37 research outputs found
The Neon Abundance in the Ejecta of QU Vul From Late-Epoch IR Spectra
We present ground-based SpectroCam-10 mid-infrared, MMT optical, and Spitzer
Space Telescope IRS mid-infrared spectra taken 7.62, 18.75, and 19.38 years
respectively after the outburst of the old classical nova QU Vulpeculae (Nova
Vul 1984 #2). The spectra of the ejecta are dominated by forbidden line
emission from neon and oxygen. Our analysis shows that neon was, at the first
and last epochs respectively, more than 76 and 168 times overabundant by number
with respect to hydrogen compared to the solar value. These high lower limits
to the neon abundance confirm that QU Vul involved a thermonuclear runaway on
an ONeMg white dwarf and approach the yields predicted by models of the
nucleosynthesis in such events.Comment: ApJ 2007 accepted, 18 pages, including 5 figures, 1 tabl
The 3D Morphology of VY Canis Majoris II: Polarimetry and the Line-of-Sight Distribution of the Ejecta
We use imaging polarimetry taken with the HST/ACS/HRC to explore the three
dimensional structure of the circumstellar dust distribution around the red
supergiant VY Canis Majoris. The polarization vectors of the nebulosity
surrounding VY CMa show a strong centro-symmetric pattern in all directions
except directly East and range from 10% - 80% in fractional polarization. In
regions that are optically thin, and therefore likely have only single
scattering, we use the fractional polarization and photometric color to locate
the physical position of the dust along the line-of-sight. Most of the
individual arc-like features and clumps seen in the intensity image are also
features in the fractioanl polarization map. These features must be distinct
geometric objects. If they were just local density enhancements, the fractional
polarization would not change so abruptly at the edge of the feature. The
location of these features in the ejecta of VY CMa using polarimetry provides a
determination of their 3D geometry independent of, but in close agreement with,
the results from our study of their kinematics (Paper I).Comment: Better figures availible at http://www.astro.umn.edu/~tj
SN 2010U: A Luminous Nova in NGC 4214
The luminosity, light curve, post-maximum spectrum, and lack of a progenitor on deep pre-outburst images suggest that SN 2010U was a luminous, fast nova. Its outburst magnitude is consistent with that for a fast nova using the maximum magnitude-rate of decline relationship for classical novae
Elemental Abundances in the Ejecta of Old Classical Novae from Late-Epoch Spitzer Spectra
We present Spitzer Space Telescope mid-infrared IRS spectra, supplemented by
ground-based optical observations, of the classical novae V1974 Cyg, V382 Vel,
and V1494 Aql more than 11, 8, and 4 years after outburst respectively. The
spectra are dominated by forbidden emission from neon and oxygen, though in
some cases, there are weak signatures of magnesium, sulfur, and argon. We
investigate the geometry and distribution of the late time ejecta by
examination of the emission line profiles. Using nebular analysis in the low
density regime, we estimate lower limits on the abundances in these novae. In
V1974 Cyg and V382 Vel, our observations confirm the abundance estimates
presented by other authors and support the claims that these eruptions occurred
on ONe white dwarfs. We report the first detection of neon emission in V1494
Aql and show that the system most likely contains a CO white dwarf.Comment: 22 pages, 12 figure
Stellar Populations and Mass-Loss in M15: A Spitzer Detection of Dust in the Intra-Cluster Medium
We present Spitzer Space Telescope IRAC and MIPS observations of the galactic
globular cluster M15 (NGC 7078), one of the most metal-poor clusters with a
[Fe/H] = -2.4. Our Spitzer images reveal a population of dusty red giants near
the cluster center, a previously detected planetary nebula (PN) designated
K648, and a possible detection of the intra-cluster medium (ICM) arising from
mass loss episodes from the evolved stellar population. Our analysis suggests 9
(+/-2) x 10^-4 solar masses of dust is present in the core of M15, and this
material has accumulated over a period of approximately 10^6 years, a timescale
ten times shorter than the last galactic plane crossing event. We also present
Spitzer IRS follow up observations of K648, including the detection of the
[NeII] 12.81 micron line, and discuss abundances derived from infrared fine
structure lines.Comment: Accepted for publication in AJ. 20 pages, 10 figures, 6 tables. Full
resolution versions of figures 1, 5, 7, and 8 are available in a PDF version
of this manuscript at http://ir.astro.umn.edu/~mboyer/ms_060906.pd
Swift X-Ray Observations of Classical Novae. II. The Super Soft Source sample
The Swift GRB satellite is an excellent facility for studying novae. Its
rapid response time and sensitive X-ray detector provides an unparalleled
opportunity to investigate the previously poorly sampled evolution of novae in
the X-ray regime. This paper presents Swift observations of 52
Galactic/Magellanic Cloud novae. We included the XRT (0.3-10 keV) X-ray
instrument count rates and the UVOT (1700-8000 Angstroms) filter photometry.
