We present H- and Ks-bands observations of the LkH 330 disk with a multi-band detection of the large gap and spiral-like structures. The morphology of the outer disk (r ∼ 0 3) at PA = 0°-45° and PA° ...= 180-290° is likely density wave-induced spirals, and comparison between our observational results and simulations suggests a planet formation. We have also investigated the azimuthal profiles at the ring and the outer-disk regions as well as radial profiles in the directions of the spiral-like structures and semimajor axis. Azimuthal analysis shows a large variety in wavelength and implies that the disk has non-axisymmetric dust distributions. The radial profiles in the major-axis direction (PA = 271°) suggest that the outer region (r ≥ 0 25) may be influenced by shadows of the inner region of the disk. The spiral-like directions (PA = 10° and 230°) show different radial profiles, which suggests that the surfaces of the spiral-like structures are highly flared and/or have different dust properties. Finally, a color map of the disk shows a lack of an outer eastern region in the H-band disk, which may hint at the presence of an inner object that casts a directional shadow onto the disk.
This paper identifies the cataclysmic variables that appear in spectra obtained in 2004 as part of the Sloan Digital Sky Survey. Spectra of 41 objects, including seven systems that were previously ...known (CC Cnc, DW Cnc, PQ Gem, AR UMa, AN UMa, RX J1131.3+4322, and UMa 6) and 34 new cataclysmic variables are presented. The positions and ugriz photometry of all 41 systems are given, as well as additional follow-up spectroscopic, photometric, and/or polarimetric observations of eight of the new systems. The new objects include three eclipsing systems, six with prominent He II emission, and six systems that show the underlying white dwarf.
We present near-infrared coronagraphic imaging polarimetry of RY Tau. The scattered light in the circumstellar environment was imaged at the H band at a high resolution (~(0".05) for the first time, ...using Subaru/HiCIAO. The observed polarized intensity (PI) distribution shows a butterfly-like distribution of bright emission with an angular scale similar to the disk observed at millimeter wavelengths. This distribution is offset toward the blueshifted jet, indicating the presence of a geometrically thick disk or a remnant envelope, and therefore the earliest stage of the Class II evolutionary phase. We perform comparisons between the observed PI distribution and disk models with (1) full radiative transfer code, using the spectral energy distribution (SED) to constrain the disk parameters; and (2) monochromatic simulations of scattered light which explore a wide range of parameters space to constrain the disk and dust parameters. We show that these models cannot consistently explain the observed PI distribution, SED, and the viewing angle inferred by millimeter interferometry. We suggest that the scattered light in the near-infrared is associated with an optically thin and geometrically thick layer above the disk surface, with the surface responsible for the infrared SED. Half of the scattered light and thermal radiation in this layer illuminates the disk surface, and this process may significantly affect the thermal structure of the disk.
We present high-contrast H-band polarized intensity images of the transitional disk around the young solar-like star LkCa 15. By utilizing Subaru/HiCIAO for polarimetric differential imaging, the ...angular resolution and the inner working angle reach 0
${^{\prime\prime}_{.}}$
07 and r = 0
${^{\prime\prime}_{.}}$
1, respectively. We obtained a clearly resolved gap (width ≲ 27 au) at ∼48 au from the central star. This gap is consistent with images reported in previous studies. We also confirmed the existence of a bright inner disk with a misaligned position angle of 13° ± 4° with respect to that of the outer disk, i.e., the inner disk is possibly warped. The large gap and the warped inner disk both point to the existence of a multiple planetary system with a mass of ≲ 1 M
Jup.
We conducted high-contrast polarimetry observations of T Tau in the H-band, using the High Contrast Instrument for the Subaru Next Generation Adaptive Optics instrument mounted on the Subaru ...Telescope, revealing structures as near as 0 1 from the stars T Tau N and T Tau S. The whole T Tau system is found to be surrounded by nebula-like envelopes, and several outflow-related structures are detected in these envelopes. We analyzed the detailed polarization patterns of the circumstellar structures near each component of this triple young star system and determined constraints on the circumstellar disks and outflow structures. We suggest that the nearly face-on circumstellar disk of T Tau N is no larger than 0 8, or 117 au, in the northwest, based on the existence of a hole in this direction, and no larger than 0 27, or 40 au, in the south. A new structure, "N5," extends to about 0 42, or 59 au, southwest of the star, and is believed to be part of the disk. We suggest that T Tau S is surrounded by a highly inclined circumbinary disk with a radius of about 0 3, or 44 au, with a position angle of about 30°, that is misaligned with the orbit of the T Tau S binary. After analyzing the positions and polarization vector patterns of the outflow-related structures, we suggest that T Tau S should trigger the well-known E-W outflow, and is also likely to be responsible for a southwest precessing outflow "coil" and a possible south outflow.
