Periodic Reporting for period 1 - GW (Analysing the heavy element factories of the Universe : photometric and spectroscopic sample study of kilonovae)
Período documentado: 2019-11-01 hasta 2021-10-31
This MC project is titled “Analysing the heavy element factories of the Universe: photometric and spectroscopic sample study of kilonovae (KNe)”. The project aims to address a question "What roles do KNe play in the production of heavy elements in the Universe?" By working at Oskar Klein Centre, I have access to Electromagnetic Counterparts of Gravitational Wave sources at the Very Large Telescope (ENGRAVE), which is a leading project set up with the explicit goal to follow-up and monitor gravitational wave electromagnetic counterparts. However, there is no KN found during the LIGO-Virgo O3 period and thus it is not possible to do a sample study of KNe, as mentioned as the potential risk in the project proposal. Hence this project naturally focuses on what other sources of heavy elements there are, with massive stars being another potential avenue, and supernovae (SNe) could provide another principle source of heavy elements in the Universe.
In order to study SNe, firstly we need to find them. Since April 2019, I co-lead one of the largest public surveys in the European Southern Observatory (ESO), advanced Public ESO Spectroscopic Survey of Transient Objects (ePESSTO+). This programme provides immediate public classifications and classification spectra for transients, mainly SNe. We report 1144 classifications that make a quarter of all transient classification in the years of 2020 and 2021 and leans towards exploring new exciting transient populations. I am very active on actions of open science to make observational alerts and data public reachable in real time. By making scientific data available, “you’re enabling a lot of new science by the community to go forward in a more efficient and powerful way.” says Kyle Cranmer, a professor at New York University (Meredith Fore, 2019). I have led 60 reports in Transient Name Server AstroNote, Astronomer’s Telegram and GRB Coordinates Network circulars. By working within sky surveys, I also have been involved in more than 1500 reports to announce newly discovered transient objects, in order to encourage the community to take further follow-up observations. Our society should be benefit from the spirit of open data like this.
I work within ENGRAVE collaboration. It is a new approach and a new attempt of many different transient communities (e.g. supernovae, gamma-ray bursts, active galactic nucleus, etc.) all working together to use ESO facilities with such big amount of telescope ToO time. There are 350 scientists within the collaboration. When looking into latest big scientific achievements, they are more often done by big groups instead of individuals. Big European wide collaborations are necessary in science as they are in society, economy and politics. A common European approach for, for example climate actions, would be much more effective than local actions. On the other hand, societies are very excited about the Cosmos and GWs. Knowing where the heavy elements come from, where the Gold comes from are important science topics, and societies are curious about the origin of the Universe.
In order to study SNe, firstly we need to find them. Since April 2019, I co-lead one of the largest public surveys in the European Southern Observatory (ESO), advanced Public ESO Spectroscopic Survey of Transient Objects (ePESSTO+). This programme provides immediate public classifications and classification spectra for transients, mainly SNe. We report 1144 classifications that make a quarter of all transient classification in the years of 2020 and 2021 and leans towards exploring new exciting transient populations. I am very active on actions of open science to make observational alerts and data public reachable in real time. By making scientific data available, “you’re enabling a lot of new science by the community to go forward in a more efficient and powerful way.” says Kyle Cranmer, a professor at New York University (Meredith Fore, 2019). I have led 60 reports in Transient Name Server AstroNote, Astronomer’s Telegram and GRB Coordinates Network circulars. By working within sky surveys, I also have been involved in more than 1500 reports to announce newly discovered transient objects, in order to encourage the community to take further follow-up observations. Our society should be benefit from the spirit of open data like this.
I work within ENGRAVE collaboration. It is a new approach and a new attempt of many different transient communities (e.g. supernovae, gamma-ray bursts, active galactic nucleus, etc.) all working together to use ESO facilities with such big amount of telescope ToO time. There are 350 scientists within the collaboration. When looking into latest big scientific achievements, they are more often done by big groups instead of individuals. Big European wide collaborations are necessary in science as they are in society, economy and politics. A common European approach for, for example climate actions, would be much more effective than local actions. On the other hand, societies are very excited about the Cosmos and GWs. Knowing where the heavy elements come from, where the Gold comes from are important science topics, and societies are curious about the origin of the Universe.
In this MC project, the objectives and goals have been addressed via three specific work packages: (1) Identify fast-evolving transients like KNe. (2) Classify stellar explosions and study the physics of these transients. (3) Investigate the role of SLSNe for dust production in the early universe.
I lead a volume-limited survey to discover KNe, called Kinder (KN finder) project, by a complete search for nearby transients found in optical surveys. This is independently of GW detections, and are therefore named “without GW triggers”. We do not find a KN, but we report several interesting events to the transient community through the Transient Name Server AstroNote, named AT2021gca (Chen et al. 2021), AT2021aczp (Yang et al. 2021) and AT2022cmc (Chen et al. 2022). The last object is a rare relativistic jet Tidal Disruption Event as the disruption of a star by a cosmological black hole (Pasham et al. 2022). I work within ENGRAVE collaboration to build the largest dataset of KNe, in order to determine the ejecta mass distribution of KNe. Although there is no KN found in O3 period, our observations allow us to place limits on the presence of any counterpart to the GW sources (Ackley et al. 2020).
