Physics and astronomy are disciplines primarily driven by experiments and observations. The main research topics of our group is observational studies of fundamental physics of accreting black holes (BHs) and neutron stars (NSs), as well as powerful explosive transient events, such as tidal disruption events and fast radio bursts, by making use of cutting-edge observing facilities in space and on the ground.
The group is led by Prof./Dr. Wenfei Yu, who worked as a postdoc in the world-leading Anton Pannekoek Institute for Astronomy of the University of Amsterdam and in the Center for Theoretical Astrophysics in the Department of Physics at the University of Illinois at Urbana-Champaign. He obtained his Ph.D in particle physics in 1998 from the Institute of High Energy Physics, Chinese Academy of Sciences. Even before, he obtained his MSc in theoretical astrophysics on black hole accretion theory. Therefore his group has unique research experience and achievements covering many aspects of high energy astrophysics and muti-wavelength astronomy, including observation, theory and instrumentation.
The group has kept breaking its own records, many of which are first discoveries made from a Chinese-led group. The group have accesses to a wide range of space or ground frontier facilities, through either competition or collaboration, such as the Neil Gehrels Swift observatory, which is capable of rapid multi-wavelength observations to transients, and the Very Large Array, which is one of the most sensitive telescopes in the radio band. The group has also been playing leading role in those Scientific Working Groups (SWGs) of quite a few planned international space missions or proposed observing facilities in the near future, such as the eXTP (China-EU joint X-ray timing mission), the Sino-French GRB mission (SVOM), and the International Square Kilometer Array (SKA). Dr. Wenfei Yu was awarded a FAST Fellowship in 2017 and has been involved in MeerKAT/ThunderKAT and ASKAP/VAST collaborations on astrophysical transients.
With InsightpHXMT's broad-band soft X-ray and hard X-ray capability, we were able to detect milli-hertz QPOs in the well-known black hole binary Cygnus X-1 with LE, ME and HE on board HXMT and determine the QPO extends beyond 50 keV, see Yan, Rapisarda & Yu, 2021, ApJ, 919, 46 and SHAO News
The discovery paper for a repeating Fast Radio Burst (FRB) FRB190520 (discovered by FAST) has been submitted to Nature. We have contributed significantly to the sub-arc-second localization of this repeating FRB - we led the VLA and VLBA DDT observations for the initial localization and discovery of a persistent radio source in association with the FRB. Check out arXiv211007418
The calibration of our Fast Optical Camera (FOC) is reported in the most recent volume of ACTA ASTRONOMICA SINICA (2021, Vol. 62, 5). By observing a black hole transient MAXI J1820+070 in its 2018 outburst, we have successfully tested the capability of FOC for optical timing observations of compact objects down to a time resolution (frame time) below 6 ms. Congratulations to the team members, past and current, who have worked on the project for a decade !
Physics of black hole accretion has been largely studies in black hole X-ray transients and dwarf novae in the past. Here we present a dedicated timing study of the X-ray variability of black hole soft state to focus on the physics of standard accretion flow. Magnetic properties of the cold accretion disk might be probed through the measurements of the Fourier power spectra, either through the power-law index or the integrated fractional rms. We have fund evidence that we can probe disk inclination in black hole soft state with timing as well. See our new paper Mao & Yu, 2021, RAA accepted .
Congratulations to our old friend Prof./Dr. Chryssa Kouveliotou, the 2021 Shaw Prize winner !
Congratulations to Mr. Dongming Mao, our new Ph.D, for his work on black hole binaries in the past few years in the group !
Our effort to zoom in a repeating FRB has continued. Our regular VLA and VLBA proposals on one of the repeating FRBs got approved as A priority by the TAC (VLA/21B-127 and VLBA/21B-125).
Cygnus X-1 is one of the most well-known black hole X-ray binary in our Galaxy. We report our detections of a mHz low frequency QPO with HXMT data, showing the modulation extends to above ~ 50 keV. See Yan, Ripisarda, and Yu, 2021
COSPAR (Committee on Space Research) is an international organization to promote scientific research in space. Dr. Wenfei Yu starts to serve in COSPAR Commission E: Research in Astrophysics from Space as the vice-Chair. We look forward to promoting scientific exchange and research in astrophysics from space at various levels and scales.
