145 research outputs found
Transit Timing Observations of the Extrasolar Hot-Neptune Planet GL 436b
Gliese 436 is an M dwarf with a mass of 0.45 Msun and hosts the extrasolar
planet GL 436b [3, 6, 7, 2], which is currently the least massive transiting
planet with a mass of ~23.17 Mearth [10], and the only planet known to transit
an M dwarf. GL 436b represents the first transiting detection of the class of
extrasolar planets known as "Hot Neptunes" that have masses within a few times
that of Neptune's mass (~17 Mearth) and orbital semimajor axis <0.1 AU about
the host star. Unlike most other known transiting extrasolar planets, GL 436b
has a high eccentricity (e~0.16). This brings to light a new parameter space
for habitability zones of extrasolar planets with host star masses much smaller
than typical stars of roughly a solar mass. This unique system is an ideal
candidate for orbital perturbation and transit-time variation (TTV) studies to
detect smaller, possibly Earth-mass planets in the system. In April 2008 we
began a long-term intensive campaign to obtain complete high-precision light
curves using the Apache Point Observatory's 3.5-meter telescope, NMSU's 1-meter
telescope (located at APO), and Sommers Bausch Observatory's 24" telescope.
These light curves are being analyzed together, along with amateur and other
professional astronomer observations. Results of our analysis are discussed.
Continued measurements over the next few years are needed to determine if
additional planets reside in the system, and to study the impact of other
manifestations on the light curves, such as star spots and active regions.Comment: 4 pages, 3 figures. To appear in "Proceedings of the 15th Cambridge
Workshop on Cool Stars, Stellar Systems and the Sun", 2009, AIP Conference
Proceedings vol. 1094, ed. Eric Stempel
New Galactic Candidate Luminous Blue Variables and Wolf-Rayet Stars
We have undertaken a near-infrared spectral survey of stars associated with
compact mid-IR shells recently revealed by the MIPSGAL (24 micron) and GLIMPSE
(8 micron) Spitzer surveys, whose morphologies are typical of circumstellar
shells produced by massive evolved stars. Through spectral similarity with
known Luminous Blue Variable (LBV) and Wolf-Rayet (WR) stars, a large
population of candidate LBVs (cLBVs) and a smaller number of new WR stars are
being discovered. This significantly increases the Galactic cLBV population and
confirms that nebulae are inherent to most (if not all) objects of this class.
Keywords - stars: emission-line, Be, stars: mass loss, stars: winds,
outflows, stars: Wolf-RayetComment: 2 pages, 1 figure. To appear in IAU 282 proceedings "From Interacting
Binaries to Exoplanets: Essential Modeling Tools", Mercedes Richards \& Ivan
Hubeny, ed
V1647 Ori (IRAS 05436-0007) in Outburst: the First Three Months
We report on photometric (BVRIJHK) and low dispersion spectroscopic
observations of V1647 Ori, the star that drives McNeil's Nebula, between 10
February and 7 May 2004. The star is photometrically variable atop a general
decline in brightness of about 0.3-0.4 magnitudes during these 87 days. The
spectra are featureless, aside from H-alpha and the Ca II infrared triplet in
emission, and a Na I D absorption feature. The Ca II triplet line ratios are
typical of young stellar objects. The H-alpha equivalent width may be modulated
on a period of about 60 days. The post-outburst extinction appears to be less
than 7 mag. The data are suggestive of an FU Orionis-like event, but further
monitoring will be needed to definitively characterize the outburst.Comment: Accepted for publication in the Astronomical Journa
Comparative analysis of atmospheric parameters from high-resolution spectroscopic sky surveys: APOGEE, GALAH, Gaia-ESO
SDSS-IV APOGEE-2, GALAH and Gaia-ESO are high resolution, ground-based,
multi-object spectroscopic surveys providing fundamental stellar atmospheric
parameters and multiple elemental abundance ratios for hundreds of thousands of
stars of the Milky Way. We undertake a comparison between the most recent data
releases of these surveys to investigate the accuracy and precision of derived
parameters by placing the abundances on an absolute scale. We discuss the
correlations in parameter and abundance differences as a function of main
parameters. Uncovering the variants provides a basis to on-going efforts of
future sky surveys. Quality samples from the APOGEE-GALAH, APOGEE-GES and
GALAH-GES overlapping catalogs are collected. We investigate the mean variants
between the surveys, and linear trends are also investigated. We compare the
slope of correlations and mean differences with the reported uncertainties. The
average and scatter of vrad, Teff, log g, [M/H] and vmicro, along with numerous
species of elemental abundances in the combined catalogs show that in general
there is a good agreement between the surveys. We find large radial velocity
scatters ranging from 1.3 km/s to 4.4 km/s when comparing the three surveys. We
observe weak trends: e.g. in Teff vs. log g for the APOGEE-GES
stars, and a clear correlation in the vmicro-vmicro planes in the
APOGEE-GALAH common sample. For [/H], [Ti/H] (APOGEE-GALAH giants) and
[Al/H] (APOGEE-GALAH dwarfs) potential strong correlations are discovered as a
function of the differences in the main atmospheric parameters, and we find
weak trends for other elements. In general we find good agreement between the
three surveys within their respective uncertainties. However, there are certain
regimes in which strong variants exist, which we discuss. There are still
offsets larger than 0.1 dex in the absolute abundance scales.Comment: Accepted in A&A, 23 pages, 13 figures, 6 tables. A minor correction
is applied to the Gaia-ESO Survey's solar reference: Grevesse et al. (2007)
instead of Grevesse & Sauval (1998
The Stony Brook / SMARTS Atlas of (mostly) Southern Novae
ABSTRACT 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 a
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
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