The R-Process Alliance: abundances of 2000 metal-poor stars

Rationale

How to make gold and silver? The long-sought-after answer to this question remains one of the most challenging open problems that ties together nuclear physics with astronomy. Heavy elements like gold and silver are produced in the so-called rapid neutron-capture (r)-process. This process only occurs in rare explosive events in the Universe, like supernovae (SNe) and neutron star mergers (NSMs), making it hard for astronomers to gather direct observations of the element creation. Likewise, it is difficult for nuclear physicists to recreate and study the nuclear process in the laboratory. These obstacles are why we today, almost seven decades after the theoretical prediction of the r-process, still don’t know where in the Universe gold and silver are made. This is the question the R-Process Alliance (RPA) is trying to answer. 

The RPA is an interdisciplinary team of researchers from the astronomy and nuclear physics communities connected to IReNA with an interest in solving the big questions related to the astrophysical r-process. The first phase of the RPA work has been focused on building a stellar sample for this work. To date, the RPA has collected so-called snapshot spectra of ∼2000 stars. These stars are selected to be bright (V < 13.5), metal-poor ([Fe/H] < −2 and cold (Teff < 5500) to facilitate abundance derivation of the neutron-capture elements Strontium, Barium, and Europium, used to characterize the r-process enrichment. Analysis of this sample is now underway with an expected finish date in spring 2026. This will be the largest homogeneously analysed sample of metal-poor stars to date, and will provide the first statistical dataset to address key questions regarding the rate of the r-process, the need for multiple sites, and the characteristics of these sites.

The purpose of the proposed meeting is (1) for the RPA core and associated students to plan the next steps of the RPA ensuring the potential of this dataset is fully explored and (2) to present the results from this new, unique stellar dataset to researchers from other areas of astronomy and work together to explore this data to advance our understanding of the r-process.

Dates

November 4-7, 2025 (Tuesday-Friday)

Workshop program

Location

University of California--Livermore Collaboration Center (UCLCC)
Lawrence Livermore National Laboratory
7000 East Ave.
Livermore, CA 94550

B6675 Rooms: Golden Gate and Tahoe

The UCLCC is located on the east side of the lab, outside the gate. From 580, take the Greenville Rd. edit south. Turn right at the Lupin Way light, then an immediate right into the parking lot. If you reach the LNLL east gate, you've gone too far.

Places to stay

There are many hotels along I-580.

• DoubleTree by Hilton Livermore (from $130/night)

• Fairfield Inn & Suites Livermore (from $133/night)

• Hawthorn Suites by Wyndham Livermore Wine Country (from $142/night)

• Hampton Inn Livermore (from $126/night)

• Quality Inn & Suites Livermore Wine Country (from $86/night)

Walking/commuting by public transport from any of these hotels to the LVOC is not feasible. Please also note that the square mile enclosed by Vasco Rd. (west), Patterson Pass Rd. (north), Greenville Rd. (east), and Tesla Rd. (south) is not public property. Any bus routes that appear to travel within these bounds are limited to LLNL employees and official badged visitors only.

Code of Conduct

CeNAM workshops and conferences are community events intended for networking and collaboration as well as learning. We value the participation of every attendee and want all attendees to have an enjoyable and productive experience. Accordingly, all attendees are expected to show respect and courtesy to other attendees throughout the workshop and to abide by the following Code of Conduct. Any participant who wishes to report a violation of this policy is encouraged to speak to Terese Hansen or Charli Sakari, as they have agreed to serve as points of contact (or if desired, to another member of the organizing team). Thank you for helping make this a welcoming, friendly event for all.

Code of Conduct

This code of conduct applies to all participants in The R-Process Alliance: abundances of 2000 metal-poor stars. We welcome comments and suggestions.

CeNAM workshops and conferences are committed to providing a welcoming, inclusive, professional, and safe environment for everyone that encourages the free expression and exchange of scientific ideas and is characterized by an atmosphere of tolerance, equity, and mutual respect, regardless of race and other personal attributes. Harassment or bullying in any form will not be tolerated. All communication should be appropriate for a professional audience including people of many different backgrounds. Be kind to others. Do not insult or put down other attendees. Behave professionally.

Harassment includes offensive verbal comments or jokes related to nationality, gender, sexual orientation, disability, physical appearance, body size, race, religion, sexual images in public spaces, deliberate intimidation, stalking, following, harassing photography or recording, sustained disruption of talks or other events, inappropriate physical contact, and unwelcome sexual attention.

Bullying is defined as unwelcome or unreasonable behavior that demeans, intimidates, humiliates, or sabotages people, either as individuals or as a group. It includes physical bullying, verbal abuse, disparagement, intimidation, exclusion, or spreading personal rumors.

Participants asked to stop unacceptable behavior are expected to comply immediately. CeNAM will not allow retaliation against any individual who makes a report of known or suspected code of conduct violation. Sanctions against attendees violating these rules are at the sole discretion of the conference organizers and may range from warnings to being asked to leave the event, and exclusion from future CeNAM sponsored meetings.

Contact

Organizers: Terese Hansen (Stockholm University), Erika Holmbeck (LLNL, local organizer)

Additional questions: rprocessalliance@gmail.com

Registration

Use the Google form here if you're interested in attending. The number of in-person participants is limited. For in-person attendance, please register by Friday, 10 October 2025. Virtual attendees can register up to Friday, 31 October 2025.