Another work using wide field-of-view hard X-ray telescope BAT on board Swift: A search for hard X-ray bursts simultaneous or quasi-simultaneous to radio bursts in FRB121102 with the wide-field-view hard X-ray monitor BAT on board the Swift mission - just accepted for publication in ApJ, see Sun et al. 2020. The paper was submitted in December 2019, well before the occurrence of the FRB200428 in the Galactic magnetar SGR 1935+2154.
Long type I bursts in NS LMXBs as seen or detected by hard X-ray telescope Swift/BAT (> 15 keV): Type I thermonuclear bursts can be so energetic that a hard X-ray wide field-of-view telescope like Swift/BAT can discover them. See our paper published in ApJ today Lin & Yu 2020, ApJ. We were able to discover one such long burst with BAT. Check out the paper.
FRBs are now thought to originate from magnetar activities (i.e., the most popular model), which are associated with dense, magnetic environments at cosmological distances. Our VLBA DDT observations, targeting at one of such active ones and physics of compact objects and highly extreme environments are performed, aiming at VLBI zoom-in imaging of one of the mysterious FRBs.
Our study of the hard X-ray sky for hard X-ray bursts with the wide-field-view Swift/BAT, including the discovery of an intermediate duration burst or a candidate superburst, has been accepted for the publication of ApJ, see Lin & Yu, 2020. These bursts should come from deep helium burning, as we suggested. The original discovery of the 2018 long duration burst was reported in 2018 and reported as ATEL #11623. These type I bursts are so energetic that, unlike those typical type I bursts (due to thermonuclear burning on the neutron star) which release the emission primarily in the soft X-ray band, these bursts contain many X-ray photons above 15 keV.
More update on time domain/multi-messenger astrophysics of relativistic transients. We just joined the ASKAP/VAST survey collaboration !
Our VLBA DDT program VLBA/20A-396 on a newly localized FRB approved.
Our VLBA 10 hr observation of the nearest TDE AT2019qiz (BY154A) has been performed.
Successful coordinated/simultaneous Swift and FAST observations of a newly localized FRB, once every two days, for a total of two weeks !
Successful precise localization of a Fast Radio Burst (FRB) with the VLA, a great effort achieved from an international collaboration ! (See our VLA DDT program VLA/20A-557).
Continuing our contribution to the MeerkAT/ThunderKAT collaboration - MeerKAT detection of the transient Galactic black hole transient Swift J1842.5-1124, see our Zhang et al. 2020, ATEL #13802. We were able to make the first detection of the Galactic blackhole transient in the radio band to date at about 208 micro Jy/beam.
MeerKAT and Swift/XRT observations of the transient Galactic black hole candidate Swift J1842.5-1124: Non-detection in the radio band with an upper limit of 80 micro Jy/beam. See ATEL 13784 (Zhang et al. 2020)
A VLA DDT program of a radio transient approved
Swift/XRT/UVOT simultaneous observations performed on a radio transient discovered by FAST.
Science for the planned Sino-EU collaborative X-ray mission eXTP "Dense Matter with eXTP" (Watts, Yu, et al. 2019) has got the 2019 excellent paper award of Science China - Physics, Mechanics, & Astronomy. Congratulations to colleagues who contributed in the science working group on ultra-dense matter.
FAST detection of a highly polarized radio burst from SGR 1935+2154 - while no FRBs were detected, we detected a radio burst from the magnetar ! See our report as ATEL #13699 (W. Yu 's affilliation should be --> SHAO).
FAST non-detection of fast radio bursts from SGR J1935+2154 - the first report from the FAST key science project on FRBs. See our report ATEL # 13697
An investigation of long-duration type I bursts - superbursts and intermediate bursts in the hard X-ray band, has just been submitted - see Lin & Yu 2020 preprint. This work followed our initial discovery of the 2018 long burst in a NS LMXB. Special thanks to Jean Int'Zand for suggestions, comments, and hospitality.
有关Fast Radio Burst (FRB) 科学问题的研究建议入选FAST优先和重大项目内容，并进入观测实施期。
MeerKAT radio non-detection of the black hole transient V4641Sgr - see our report (Zhang et al. 2020, ATEL# 13471)
VLBA DDT observation of AT2019qiz - performed !
The Chinese SKA science documents: - we organized/coordinated the team work on radio transients
SKA 科学报告 和 Scientific Probe of Radio Transients
A 6 hour VLBA DDT observation of the nearest TDE AT2019qiz approved !
Collaborative JCMT large project PITCH-BLACK on black holes has just been accepted ! The project is a joint effort of more than 30 astronomers across the globe on black hole transients.
