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SUMMARY:Source-frequency Phase-referencing Observations of AGNs with EAVN 
 and Yebes
DTSTART;VALUE=DATE-TIME:20240905T113000Z
DTEND;VALUE=DATE-TIME:20240905T114500Z
DTSTAMP;VALUE=DATE-TIME:20260306T142541Z
UID:indico-contribution-15-0-33@cern.ch
DESCRIPTION:Speakers: Dr. ZHAO\, Guang-Yao (MPIfR)\nWe report results from
  the first successful simultaneous 22/43 GHz dual-frequency observing camp
 aign with a joint array of the KVN\, VERA\, and Yebes 40m RT in 2018.\n\nS
 imultaneous receiving makes it straightforward to apply frequency phase tr
 ansfer (FPT) and source frequency phase referencing (SFPR) methods\, which
  are essential for overcoming the main challenges of mm-VLBI observations 
 and achieving astrometry.\n\nOur analysis confirms the coherence time at 4
 3 GHz was extended to tens of minutes after applying FPT from 22 GHz on al
 l baselines to Yebes. These results mark the longest baseline to date (10\
 ,138 km) for the successful application of this method.\n\n Combined with 
 the regularized maximum likelihood (RML) imaging methods\, we have achieve
 d unprecedented angular resolutions of the observed targets.\n\nThe SFPR d
 ata also enabled us to measure the core shift of the targets and explore t
 he magnetic field properties. Thanks to the long baseline lengths and the 
 high-fidelity RML images\, we are able to obtain core shift measurements w
 ith high precision\, reaching 17$\\sim$30 microarcseconds.\n\nhttps://even
 ts.mpifr-bonn.mpg.de/indico/event/371/session/15/contribution/33
LOCATION:CJD Bonn Castell
URL:https://events.mpifr-bonn.mpg.de/indico/event/371/session/15/contribut
 ion/33
END:VEVENT
BEGIN:VEVENT
SUMMARY:Toward Tracking SMBH Binary Orbits: Pilot K/Q Simultaneous Observa
 tion Using KVN and Yebes-40m Telescope
DTSTART;VALUE=DATE-TIME:20240905T114500Z
DTEND;VALUE=DATE-TIME:20240905T120000Z
DTSTAMP;VALUE=DATE-TIME:20260306T142541Z
UID:indico-contribution-15-0-62@cern.ch
DESCRIPTION:Speakers: Dr. RO\, Hyunwook (Korea Astronomy and Space Science
  Institute)\nWe present the results of a pilot observation testing the per
 formance of Frequency Phase Transfer (FPT) and Source/Frequency Phase Refe
 rencing (SFPR) at 22 and 43 GHz using the Korean VLBI Network (KVN) and th
 e Yebes-40m telescope in Spain\, with a baseline length of $\\sim$9\,000 k
 m. The ultimate goal of this project is to monitor the orbital motion of s
 upermassive black hole binaries (SMBHBs) using high-precision VLBI astrome
 try\, which requires a precision of a few micro-arcseconds. We find that t
 he FPTed visibility phase at 43 GHz on Yebes-KVN baselines shows a signifi
 cant improvement in coherence time compared to the non-FPT phase\, demonst
 rating that FPT is effective even with long baselines. We also present pre
 liminary SFPR maps showing the feasibility of high astrometric precision w
 ithin 10 μas. We discuss remaining issues\, such as the time evolution of
  residual phases at long baselines\, and outline future observation plans 
 for long baseline SFPR\, including multi-frequency antennas up to 86 GHz.\
 n\nhttps://events.mpifr-bonn.mpg.de/indico/event/371/session/15/contributi
 on/62
LOCATION:CJD Bonn Castell
URL:https://events.mpifr-bonn.mpg.de/indico/event/371/session/15/contribut
 ion/62
END:VEVENT
BEGIN:VEVENT
SUMMARY:VLBI Observations of compact sources in the Galactic Plane
DTSTART;VALUE=DATE-TIME:20240905T120000Z
DTEND;VALUE=DATE-TIME:20240905T121500Z
DTSTAMP;VALUE=DATE-TIME:20260306T142541Z
UID:indico-contribution-15-0-105@cern.ch
DESCRIPTION:Speakers: BRUNTHALER\, Andreas ()\nThe GLOSTAR galactic plane 
 survey conducted with the VLA and Effelsberg telescopes led to the detecti
 on of thousands of compact continuum sources in the Galactic Plane with si
 zes of less than one arcsecond. We observed 1782 of these compact sources 
