410 research outputs found
Double-core evolution and the formation of neutron-star binaries with compact companions
We present the results of a systematic exploration of an alternative
evolutionary scenario to form double neutron-star binaries, first proposed by
Brown (1995), which does not involve a neutron star passing through a common
envelope. In this scenario, the initial binary components have very similar
masses, and both components have left the main sequence before they evolve into
contact; preferably the primary has already developed a CO core. We have
performed population synthesis simulations to study the formation of double
neutron star binaries via this channel and to predict the orbital properties
and system velocities of such systems. We obtain a merger rate for DNSs in this
channel in the range of 0.1 - 12/Myr. These rates are still subject to
substantial uncertainties such as the modelling of the contact phase.Comment: MNRAS, accepte
The formation of the double neutron star pulsar J0737--3039
We find that the orbital period (2.4 hours), eccentricity (0.09), dipole
magnetic field strength (6.9 x 10^9 Gauss) and spin period (22 ms) of the new
highly relativistic double neutron star system PSR J0737-3039 can all be
consistently explained if this system originated from a close helium star plus
neutron star binary (HeS-NS) in which at the onset of the evolution the helium
star had a mass in the range 4.0 to 6.5 M_sun and an orbital period in the
range 0.1 to 0.2 days. Such systems are the post-Common-Envelope remnants of
wide Be/X-ray binaries (orbital period ~ 100 to 1000 days) which consist of a
normal hydrogen-rich star with a mass in the range 10 - 20 M_sun and a neutron
star. The close HeS-NS progenitor system went through a phase of mass transfer
by Roche-lobe overflow at a high rate lasting a few times 10^4 years; assuming
Eddington-limited disk accretion onto the neutron star this star was spun up to
its present rapid spin rate. At the moment of the second supernova explosion
the He star had a mass in the range 2.3 to 3.3 M_sun and in order to obtain the
present orbital parameters of PSR J0737-3039 a kick velocity in the range 70 -
230 km/s must have been imparted to the second neutron star at its birth.Comment: accepted by MNRA
Hubungan Lingkungan Kerja dengan Perilaku Caring Perawat di RS Pgi Jakarta
Meilati Suryani*Junaiti Sahar**Dewi gayatri** ABSTRAKKepuasan pasien terhadap pelayanan keperawatan lebih didasarkan kepada perilaku caring perawat seperti sikap yang ramah, cepat tanggap terhadap kebutuhan pasien serta mau mendengarkan keluhan pasien yang disebut dengan perilaku caring. Perilaku caring perawat selain ditentukan oleh faktor individu juga didukung oleh lingkungan kerja yang baik. Penelitian ini untuk mengetahui hubungan lingkungan kerja dengan perilaku caring. Jenis penelitian deskriptif korelasi dengan sampel 95 pasien dan 95 perawat. Persentase perawat yang berperilaku caring tinggi menurut persepsi pasien adalah 53%. Hasil analisis menggunakan uji Chi Square menyatakan pengaturan beban kerja dan pengembangan profesional berhubungan dengan perilaku caring (p = 0,000). Perawat perlu meningkatkan kompetensi dan komunikasi dengan pasien. Rumah sakit perlu meninjau kembali kebutuhan tenaga dan beban kerja perawat, menjadikan caring sebagai salah satu komponen penilaian kinerja perawat, serta meningkatkan role model kepala ruangan. Kata Kunci: Lingkungan kerja, Perilaku caring perawat, Persepsi pasien ABSTRACTPatient satisfaction to nursing delivery service is most base on nurse attitude which called caring. Caring nurse behavior not only determined by individual factor but also supported by good work environment. This research was to recognize the relationship between work environment and nursing caring behavior according to patient\u27s perception. This is descriptive correlation with 95 patient and 95 nurse as samples. According to patient\u27s perception, as much as 53% of nurses are caring. The result showed that professional development and workload management are significantly associated with nursing caring behavior (p=0.000). Nurses require to improve communication skill. The hospital require improve head nurse as role model, make caring as component for nursing appraisal performance, asses the need for nursing workload and staffing
