246,785 research outputs found
The Ultraluminous X-ray Sources NGC 1313 X-1 and X-2
We present a detailed analysis of XMM archival data of two Ultraluminous
X-ray Sources (ULXs) in the nearby spiral galaxy NGC 1313: NGC 1313 X-1 and
X-2. The spectral continuum of these sources was modeled with a soft thermal
component plus a power-law. If the soft component originates from an accretion
disk, the inferred mass of the compact remnant is > 100 M_sun, making it an
Intermediate Mass Black Hole (IMBH). A detailed analysis of the residuals of
the XMM EPIC-pn spectrum shows some evidence for the presence of an Oxygen
emission line in NGC 1313 X-1. The simultaneous presence of an excess in
emission, although at a much reduced significance level, at different energies
in the X-ray spectra of NGC 1313 X-1 and X-2 is suggestive of typical emission
lines from young supernova remnants. An optical counterpart for NGC 1313 X-2
was also identified. On an ESO 3.6 m image, the Chandra error box embraces a R
\~ 23 mag stellar-like object and excludes a previously proposed optical
counterpart.Comment: 7 pages, 2 figures, to be published in Advances in Space Researc
VLT Observations of the Ultraluminous X-ray Source NGC 1313 X-2
We present archive ESO VLT photometric and spectroscopic data of the
Ultraluminous X-ray source NGC 1313 X-2. The superb quality of the VLT images
reveals that two distinct objects, with R magnitudes 23.7 and 23.6, are visible
inside the Chandra error box. The two objects, separated by 0.75 arcsec, were
unresolved in our previous ESO 3.6 m+EFOSC image. We show that both are stars
in NGC 1313, the first a B0-O9 main sequence star of ~20 Msun, while the second
a G supergiant of ~10 Msun. Irrespectively of which of the two objects the
actual counterpart is, this implies that NGC 1313 X-2 is a high mass X-ray
binary with a very massive donor.Comment: 7 pages, 4 figures, accepted for publication in ApJ Letter
Spartan Daily December 2, 2009
Volume 133, Issue 46https://scholarworks.sjsu.edu/spartandaily/1313/thumbnail.jp
Soft X-ray Emission from the Spiral Galaxy NGC 1313
The nearby barred spiral galaxy NGC 1313 has been observed with the PSPC
instr- ument on board the ROSAT X-ray satellite. Ten individual sources are
found. Three sources (X-1, X-2 and X-3 [SN~1978K]) are very bright (~10^40
erg/s) and are unusual in that analogous objects do not exist in our Galaxy. We
present an X-ray image of NGC~1313 and \xray spectra for the three bright
sources. The emission from the nuclear region (R ~< 2 kpc) is dominated by
source X-1, which is located ~1 kpc north of the photometric (and dynamical)
center of NGC~1313. Optical, far-infrared and radio images do not indicate the
presence of an active galactic nucleus at that position; however, the compact
nature of the \xray source (X-1) suggests that it is an accretion-powered
object with central mass M >~ 10^3 Msun. Additional emission (L_X ~ 10^39
erg/s) in the nuclear region extends out to ~2.6 kpc and roughly follows the
spiral arms. This emission is from 4 sources with luminosity of several x 10^38
erg/s, two of which are consistent with emission from population I sources
(e.g., supernova remnants, and hot interstellar gas which has been heated by
supernova remnants). The other two sources could be emission from population II
sources (e.g., low-mass \xray binaries). The bright sources X-2 and SN~1978K
are positioned in the southern disk of NGC~1313. X-2 is variable and has no
optical counterpart brighter than 20.8 mag (V-band). It is likely that it is an
accretion-powered object in NGC~1313. The type-II supernova SN~1978K (Ryder
\etal 1993) has become extra- ordinarily luminous in X-rays 13 years
after optical maximum.Comment: to appear in 10 Jun 1995 ApJ, 30 pgs uuencoded compressed postscript,
25 pgs of figures available upon request from colbert, whole preprint
available upon request from Sandy Shrader ([email protected]),
hopefully fixed unknown problem with postscript fil
A survey of the Wolf-Rayet population of the barred, spiral galaxy NGC 1313
