little bit evolved hot (\log T (K) \gtrsim 4.5) star with
the mass of M_He \gtrsim 0.8 M_\sun. We then emphasize importance of
observations in the near future quiescent phase after the thick circumstellar
dust dissipates away, especially its color and magnitude to specify the nature
of the companion star. We have also calculated helium ignition masses for
helium shell flashes against various helium accretion rates and discussed the
recurrence period of helium novae.Comment: 8 pages including 12 figures, to appear in Ap
Line Evolution of the Nova V5587 Sgr from Early to Nebula Phase
The spectral evolution of the nova V5587 Sgr has been monitored at Koyama Astronomical Observatory and Higashi-Hiroshima Observatory, Japan, from the early to nebula phase. The nova rebrightened several times. The spectra during the early phase showed emission lines of H α, H β, O I, He I, He II, N II, Fe II. Nova V5587 Sgr is classified into the Fe II type. The helium abundance of the nova is estimated as N(He)/N(H) = 0.134 ± 0.09. The light curve, the spectral evolution, and the helium abundance in V5587 Sgr are similar to those of the nova PW Vul
The Hydrogen Burning Turn-off of RS Ophiuchi 2006
We report a coordinated multi-band photometry of the RS Oph 2006 outburst and
highlight the emission line free y-band photometry that shows a mid-plateau
phase at y ~ 10.2 mag from day 40 to day 75 after the discovery followed by a
sharp drop of the final decline. Such mid-plateau phases are observed in other
two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk
irradiated by the white dwarf. We have calculated theoretical light curves
based on the optically thick wind theory and have reproduced the observed light
curves including the mid-plateau phase and the final sharp decline. This final
decline is identified with the end of steady hydrogen shell-burning, which
turned out the day ~80. This turnoff date is consistent with the end of a
supersoft X-ray phase observed with Swift. Our model suggests a white dwarf
mass of 1.35 \pm 0.01 M_\sun, which indicates that RS Oph is a progenitor of
Type Ia supernovae. We strongly recommend the y-filter observation of novae to
detect both the presence of a disk and the hydrogen burning turn-off.Comment: to appear in ApJL, 4 pages including 4 figure
Lenvatinib and its use in the treatment of unresectable hepatocellular carcinoma
Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver accounting for approximately 90% of cases. Patients often present at an advanced stage when treatment options are limited. Sorafenib, a multitargeted tyrosine kinase inhibitor, has been the first-line treatment in this setting for almost a decade. Several subsequent targeted therapies have failed to demonstrate significant improvement in survival. The results of the REFLECT study suggest that lenvatinib, a multikinase inhibitor, may have promised as a first-line treatment in patients with advanced HCC. This article will review the development of lenvatinib and the evidence behind its potential use in patients with advanced HCC
- …