 in the galactic longitude range from 28 to 36 degrees with the VLBA to inv
 estigate the fraction of sources which are detectable with VLBI and to dis
 tinguish between galactic and extragalactic sources based on their proper 
 motions. By measuring scatter broadened source sizes as a function of freq
 uency we also gain invaluable insights into the scattering properties of t
 he interstellar medium. Here we will report on first results from this sur
 vey\, placing sources among the most heavily scattered AGN known to date\,
  which indicate much stronger and more widespread scattering than anticipa
 ted.\n\nhttps://events.mpifr-bonn.mpg.de/indico/event/371/session/15/contr
 ibution/105
LOCATION:CJD Bonn Castell
URL:https://events.mpifr-bonn.mpg.de/indico/event/371/session/15/contribut
 ion/105
END:VEVENT
BEGIN:VEVENT
SUMMARY:VLBI astrometry for OH/IR stars and Period-Luminosity relation in 
 very long period range
DTSTART;VALUE=DATE-TIME:20240905T121500Z
DTEND;VALUE=DATE-TIME:20240905T123000Z
DTSTAMP;VALUE=DATE-TIME:20260306T142541Z
UID:indico-contribution-15-0-63@cern.ch
DESCRIPTION:Speakers: Dr. NAKAGAWA\, Akiharu (Kagoshima Univ.)\nWe will pr
 esent astrometric VLBI studies for OH/IR stars conducted with the Japanese
  VLBI array VERA (VLBI Exploration of Radio Astrometry). \nUsing several O
 H/IR stars\, we have been explored period-luminosity relation (PLR) in the
  quite long pulsation period range ($\\geq$1000 d). \nA preliminary result
  of the new PLR will be presented. \nWe will emphasize advantages of VLBI 
 in parallax measurements of dust-obscured stars\, and complementarity betw
 een VLBI and Gaia will also be mentioned. \n\nIn a late stage of stellar e
 volution with initial masses of $0.8-10M_{\\odot}$\, they spend time as As
 ymptotic Giant Branch (AGB) stars. \nMira variables are thought to be in e
 arly phase of the AGB exhibiting a PLR\, which is a well known tool for di
 stance estimation. \nAs they evolve\, they will be surrounded by dust shel
 ls.\nThen\, due to detection of OH masers and IR excess\, they will be rec
 ognized as OH/IR stars. \nDue to extinction by circumstellar dust\, parall
 ax measurements of the OH/IR stars in optical bands are difficult. \nHowev
 er\, VLBI astrometry for H$_2$O masers associated with the OH/IR stars are
  effective to measure their parallaxes. \nSince OH/IR stars with thick dus
 t shells tend to show quite long pulsation periods ($P \\geq$1000 days)\, 
 extensions of the PLR to longer period range may provide new distance esti
 mator for the OH/IR stars. \nSince they are more massive than typical Mira
  variables\, they can also be used in the study of Galactic dynamics. \n\n
 At the EVN symposium 2016\, we reported the start of new research targetin
 g the OH/IR stars with very long periods. \nNow\, eight years later\, we h
 ave been observed OH/IR stars with periods of 500-1500 days. \nWe present 
 current status of our studies using an OH/IR star NSV17351 together with p
 arallaxes of other sources. \nA prelimialy result of the PLR of $ M_{\\mat
 hrm{bol}} = (-3.31 \\pm 0. 08) \\log P+(-3.94 \\pm 0.20) $ was obtained co
 nsidering spectral energy distributions (SEDs) of the sources.\n\nhttps://
 events.mpifr-bonn.mpg.de/indico/event/371/session/15/contribution/63
LOCATION:CJD Bonn Castell
URL:https://events.mpifr-bonn.mpg.de/indico/event/371/session/15/contribut
 ion/63
END:VEVENT
BEGIN:VEVENT
SUMMARY:Imaging VGOS observations and modeling source structure effects
DTSTART;VALUE=DATE-TIME:20240905T123000Z
DTEND;VALUE=DATE-TIME:20240905T124500Z
DTSTAMP;VALUE=DATE-TIME:20260306T142541Z
UID:indico-contribution-15-0-87@cern.ch
DESCRIPTION:Speakers: Dr. XU\, Ming Hui (GFZ)\nThe new generation of geode
 tic Very Long Baseline Interferometry (VLBI)\, VLBI Global Observing Syste
 m (VGOS)\, is now regularly observing to produce the best geodetic VLBI da
 ta\, with a thermal noise level of about 3 ps. It now approaches to the de