Confirmation of AT2019qiz in the rise of its radio emission (O'Brien, Kaplan, Murphy, Yu and Zhang 2019) ATEL #13334)
First detection of the nearest TDE - AT2019qiz in the radio with ACTA ! Joint effort from colleagues in Australia, US and Shanghai. See O'Brien, Kaplan, Murphy, Yu and Zhang 2019 ATEL #13310
Continuing monitoring of the candidate tidal disruption event AT2019qiz found in the rise, see also (Zhang et al. ATEL #13146; Zhang et al. ATEL #13193)
HXMT ToO observations of a new BH candidate MAXI J0637-430
Tracing the decay of MAX J1807+132 on a weekly cadence
X-ray flaring variability: Rapisarda et al. 2019 ATEL #13173
The first report from our group in the ThunderKAT collaboration - congratulations to Xian Zhang !
MeerKAT observations of MAXI J1807+132: non detection with upper limits at the ~ 100 uJy level (Zhang et al. ATEL #13142)
Discovery of quasi-periodic oscillation feature in MAXI J1807+132 with NICER from our group (Rapisarda et al. 2019, ATEL #13139)
Swift daily monitoring campaign of a tidal disruption event in the early rising phase AT2019qiz started !
Our first paper on Fast Radio Bursts (FRBs) "A search for short-term hard X-ray bursts in the direction of the repeating FRB 121102" has been accepted for publication in ApJ (Sun, Yu et al. 2019), available as arXiv:1909.07626. The study made use of the BAT on board the multi-wavelength space mission Swift.
The first NICER ToO observations (on the X-ray transient MAXI J1807+132) proposed from our group: congratulations to Stefano !
Multi-wavelength campaign on the X-ray transient MAXI J1807+132 in the ThunderKAT collaboration started. The X-ray transient MAXI J1807+132 was found in 2017 and now it undergoes its second outburst in history.
A heavyweight paper on relativistic astrophysics in tidal disruption events has just been accepted for the publication in ApJ
"Probing the Bardeen-Petterson effect in tidal disruption events with spectral line reverberation mapping" (Zhang, Yu, Karas & Dovciak 2019, ApJ):
"Time-resolved X-ray spectroscopy can be a powerful tool to probe the Bardeen-Petterson effect in TDE flares and can be used to measure the Bardeen-Petterson radius as well as put constraint on the black hole mass and spin." This will become one of the most exciting research topics of the eXTP mission in the time domain astrophysics era.
GRID is a student CubSats project led by Tsinghua Univ. to monitor the transient gamma-ray sky in the multi-messenger astronomy era. The first paper of the collaboration has just been accepted to publish in Experimental Astronomy.
Our collaboration with the Prague Relativistic Astrophysics group on the eXTP science on general relativistic effects is awarded grants from both countries - 中国-捷克科技合作委员会第43届例会人员交流项目获批(全国总共17个跨学科项目）。
Graduation ! Dr. Jie Lin is going for a postdoc in Tsinghua Univ., and MSc Miss Yuanming Wang is going to take a Ph.D fellowship to continue in the University of Sydney.
Progress of the China-EU Space eXTP mission: Science News 新闻
Science CHINA Physics, Mechanics & Astronomy: Special topic on the X-ray Timing and Polarimetry Frontier with eXTP
We co-led the contribution to the major scientific objective of the mission - the physics of the ultradense matter: "Dense Matter with eXTP" (Watts, Yu, et al. 2019)
Insight-HXMT (慧眼卫星) has just released the HXMT AO-2 Guest Observer Program. Five proposals on black hole and neutron stars are accepted from our group ! Congratulations !
MWA is one of the precursors of the SKA in Australia. It is a multi-million dollar international low-frequency telescope in Australia's Midwest. We just set up a research project on microquasars in the MWA collaboration.
We focus more on the physics might be learned from signals from the very vicinities of black holes and neutron stars:
Our first paper on Fast Radio Bursts (FRBs) "A search for short-term hard X-ray bursts in the direction of the repeating FRB 121102" has been accepted for publication in ApJ (Sun, Yu et al. 2019), available as arXiv:1909.07626. The study made use of the wide FOV X-ray instrument BAT on board the multi-wavelength space mission Swift.
