Multiwavelength Observations of the RV Tauri Variable System U Monocerotis: Long-Term Variability Phenomena That Can Be Explained by Binary Interactions with a Circumbinary Disk

Abstract

We present X-ray through submillimeter observations of the classical RV Tauri (RVb-type) variable U Mon, a post-AGB binary with a circumbinary disk (CBD). Our SMA observations indicate a CBD diameter of $\lesssim$550 au. Our XMM-Newton observations make U Mon the first RV Tauri variable detected in X-rays. The X-ray emission is characteristic of a hot plasma ($\sim$10 MK), with L${}_X=5\times 10^{30}\mathrm{erg}{\mathrm{s}}^{-1}$, and we consider its possible origin from U Mon, its companion, and/or binary system interactions. Combining DASCH and AAVSO data, we extend the time-series photometric baseline back to the late 1880s and find evidence that U Mon has secular changes that appear to recur on a timescale of $\sim$60 yr, possibly caused by a feature in the CBD. From literature radial velocities we find that the binary companion is a $\sim$2 M${}_{\odot }$ A-type main-sequence star. The orientation of the binary's orbit lies along our line of sight ($\omega =95^{\circ }$), such that apastron corresponds to photometric RVb minima, consistent with the post-AGB star becoming obscured by the near side of the CBD. In addition, we find the size of the inner-CBD hole ($\sim$4.5-9 au) to be comparable to the binary separation, implying that one or both stars may interact with the CBD at apastron. The obscuration of the post-AGB star implicates the companion as the likely source of the enhanced H$\alpha$ observed at RVb minima and of the X-ray emission that may arise from accreted material.

arXiv comment19 pages, 9 figures, 4 tables, in aastex62 format, published in ApJ, NASA news feature available upon request. Light curve in Figure 2 available as "Data behind the Figure"

References in corpus (67)

• Astropy: A Community Python Package for Astronomy
• Gaia Data Release 2. Summary of the contents and survey properties
• On the Absorption of X-rays in the Interstellar Medium
• Collisional Plasma Models with APEC/APED: Emission Line Diagnostics of Hydrogen-like and Helium-like Ions
• The VizieR database of Astronomical Catalogues
• Long-Term Stability of Planets in Binary Systems
• Passive irradiated circumstellar disks with an inner hole
• The XMM-Newton Optical/UV Monitor Telescope
• Updated Atomic Data and Calculations for X-ray Spectroscopy
• Unresolved stellar companions with Gaia DR2 astrometry
• Far-infrared Spectral Energy Distribution Fitting for Galaxies Near and Far
• Physics Of Eclipsing Binaries. II. Towards the Increased Model Fidelity
• An Analysis of the Shapes of Interstellar Extinction Curves. VII. Milky Way Spectrophotometric Optical-through-Ultraviolet Extinction and Its R-Dependence
• The astrometric core solution for the Gaia mission. Overview of models, algorithms and software implementation
• On the Interferometric Sizes of Young Stellar Objects
• On a new theoretical framework for RR Lyrae stars I: the metallicity dependence
• Keplerian discs around post-AGB stars: a common phenomenon?
• The near-infrared size-luminosity relations for Herbig Ae/Be disks
• Luminosities and mass-loss rates of SMC and LMC AGB stars and Red Supergiants
• Structure of Herbig AeBe disks at the milliarcsecond scale A statistical survey in the H band using PIONIER-VLTI
• Post-AGB stars with hot circumstellar dust: binarity of the low-amplitude pulsators
• Classical Cepheid Pulsation Models. III. The Predictable Scenario
• The Inner Rim Structures of Protoplanetary Discs
• Global X-ray properties of the O and B stars in Carina
• Orbital properties of binary post-AGB stars
• Extended rotating disks around post-AGB stars
• A triple star system with a misaligned and warped circumstellar disk shaped by disk tearing
• The MACHO Project LMC Variable Star Inventory: The Discovery of RV Tauri stars and New Type II Cepheids in the LMC
• On the origin of the X-ray emission from Herbig Ae/Be stars
• Silicate features in Galactic and extragalactic post-AGB discs
• The WISE View of RV Tauri Stars
• A newly discovered stellar type: dusty post-red giant branch stars in the Magellanic Clouds
• Abundance Analyses of Field RV Tauri Stars, VI: An Extended Sample
• Abundance Analyses of Field RV Stars, V: DS Aquarii, UY Arae, TW Camelopardis, BT Librae, U Moncerotis, TT Ophiuchi, and RV Tauri
• Establishing binarity amongst Galactic RV Tauri stars with a disc
• Strong dust processing in circumstellar discs around 6 RV Tauri stars. Are dusty RV Tauri stars all binaries?
• Further X-ray detections of Herbig stars
• High-resolution observations of IRAS 08544-4431. Detection of a disk orbiting a post-AGB star and of a slow disk wind
• Time resolved spectroscopy of BD+46 442: gas streams and jet creation in a newly discovered evolved binary with a disk
• A mid-IR interferometric survey with MIDI/VLTI: resolving the second-generation protoplanetary disks around post-AGB binaries
• The period-luminosity and period-radius relations of Type II and anomalous Cepheids
• First detection of surface magnetic fields in Post-AGB stars : the cases of U Monocerotis and R Scuti
• Improved Photometry for the DASCH Pipeline
• Exploring wind-driving dust species in cool luminous giants II. Constraints from photometry of M-type AGB stars
• The evolved circumbinary disk of AC Her: a radiative transfer, interferometric and mineralogical study
• Jet creation in post-AGB binaries: the circum-companion accretion disc around BD+46${}^{\circ }$442
• The Secret Lives of Cepheids: $\delta$ Cep -- the Prototype of a New Class of Pulsating X-ray Variable Stars
• The perturbed sublimation rim of the dust disk around the post-AGB binary IRAS08544-4431
• The OGLE Collection of Variable Stars. Classical, Type II, and Anomalous Cepheids toward the Galactic Center
• VLTI/PIONIER survey of disks around post-AGB binaries. Dust sublimation physics rules!
• 870 um observations of evolved stars with LABOCA
• ALMA detection of a tentative nearly edge-on rotating disk around the nearby AGB star R~Doradus
• The Detection of Dust around NN Ser
• A Pilot Deep Survey for X-Ray Emission from fuvAGB Stars
• An evla and carma study of dusty disks and torii with large grains in dying stars
• Disc-binary interactions in depleted post-AGB binaries
• A spatio-kinematic model for jets in post-AGB stars
• The evolutionary nature of RV Tauri stars in the SMC and LMC
• Searching for Dust around Hyper Metal-Poor Stars
• Amplitude variations of modulated RV Tauri stars support the dust obscuration model of the RVb phenomenon
• Evidence for Binarity and Possible Disk Obscuration in Kepler Observations of the Pulsating RV Tau Variable DF Cygni
• The spectroscopic binaries RV Tauri and DF Cygni
• Determining mass accretion and jet mass-loss rates in post-asymptotic giant branch binary systems
• Physical properties of galactic RV Tauri stars from Gaia DR2 data
• Chaotic dynamics in the pulsation of DF Cygni, as observed by Kepler
• Observed relationship between CO2-1 and dust emission during post-AGB phase
• Additional Galactic Cepheids from the OGLE Survey

Cited by in corpus (3)

• A population of transition disks around evolved stars: Fingerprints of planets? Catalog of disks surrounding Galactic post-AGB binaries
• Second-generation protoplanetary discs around evolved binaries: a high-resolution polarimetric view with SPHERE/IRDIS
• Circumbinary disc interactions and stochastic dust obscuration in the post-asymptotic-giant-branch binary HD 213985