 signed observing strategy\, i.e.\, scan lengths of on average 10 seconds a
 nd switching time of about 20 seconds. However\, the systematic errors due
  to the angular structure of the radio sources are becoming prominent in t
 hese high-precision VGOS observations. It is important to understand\, stu
 dy\, and monitor these systematic errors. Project Astrogeodesy (also a new
  research group at the GFZ)\, funded by European Research Council\, aims t
 o developing a data processing/calibrating pipeline to model these systema
 tic errors. Improvements have been made to derive images of the source str
 ucture -- and subsequently model it with a small number of Gaussian compon
 ents -- through closure imaging at the four bands (3 -- 14 GHz) directly f
 rom VGOS observations on a regular basis. We will report on our imaging re
 sults and the current research activities about source structure in VGOS o
 bservations.\n\nhttps://events.mpifr-bonn.mpg.de/indico/event/371/session/
 15/contribution/87
LOCATION:CJD Bonn Castell
URL:https://events.mpifr-bonn.mpg.de/indico/event/371/session/15/contribut
 ion/87
END:VEVENT
BEGIN:VEVENT
SUMMARY:Densification of VLBI radio sources around the JUICE spacecraft tr
 ajectory during its Venus flyby
DTSTART;VALUE=DATE-TIME:20240905T124500Z
DTEND;VALUE=DATE-TIME:20240905T130000Z
DTSTAMP;VALUE=DATE-TIME:20260306T142541Z
UID:indico-contribution-15-0-50@cern.ch
DESCRIPTION:Speakers: Dr. PERGER\, Krisztina (HUN-REN Research Centre For 
 Astronomy and Earth Sciences)\nThe European Space Agency's (ESA) large-cla
 ss mission Jupiter Icy Moons Explorer (JUICE) was launched on 2023 April 1
 4\, and started its interplanetary journey towards the Jovian system. The 
 primary science goal of the mission is a complex study of the icy Galilean
  moons of Jupiter\, Ganymede\, Europa\, and Callisto. One of the eleven sc
 ientific experiments of JUICE is the Planetary Radio Interferometry and Do
 ppler Experiment (PRIDE). Without a specific on-board payload\, PRIDE will
  use the communication system of the spacecraft to determine its accurate 
 position with respect to bright extragalactic radio sources\, through phas
 e-referencing very long baseline interferometry (VLBI) observations\, pref
 erably in the in-beam mode. Our main goal is to find suitable new referenc
 e sources around JUICE's trajectory to support its navigation on the way t
 o and in the Jovian system. As there is approximately only one known refer
 ence source per 2.5 square degrees alongside the Ecliptic and thus the tra
 jectory of JUICE\, finding new sources and densifying the reference frame 
 is an important amplification of PRIDE. To identify suitable in-beam refer
 ence sources\, test and tune-up data reduction methodology and algorithms\
 , and assess the quality and accuracy of the JUICE state vector determinat
 ion\, we planned several VLBI experiments using the European VLBI Network 
 (EVN)\, the Australian Long Baseline Array (LBA)\, and a global VLBI netwo
 rk. Here we present the results of our latest experiment. These observatio
 ns will serve as a pilot study for finding new potential reference sources
  close to the trajectory of JUICE during its upcoming Venus flyby in Augus
 t 2025. The X-band observations were carried out using 12 antennae of the 
 EVN in February 2024\, targeting 9 weak sources selected from the VLA Sky 
 Survey and the mJIVE-20 collection\, and 3 bright sources from the Radio F
 undamental Catalog (RFC). Our aims are to detect new in-beam phase referen
 ce calibrators among the 9 in-beam targets\, and to link the RFC sources i
 nto the International Celestial Reference Frame.\n\nhttps://events.mpifr-b
 onn.mpg.de/indico/event/371/session/15/contribution/50
LOCATION:CJD Bonn Castell
URL:https://events.mpifr-bonn.mpg.de/indico/event/371/session/15/contribut
 ion/50
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