N. L. J. Cox

ACRI Group (France)

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F. Patat

European Southern Observatory

P. Ehrenfreund

Leiden University

L. Kaper

University of Amsterdam

J. Sollerman

Stockholm University

P. Royer

KU Leuven

Martin Cordiner

Goddard Space Flight Center

J. Cami

Western University

P. J. Sarre

University of Nottingham

ÁR

Álvaro Ribas

University of Cambridge

L. Spezzi

European Organisation for the Exploitation of Meteorological Satellites

Cooperative Institutions

Centre National de la Recherche Scientifique

European Southern Observatory

Carnegie Institution for Science

Carnegie Observatories

European Southern Observatory

Leiden University

University of Copenhagen

Max Planck Society

California Institute of Technology

National Institute for Astrophysics

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Multi-epoch high-resolution spectroscopy of SN 2011fe

Astronomy and Astrophysics (2012)

F. Patat Martin Cordiner N. L. J. Cox R. I. Anderson A. Harutyunyan

Aims. The nearby Type Ia supernova (SN) 2011fe has provided an unprecedented opportunity for deriving some of the properties of its progenitor. This work provides additional and independent information on the circumstellar environment in which the explosion took place.

Epoch (astronomy)

10.1051/0004-6361/201118556

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Citations (63)

The Herschel Gould Belt Survey in Chamaeleon II - Properties of cold dust in disks around young stellar objects

L. Spezzi N. L. J. Cox T. Prusti B. Merín Álvaro Ribas

We report on the Herschel Gould Belt survey (HGBS) of ChaII, focusing on the detection of Class I to III young stellar objects (YSOs). We aim at characterizing the circumstellar material around these YSOs and understanding which disk parameters are most likely constrained by the new HGBS data. We recovered 29 out of the 63 known YSOs in ChaII with a detection in at least one of the PACS/SPIRE pass-bands: 3 Class I YSOs (i.e.,100%), 1 Flat source (i.e., 50%), 21 Class II objects (i.e., 55%), 3 Class III objects (i.e, 16%) and the unclassified source IRAS 12522-7640. We explore PACS/SPIRE colors of this sample and present modeling of their SEDs using the RADMC-2D radiative transfer code. We find that YSO colors are confined in specific regions of PACS/SPIRE color-color diagrams. These color ranges are expected to be only marginally contaminated by extragalactic sources and field stars and, hence, provide a useful YSO selection tool when applied altogether. We were able to model the SED of 26 out of the 29 detected YSOs. We discuss the degeneracy/limitations of our SED fitting results and adopt the Bayesian method to estimate the probability of different values for the derived disk parameters. The Cha II YSOs present typical disk inner radii around 0.1 AU. The lower limit to Rc is typically around 50 AU. The lower limits to Mdisk are proportional to the stellar masses with a typical 0.3% ratio, i.e., in the range estimated in the literature for young Class II stars and brown dwarfs across a broad range of stellar masses. The estimated flaring angles, although very uncertain, point towards rather flat disks (1+phi less than 1.2), as found for low-mass M-type YSO samples in other star forming regions. Thus, our results support the idea that disk properties show a dependence on stellar properties.

Young stellar object

Spire (mollusc)

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Depleted diffuse bands in circumstellar envelopes of post-AGB stars

Proceedings of the International Astronomical Union (2008)

N. L. J. Cox R. Luna M. Á. Satorre D. A. García–Hernández Olga Suárez

Abstract We report on new results in the search for diffuse bands, signatures of still unknown origin, in the circumstellar envelopes of evolved (post-AGB) stars.

Circumstellar envelope

Circumstellar dust

10.1017/s1743921308021200

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The EDIBLES Survey IX: Simulations of the λ6614 DIB Profile Variations: A Surprising Connection with CH⁺

ACS Earth and Space Chemistry (2025)

