Formaldehyde Masers: Exclusive Tracers of High-Mass Star Formation

Araya, E. D.; Olmi, L.; Ortiz, J. Morales; Brown, Joanna; Höfner, P.; Kurtz, S.; Linz, H.; Creech‐Eakman, M. J.

doi:10.1088/0067-0049/221/1/10

Cited by 11 publications

(16 citation statements)

References 69 publications

(76 reference statements)

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“…The 6 cm line of formaldehyde (H 2 CO) is a rare maser transition that has been reported toward nine HMSFRs in our Galaxy: NGC 7538 IRS 1 (Downes & Wilson 1974;Hoffman et al 2003), Sgr B2 (Whiteoak & Gardner 1983;Mehringer et al 1994;Hoffman et al 2007), G29.96−0.02 (Pratap et al 1994;Hoffman et al 2003), IRAS 18566+0408 (G37.55+0.20; Araya et al 2004b), G23.71−0.20 (Araya et al 2006), G23.01−0.41 (Araya et al 2008), G25.83−0.18 (Araya et al 2008), G32.74−0.07 (Araya et al 2015), and G0.38+0.04 (Ginsburg et al 2015), and three extragalactic regions (Baan et al 1986;Araya et al 2004a; see however Mangum et al 2008). …”

Section: Introductionsupporting

confidence: 68%

“…In addition, masers and megamasers have been found in extragalactic environments (e.g., Baan 1985;Haschick et al 1994;Lo 2005;Sjouwerman et al 2010). There are several types of masers which have been detected exclusively in high-mass star forming regions (HMSFR) including 6.7 and 12.2 GHz methanol and 6 cm (4.83 GHz) formaldehyde masers (e.g., Walsh et al 1998;Breen et al 2013;Araya et al 2007a;Araya et al 2015). These masers are not only signposts of high-mass star formation but also help trace small-scale dynamics, morphology, and the locations of outflows and accretion disks (e.g., Bartkiewicz et al 2009;Sanna et al 2010;Goddi et al 2011;Torrelles et al 2011;Moscadelli et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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Long-term Variability of H₂CO Masers in Star-forming Regions

Andreev¹,

Araya²,

Hoffman³

et al. 2017

ApJS

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We present results of a multi-epoch monitoring program on variability of 6 cm formaldehyde (H 2 CO) masers in the massive star forming region NGC 7538 IRS 1 from 2008 to 2015 conducted with the GBT, WSRT, and VLA. We found that the similar variability behaviors of the two formaldehyde maser velocity components in NGC 7538 IRS 1 (which was pointed out by Araya and collaborators in 2007) have continued. The possibility that the variability is caused by changes in the maser amplification path in regions with similar morphology and kinematics is discussed. We also observed 12.2 GHz methanol and 22.2 GHz water masers toward NGC 7538 IRS 1. The brightest maser components of CH 3 OH and H 2 O species show a decrease in flux density as a function of time. The brightest H 2 CO maser component also shows a decrease in flux density and has a similar LSR velocity to the brightest H 2 O and 12.2 GHz CH 3 OH masers. The line parameters of radio recombination lines and the 20.17 and 20.97 GHz CH 3 OH transitions in NGC 7538 IRS 1 are also reported. In addition, we observed five other 6 cm formaldehyde maser regions. We found no evidence of significant variability of the 6 cm masers in these regions with respect to previous observations, the only possible exception being the maser in G29.96−0.02. All six sources were also observed in the H 13 2 CO isotopologue transition of the 6 cm H 2 CO line; H

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Section: Introductionsupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Long-term Variability of H₂CO Masers in Star-forming Regions

Andreev¹,

Araya²,

Hoffman³

et al. 2017

ApJS

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“…The 4765 MHz line corresponds to the transition 2 Π 1/2 J = 1/2 F = 1 − 0 (E u = 181.94 K) 3 , which is analogous to the 1720 MHz OH ground state line but in the 2 Π 1/2 ladder instead of the 2 Π 3/2 (e.g., Pihlström et al 2008, see also Figure 5.2 in Gray 2012). The emission was first detected in the May 2008 observations (Araya et al 2015), and then confirmed in October 2008. Figure Table 1.…”

