97 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
Spatial variation in brook trout (Salvelinus fontinalis ) population dynamics and juvenile recruitment potential in an Appalachian watershed
I examined the spatial variation in brook trout population dynamics and juvenile recruitment potential in the upper Shavers Fork watershed, West Virginia. The objectives of my research were to (1) identify physico-chemical factors contributing to the spatial variation in the abundance of juvenile brook trout within small basin area stream reaches, (2) quantify patterns of brook trout distribution, movement, and post reproductive demographic parameters across multiple spatial scales, and (3) place the upper Shavers Fork watershed brook trout population along the continuum of watershed-scale metapopulation models. I sampled brook trout population size structure, physical habitat, and water chemistry at the reach- and watershed-scale. The results of my research showed that (1) both water quality and physical habitat influenced the spatial variation in juvenile recruitment potential within small basin area stream reaches, (2) small basin area tributary networks played an important role in structuring the upper Shavers Fork brook trout population, and (3) the brook trout population within the upper Shavers Fork watershed reflects a complex mosaic of elements found in metapopulation, source-sink and patchy population models
XMM-Newton observations of Nova Sgr 1998
We report on X-ray observations of Nova Sagittarius 1998 (V4633 Sgr),
performed with XMM-Newton at three different epochs, 934, 1083 and 1265 days
after discovery. The nova was detected with the EPIC cameras at all three
epochs, with emission spanning the whole energy range from 0.2 to 10 keV.
The X-ray spectra do not change significantly at the different epochs, and
are well fitted for the first and third observations with a multi-temperature
optically thin thermal plasma, while lower statistics in the second
observations lead to a poorer fit. The thermal plasma emission is most probably
originated in the shock heated ejecta, with chemical composition similar to
that of a CO nova. However, we can not completely rule out reestablished
accretion as the origin of the emission. We also obtain upper limits for the
temperature and luminosity of a potential white dwarf atmospheric component,
and conclude that hydrogen burning had already turned-off by the time of our
observations.Comment: 18 pages, 3 figures. Accepted in Astrophysical Journa
The Stony Brook / SMARTS Atlas of mostly Southern Novae
We introduce the Stony Brook / SMARTS Atlas of (mostly) Southern Novae. This
atlas contains both spectra and photometry obtained since 2003. The data
archived in this atlas will facilitate systematic studies of the nova
phenomenon and correlative studies with other comprehensive data sets. It will
also enable detailed investigations of individual objects. In making the data
public we hope to engender more interest on the part of the community in the
physics of novae. The atlas is on-line at
\url{http://www.astro.sunysb.edu/fwalter/SMARTS/NovaAtlas/} .Comment: 11 figures; 5 table
An Investigation of Gravitational Lensing in the Southern BL Lac PKS 0537-441
The BL-Lac family of active galaxies possess almost featureless spectra and
exhibit rapid variability over their entire spectral range. A number of models
have been developed to explain these extreme properties, several of which have
invoked the action of microlensing by sub-stellar mass objects in a foreground
galaxy; this not only introduces variability, but also amplifies an otherwise
normal quasar source. Here we present recent spectroscopy and photometry of the
southern BL Lac PKS 0537-441; with an inferred redshift of z~0.9 it represents
one of the most distant and most luminous members of the BL Lac family. The
goal of the observations was not only to confirm the redshift of PKS~0537-441,
but also to determine the redshift of a putative galaxy along the line of sight
to the BL-Lac; it has been proposed that this galaxy is the host of
microlensing stars that account for PKS 0537-441's extreme properties. While
several observations have failed to detect any extended emission in PKS
0537-441, the HST imaging data presented here indicate the presence of a
galactic component, although we fail to identify any absorption features that
reveal the redshift of the emission. It is also noted that PKS 0537-441 is
accompanied by several small, but extended companions, located a few arcseconds
from the point-like BL-Lac source. Two possibilities present themselves; either
they represent true companions of PKS 0537-441, or are themselves