On the Binding Energy Parameter of Common Envelope Evolution. Dependency on the Definition of the Stellar Core Boundary during Spiral-in
According to the standard picture for binary interactions, the outcome of
binaries surviving the evolution through a common envelope (CE) and spiral-in
phase is determined by the internal structure of the donor star at the onset of
the mass transfer, as well as the poorly-known efficiency parameter, eta_CE},
for the ejection of the H-envelope of the donor. In this Research Note we
discuss the bifurcation point which separates the ejected, unprocessed H-rich
material from the inner core region of the donor (the central part of the star
which will later contract to form a compact object). We demonstrate that the
exact location of this point is very important for evaluating the binding
energy parameter, lambda, which is used to determine the post-CE orbital
separation. Here we compare various methods to define the bifurcation point
(core/envelope boundary) of evolved stars with masses 4, 7, 10 and 20 M_sun. We
consider the specific nuclear energy production rate profile, the change in the
mass-density gradient (Bisscheroux 1998), the inner region containing less than
10% hydrogen, the method suggested by Han et al. (1994) and the entropy
profile. We also calculated effective polytropic index profiles. The entropy
profile method measures the convective boundary (at the onset of flatness in
the specific entropy) which is not equivalent to the core boundary for RGB
stars. Hence, this method is not applicable for RGB stars, unless the actual
bifurcation point of a CE is located at the bottom of the outer convection zone
(resulting in larger values of lambda and larger post-CE orbital separations).
On the AGB, where highly degenerate and condensed cores are formed, we find
good agreement between the various methods, except for massive (20 M_sun)
stars.Comment: 4 pages, 1 figure, A&A in pres
The spin period - eccentricity relation of double neutron stars: evidence for weak supernova kicks?
Double neutron stars (DNSs), binary systems consisting of a radio pulsar and
a generally undetected second neutron star (NS), have proven to be excellent
laboratories for testing the theory of general relativity. The seven systems
discovered in our Galaxy exhibit a remarkably well-defined relation between the
pulsar spin period and the orbital eccentricity. Here we show, using a simple
model where the pulsar is spun up by mass transfer from a helium-star
companion, that this relation can only be produced if the second neutron star
received a kick that is substantially smaller (with a velocity dispersion of
less than 50 km/s) than the standard kick received by a single radio pulsar.
This demonstrates that the kick mechanism depends on the evolutionary history
of the NS progenitor and that the orbital parameters of DNSs are completely
determined by the evolution in the preceding helium star - neutron star phase.
This has important implications for estimating the rates of NS-NS mergers, one
of the major potential astrophysical sources for the direct detection of
gravitational waves, and for short-period gamma-ray bursts.Comment: 5 pages, MNRAS Letters, accepte
Recycled Pulsars Discovered at High Radio Frequency
We present the timing parameters of nine pulsars discovered in a survey of
intermediate Galactic latitudes at 1400 MHz with the Parkes radio telescope.
Eight of these pulsars possess small pulse periods and period derivatives
thought to be indicative of ``recycling''. Six of the pulsars are in circular
binary systems, including two with relatively massive white dwarf companions.
