23 research outputs found
Benzyne in V4334 Sqr: A Quest for the Ring with SOFIA/EXES
Large aromatic molecules are ubiquitous in both circumstellar and interstellar environments. Detection of small aromatic molecules, such as benzene (C6H6) and benzyne (C6H4), are rare in astrophysical environments. Detection of such species will have major implications for our understanding of the astrochemistry involved in the formation of the molecules necessary for life, including modeling the chemical pathways to the formation of larger hydrocarbon molecules. We conducted a search for the infrared 18 μm spectral signature of benzyne in V4334 Sgr with the Stratospheric Observatory for Infrared Astronomy (SOFIA)/Echelon-Cross-Echelle Spectrograph (EXES) finding no evidence for a feature at the sensitivity of our observations
VLTI monitoring of the dust formation event of the Nova V1280 Scorpii
This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.Context. We present the first high spatial-resolution monitoring of the dust-forming nova V1280 Sco, performed with the Very Large
Telescope Interferometer (VLTI).
Aims. These observations promise to improve the distance determination of such events and constrain the mechanisms leading to very
efficient dust formation under the harsh physical conditions encountered in novae ejecta.
Methods. Spectra and visibilities were regularly acquired between the onset of dust formation, 23 days after discovery (or 11 days
after maximum), and day 145, using the beam-combiner instruments AMBER (near-IR) and MIDI (mid-IR). These interferometric
observations were complemented by near-infrared data from the 1.2 m Mt. Abu Infrared Observatory, India. The observations are
initially interpreted in terms of simple uniform models; however more complex models, probably involving a second shell, are required
to explain data acquired following t = 110 d after outburst. This behavior is in accordance with the light curve of V1280 Sco, which
exhibits a secondary peak at about t = 106 d, followed by a new, steep decline, suggesting a new dust-forming event. Spherical dust
shell models generated with the DUSTY code are used to investigate the parameters of the main dust shell.
Results. Using uniform disk models, these observations allow us to determine an apparent linear expansion rate for the dust shell of
0.35 ± 0.03 mas day−1 and the approximate ejection time of the matter in which dust formed of tejec = 10.5 ± 7 d, i.e. close to the
maximum brightness. This information, combined with the expansion velocity of 500 ± 100 km s−1, implies a distance estimate of
1.6 ± 0.4 kpc. The sparse uv coverage does not enable deviations from spherical symmetry to be clearly discerned. The dust envelope
parameters were determined. The dust mass generated was typically 2–8 × 10−9 M day−1, with a probable peak in production at
about 20 days after the detection of dust and another peak shortly after t = 110 d, when the amount of dust in the shell was estimated
as 2.2 × 10−7 M. Considering that the dust-forming event lasted at least 200–250 d, the mass of the ejected material is likely to have
exceeded 10−4 M. The conditions for the formation of multiple shells of dust are also discussed.
K
The Expanding Fireball of Nova Delphini 2013
A classical nova occurs when material accreting onto the surface of a white
dwarf in a close binary system ignites in a thermonuclear runaway. Complex
structures observed in the ejecta at late stages could result from interactions
with the companion during the common envelope phase. Alternatively, the
explosion could be intrinsically bipolar, resulting from a localized ignition
on the surface of the white dwarf or as a consequence of rotational distortion.
Studying the structure of novae during the earliest phases is challenging
because of the high spatial resolution needed to measure their small sizes.
Here we report near-infrared interferometric measurements of the angular size
of Nova Delphini 2013, starting from one day after the explosion and continuing
with extensive time coverage during the first 43 days. Changes in the apparent
expansion rate can be explained by an explosion model consisting of an
optically thick core surrounded by a diffuse envelope. The optical depth of the
ejected material changes as it expands. We detect an ellipticity in the light
distribution, suggesting a prolate or bipolar structure that develops as early
as the second day. Combining the angular expansion rate with radial velocity
measurements, we derive a geometric distance to the nova of 4.54 +/- 0.59 kpc
from the Sun.Comment: Published in Nature. 32 pages. Final version available at
http://www.nature.com/nature/journal/v515/n7526/full/nature13834.htm
The rise of SN 2014J in the nearby galaxy M82
We report on the discovery of SN 2014J in the nearby galaxy M82. Given its proximity, it offers the best opportunity to date to study a thermonuclear supernova (SN) over a wide range of the electromagnetic spectrum. Optical, near-IR, and mid-IR observations on the rising light curve, orchestrated by the intermediate Palomar Transient Factory, show that SN 2014J is a spectroscopically normal Type Ia supernova (SN Ia), albeit exhibiting high-velocity features in its spectrum and heavily reddened by dust in the host galaxy. Our earliest detections start just hours after the fitted time of explosion. We use high-resolution optical spectroscopy to analyze the dense intervening material and do not detect any evolution in the resolved absorption features during the light curve rise. Similar to other highly reddened SNe Ia, a low value of total-to-selective extinction, RV ≲ 2, provides the best match to our observations. We also study pre-explosion optical and near-IR images from Hubble Space Telescope with special emphasis on the sources nearest to the SN location. © 2014. The American Astronomical Society. All rights reserved