398 research outputs found
Recurrent Nova IM Normae
We detected the second historical outburst of the 1920 nova IM Nor. Accurate
astrometry of the outbursting object revealed the true quiescent counterpart
having a magnitude of R=17.0 mag and B=18.0 mag. We show that the quiescent
counterpart shows a noticeable variation. From the comparison of light curves
and spectroscopic signatures, we propose that IM Nor and CI Aql comprise a new
class of recurrent novae bearing some characteristics similar to those of
classical novae. We interpret that the noticeable quiescent variation can be a
result of either high orbital inclination, which may be also responsible for
the low quiescent brightness, or the presence of high/low states. If the second
possibility is confirmed by future observations, IM Nor becomes the first
recurrent nova showing state changes in quiescence. Such state changes may
provide a missing link between recurrent novae and supersoft X-ray sources.Comment: 4 pages, 3 figures, submitted to Astronomy and Astrophysics Letter
Evidence from stellar rotation of enhanced disc dispersal: (I) The case of the triple visual system BD-21 1074 in the Pictoris association
The early stage of stellar evolution is characterized by a star-disc locking
mechanism. The disc-locking prevents the star to spin its rotation up, and its
timescale depends on the disc lifetime. Some mechanisms can significantly
shorten this lifetime, allowing a few stars to start spinning up much earlier
than other stars. In the present study, we aim to investigate how the
properties of the circumstellar environment can shorten the disc lifetime. We
have identified a few multiple stellar systems, composed of stars with similar
masses, which belong to associations with a known age. Since all parameters
that are responsible for the rotational evolution, with the exception of
environment properties and initial stellar rotation, are similar for all
components, we expect that significant differences among the rotation periods
can only arise from differences in the disc lifetimes. A photometric timeseries
allowed us to measure the rotation periods of each component, while
high-resolution spectra provided us with the fundamental parameters,
and chromospheric line fluxes. The rotation periods of the components differ
significantly, and the component B, which has a closer companion C, rotates
faster than the more distant and isolated component A. We can ascribe the
rotation period difference to either different initial rotation periods or
different disc-locking phases arising from the presence of the close companion
C. In the specific case of BD21 1074, the second scenario seems to be more
favored. In our hypothesis of different disc-locking phase, any planet orbiting
this star is likely formed very rapidly owing to a gravitational instability
mechanism, rather than core accretion. Only a large difference of initial
rotation periods alone could account for the observed period difference,
leaving comparable disc lifetimes.Comment: Accepted by Astronomy & Astrophysics on July 31, 2014; Pages 12,
Figs.
Photometric study of southern SU UMa-type dwarf novae and candidates -- III: NSV 10934, MM Sco, AB Nor, CAL 86
We photometrically observed four southern dwarf novae in outburst (NSV 10934,
MM Sco, AB Nor and CAL 86). NSV 10934 was confirmed to be an SU UMa-type dwarf
nova with a mean superhump period of 0.07478(1) d. This star also showed
transient appearance of quasi-periodic oscillations (QPOs) during the final
growing stage of the superhumps. Combined with the recent theoretical
interpretation and with the rather unusual rapid terminal fading of normal
outbursts, NSV 10934 may be a candidate intermediate polar showing SU UMa-type
properties. The mean superhump periods of MM Sco and AB Nor were determined to
be 0.06136(4) d and 0.08438(2) d, respectively. We suggest that AB Nor belongs
to a rather rare class of long-period SU UMa-type dwarf novae with low
mass-transfer rates. We also observed an outburst of the suspected SU UMa-type
dwarf nova CAL 86. We identified this outburst as a normal outburst and
determined the mean decline rate of 1.1 mag/d.Comment: 13 pages, 23 figures, to appear in MNRAS. For more information, see
http://www.kusastro.kyoto-u.ac.jp/vsnet
Secretory Phase and Implantation