I achieve a leadership on the international collaborations. I co-lead ePESSTO+ with C. Inserra (Cardiff) and J. Anderson (ESO Chile). There are 270 scientists within the collaboration. The operational mode of 90 nights during a year uses 3.58m-New Technology Telescope at La Silla Observatory. I am the chair of the Target and Alert Team and a member of the science board. I am mainly responsible for setting up and managing a team to select targets for classifications, to give a tutorial for team members for choosing good and interesting objects, to approve and coordinate follow-up observation requests from different science groups and to be on-call during observations when team members have questions. Based on my contribution as a builder of ePESSTO+ and data collection, I co-author 19 publications. We studied different populations of core-collapse SNe, which infers different stellar evolution path so the massive stars end up in different subtypes of SNe. We also focus on unusual stellar transients, such as fast evolving objects from white dwarf star mergers. I particularly explore the brightest transients such like superluminous SNe (SLSNe), to address the question about their role on dust production in the early universe.
I lead a volume-limited survey to discover KNe, called Kinder (KN finder) project, by a complete search for nearby transients found in optical surveys. This is independently of GW detections, and are therefore named “without GW triggers”. We do not find a KN, but we report several interesting events to the transient community through the Transient Name Server AstroNote, named AT2021gca (Chen et al. 2021), AT2021aczp (Yang et al. 2021) and AT2022cmc (Chen et al. 2022). The last object is a rare relativistic jet Tidal Disruption Event as the disruption of a star by a cosmological black hole (Pasham et al. 2022). I work within ENGRAVE collaboration to build the largest dataset of KNe, in order to determine the ejecta mass distribution of KNe. Although there is no KN found in O3 period, our observations allow us to place limits on the presence of any counterpart to the GW sources (Ackley et al. 2020).
I achieve a leadership on the international collaborations. I co-lead ePESSTO+ with C. Inserra (Cardiff) and J. Anderson (ESO Chile). There are 270 scientists within the collaboration. The operational mode of 90 nights during a year uses 3.58m-New Technology Telescope at La Silla Observatory. I am the chair of the Target and Alert Team and a member of the science board. I am mainly responsible for setting up and managing a team to select targets for classifications, to give a tutorial for team members for choosing good and interesting objects, to approve and coordinate follow-up observation requests from different science groups and to be on-call during observations when team members have questions. Based on my contribution as a builder of ePESSTO+ and data collection, I co-author 19 publications. We studied different populations of core-collapse SNe, which infers different stellar evolution path so the massive stars end up in different subtypes of SNe. We also focus on unusual stellar transients, such as fast evolving objects from white dwarf star mergers. I particularly explore the brightest transients such like superluminous SNe (SLSNe), to address the question about their role on dust production in the early universe.
During the period of MC project from Nov. 2019 to Oct. 2021, I have published 18 refereed publications (including 1 second author, 1 third author). I have one first-authored paper recently submitted to Nature Astronomy under review process (Chen et al. 2021, eprint arXiv:2109.07942 September 2021, 9 citations so far).
One main science result I archive is to address a considerable debate on the main producers of dust in the early Universe. SNe are an attractive candidate, not least because they can produce dust very early in the Universe (compared to other channels such as AGB stars that will not produce dust on such a short timescale). However, a question remains as to whether core-collapse supernovae form sufficient quantities of dust. In my first-authored paper, we present a unique late-time infrared dataset for the nearby SLSN 2018bsz. From modelling the infrared evolution of this SN we find that it forms ten times more dust than normal core-collapse SNe at similar epochs. Together with the preference of SLSNe for low mass, low metallicity host galaxies, we suggest that similar supernovae may be a significant contributor to dust formation in the early Universe. I believe our exciting results of SLSN 2018bsz with dust formation will help spur interest in a potential new channel for dust formation in the early Universe. This is especially timely given the coming era of the James Webb Space Telescope. Finally, even we do not find any KN. I believe that by detailed studying such fast-evolving objects can help us to identify a KN in the future GW events and/or without GW triggers, and it can better constrain the rate of KNe and allow us to accurately compare with the abundance of elements that presents in the Universe.
One main science result I archive is to address a considerable debate on the main producers of dust in the early Universe. SNe are an attractive candidate, not least because they can produce dust very early in the Universe (compared to other channels such as AGB stars that will not produce dust on such a short timescale). However, a question remains as to whether core-collapse supernovae form sufficient quantities of dust. In my first-authored paper, we present a unique late-time infrared dataset for the nearby SLSN 2018bsz. From modelling the infrared evolution of this SN we find that it forms ten times more dust than normal core-collapse SNe at similar epochs. Together with the preference of SLSNe for low mass, low metallicity host galaxies, we suggest that similar supernovae may be a significant contributor to dust formation in the early Universe. I believe our exciting results of SLSN 2018bsz with dust formation will help spur interest in a potential new channel for dust formation in the early Universe. This is especially timely given the coming era of the James Webb Space Telescope. Finally, even we do not find any KN. I believe that by detailed studying such fast-evolving objects can help us to identify a KN in the future GW events and/or without GW triggers, and it can better constrain the rate of KNe and allow us to accurately compare with the abundance of elements that presents in the Universe.