869 research outputs found
Mississippi\u27s New Equitable Distribution Rules: The Ferguson Guidelines and Valuation`
Mississippi Focu
Follow-Up Observations of PTFO 8-8695: A 3 MYr Old T-Tauri Star Hosting a Jupiter-mass Planetary Candidate
We present Spitzer 4.5\micron\ light curve observations, Keck NIRSPEC radial
velocity observations, and LCOGT optical light curve observations of
PTFO~8-8695, which may host a Jupiter-sized planet in a very short orbital
period (0.45 days). Previous work by \citet{vaneyken12} and \citet{barnes13}
predicts that the stellar rotation axis and the planetary orbital plane should
precess with a period of days. As a consequence, the observed
transits should change shape and depth, disappear, and reappear with the
precession. Our observations indicate the long-term presence of the transit
events ( years), and that the transits indeed do change depth, disappear
and reappear. The Spitzer observations and the NIRSPEC radial velocity
observations (with contemporaneous LCOGT optical light curve data) are
consistent with the predicted transit times and depths for the $M_\star = 0.34\
M_\odot$ precession model and demonstrate the disappearance of the transits. An
LCOGT optical light curve shows that the transits do reappear approximately 1
year later. The observed transits occur at the times predicted by a
straight-forward propagation of the transit ephemeris. The precession model
correctly predicts the depth and time of the Spitzer transit and the lack of a
transit at the time of the NIRSPEC radial velocity observations. However, the
precession model predicts the return of the transits approximately 1 month
later than observed by LCOGT. Overall, the data are suggestive that the
planetary interpretation of the observed transit events may indeed be correct,
but the precession model and data are currently insufficient to confirm firmly
the planetary status of PTFO~8-8695b.Comment: Accepted for publication in The Astrophysical Journa
Supernovae and radio transients in M 82
We present optical and near-infrared (IR) photometry and near-IR spectroscopy
of SN 2004am, the only optically detected supernova (SN) in M 82. These
demonstrate that SN 2004am was a highly reddened type II-P SN similar to the
low luminosity type II-P events such as SNe 1997D and 2005cs. We show that SN
2004am was located coincident with the obscured super star cluster M 82-L, and
from the cluster age infer a progenitor mass of 12 +7/-3 Msun. In addition to
this, we present a high spatial resolution Gemini-N K-band adaptive optics
image of the site of SN 2008iz and a second transient of uncertain nature, both
detected so far only at radio wavelengths. Using image subtraction techniques
together with archival data from the Hubble Space Telescope, we are able to
recover a near-IR transient source co-incident with both objects. We find the
likely extinction towards SN 2008iz to be not more than Av ~ 10. The nature of
the second transient remains elusive and we regard an extremely bright
microquasar in M 82 as the most plausible scenario.Comment: 14 pages, 8 figures, accepted for publication in MNRA
Reversal of infall in SgrB2(M) revealed by Herschel/HIFI observations of HCN lines at THz frequencies
To investigate the accretion and feedback processes in massive star
formation, we analyze the shapes of emission lines from hot molecular cores,
whose asymmetries trace infall and expansion motions. The high-mass star
forming region SgrB2(M) was observed with Herschel/HIFI (HEXOS key project) in
various lines of HCN and its isotopologues, complemented by APEX data. The
observations are compared to spherically symmetric, centrally heated models
with density power-law gradient and different velocity fields (infall or
infall+expansion), using the radiative transfer code RATRAN. The HCN line
profiles are asymmetric, with the emission peak shifting from blue to red with
increasing J and decreasing line opacity (HCN to HCN). This is most
evident in the HCN 12--11 line at 1062 GHz. These line shapes are reproduced by
a model whose velocity field changes from infall in the outer part to expansion
in the inner part. The qualitative reproduction of the HCN lines suggests that
infall dominates in the colder, outer regions, but expansion dominates in the
warmer, inner regions. We are thus witnessing the onset of feedback in massive
star formation, starting to reverse the infall and finally disrupting the whole
molecular cloud. To obtain our result, the THz lines uniquely covered by HIFI
were critically important.Comment: A&A, HIFI special issue, accepte
Herschel observations of deuterated water towards Sgr B2(M)
Observations of HDO are an important complement for studies of water, because
they give strong constraints on the formation processes -- grain surfaces
versus energetic process in the gas phase, e.g. in shocks. The HIFI
observations of multiple transitions of HDO in Sgr~B2(M) presented here allow
the determination of the HDO abundance throughout the envelope, which has not
been possible before with ground-based observations only. The abundance
structure has been modeled with the spherical Monte Carlo radiative transfer
code RATRAN, which also takes radiative pumping by continuum emission from dust
into account. The modeling reveals that the abundance of HDO rises steeply with
temperature from a low abundance () in the outer envelope
at temperatures below 100~K through a medium abundance () in
the inner envelope/outer core, at temperatures between 100 and 200~K, and
finally a high abundance () at temperatures above 200~K in
the hot core.Comment: A&A HIFI special issue, accepte
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