J/ApJ/909/138 AAVSO and DASCH light curve of U Mon (Vega+, 2021)
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.
Vega L.D., Stassun K.G., Montez R., Kaminski T., Sabin L., Schlegel E.M.,
Vlemmings W.H.T., Kastner J.H., Ramstedt S., Boyd P.T.
<Astrophys. J., 909, 138 (2021)>
=2021ApJ...909..138V 2021ApJ...909..138V
ADC_Keywords: Stars, giant; Stars, double and multiple; Photometry, UBV
Keywords: Binary stars ; Circumstellar matter ; RV Tauri variable stars ;
Spectral energy distribution ; Submillimeter astronomy ;
X-ray astronomy ; Post-asymptotic giant branch stars
Abstract:
We present an X-ray through submillimeter observations of the
classical RV Tauri (RVb-type) variable U Mon, a post-asymptotic giant
branch (AGB) binary with a circumbinary disk (CBD). Our SMA
observations indicate a CBD diameter of ≲550au. 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 (∼10MK),
with LX=5x1030erg/s, 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 ∼60yr, possibly caused
by a feature in the CBD. From literature radial velocities we find
that the binary companion is a ∼2M☉ A-type main-sequence star.
The orientation of the binary's orbit lies along our line of sight
(ω=95°), 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 (∼4.5-9au) 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 Hα observed at RVb minima and of
the X-ray emission that may arise from accreted material.
Description:
The American Association of Variable Star Observers (AAVSO) is a
global network of amateur and professional astronomers dedicated to
monitoring variable stars. The earliest observation of U Mon in the
AAVSO archive was made by Ernest E. Markwick on 1888 December 25
(JD 2410997.0), and after a few observations there followed a 49yr gap
between 1896 and 1945. More regular monitoring began in the mid-1940s
and continues to the present day.
The Digital Access to a Sky Century at Harvard (DASCH) survey is an
ongoing effort to digitize about 0.5 million photographic plates
covering the northern and southern sky from 1880 to 1985
(Grindlay+ 2009ASPC..410..101G 2009ASPC..410..101G). Data for U Mon were released in the
DASCH Data Release 6 (DR6).
We observed U Mon on three occasions with the SMA interferometer on
2018 February 1 (frequency ranges at 223.6-231.6GHz and
239.6-247.5GHz), on 2018 October 2 (328.8 to 360.8GHz) and on
2019 March 15 (209.1-212.8GHz, 214.9-216.7GHz, 225.1-226.9GHz,
229.2-238.8GHz, 332.8-340.8GHz, and 348.8-356.8GHz). See Section 3.3.
U Mon was observed by the X-ray Multiple Mirror (XMM-Newton)
observatory on 2016 October 23 for 58.3ks. The XMM-Newton observations
include 15 imaging exposures: three X-ray images on the EPIC-pn (55.3ks),
EPIC-MOS1 (57.0ks), and EPIC-MOS2 (56.9ks) detectors, and 12 exposures
(each ∼2.2-4.4ks) with the Optical Monitor (OM) using the UVW1, UVM2,
and UVW2 filters. See Section 3.4.
Objects:
---------------------------------------------------------
RA (ICRS) DE Designation(s) (Per)
---------------------------------------------------------
07 30 47.47 -09 46 36.8 U Mon = V* U Mon (P=2451d)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig2.dat 31 4753 AAVSO + DASCH light curve of U Mon
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See also:
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/MNRAS/376/313 : Carbon star in Magellanic Cloud (Groenewegen+, 2007)
J/A+A/506/1277 : Modelisation of MCs C/O stars (Groenewegen+, 2009)
J/A+A/513/A53 : LABOCA 870um images of evolved stars (Ladjal+, 2010)
J/ApJS/194/7 : X-ray properties of O and B stars in Carina (Naze+, 2011)
J/A+A/557/A104 : CO observations of post-AGB stars (Bujarrabal+, 2013)
J/MNRAS/453/133 : WISE view of RV Tauri stars (Gezer+, 2015)
J/A+A/607/A60 : BD+46 442 optical spectra (Bollen+, 2017)
J/A+A/604/A29 : MC Type II & anomalous Cepheids PL & PR (Groenewegen+, 2017)
J/A+A/599/A85 : Structure of Herbig AeBe disks at mas scale (Lazareff+, 2017)
J/A+A/597/A129 : Galactic RV Tauri stars velocities (Manick+, 2017)
J/AcA/67/297 : OGLE Galactic center Cepheids and RR Lyrae (Soszynski+, 2017)
J/A+A/620/A85 : Binary post-AGB stars radial velocities (Oomen+, 2018)
J/A+A/631/A53 : 1-D optical spectra for IRAS19135+3937 (Bollen+, 2019)
J/A+A/631/A108 : Disks around post-AGB binaries fit results (Kluska+, 2019)
http://dasch.rc.fas.harvard.edu/lightcurve.php : DASCH lightcurve home page
Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 9 F9.1 d JD Julian Day of observation (1)
11- 25 F15.6 --- Flux [1.58e+6/6e+7] Arbitrary flux (2)
27- 31 A5 --- Ref AAVSO or DASCH catalog
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Note (1): Light curve binned by 5 days
Note (2): AAVSO MagV and DASCH MagB data were converted to arbitrary flux units
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 10-Aug-2022