We discuss the implications of these new systems for theories of binary
formation and evolution. One long-period pulsar (J1410-7404) has a moderately
weak magnetic field and an exceedingly narrow average pulse profile, similar to
other recycled pulsars.Comment: 9 pages, 4 figures. Accepted for publication in Ap
Perlindungan Hukum terhadap Anak Korban Eksploitasi Seksual dalam Pernikahan Dini (Studi Putusan Mahkamah Agung Indonesia Nomor 690k/pid.sus/2010)
Sexual exploitation of children is a serious violation of Human Rights. Handling of this problem is being the main destination countries in the world including Indonesia. Child marriage is one of sexual exploitation crimes againts children, specially to the girls. It has increased year by year. Decision of court with Number 690K/PID.SUS/2010 is one of sexual exploitation of children in the marriage. Based on the survey results revealed that the settings on the prohibition of sexual exploitation in the early marriage is not expressly regulated in the law, but the actions are prohibited. Judge's decision not to accommodate the implementation of the protection of children who are victims of sexual exploitation in the early marriage, because it is concentrated to criminal punishment only. Recommended to the government to immediately assess, formulate, and implement policies abolition of child marriages below the age of criminal sanctions is high, in order to create legal certainty. Revise the Marriage Act by raising the marriage age limit for women. Conduct an education and specialized training to judges on the application of the law of the child, as well as involving them in seminars or forums that discuss the issue of children, in order to create a child protection efforts
The late stages of evolution of helium star-neutron star binaries and the formation of double neutron star systems
With a view to understanding the formation of double neutron-stars (DNS), we
investigate the late stages of evolution of helium stars with masses of 2.8 -
6.4 Msun in binary systems with a 1.4 Msun neutron-star companion. We found
that mass transfer from 2.8 - 3.3 Msun helium stars and from 3.3 - 3.8 Msun in
very close orbits (P_orb > 0.25d) will end up in a common-envelope (CE) and
spiral-in phase due to the development of a convective helium envelope. If the
neutron star has sufficient time to complete the spiraling-in process before
the core collapses, the system will produce very tight DNSs (P_orb ~ 0.01d)
with a merger timescale of the order of 1 Myr or less. These systems would have
important consequences for the detection rate of GWR and for the understanding
of GRB progenitors. On the other hand, if the time left until the explosion is
shorter than the orbital-decay timescale, the system will undergo a SN
explosion during the CE phase. Helium stars with masses 3.3 - 3.8 Msun in wider
orbits (P_orb > 0.25d) and those more massive than 3.8 Msun do not go through
CE evolution. The remnants of these massive helium stars are DNSs with periods
in the range of 0.1 - 1 d. This suggests that this range of mass includes the
progenitors of the galactic DNSs with close orbits (B1913+16 and B1534+12). A
minimum kick velocity of 70 km/s and 0 km/s (for B1913+16 and B1534+12,
respectively) must have been imparted at the birth of the pulsar's companion.
The DNSs with wider orbits (J1518+4904 and probably J1811-1736) are produced
from helium star-neutron star binaries which avoid RLOF, with the helium star
more massive than 2.5 Msun. For these systems the minimum kick velocities are
50 km/s and 10 km/s (for J1518+4904 and J1811-1736, respectively).Comment: 16 pages, latex, 12 figures, accepted for publication in MNRA
The evolution of naked helium stars with a neutron-star companion in close binary systems
The evolution of helium stars with masses of 1.5 - 6.7 M_sun in binary
systems with a 1.4 M_sun neutron-star companion is presented. Such systems are
assumed to be the remnants of Be/X-ray binaries with B-star masses in the range
of 8 - 20 M_sun which underwent a case B or case C mass transfer and survived
the common-envelope and spiral-in process. The orbital period is chosen such
that the helium star fills its Roche lobe before the ignition of carbon in the
centre. We distinguish case BA (in which mass transfer is initiated during
helium core burning) from case BB (onset of Roche-lobe overflow occurs after
helium core burning is terminated, but before the ignition of carbon). We found
that the remnants of case BA mass transfer from 1.5 - 2.9 M_sun helium stars
are heavy CO white dwarfs. This implies that a star initially as massive as 12
M_sun is able to become a white dwarf. CO white dwarfs are also produced from
case BB mass transfer from 1.5 - 1.8 M_sun helium stars, while ONe white dwarfs
are formed from 2.1 - 2.5 M_sun helium stars. Case BB mass transfer from
more-massive helium stars with a neutron-star companion will produce a double
neutron-star binary. We are able to distinguish the progenitors of type Ib
supernovae (as the high-mass helium stars or systems in wide orbits) from those
of type Ic supernovae (as the lower-mass helium stars or systems in close
orbits). Finally, we derive a "zone of avoidance" in the helium star mass vs.
initial orbital period diagram for producing neutron stars from helium stars.Comment: 16 pages, latex, 11 figures, accepted for publication in MNRA
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