Charmi Bhatt J. Cami P. J. Sarre H. Linnartz N. L. J. Cox

The profiles of several diffuse interstellar bands (DIBs) show substructures that resemble unresolved rotational bands of the electronic transitions of large molecules. Their profiles show clear variations along the lines of sight, probing different physical conditions. Analysis of variations in such profiles can constrain the sizes and geometries of the DIB carriers and the physical conditions of the interstellar environments in which they reside. We investigate the properties of rotational band contours for perpendicular transitions in planar, oblate symmetric top molecules and compare such contours to the observed profile of the λ6614 DIB. We examine the shapes of the profiles as a function of the model parameters: the rotational constant B in the ground state, the relative change in the rotational constant of the excited state ΔB, the Coriolis coupling constant ζ, the rotational excitation temperature Trot, and line width σ. We determine which parameters can reproduce the overall triple-peak profile of the λ6614 DIB and the variations across different lines of sight. We find that the substructures in the λ6614 DIB can be reproduced with an oblate top with rotational constant B = (2.2 ± 1.8) × 10–3 cm–1, ΔB = (−7.2 ± 0.4) × 10–2%, and Coriolis coupling constant ζ = (2.9 ± 0.1) × 10–1 cm–1. Thus, if the λ6614 DIB carrier conforms to an oblate symmetric top geometry, it is most likely to be a ∼54C atom molecule. The profile variations correspond to changes in the rotational temperature from 81 to 92 K. We furthermore find that the intrinsic line width is a key parameter for each sightline and requires a range from 0.14 to 0.21 cm–1 (or 2.8 to 4.2 km s–1) across our sample to reproduce the observations. The intrinsic line width of the λ6614 DIB correlates with the width of the CH+ lines, suggesting an origin in the same environment. We conclude that the λ6614 DIB carrier resides in the same hot gas at low density that is probed by CH+.

10.1021/acsearthspacechem.4c00238

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TheHerschelGould Belt Survey in Chamaeleon II

Astronomy and Astrophysics (2013)

L. Spezzi N. L. J. Cox T. Prusti B. Merín Álvaro Ribas

Context. We report on the Herschel Gould Belt survey (HGBS) of the Chamaeleon II (Cha II) star-forming region, focusing on the detection of Class I to III young stellar objects (YSOs).

Young stellar object

10.1051/0004-6361/201321444

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Citations (25)

Large Interstellar Polarisation Survey (LIPS)

Astronomy and Astrophysics (2017)

S. Bagnulo N. L. J. Cox Aleksandar Cikota R. Siebenmorgen Н. В. Вощинников

Polarimetric studies of light transmitted through interstellar clouds may give constraints on the properties of the interstellar dust grains. Traditionally, broadband linear polarisation (BBLP) measurements have been considered an important diagnostic tool for the study of the interstellar dust, while comparatively less attention has been paid to spectropolarimetric measurements. However, spectropolarimetry may offer stronger constraints than BBLP, for example by revealing narrowband features, and by allowing us to distinguish the contribution of dust from the contribution of interstellar gas. Therefore, we have decided to carry out a Large Interstellar Polarisation Survey (LIPS) using spectropolarimetric facilities in both hemispheres. Here we present the results obtained in the Southern Hemisphere with the FORS2 instrument of the ESO Very Large Telescope. Our spectra cover the wavelength range 380--950\,nm at a spectral resolving power of about 880. We have produced a publicly available catalogue of 127 linear polarisation spectra of 101 targets. We also provide the Serkowski-curve parameters, as well as the wavelength gradient of the polarisation position angle for the interstellar polarisation along 76 different lines of sight. In agreement with previous literature, we found that the best-fit parameters of the Serkowski-curve are not independent of each other. However, the relationships that we obtained are not always consistent with what was found in previous studies.

10.1051/0004-6361/201731459

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Citations (36)

Multi-epoch high-resolution spectroscopy of SN 2011fe - Linking the progenitor to its environment

Astronomy and Astrophysics (2013)

