197 research outputs found
Photometry of GSC 762-110, a new triple-mode radially pulsating star
Stars pulsating in three radial modes are very rare; only three examples are
known in the Galaxy. These stars are very useful since their periods may be
measured very precisely, and this will constrain the global stellar parameters
and the models of the star's interior. The purpose of this paper is to present
a new example of the class of triple-mode radial pulsators. A search for
candidate multi-mode pulsators was carried out in public survey data.
Time-series photometry of one of the candidates, GSC 762-110, was performed.
GSC 762-110 was found to be a triple-mode radial pulsator, with a fundamental
period of 0.1945d and period ratios of 0.7641 and 0.8012. In addition two
non-radial modes were found, for which the amplitude has diminished
considerably over the last few years.Comment: Accepted for publication in Astronomy & Astrophysic
Constraining the period of the ringed secondary companion to the young star J1407 with photographic plates
Context. The 16 Myr old star 1SWASP J140747.93-394542.6 (V1400 Cen) underwent
a series of complex eclipses in May 2007, interpreted as the transit of a giant
Hill sphere filling debris ring system around a secondary companion, J1407b. No
other eclipses have since been detected, although other measurements have
constrained but not uniquely determined the orbital period of J1407b. Finding
another eclipse towards J1407 will help determine the orbital period of the
system, the geometry of the proposed ring system and enable planning of further
observations to characterize the material within these putative rings. Aims. We
carry out a search for other eclipses in photometric data of J1407 with the aim
of constraining the orbital period of J1407b. Methods. We present photometry
from archival photographic plates from the Harvard DASCH survey, and Bamberg
and Sonneberg Observatories, in order to place additional constraints on the
orbital period of J1407b by searching for other dimming and eclipse events.
Using a visual inspection of all 387 plates and a period-folding algorithm we
performed a search for other eclipses in these data sets. Results. We find no
other deep eclipses in the data spanning from 1890 to 1990, nor in recent
time-series photometry from 2012-2018. Conclusions. We rule out a large
fraction of putative orbital periods for J1407b from 5 to 20 years. These
limits are still marginally consistent with a large Hill sphere filling ring
system surrounding a brown dwarf companion in a bound elliptical orbit about
J1407. Issues with the stability of any rings combined with the lack of
detection of another eclipse, suggests that J1407b may not be bound to J1407.Comment: 8 pages, 3 tables, 4 figures, accepted for publication in A&A. LaTeX
files of the paper, scripts for the figures, and a minimal working FPA can be
found under https://github.com/robinmentel/Constraining-Period
CC Sculptoris: A superhumping intermediate polar
We present high speed optical, spectroscopic and Swift X-ray observations
made during the dwarf nova superoutburst of CC Scl in November 2011. An orbital
period of 1.383 h and superhump period of 1.443 h were measured, but the
principal new finding is that CC Scl is a previously unrecognised intermediate
polar, with a white dwarf spin period of 389.49 s which is seen in both optical
and Swift X-ray light curves only during the outburst. In this it closely
resembles the old nova GK Per, but unlike the latter has one of the shortest
orbital periods among intermediate polars.Comment: Accepted for publication in MNRAS; 11 pages, 19 figure
IGR J19552+0044: A new asynchronous short period polar: "Filling the gap between intermediate and ordinary polars"
Based on XMM--Newton X-ray observations IGR J19552+0044 appears to be either
a pre-polar or an asynchronous polar. We conducted follow-up optical
observations to identify the sources and periods of variability precisely and
to classify this X-ray source correctly. Extensive multicolor photometric and
medium- to high-resolution spectroscopy observations were performed and period
search codes were applied to sort out the complex variability of the object. We
found firm evidence of discording spectroscopic (81.29+/-0.01m) and photometric
(83.599+/-0.002m) periods that we ascribe to the white dwarf (WD)\ spin period
and binary orbital period, respectively. This confirms that IGR J19552+0044 is
an asynchronous polar. Wavelength-dependent variability and its continuously
changing shape point at a cyclotron emission from a magnetic WD with a
relatively low magnetic field below 20 MG.
The difference between the WD spin period and the binary orbital period
proves that IGR J19552+0044 is a polar with the largest known degree of
asynchronism (0.97 or 3%).Comment: 9 pages, 10 figures, A&A accepte
Fission-fragment total kinetic energy and mass yields for neutron-induced fission of 235
The average Total Kinetic Energy (TKE) release and fission-fragment yields in neutron-induced fission of 235U and 238U was measured using a Frisch-gridded ionization chamber. These observables are important nuclear data quantites that are relevant to applications and for informing the next generation of fission models. The measurements were performed a the Los Alamos Neutron Science Center and cover En = 200 keV – 30 MeV. The double-energy (2E) method was used to determine the fission-fragment yields and two methods of correcting for prompt-neutron emission were explored. The results of this study are correlated mass and TKE data
Fission fragment mass and total kinetic energy distributions of spontaneously fissioning plutonium isotopes
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