We present a VLT/FORS1 survey of Wolf-Rayet (WR) stars in the spiral galaxy
NGC 1313. In total, 94 WR candidate sources have been identified from
narrow-band imaging. Of these, 82 have been spectroscopically observed, for
which WR emission features are confirmed in 70 cases, one of which also
exhibits strong nebular HeII 4686 emission. We also detect strong nebular HeII
4686 emission within two other regions of NGC 1313, one of which is a possible
supernova remnant. Nebular properties confirm that NGC 1313 has a metal-content
log(O/H)+12=8.23+/-0.06, in good agreement with previous studies. From
continuum subtracted Halpha images we infer a global star formation rate of 0.6
Msun/yr. Using template LMC WR stars, spectroscopy reveals that NGC 1313 hosts
a minimum of 84 WR stars. Our census comprises 51 WN stars, including a rare
WN/C transition star plus 32 WC stars. In addition, we identify one WO star
which represents the first such case identified beyond the Local Group. The
bright giant HII region PES 1, comparable in Halpha luminosity to NGC 595 in M
33, is found to host a minimum of 17 WR stars. The remaining photometric
candidates generally display photometric properties consistent with WN stars,
such that we expect a global WR population of ~115 stars with N(WR)/N(O)~0.01
and N(WC)/N(WN)~0.4.Comment: Accepted for publication in MNRAS. Finding charts omitted, full
version available by anonymous ftp (ftp:
hydra.shef.ac.uk/pub/lh/ngc1313-fullversion.pd
Searching for Massive Outflows in Holmberg IX X-1 and NGC 1313 X-1: The Iron K Band
We have analysed all the good quality XMM-Newton data publicly available for
the bright ULXs Holmberg IX X-1 and NGC 1313 X-1, with the aim of searching for
discrete emission or absorption features in the Fe K band that could provide
observational evidence for the massive outflows predicted if these sources are
accreting at substantially super-Eddington rates. We do not find statistically
compelling evidence for any atomic lines, and the limits that are obtained have
interesting consequences. Any features in the immediate Fe K energy band (6-7
keV) must have equivalent widths weaker than ~30 eV for Holmberg IX X-1, and
weaker than ~50 eV for NGC 1313 X-1 (at 99 per cent confidence). In comparison
to the sub-Eddington outflows observed in GRS 1915+105, which imprint iron
absorption features with equivalent widths of ~30 eV, the limits obtained here
appear quite stringent, particularly when Holmberg IX X-1 and NGC 1313 X-1 must
be expelling at least 5-10 times as much material if they host black holes of
similar masses. The difficulty in reconciling these observational limits with
the presence of strong line-of-sight outflows suggests that either these
sources are not launching such outflows, or that they must be directed away
from our viewing angle.Comment: 11 pages, 5 figures, accepted for publication in MNRA
Haro 11, Pox 186, and VCC 1313: The Enigmatic Behavior of HI Non-Emitters
We present neutral hydrogen (HI) observations from the Very Large Array (VLA) telescope of the galaxies Haro 11, Pox 186, and VCC 1313. 24 hours of deep spectral line observation at the 21 cm line were obtained from the program 17B-287 of Haro 11, the primary galaxy studied in this capstone, and 176 and 203 respective minutes of archival VLA data at the 21 cm line were obtained from the program AS0832 of Pox 186 and VCC 1313, the secondary and tertiary sources of study for this capstone. Haro 11 is one of a very small number of local dwarf galaxies to be both a Lyα and LyC emitter. While it harbors ongoing aggressive star formation (with sources reporting up to 32.8 M☉ yr-1), the neutral hydrogen gas in the system has been notoriously difficult to detect. Previous interferometric observations have resulted in non-detections, while a deep Green Bank Telescope (GBT) spectrum reveals a weak spectral line. Our emission result is a non-detection, while our absorption result is a detection, confirming the results of similar, previously conducted absorption work. Past interferometric research has additionally resulted in HI non-detections for both Pox 186 and VCC 1313. Our results from archival data are also two HI non-detections, confirming the results of past research. For all three systems, given their aggressive star formation rates, these HI non-detection results are surprising. The behavior of these systems remains highly enigmatic
