A Submillimeter HCN Laser in IRC +10216

We report the detection in IRC +10216 of 63 rotational transitions of HCN, most of them with quantum numbers J = 3-2, pertaining to 28 different vibrational states with energies up to 10 700 K (ν 1 +3ν 2 +ν 3 ). Some of the transitions were also observed for the rare isotopologue H 13 CN. The observations were carried out with the IRAM 30-m telescope. The HCN lines with level energies above 5000 K arise within 1.5 stellar radius from the photosphere. Their intensities imply a vibrational temperature of T vib 2400 K and a fractional HCN abundance relative to H 2 , x(HCN) = 5-7 × 10 −5 . These high-energy levels are mainly populated by photospheric radiation, and their vibrational temperature yields a direct measurement of the stellar photospheric temperature. The lines with energy levels between 2000 and 5000 K yield T vib 1300 K and x(HCN) 0.8-2 × 10 −5 . They are radiatively excited and arise from a shell extending between 1.5 and 5 stellar radii. Finally, the lines from the low-energy vibrational states (<2000 K) trace a larger region of the envelope (5-28 stellar radii) with T vib = 400-600 K and x(HCN) = 4-6× 10 −6 . They are strongly affected by mid and near-infrared pumping. The line widths increase from 5 km s −1 near the 2400 K photosphere, to 19 km s −1 in the warm 400 K shell. This provides a unique insight into the physical conditions of the gas acceleration and dust formation region.

show abstract

“…This may lead to strong and narrow maser emission (Schilke et al 2000;Schilke & Menten 2003). Strong masers are not observed in our spectra.…”

Section: Discussionmentioning

confidence: 68%

“…It is particularly strong towards IRC +10216 and CIT6 (Lucas & Cernicharo 1989;Schilke et al 2000;Schilke & Menten 2003;Avery et al 1994;Bieging et al 2000). Interpretating it is complicated by a wealth This work was based on observations carried out with the IRAM 30-m telescope.…”

Section: Introductionmentioning

confidence: 99%

Probing the dust formation region in IRC +10216 with the high vibrational states of hydrogen cyanide

Cernicharo

Agúndez

Kahane

et al. 2011

A&A

View full text Add to dashboard Cite

show abstract

“…Furthermore, Lucas & Cernicharo (1989) reported the detection of HCN v 2 = 1 1 c maser emission with a peak-flux density ∼400 Jy at 177 GHz. Schilke et al (2000) reported the detection of the vibrationally excited HCN (04 0 0) J = 9−8 maser line near 805 GHz with a flux density of ∼1500 Jy.…”

Section: Observing Maser Polarization With Almamentioning

confidence: 99%

Linear polarization of submillimetre masers

Pérez-Sánchez

Vlemmings

2013

A&A

View full text Add to dashboard Cite

Context. Once ALMA full polarization capabilities are offered, it will become possible to perform detailed studies of polarized maser emission towards star-forming regions and late-type stars, such as (post-) asymptotic giant branch stars and young planetary nebulae. To derive the magnetic field orientation from maser linear polarization, a number of conditions involving the rate of stimulated emission R, the decay rate of the molecular state Γ, and the Zeeman frequency gΩ need to be satisfied. Aims. The goal of this work is to investigate if SiO, H 2 O and HCN maser emission within the ALMA frequency range can be detected with observable levels of fractional linear polarization in the regime where the Zeeman frequency is greater than the stimulated emission rate. Methods. We used a radiative transfer code to calculate the fractional linear polarization as a function of the emerging brightness temperature for a number of rotational transition of SiO, H 2 O and HCN that have been observed to display maser emission at submillimetre wavelengths. We assumed typical magnetic field strengths measured towards galactic star-forming regions and circumstellar envelopes of late-type stars from previous VLBI observations. Since the Landé g-factors have not been reported for the different rotational transitions we modelled, we performed our calculations assuming conservative values of the Zeeman frequency for the different molecular species. Results. Setting a lower limit for the Zeeman frequency that still satisfies the criteria gΩ > R and gΩ > Γ, we find fractional polarization levels of up to 13%, 14% and 19% for the higher J transitions analysed for SiO, H 2 O and HCN, respectively, without considering anisotropic pumping or any other non-Zeeman effect. These upper limits were calculated assuming a magnetic field oriented perpendicular to the direction of propagation of the maser radiation. Conclusions. According to our results, SiO, H 2 O, and HCN maser emission within the ALMA frequency range can be detected with suitable linear polarization to trace the magnetic field structure towards star-forming regions and late-type stars even if the detected polarization has been enhanced by non-Zeeman effects.

show abstract

“…INTRODUCTION The observation of rotational transitions of vibrationally excited molecules is a unique probe of very hot gas around stars and young stellar objects (see, e.g., Schilke et al 1992bSchilke et al , 2000Walmsley 1999 andreferences therein). This is because vibrational transitions are generally pumped by IR radiation, and thus the excitation analysis offers a probe of the IR radiation field close to the exciting object, often at wavelengths at which direct observations in the IR are not possible, because the dust in the object is optically thick there.…”

mentioning

confidence: 99%

“…In the millimeter/submillimeter range at which the rotational lines are usually observed, the dust optical depth is usually negligible. Particularly in the carbon star IRC ϩ10216, rotational lines of vibrationally excited HCN have been observed in a variety of vibrational states, up to 4000 K above the ground level (Schilke et al 2000), and a careful study of these transitions can reveal the structure of the inner envelope in the dust formation zone.…”

mentioning

confidence: 99%

First Detection of Vibrationally Excited HNC in Space

Schilke

Comito

Thorwirth

2003

The Astrophysical Journal

Self Cite

View full text Add to dashboard Cite

We report the first detection of vibrationally excited HNC in space, found toward the proto-planetary nebula CRL 618. Three lines of HNC in the vibrationally excited state have been found, making the detectionunambiguous. The lines are emitted in a hot region close to the inner radius of the molecular envelope of CRL 618, but quantitative estimates of the column density are not possible, since the lines are most likely optically thick. In other astrophysical environments, HNC is found only in cold gas, and the presence of HNC in the hot layer toward CRL 618 is most likely due to time-dependent photochemistry in the boundary between the inner H ii region and the molecular envelope.

show abstract

A Submillimeter HCN Laser in IRC +10216

Cited by 33 publications

References 27 publications

Probing the dust formation region in IRC +10216 with the high vibrational states of hydrogen cyanide

Probing the dust formation region in IRC +10216 with the high vibrational states of hydrogen cyanide

Linear polarization of submillimetre masers

First Detection of Vibrationally Excited HNC in Space

Contact Info

Product

Resources

About