F. Patat Martin Cordiner N. L. J. Cox R. I. Anderson A. Harutyunyan

Context. The nearby Type Ia SN 2011fe has provided an unprecedented opportunity to derive some of the properties of the progenitor system, which is one of the key open problems in the supernova (SN) field. Aims. This study attempts to establish a link between the reasonably well known nature of the progenitor and its surrounding environment. This is done with the aim of enabling the identification of similar systems in the vast majority of the cases, when distance and epoch of discovery do not allow a direct approach. Methods. To study the circumstellar environment of SN 2011fe we have obtained high-resolution spectroscopy of SN 2011fe on 12 epochs, from 8 to 86 days after the estimated date of explosion, targeting in particular at the time evolution of Caii and Nai. Results. Three main absorption systems are identified from Caii and Nai, one associated to the Milky Way, one probably arising within a high-velocity cloud, and one most likely associated to the halo of M101. The Galactic and host galaxy reddening, deduced from the integrated equivalent widths (EW) of the Nai lines are EB V=0.011 0.002 and EB V=0.014 0.002 mag, respectively. The host galaxy absorption is dominated by a component detected at the same velocity measured from the 21-cm Hi line at the projected SN position ( 180 km s 1 ). During the 3 months covered by our observations, its EW changed by 15.6 6.5 mA. This small variation is shown to be compatible with the geometric e ects produced by the rapid SN photosphere expansion coupled to the patchy fractal structure of the ISM. The observed behavior is fully consistent with ISM properties similar to those derived for our own Galaxy, with evidences for structures on scales .100 AU. Conclusions. SN 2011fe appears to be surrounded by a ”clean” environment. The lack of blue-shifted, time-variant absorption features is fully consistent with the progenitor being a binary system with a main-sequence, or even another degenerate star.

Line (geometry)

Source

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Citations (51)

Extra-Galactic Diffuse Interstellar Bands

Astrochemistry: Recent Successes and Current Challenges (2005)

N. L. J. Cox P. Ehrenfreund L. Kaper Marco Spaans Bernard Foing

Source

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Diffuse interstellar bands in Upper Scorpius: probing variations in the DIB spectrum due to changing environmental conditions

Astronomy and Astrophysics (2011)

D. A. I. Vos N. L. J. Cox L. Kaper M. Spaans P. Ehrenfreund

We study the effects of local environmental conditions affecting the diffuse interstellar band (DIB) carriers within the Upper Scorpius subgroup of the Sco OB2 association. We obtained optical spectra with FEROS, and measured the equivalent widths of five DIBs (at 5780, 5797, 6196, 6379, and 6613 Angstrom) as well as those of absorption lines of di-atomic molecules (CH, CH+, CN) and atoms (KI, CaI) towards 89 targets in the direction of Upper Scorpius. We construct a simple radiative transfer and chemical network model of the diffuse interstellar medium (ISM) sheet in front of Upp Sco to infer the effective radiation field. Both the interstellar radiation field strength, I_UV, and the molecular hydrogen fraction, f_H2, have been derived for 55 sightlines probing the Upp Sco ISM. We discuss the relations between DIB strengths, CH and CH+ line strengths, E(B-V), I_UV, and f_H2. The ratio between the 5780 and 5797 DIBs reveals a (spatial) dependence on the local environment in terms of cloud density and exposure to the interstellar radiation field, reflecting the molecular nature of these DIB carriers.

10.1051/0004-6361/200809746

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Citations (72)

Discovery of multiple dust shells beyond 1 arcmin in the circumstellar envelope of IRC +10216 usingHerschel/PACS

Astronomy and Astrophysics (2011)

L. Decin P. Royer N. L. J. Cox B. Vandenbussche R. Ottensamer

We present new Herschel/PACS images at 70, 100, and 160 micron of the well-known, nearby, carbon-rich asymptotic giant branch star IRC+10216 revealing multiple dust shells in its circumstellar envelope. For the first time, dust shells (or arcs) are detected until 320 arcsec. The almost spherical shells are non-concentric and have an angular extent between 40 deg and 200 deg. The shells have a typical width of 5 arcsec - 8 arcsec, and the shell separation varies in the range of 10 arcsec - 35 arcsec, corresponding to 500-1700 yr. Local density variations within one arc are visible. The shell/intershell density contrast is typically 4, and the arcs contain some 50% more dust mass than the smooth envelope. The observed (nested) arcs record the mass-loss history over the past 16 000 yr, but Rayleigh-Taylor and Kelvin-Helmholtz instabilities in the turbulent astropause and astrosheath will erase any signature of the mass-loss history for at least the first 200 000 yr of mass loss. Accounting for the bowshock structure, the envelope mass around IRC+10216 contains >2Msun of gas and dust mass. It is argued that the origin of the shells is related to non-isotropic mass-loss events and clumpy dust formation.

Circumstellar envelope

Asymptotic giant branch

Envelope (radar)

Circumstellar dust

Carbon star

Protostar

10.1051/0004-6361/201117360

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Citations (41)