SD 1313-0019 -- Another second-generation star with [Fe/H] = -5.0, observed with the Magellan Telescope
We present a Magellan/MIKE high-resolution (R ~ 35,000) spectrum of the
ancient star SD 1313-0019 which has an iron abundance of [Fe/H] = -5.0, paired
with a carbon enhancement of [C/Fe] ~ 3.0. The star was initially identified by
Allende Prieto et al. in the BOSS survey. Its medium-resolution spectrum
suggested a higher metallicity of [Fe/H] = -4.3 due to the CaII K line blending
with a CH feature which is a common issue related to the search for the most
iron-poor stars. This star joins several other, similar stars with [Fe/H] <
-5.0 that all display a combination of low iron and high carbon abundances.
Other elemental abundances of SD 1313-0019 follow that of more metal-rich halo
stars. From fitting the abundance pattern with yields of Population III
supernova, we conclude that SD 1313-0019 had only one massive progenitor star
with 20 - 30 M_sun that must have undergone a mixing and fallback episode.
Overall, there are now five stars known with [Fe/H] < -5.0 (1D LTE abundances).
This population of second-generation stars strongly suggests massive first
stars that almost exclusively produced large amounts of carbon through stellar
winds and/or their mixing and fallback supernova explosions. As a consequence,
their natal clouds -- presumably some early minihalo structures -- contained
ample amounts of carbon and oxygen that likely facilitated the formation of
these first low-mass stars.Comment: 7 pages and 3 figures, accepted by ApJ
The metallicity of the nebula surrounding the ultra-luminous X-ray source NGC 1313 X-2
Recent models of the formation of ultra-luminous X-ray sources (ULXs) predict
that they preferentially form in low-metallicity environments. We look at the
metallicity of the nebula surrounding NGC 1313 X-2, one of the best-studied
ULXs. Simple estimates, based on the extrapolation of the metallicity gradient
within NGC 1313, or on empirical calibrations (relating metallicity to strong
oxygen lines) suggest a quite low metal content (Z ~ 0.1 Zsun). But such
estimates do not account for the remarkably strong X-ray flux irradiating the
nebula. Then, we build photoionization models of the nebula using CLOUDY; using
such models, the constraints on the metallicity weaken substantially, as we
find 0.15 Zsun <= Z <= 0.5 Zsun.Comment: 4 pages. Accepted for publication in the Astronomische Nachrichten,
to appear in the proceedings of the conference "Ultra-Luminous X-ray sources
and Middle Weight Black Holes" (Madrid, May 24-26, 2010
Modeling the radial abundance distribution of the transition galaxy ngc 1313
NGC 1313 is the most massive disk galaxy showing a flat radial abundance
distribution in its interstellar gas, a behavior generally observed in
magellanic and irregular galaxies. We have attempted to reproduce this flat
abundance distribution using a multiphase chemical evolution model, which has
been previously used sucessfully to depict other spiral galaxies along the
Hubble morphological sequence. We found that it is not possible to reproduce
the flat radial abundance distribution in NGC 1313, and at the same time, be
consistent with observed radial distributions of other key parameters such the
surface gas density and star formation profiles. We conclude that a more
complicated galactic evolution model including radial flows, and possibly mass
loss due to supernova explosions and winds, is necessary to explain the
apparent chemical uniformity of the disk of NGC 1313Comment: 14 paginas, 4 figures, to be published in ApJ, apri
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