The second paper on probing dormant supermassive black hole mass and spin and general relativistic effect in tidal disruption flares: "Probing the Bardeen-Petterson effect in tidal disruption events with spectral line reverberation mapping" (Zhang, Yu, Karas & Dovciak 2019, ApJ). Together with our first paper published in ApJ in 2015, these papers lay out the scientific motivation for our on-going ToO triggers for space X-ray observations.
The first collaboration paper from the GRID collaboration led by Tsinghua Univ: GRID - a student CubSats project to monitor the transient gamma-ray sky in the multi-messenger astronomy era (Wen et al 2019, Experimental Astronomy)
Outbursts of low mass X-ray binary transients: relation between the outburst rate and the orbital period (Lin et al. 2019, MNRAS)
Discovery of a new outburst of the black hole transient 4U 1630-47 and its soft energy spectra (Mao, Lin et al. 2018, ATEL #11722)
Discovery of a hard X-ray flare in SAX J1712.6-3739: A likely superburst in the NS LMXB on May 8th, 2018 (Lin & Yu 2018, ATEL #11623)
Further detection of the optical low frequency QPOs in the black hole transient MAXI J1820+070 again but with our Fast Optical Camera (FOC) (Yu et al. 2018, ATEL # 11591)
Discovery of optical low frequency QPOs in a newly discovered black hole transient MAXI J1820+070 with YFOSC on the Lijiang 2.4 m telescope (Yu et al. 2018, ATEL # 11510)
XMM-Newton AO-17: our proposal on extragalactic transients is awarded time again for joint XMM/Swift observations of a future TDE flare
State Transitions in Ultracompact Neutron Star LMXBs: towards the Low Luminosity Limit (Lin & Yu 2018, MNRAS)
Detection of X-ray Spectral State transitions in Mini-outbursts of Black Hole Transient GRS 1939-278 (Yan & Yu 2017, MNRAS)
Discovery of a New Outburst of the Black Hole Transient 1H 1743-322 (Zhang et al. 2017, ATEL # 10599)
Discovery of a New Outburst of the Ultraluminous X-ray Source ESO 243-49 HLX-1 (Yan & Yu 2017, ATEL #10137)
....
Multi-wavelength monitoring, X-ray timing and spectral analysis, and space or ground Target-of-Opportunity observations are widely used in our daily research. Here below are some of our primary research projects:
Project 1: X-ray Timing Studies of Black Holes and Neutron Stars - the Probe of General Relativity (GR) Effects and Ultra-dense Matter
Project 2: Relativistic Line Reverberation in Tidal Disruption Events – the Probe of GR Effects and Mass and Spin of Dormant SMBHs
Project 3: X-ray Monitoring of Black Hole and Neutron Star Transients and Multi-wavelength Target-of-Opportunity Observations – the Investigation of Black Hole Accretion and Jet Physics
Project 4: Energetic Transients in the Multi-wavelength Wide Field-of-View Era - X-ray Transients (Swift, MAXI, HXMT, SVOM), Radio Transients (SKA, FAST), Optical Transients (LSST)
Our research projects are supported by the following major PI grants:
NSFC Key Project (重点项目):
NSFC-CAS Key Project on HXMT Observations of X-ray Binaries (重点项目):
Dr. Zhen Yan (Ph.D of SHAO)
Dr. Shangyu Sun (current postdoc, Ph.D of MPIP 博士后引进交流项目)
Dr. Stefano Rapisarda (current postdoc, Ph.D of U of Amsterdam, CAS PIFI Fellowship 博士后引进交流项目)
Mr. Jie Lin (Ph.D student -> Tsinghua Univ. )
Mr. Dongming Mao (Ph.D student)
Ms. Yuanming Wang (MSc student -> Univ. of Sydney)
Mr. Bing Lv (joint Ph.D student - HUST)
Mr. Xian Zhang (MSc student)
Visiting scientists and students:
Dr. Wenda Zhang (visiting scientist - Ph.D of SHAO in 2015)
Dr. Hui Zhang (visiting scientist - Ph.D of SHAO in 2010)
Mr. Yuexin Zhang (2019 summer student - BSc of Fudan Univ. )
Previous postdocs:
Dr. Holger Stiele (Ph.D of MPE, 2013.4-2015.2)
Dr. Yi Jung Yang (Ph.D of UvA, 2013.11-2014.7)
Dr. Wenfei Yu
Shanghai Astronomical Observatory
80 Nandan Road
Shanghai 200030, China
E-mail: wenfei @shao.ac.cn
[ version updated: 2020.5.1 wenfei @shao.ac.cn ]
