Time Variation in the Radio Flux Density from the Bipolar Ultracompact H II Region NGC 7538 IRS1

Abstract

We present high angular resolution ($\sim 0\text{.}{}^{\prime \prime }1$-$0\text{.}{}^{\prime \prime }4$) VLA observations at 2 and 6 cm made in 1983, 1986, and 1995 toward the ultracompact bipolar H II region NGC 7538 IRS1. We find, at both wavelengths, clear evidence of a decrease in the emission from the lobes. This decrease, of orden 20-30%, has not been observed previously in any ultracompact H II region. Most likely, it is due to recombination of the ionized gas in the lobes as a result of a decrease in the available ionizing photon flux. It is unclear if this decrease in the ionizing photon flux is due to an intrinsic change in the exciting star or to increased absorption of ionizing photons in the optically-thick core of the nebula.

arXiv comment12 pages, 3 figures

References in corpus (2)

• The Formaldehyde Masers in NGC 7538 and G29.96-0.02: VLBA, MERLIN, and VLA Observations
• NGC7538S - a High-Mass Protostar with a Massive Rotating Disk

Cited by in corpus (39)

• H II regions: Witnesses to massive star formation
• Understanding Spatial and Spectral Morphologies of Ultracompact H II Regions
• From the Convergence of Filaments to Disk-Outflow Accretion: Massive-Star Formation in W33A
• Forming spectroscopic massive proto-binaries by disk fragmentation
• Outflow-Confined H II Regions. I. First Signposts of Massive Star Formation
• Outflows, Accretion, and Clustered Protostellar Cores around a Forming O Star
• On the methanol masers in G9.62+0.20E and G188.95+0.89
• Characterization of the MALT90 Survey and the Mopra Telescope at 90 GHz
• Time Variation in G24.78+0.08 A1: Evidence for an Accreting Hypercompact H II Region?
• Investigating the Nature of the Dust Emission around Massive Protostar NGC 7538 IRS 1: Circumstellar Disk and Outflow?
• An Extensive, Sensitive Search for SiO Masers in High- and Intermediate-Mass Star-Forming Regions
• Outflows from the high-mass protostars NGC 7538 IRS1/2 observed with bispectrum speckle interferometry -- Signatures of flow precession
• The properties and polarization of the H2O and CH3OH maser environment of NGC7538-IRS1
• The Coordinated Radio and Infrared Survey for High-Mass Star Formation III. A catalogue of northern ultra-compact H II regions
• NGC7538 IRS1 - an ionized jet powered by accretion
• Massive Star Formation
• Extremely large and hot multilayer Keplerian disk around the O-type protostar W51N: The precursors of the HCHII regions?
• Evidence of Short Timescale Flux Density Variations of UC HII regions in Sgr B2 Main and North
• Simulating protostellar evolution and radiative feedback in the cluster environment
• Shaping a high-mass star-forming cluster through stellar feedback. The case of the NGC 7538 IRS 1-3 complex
• NGC 7538 : Multiwavelength Study of Stellar Cluster Regions associated with IRS 1-3 and IRS 9 sources
• Impact of initial models and variable accretion rates on the pre-main-sequence evolution of massive and intermediate-mass stars and the early evolution of HII regions
• NGC7538 IRS1 -- an O star driving an ionized jet and giant N-S outflow
• HII region variability and pre-main-sequence evolution
• Time-Variable Radio Recombination Line Emission in W49A
• The compact, time-variable radio source projected inside W3(OH): Evidence for a Photoevaporated Disk?
• Searching for compact radio sources associated to UCHII regions
• The ionized heart of a molecular disk. ALMA observations of the hyper-compact HII region G24.78+0.08 A1
• The Rare 23.1-GHz Methanol Masers in NGC 7538 IRS 1
• Surveys of Clumps, Cores, and Condensations in the Cygnus X: II. Radio Properties of the Massive Dense Cores
• Gas Kinematics in the HII regions G351.69-1.15 and G351.63-1.25
• Flux Density Variations at 3.6 cm in the Massive Star-Forming Region W49A
• Ultracompact HII regions with extended emission: The case of G43.89-0.78 and its molecular environment
• [Fe II] 1.64 um Imaging Observations of the Outflow Features around Ultracompact H II Regions in the 1st Galactic Quadrant
• Modeling High-Mass Star Formation and Ultracompact HII Regions
• Radio Imaging of the NGC 2024 FIR 5/6 Region: a Hypercompact H II Region Candidate in Orion
• Dynamic Massive Star Formation: Radio Flux Variability in UCHII Regions
• Interstellar medium and star formation studies with the Square Kilometre Array
• Time Variability in Simulated Ultracompact and Hypercompact HII Regions