The dusty Nebula surrounding HR Car: a Spitzer view

Abstract

We present mid-IR observations of the Galactic Luminous Blue Variable (LBV) HR Car and its associated nebula carried out with the Spitzer Space Telescope using both IRAC and IRS, as part of a GTO program aimed to study stellar ejecta from evolved stars. Our observations reveal a rich mid-IR spectrum of the inner nebula showing both solid state and atomic gas signatures. Strong low-excitation atomic fine structure lines such as $26.0\mu$m [\ion{Fe}{2}] and $34.8\mu$m [\ion{Si}{2}], indicate, for the first time, the presence of a PDR in this object class. While the physics and chemistry of the low-excitation gas appears to be dominated by photodissociation, a possible contribution due to shocks can be inferred from the evidence of gas phase Fe abundance enhancement. The presence of amorphous silicates, inferred from the observed characteristic broad feature at $10\mu$m located in the inner nebula, suggests that dust has formed during the LBV outburst. This is in contrast with the detection of crystalline dust in other probably more evolved Galactic LBVs, which is similar to the crystalline dust observed in red supergiants. This has been considered to be evidence of dust production during evolutionary phases prior to the outburst.

27 pages, 6 figures. accepted by ApJ

References in corpus (8)

• The Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• The Spitzer Space Telescope Mission
• The Infrared Spectrograph on the Spitzer Space Telescope
• The SMART Data Analysis Package for the Infrared Spectrograph on the Spitzer Space Telescope
• The H II Region/PDR Connection: Self-Consistent Calculations of Physical Conditions in Star-Forming Regions
• Spitzer IRS Observations of the Galactic Center: Shocked Gas in the Radio Arc Bubble
• In-flight performance and calibration of the Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• Discovery of warm and dense molecular gas surrounding the ring nebula G79.29+0.46

Cited by in corpus (20)

• Production of dust by massive stars at high redshift
• It's Alive! The Supernova Impostor 1961V
• Eta Carinae and the Luminous Blue Variables
• Supernova 2014C: ongoing interaction with extended circumstellar material with silicate dust
• Multiple shells around G79.29+0.46 revealed from near-IR to millimeter data
• Herschel imaging and spectroscopy of the nebula around the luminous blue variable star WRAY 15-751
• The Herschel view of the nebula around the luminous blue variable star AG Carinae
• The candidate luminous blue variable G79.29+0.46: a comprehensive study of its ejecta through a multiwavelength analysis
• VISIR/VLT and VLA joint imaging analysis of the circumstellar nebula around IRAS~18576+0341
• SOFIA Observations of SN 2010jl: Another Non-Detection of the 9.7 $\mu$m Silicate Dust Feature
• Exploring the multifaceted circumstellar environment of the Luminous Blue Variable HR Carinae
• Spitzer/infrared spectrograph investigation of MIPSGAL 24 μm compact bubbles : Low resolution observations
• Herschel observations of the nebula M1-67 around the Wolf-Rayet star WR 124
• Luminous Blue Variables
• A massive nebula around the Luminous Blue Variable star RMC143 revealed by ALMA
• Galactic Structure Toward the Carina Tangent
• The contribution by luminous blue variable stars to the dust content of the Magellanic Clouds
• A warm molecular ring in AG Car: composing the mass-loss puzzle
• Spitzer observations of a circumstellar nebula around the candidate Luminous Blue Variable MWC 930
• The rich molecular environment of the luminous blue variable star AFGL 2298