(May 2024) The recent Gaia data release 3 has resulted in an abundance of bright metal-poor candidates, for example using the Pristine photometric method (Martin, Starkenburg et al. 2023). We successfully followed up a large sample of very/extremely metal-poor stars with spectra using the Isaac Newton Telescope (INT). In this work, we study their dynamical properties - e.g. are they mostly prograde or retrograde? what substructures do they belong to? Have a look at the paper for all the details: 

Viswanathan et al. (2024, preprint): link

(August 2023) Using the recently commissioned GHOST spectrograph at the Gemini South telescope, we studied the detailed chemistry of an intriguing PIGS star that is moving on an elliptical orbit close to the Galactic plane. Our analysis reveals it has been enriched by only a few (energetic) supernovae, and that it likely formed in a small dwarf galaxy that was brought into the Milky Way during early Galactic assembly. All the details can be found here: 

Sestito et al. (2023, preprint): link

(August 2023) Exciting news: our first data release is now available! We also extend the "Pristine-like photometric metallicities" to the full sky using synthetic CaHK magnitudes derived from the Gaia BP/RP spectra. These magnitudes have also been extremely useful to calibrate the Pristine photometry. Combined, both catalogues include more than 2 million metal-poor star candidates as well as more than 200,000 and ~8,000 very and extremely metal-poor candidates. Have a look and explore! The preprint can be found here: 

Martin & Starkenburg et al. (2023): link

(May 2023) In this paper we study an inner Galaxy carbon-enhanced metal-poor (CEMP) in detail, and derive abundances for 32 different elements. We find that this star is in a binary system, and that it is enhanced in both slow and rapid neutron-capture process elements − the first of its kind in the Galactic bulge. When we fit different model predictions, the best fit is for intermediate neutron-capture models. Read more here: 

Mashonkina et al. (2023): link

(April 2023) In preparation for Pristine follow-up with WEAVE, we have explored the extreme regions of the Pristine colour-colour space by targeting stars with photometric [Fe/H] < −3.5 for high-resolution spectroscopic follow-up. We found that it is crucial to remove photometrically variable stars for a clean selection of true extremely metal-poor stars. For more details, have a look at our latest paper: 

Lombardo et al. (2023): link

(April 2023) In the latest Pristine Dwarf Galaxy Survey paper, we study the Hercules dwarf galaxy. We find three new members using our metallicity-sensitive photometry, one of which is located in the very outskirts of the dwarf galaxy. After careful removal of foreground contamination, we find that there is no sign of a velocity gradient in Hercules, and conclude that there is no clear evidence for tidal disruption of this dwarf galaxy. Read more:

Longeard et al. (2023, preprint): link

(April 2023) This week we are meeting on La Palma, La Isla Bonita, to discuss the latest updates and plans for the Pristine survey. One of the highlights: seeing the WEAVE multi-object spectroscopic instrument on the William Herschel Telescope! We are excitedly looking forward to the upcoming WEAVE spectra, especially for (Pristine-selected) extremely metal-poor stars. 

(January 2023) In the latest Pristine paper we combined the strengths of photometric pre-selection of metal-poor candidates from Pristine with the large LAMOST spectroscopic database, with the goal of finding the undiscovered most metal-poor stars in LAMOST. We followed up a number of promising candidates using the GTC, and present our results here:

Arentsen et al. (2023, accepted for publication in MNRAS): link

(November 2022) In this work we selected very bright (9.5 < G < 11) metal-poor candidates from Pristine photometry and observed them with high-resolution spectroscopy. We focused on the often-neglected abundances copper and zinc, which are sensitive probes of Pair Instability Supernovae (PISNe) events. Have a read of the paper for more details: 

Caffau, Lombardo et al. (2023): link

Figure caption: relative strength of the two DIBs at 442.8nm and 862.1nm as a function of reddening (top) and Galactic latitude (bottom). If the two DIBs had a similar carrier and/or similar spatial distributions, their ratio should not show clear trends - but this is not what we find. 

(March 2022) This week there are two new Pristine papers out on the fascinating and puzzling extremely metal-poor C-19 system (see previous post). Yuan et al. present UVES spectroscopy of seven member stars (among which two new members), and find that chemically C-19 looks like a globular cluster (GC) stream, but dynamically it is hotter than expected for a stream of GC origin. Errani et al. study the origin of C-19 using N-body simulations, and find that one way to reproduce the characteristics of C-19 would be if its GC progenitor was embedded in a dark matter halo − something not typically expected for GCs. There might be a second part of the stream hiding in a different region of the sky, which could shed more light on the properties of the stream progenitor. Stay tuned for more on C-19 in the future! 