Also included in the analysis are the publicly available pointed observations
of 10 additional novae the X-ray archives. This is the largest X-ray sample of
Galactic/Magellanic Cloud novae yet assembled and consists of 26 novae with
super soft X-ray emission, 19 from Swift observations. The data set shows that
the faster novae have an early hard X-ray phase that is usually missing in
slower novae. The Super Soft X-ray phase occurs earlier and does not last as
long in fast novae compared to slower novae. All the Swift novae with
sufficient observations show that novae are highly variable with rapid
variability and different periodicities. In the majority of cases, nuclear
burning ceases less than 3 years after the outburst begins. Previous
relationships, such as the nuclear burning duration vs. t_2 or the expansion
velocity of the eject and nuclear burning duration vs. the orbital period, are
shown to be poorly correlated with the full sample indicating that additional
factors beyond the white dwarf mass and binary separation play important roles
in the evolution of a nova outburst. Finally, we confirm two optical phenomena
that are correlated with strong, soft X-ray emission which can be used to
further increase the efficiency of X-ray campaigns.Comment: Accepted to ApJ Supplements. Full data for Table 2 and Figure 17
available in the electronic edition. New version of the previously posted
paper since the earlier version was all set in landscape mod
The 3D Morphology of VY Canis Majoris. I The Kinematics of the Ejecta
Images of the complex circumstellar nebula associated with the famous red
supergiant VY CMa show evidence for multiple and asymmetric mass loss events
over the past 1000 yrs. Doppler velocities of the arcs and knots in the ejecta
showed that they are not only spatially distinct but also kinematically
separate from the surrounding diffuse material. In this paper we describe
second epoch HST/WFPC2 images to measure the transverse motions which when
combined with the radial motions provide a complete picture of the kinematics
of the ejecta including the total space motions and directions of the outflows.
Our results show that the arcs and clumps of knots are moving at different
velocities, in different directions, and at different angles relative to the
plane of the sky and to the star, confirming their origin from eruptions at
different times and from physically separate regions on the star. We conclude
that the morphology and kinematics of the arcs and knots are consistent with a
history of mass ejections not aligned with any presumed axis of symmetry. The
arcs and clumps represent relatively massive outflows and ejections of gas very
likely associated with large -- scale convective activity and magnetic fields.Comment: 20 pages, 10 figures, 5 table
Capabilities, Performance, and Status of the SOFIA Science Instrument Suite
The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne observatory, carrying a 2.5 m telescope onboard a heavily modified Boeing 747SP aircraft. SOFIA is optimized for operation at infrared wavelengths, much of which is obscured for ground-based observatories by atmospheric water vapor. The SOFIA science instrument complement consists of seven instruments: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), GREAT (German Receiver for Astronomy at Terahertz Frequencies), HIPO (High-speed Imaging Photometer for Occultations), FLITECAM (First Light Infrared Test Experiment CAMera), FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), EXES (Echelon-Cross-Echelle Spectrograph), and HAWC (High-resolution Airborne Wideband Camera). FORCAST is a 540 m imager with grism spectroscopy, developed at Cornell University. GREAT is a heterodyne spectrometer providing high-resolution spectroscopy in several bands from 60240 m, developed at the Max Planck Institute for Radio Astronomy. HIPO is a 0.31.1 m imager, developed at Lowell Observatory. FLITECAM is a 15 m wide-field imager with grism spectroscopy, developed at UCLA. FIFI-LS is a 42210 m integral field imaging grating spectrometer, developed at the University of Stuttgart. EXES is a 528 m high-resolution spectrograph, developed at UC Davis and NASA ARC. HAWC is a 50240 m imager, developed at the University of Chicago, and undergoing an upgrade at JPL to add polarimetry capability and substantially larger GSFC detectors. We describe the capabilities, performance, and status of each instrument, highlighting science results obtained using FORCAST, GREAT, and HIPO during SOFIA Early Science observations conducted in 2011
The galaxies missed by Hubble and ALMA: the contribution of extremely red galaxies to the cosmic census at 3<z<8
Using deep JWST imaging from JADES, JEMS and SMILES, we characterize
optically-faint and extremely red galaxies at that were previously
missing from galaxy census estimates. The data indicate the existence of
abundant, dusty and post-starburst-like galaxies down to M, below
the sensitivity limit of Spitzer and ALMA. Modeling the NIRCam and HST
photometry of these red sources can result in extreme, high values for both
stellar mass and star formation rate (SFR); however, including 7 MIRI filters
out to 21m results in decreased mass (median 0.6 dex for
logM/M10), and SFR (median 10 for SFR100
M/yr). At , our sample includes a high fraction of little red
dots (LRDs; NIRCam-selected dust-reddened AGN candidates). We significantly
measure older stellar populations in the LRDs out to rest-frame 3m (the
stellar bump) and rule out a dominant contribution from hot dust emission, a
signature of AGN contamination to stellar population measurements. This allows
us to measure their contribution to the cosmic census at , below the
typical detection limits of ALMA (). We find that
these sources, which are overwhelmingly missed by HST and ALMA, could
effectively double the obscured fraction of the star formation rate density at
compared to some estimates, showing that prior to JWST, the obscured
contribution from fainter sources could be underestimated. Finally, we identify
five sources with evidence for Balmer breaks and high stellar masses at
. While spectroscopy is required to determine their nature, we
discuss possible measurement systematics to explore with future data.Comment: submitted to AAS Journals, comments welcome