The 28 cataclysmic variables (CVs) found in 2005 in the Sloan Digital Sky Survey are presented with their coordinates, magnitudes, and spectra. Five of these systems are previously known CVs (HH Cnc, ...SX LMi, QZ Ser, AP CrB, and HS 1016+3412), and the rest are new discoveries. Additional spectroscopic, photometric, and/or polarimetric observations of 10 systems were carried out, resulting in estimates of the orbital periods for seven of the new binaries. The 23 new CVs include one eclipsing system, one new Polar, and five systems whose spectra clearly reveal atmospheric absorption lines from the underlying white dwarf.
In the spring of 2017, the "Harvard Educational Review" ("HER") published the first part of a symposium on the intersection of incarceration and education. That collection of articles offers ...scholarly perspectives on the purpose, challenges, and potential of education in carceral settings, as well as the origins and consequences of the carceral system. To continue the conversation, the editors sought out the voices and expertise of those who work at the nexus of education and incarceration. As such, "HER" sought to identify practitioners whose work bridges the two spheres and held interviews with four leaders and innovators in this space. HER editor Simone A. Fried prepared interview questions, and editors Krista Goldstine-Cole, Celia Reddick, and Lauren Yoshizawa conducted the interviews. Each conversation was digitally recorded and later transcribed, then edited and condensed into the narratives presented below. These four interviews illuminate the promise and possibility, as well as the challenge, of educational practice in the context of incarceration and its effects. Jody Becker, the secretary of Washington State Department of Corrections, reflects on the consequences of parental incarceration for children, highlighting the agency's strategic commitment and practical efforts to enhance educational opportunity for both generations. Barbara Carr, Juvenile Court administrator in Jefferson County, Washington, enumerates the growing effects of evidence-based programming in juvenile courts and, in particular, the increasing role for probation counselors as educational advocates for youth in the justice system. Gillian Knapp, a professor of astrophysics and one of the founders of the Prison Teaching Initiative at Princeton University, looks back over eleven years of teaching science and mathematics in New Jersey prisons. By focusing attention on the impact of learning math on educational choice and competence across the curriculum, Knapp reminds us that everyone should receive a decent education. Finally, Luis Giraldo, director of Equity, Diversity, and Cultural Competency at Santa Barbara City College, shares stories from his work at Homeboy Industries. Giraldo pushes us to hear, understand, and respond to the "invisible needs" of previously incarcerated and gang-involved individuals as they transition to being students.
CARBON STARS Wallerstein, George; Knapp, Gillian R
Annual review of astronomy and astrophysics,
01/1998, Letnik:
36, Številka:
1
Journal Article
Recenzirano
Absolute magnitudes are estimated for carbon stars of various subtypes in
the Hipparcos catalogue and as found in the Magellanic Clouds. Stellar radii
fall within the limits of 2.4-4.7 AU. The ...chemical composition of carbon
stars indicates that the C-N stars show nearly solar C/H, N/H, and
12
C/
13
C ratios. This indicates that much of the C and N
in our Galaxy came from mass-losing carbon stars. Special carbon stars such as
the C-R, C-H, and dC stars are described.
Mass loss from asymptotic giant branch carbon stars, at rates up to several
× 10
−5
M
year
−1
, contributes about half of the total mass return to the
interstellar medium. R stars do not lose mass and may be carbon-rich red
giants. The mass loss rates for Miras are about 10 times higher than for SRb
and Lb stars, whose properties are similar enough to show that they are likely
to belong to the same population. The distribution of carbon star mass loss
rates peaks at about 10
−7
M
year
−1
, close to the rate of growth of the core mass and
demonstrative of the close relationship between mass loss and evolution.
Infrared spectroscopy shows that dust mixtures can occur. Detached shells are
seen around some stars; they appear to form on the time scales of the helium
shell flashes and to be a normal occurrence in carbon star evolution.
Celotno besedilo
Dostopno za:
CMK, DOBA, FMFMET, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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