Yuan et al. (2022, preprint): link
Errani et al. (2022, preprint): link

(January 2022) In this paper we use the powerful combination of the Pristine photometric metallicities with the stream discoveries from STREAMFINDER + Gaia EDR3. We estimate metallicities for 26 stellar streams - several of these streams are new candidates, and three of the streams appear to be extremely metal-poor! Read more: 

Martin et al. (2022, preprint): link

(September 2021) One of the main purposes of the Pristine survey is to identify and study in detail the most metal-poor stars. In this paper, we present new data for two previously discovered ultra metal-poor stars, Pr 221 and Pr 237. We derive non-LTE corrected abundances, and find that both stars likely had low-energy supernova progenitors. Read more here: 

Lardo et al. (2021, preprint): link 

(July 2021) In the fourth instalment of the Pristine Dwarf-Galaxy Survey, we studied the outskirts of the ultrafaint dwarf galaxy Boötes I, using spectra from AAT with AAOmega+2dF. We detect a velocity gradient and a metallicity gradient, and we find a larger elongation than previously found. These observations suggest that Boötes I may have been affected by tidal interactions with the Milky Way. Read more: 

Longeard et al. (2021, preprint): link

(June 2021) In this new Pristine paper, we combine our CaHK photometry with the excellent astrometry from Gaia EDR3 to study the rotational properties of stars towards the Galactic anti-centre. Intriguingly, we find a well populated extension of the kinematical thin disc down to [Fe/H] ~ −2, with a scarcer extension reaching the extremely metal-poor regime, down to [Fe/H] ∼ −3.5 dex. To read more:

Fernández-Alvar et al. (2021, preprint): link

(May 2021) In the newest Pristine Inner Galaxy Survey (PIGS) paper, we study the occurrence of carbon-enhanced metal-poor (CEMP) stars in the bulge region. Previously only a handful of CEMP stars were known there, and with PIGS we increase this by 96 CEMP stars! However, the fraction of CEMP stars seems to be smaller than in the rest of the halo. Why could that be? Read more:

Arentsen et al. (2021): link

(March 2021) This year we met online for our "face-to-face" collaboration meeting, which was very fruitful despite happening quite early and/or late across various timezones. We discussed ongoing data efforts, projects, papers, proposals and interesting related science - there are a lot of exciting things happening, so keep an eye out!

(June 2020) One of the most challenging places to look for metal-poor stars is in the Galactic bulge. It is plagued by lots of dust, stellar crowding and huge numbers of metal-rich stars that need to be filtered out. In the recent second Pristine Inner Galaxy Survey (PIGS) paper, we present our successful efforts at finding these stars. 

Arentsen et al. (2020): link 

(May 2020) It is not trivial to determine the nature of the faintest satellites around the Milky Way – globular clusters and small dwarf galaxies can look very similar. One particularly challenging case is that of Sagittarius II, which was also the topic of a previous Pristine paper. In this new paper we present convincing evidence that this system is a globular cluster, although it is quite unique due to its relatively large size. 

Longeard et al. (2020): link

(March 2020) In the Pristine XI paper, we analyse a sample of low-resolution spectra of metal-poor stars, observed with FORS2 at the ESO VLT. We test the power of combining Gaia information with the Pristine CaHK photometry to pre-select metal-poor candidates. 

Two interesting results: we find some very metal-poor stars that are not enhanced in α-elements, and we find that this sample has a low fraction of carbon-enhanced metal-poor (CEMP) stars. A deeper investigation of both is necessary in the future. 

Caffau et al. (2020): link

(February 2020) From February 10-14, we are meeting at the ISSI in Bern, Switzerland for our Pristine collaboration meeting. Since the team is always growing, these meetings are useful to hear what's going on. Besides such updates, we have two days of discussion on preparation for WEAVE. We are excited about the next few years! 

Our ISSI website: https://www.issibern.ch/teams/pristine/

(January 2020) Both from the theoretical and the observational perspective, the number of extremely and ultra metal-poor stars in the Milky Way is poorly constrained. In this work, we use the unique capabilities of Pristine to produce photometric metallicities down to [Fe/H] = −4 for ten thousands of (turnoff) stars. We find that there may be more of the most metal-poor stars than expected previously!

Youakim et al. (2020): link 

(November 2019) Today marks a special day: the tenth Pristine paper is now available as a preprint! In this paper, we studied the orbital properties of our spectroscopic Pristine sample and a sample of LAMOST very metal-poor stars. We found that many of them have orbits that stay within the plane of the Milky Way, which is quite unexpected!

Sestito et al. (2020): link 

(October 2019) We are happy to present the first paper in the Pristine Inner Galaxy Survey (PIGS) series! In this paper, we study the kinematics of metal-poor stars in the Galactic bulge region.

Arentsen et al. (2019): link

(October 2019) We are skipping two papers into the future: the preprint for the Pristine IX paper is now available. In it we look at a sample of bright (V<15) very metal-poor stars with the CFHT ESPaDOnS spectrograph, studying a subset of abundances and the orbital properties of the stars. 

Venn et al. (preprint): link

(May 2019) The fifth Pristine survey paper (Bonifacio et al. 2019) is now accepted and online. In this paper, we determined atmospheric parameters, chemical abundances and orbital parameters for 40 bright Pristine candidates observed with SOPHIE@OHP.

We investigated a new method for estimating metallicity, Teff and log g combining Pristine photometry with Gaia photometry and parallaxes.

Links to the paper: MNRAS or open access

(October 2018) - Recently, the Pristine survey discovered of one of the most metal-poor stars known. A press release can be found here. 

(September 2018) - Recently, we had our Pristine face-to-face meeting at the NRC Herzberg Institute in Victoria, Canada. We shared updates about the photometry, low- and high-resolution spectroscopic follow-up and different ongoing projects. We are looking forward to publishing many interesting papers in the (near) future!