Section: Resultsmentioning

confidence: 87%

“…However, using the 305 m Arecibo Telescope, we have detected a narrow line corresponding to the 4765 MHz transition of OH. The detection of this line was a by-product of a survey for H 2 CO masers reported in Araya et al (2015). In this work we focus on the 4765 MHz OH detection, and present complementary observations also conducted with the Arecibo Telescope.…”

Section: Introductionmentioning

confidence: 95%

Detection of 4765 MHz OH Emission in a Preplanetary Nebula: CRL 618

Strack

Araya

Lebrón

et al. 2019

ApJ

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Jets and outflows are ubiquitous phenomena in astrophysics, found in our Galaxy in diverse environments, from the formation of stars to late-type stellar objects. We present observations conducted with the 305m Arecibo Telescope of the pre-planetary nebula CRL 618 (Westbrook Nebula) − a well studied late-type star that has developed bipolar jets. The observations resulted in the first detection of 4765 MHz OH in a late-type stellar object. The line was narrow (FWHM ∼ 0.6 km s −1 ) and ∼40 km s −1 blueshifted with respect to the systemic velocity, which suggests association with the expanding jets/bullets in CRL 618. We also report non-detection at Arecibo of any other OH transition between 1 and 9 GHz. The non-detections were obtained during the observations in 2008, when the 4765 MHz OH line was first discovered, and also in 2015 when the 4765 MHz OH line was not detected. Our data indicate that the 4765 MHz OH line was a variable maser. Modeling of the 4765 MHz OH detection and non-detection of the other transitions is consistent with the physical conditions expected in CRL 618. The 4765 MHz OH maser could originate from dissociation of H 2 O by shocks after sublimation of icy objects in this dying carbon-rich stellar system, although other alternatives such as OH in an oxygen-rich circumstellar region associated with a binary companion are also possible.

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“…Example spectra from two epochs, first detection (upper panel; see observation details inAraya et al 2015) and 2017 (lower panel) non-detection. The upper panel shows a high spectral resolution spectrum (blue-dashed) and the smoothed spectrum (black-solid).…”

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confidence: 99%

Excited OH Masers in Late-Type Stellar Objects

et al. 2017

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The final stages of low-mass stellar evolution are characterized by significant mass loss due to stellar pulsations during the AGB phase, which lead to the development of planetary nebulae. Molecular masers of H2O, SiO, and ground state OH transitions are commonly detected in oxygen-rich late-type stars (OH/IR objects). In contrast, excited OH maser transitions are rare. We discuss our study of the carbon-rich pre-planetary nebula CRL618 (a prototypical post-AGB star). Observations conducted in May 2008 with the 305m Arecibo Telescope resulted in the first detection of a 4765MHz OH maser line in a late-type stellar object; the detection was confirmed a few months later also with Arecibo. Subsequent observations in 2015 and 2017 resulted in non-detection of the 4765MHz OH line. Our observations indicate that the 4765MHz OH maser in CRL 618 is highly variable, possibly tracing a short-lived phenomenon during the development of a pre-planetary nebula.

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Formaldehyde Masers: Exclusive Tracers of High-Mass Star Formation

Cited by 11 publications

References 69 publications

Long-term Variability of H₂CO Masers in Star-forming Regions

Long-term Variability of H₂CO Masers in Star-forming Regions

Detection of 4765 MHz OH Emission in a Preplanetary Nebula: CRL 618

Excited OH Masers in Late-Type Stellar Objects

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Formaldehyde Masers: Exclusive Tracers of High-Mass Star Formation

Cited by 11 publications

References 69 publications

Long-term Variability of H2CO Masers in Star-forming Regions

Long-term Variability of H2CO Masers in Star-forming Regions

Detection of 4765 MHz OH Emission in a Preplanetary Nebula: CRL 618

Excited OH Masers in Late-Type Stellar Objects

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Long-term Variability of H₂CO Masers in Star-forming Regions

Long-term Variability of H₂CO Masers in Star-forming Regions