gravitationally lensed images of more distant sources.Comment: 13 Pages with 4 Figures; Accepted for Publication by the
Astrophysical Journa
The Discovery of Infrared Rings in the Planetary Nebula NGC 1514 During the WISE All-Sky Survey
We report the discovery of a pair of infrared, axisymmetric rings in the
planetary nebula NGC 1514 during the course of the WISE all-sky mid-infrared
survey. Similar structures are seen at visible wavelengths in objects such as
the "Engraved Hourglass Nebula" (MyCn 18) and the "Southern Crab Nebula" (Hen
2-104). However, in NGC 1514 we see only a single pair of rings and they are
easily observed only in the mid-infrared. These rings are roughly 0.2 pc in
diameter, are separated by 0.05 pc, and are dominated by dust emission with a
characteristic temperature of 160 K. We compare the morphology and color of the
rings to the other nebular structures seen at visible, far-infrared, and radio
wavelengths, and close with a discussion of a physical model and formation
scenario for NGC 1514.Comment: 16 pages, 10 figures, final version published in 2010 December
Astronomical Journa
A Radio and X-Ray Study of Historical Supernovae in M83
We report the results of 15 years of radio observations of the six historical
supernovae (SNe) in M83 using the Very Large Array. We note the near linear
decline in radio emission from SN 1957D, a type II SN, which remains a
non-thermal radio emitter. The measured flux densities from SNe 1923A and 1950B
have flattened as they begin to fade below detectable limits, also type II SNe.
The luminosities for these three SNe are comparable with the radio luminosities
of other decades-old SNe at similar epochs. SNe 1945B, 1968L, and 1983N were
not detected in the most recent observations and these non-detections are
consistent with previous studies. We report the X-ray non-detections of all six
historical SNe using the Chandra X-ray Observatory, consistent with previous
X-ray searches of other decades-old SNe, and low inferred mass loss rates of
the progenitors.Comment: 3 color ps figure
Nova light curves from the Solar Mass Ejection Imager (SMEI) - II. The extended catalogue
We present the results from observing nine Galactic novae in eruption with the Solar Mass Ejection Imager (SMEI) between 2004 and 2009. While many of these novae reached peak magnitudes that were either at or approaching the detection limits of SMEI, we were still able to produce light curves that in many cases contained more data at and around the initial rise, peak, and decline than those found in other variable star catalogs. For each nova, we obtained a peak time, maximum magnitude, and for several an estimate of the decline time (t2). Interestingly, although of lower quality than those found in Hounsell et al. (2010a), two of the light curves may indicate the presence of a pre-maximum halt. In addition the high cadence of the SMEI instrument has allowed the detection of low amplitude variations in at least one of the nova light curves
M31N 2007-11d: A Slowly-Rising, Luminous Nova in M31
We report a series of extensive photometric and spectroscopic observations of
the luminous M31 nova M31N 2007-11d. Our photometric observations coupled with
previous measurements show that the nova took at least four days to reach peak
brightness at R~14.9 on 20 Nov 2007 UT. After reaching maximum, the time for
the nova to decline 2 and 3 magnitudes from maximum light (t_2 and t_3) was
~9.5 and ~13 days, respectively, establishing that M31N 2007-11d was a
moderately fast declining nova. During the nova's evolution a total of three
spectra were obtained. The first spectrum was obtained one day after maximum
light (5 days post-discovery), followed by two additional spectra taken on the
decline at two and three weeks post-maximum. The initial spectrum reveals
narrow Balmer and Fe II emission with P Cygni profiles superimposed on a blue
continuum. These data along with the spectra obtained on the subsequent decline
clearly establish that M31N 2007-11d belongs to the Fe II spectroscopic class.
The properties of M31N 2007-11d are discussed within the context of other
luminous novae in M31, the Galaxy, and the LMC. Overall, M31N 2007-11d appears
to be remarkably similar to Nova LMC 1991, which was another bright,
slowly-rising, Fe II nova. A comparison of the available data for luminous
extragalactic novae suggest that the >~4 day rise to maximum light seen in M31N
2007-11d may not be unusual, and that the rise times of luminous Galactic
novae, usually assumed to be <~2 days, may have been underestimated.Comment: Accepted for publication in The Astrophysical Journal (28 pages, 6
figures
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