This chapter will explore the latter phase of the menstrual cycle focusing on the secretory phase of the endometrium. In particular, focus will be on the mid-secretory endometrium and appropriate markers and hormonal environment for successful implantation. This will be put in the context of the luteal phase of ovulation and the hormonal support that progesterone provides. We will also review pathologic states, such as endometriosis and related progesterone resistance, which affect mid-secretory phase and implantation. Finally, we will provide a detailed review of the literature on what the current state of knowledge is regarding receptivity and the microenvironment of the mid-secretory endometrium which is essential to implantation
V803 Centauri: Helium Dwarf Nova Mimicking a WZ Sge-Type Superoutburst
We observed long-term behavior of the helium dwarf nova V803 Cen, and
clarified the existence of at least two distinct states (state with 77-d
supercycles and standstill-like state) which interchangeably appeared with a
time-scale of 1--2 yr. We also conducted a time-resolved CCD photometry
campaign during the bright outburst in 2003 June. The overall appearance of the
outburst closely resemble that of the late stage of the 2001 outburst of WZ
Sge, consisting of the initial peak stage (superoutburst plateau), the dip, and
the oscillating (rebrightening) states. During the initial peak stage, we
detected large-amplitude superhump-type variation with a period of 0.018686(4)
d = 1614.5(4) s, and during the oscillation stage, we detected variations with
a period of 0.018728(2) d = 1618.1(2) s. We consider that the former period
better represents the superhump period of this system, and the latter
periodicity may be better interpreted as arising from late superhumps. The
overall picture of the V803 Cen outburst resembles that of a WZ Sge-type
outburst, but apparently with a higher mass-transfer rate than in hydrogen-rich
WZ Sge-type stars. We suggest that this behavior may be either the result of
difficulty in maintaining the hot state in a helium disk, or the effect of an
extremely low tidal torque resulting from the extreme mass ratio.Comment: 13 pages, 11 figures, to appear in PAS
The Peculiar 2004 Superoutburst in the Helium Dwarf Nova, 2003aw
We conducted a time-resolved photometric campaign of the helium dwarf nova,
2003aw in 2004 May--June. 2003aw stayed at 14.7--15.7 mag for the first several
days during this campaign, which is the plateau phase of this superoutburst.
This variable then rapidly decayed to 18.0 mag, still brighter by about 2
mag than its quiescence magnitude, and maintained this brightness for about 20
days, having short flares of 2 mag. A long fading tail followed it. We
detected superhumps with a period of 0.02357(4) d [= 2036(3) s] during the
plateau phase. The whole light curve of the superoutburst in 2003aw, taking
into account the present data and those in the literature, perfectly resembles
that of the 1996-1997 superoutburst of the peculiar WZ Sge-type hydrogen-rich
dwarf nova, EG Cnc.Comment: 5 pages, 4 figures, PASJ Letter in pres
Recurrent mini-outbursts and a magnetic white dwarf in the symbiotic system FN Sgr
AIMS: We investigated the optical variability of the symbiotic binary FN Sgr,
with photometric monitoring during 55 years and with a high-cadence
Kepler light curve lasting 81 days. METHODS: The data obtained in the V and I
bands were reduced with standard photometric methods. The Kepler data were
divided into subsamples and analyses with the Lomb-Scargle algorithm. RESULTS:
The V and I band light curves showed a phenomenon never before observed with
such recurrence in any symbiotic system, namely short outbursts, starting
between orbital phase 0.3 and 0.5 and lasting about a month, with a fast rise
and a slower decline, and amplitude of 0.5-1 mag. In the Kepler light curve we
discovered three frequencies with sidebands. We attribute a stable frequency of
127.5 d (corresponding to an 11.3 minutes period) to the white dwarf
rotation. We suggest that this detection probably implies that the white dwarf
accretes through a magnetic stream, like in intermediate polars. The small
outbursts may be ascribed to the stream-disc interaction. Another possibility
is that they are due to localized thermonuclear burning, perhaps confined by
the magnetic field, like recently inferred in intermediate polars, albeit on
different timescales. We measured also a second frequency around 116.9 d
(corresponding to about 137 minutes), which is much less stable and has a
drift. It may be due to rocky detritus around the white dwarf, but it is more
likely to be caused by an inhomogeneity in the accretion disk. Finally, there
is a third frequency close to the first one that appears to correspond to the
beating between the rotation and the second frequency.Comment: Accepted for publication in Astronomy and Astrophysic
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