# Exotic objects (`data/exotic_objects.csv`) — sources and terms

`data/exotic_objects.csv` lists pulsars, magnetars, isolated neutron stars and
black holes for the holo map (`scripts/exotic_objects.gd`). It is generated by
`tools/build_exotic.py` (run it to reproduce the file). The table is a
compilation of published measurements. Expanse distributes it under
**Creative Commons Attribution 4.0 (CC BY 4.0)** —
https://creativecommons.org/licenses/by/4.0/ — and asks users to keep the
catalogue citations below, which the catalogues request.

## Catalogues

* **ATNF Pulsar Catalogue**, version 2.6.1 — Manchester, R. N., Hobbs, G. B.,
  Teoh, A. & Hobbs, M. 2005, *AJ* 129, 1993 —
  https://www.atnf.csiro.au/research/pulsar/psrcat/. The catalogue asks users
  to cite this paper. Used for the pulsar positions, spin periods and
  period derivatives (measured), dispersion measures, parallaxes and the
  catalogue's distances (`DIST`: parallax where one exists, otherwise an
  independent estimate `DIST_A` or the YMW16 dispersion-measure model),
  dipole surface fields and characteristic ages (derived, so tagged
  *inferred*), binary companion types and orbital periods. Rows were taken
  with the catalogue's web query on 2026-09-27: every pulsar with
  `Dist < 0.32 kpc`, plus the named pulsars in `ATNF_FAMOUS`. The build tool
  holds that snapshot and the query URL.
* **McGill Online Magnetar Catalog** — Olausen, S. A. & Kaspi, V. M. 2014,
  *ApJS* 212, 6 — https://www.physics.mcgill.ca/~pulsar/magnetar/main.html
  (table `TabO1.csv`). Its authors allow use of the information and ask
  users to cite the paper and give the URL. Used for the magnetar positions,
  periods and period derivatives (measured), and for dipole fields, ages and
  distances (inferred; the per-object distance reference key is kept in
  `dist_method`). Candidates with no measured period, and objects with no
  distance, are left out.

## Literature (per object; also in the `*_ref` columns)

* Vela Pulsar distance: Dodson et al. 2003, ApJ 596, 1137 (VLBI parallax).
* Geminga distance: Faherty, Walter & Anderson 2007, Ap&SS 308, 225 (HST parallax).
* PSR J0437−4715: Reardon et al. 2016, MNRAS 455, 1751 (distance); Reardon et al.
  2024, ApJL 971, L18 (mass); Choudhury et al. 2024, ApJL 971, L20 (NICER radius).
* PSR B0656+14: Brisken et al. 2003, ApJ 593, L89. PSR B0950+08: Brisken et al.
  2002, ApJ 571, 906. PSR J2144−3933, J0108−1431: Deller et al. 2009, ApJ 701, 1243.
* Crab Pulsar distance: Trimble 1973, PASP 85, 579 (as `data/deep_sky.csv`).
* Hulse–Taylor mass: Weisberg & Huang 2016, ApJ 829, 55. Double Pulsar: Kramer
  et al. 2021, PRX 11, 041050. PSR J0030+0451: Riley et al. 2019, ApJL 887, L21.
  PSR J0740+6620: Fonseca et al. 2021, ApJL 915, L12; Riley et al. 2021, ApJL 918,
  L27. PSR J0952−0607: Romani et al. 2022, ApJL 934, L17.
* The Magnificent Seven: positions from Kaplan 2008 (AIP Conf. Proc. 968, 129)
  and Haberl 2007 (Ap&SS 308, 181); RX J1856.5−3754 distance Walter et al. 2010,
  ApJ 724, 669; RX J0720.4−3125 Kaplan, van Kerkwijk & Anderson 2007, ApJ 660,
  1428; the other five from X-ray absorption and a 3D ISM model, Posselt et al.
  2007, Ap&SS 308, 171 (inferred). Timing: van Kerkwijk & Kaplan 2008, ApJ 673,
  L163; Kaplan & van Kerkwijk 2005 (ApJ 628, L45; ApJ 635, L65), 2009 (ApJ 692,
  L62; ApJ 705, 798), 2011 (ApJ 740, L30).
* SGR 1935+2154 distance: Zhou et al. 2020, ApJ 905, 99 (host SNR G57.2+0.8).
* Gaia BH1: El-Badry et al. 2023, MNRAS 518, 1057. Gaia BH2: El-Badry et al.
  2023, MNRAS 521, 4323. Gaia BH3: Gaia Collaboration, Panuzzo et al. 2024,
  A&A 686, L2.
* Cygnus X-1: Miller-Jones et al. 2021, Science 371, 1046. V404 Cygni:
  Miller-Jones et al. 2009, ApJ 706, L230; Khargharia et al. 2010, ApJ 716, 1105;
  Casares et al. 1992, Nature 355, 614. A0620−00: Cantrell et al. 2010, ApJ 710,
  1127; McClintock & Remillard 1986, ApJ 308, 110. GRS 1915+105: Reid et al. 2014,
  ApJ 796, 2; Steeghs et al. 2013, ApJ 768, 185. MAXI J1820+070: Atri et al. 2020,
  MNRAS 493, L81; Torres et al. 2019, ApJL 882, L21; 2020, ApJL 893, L37.
* M87*: Event Horizon Telescope Collaboration 2019, ApJL 875, L1 and L6.
* Sgr A* (shown on the deep-sky Galactic Centre, not duplicated here): GRAVITY
  Collaboration 2022, A&A 657, L12 (mass); EHT Collaboration 2022, ApJL 930, L12.
* White-dwarf companions (`ExoticObjects.WHITE_DWARF_COMPANIONS`): Sirius B —
  Bond et al. 2017, ApJ 840, 70; Barstow et al. 2005, MNRAS 362, 1134. Procyon B —
  Bond et al. 2015, ApJ 813, 106. 40 Eridani B — Bond et al. 2017, ApJ 848, 16.

## Provenance

Every value in the CSV has a tag column (`dist_src`, `period_src`,
`derived_src`, `mass_src`, `radius_src`, `orbit_src`): *measured* for
observations (pulse timing, parallax, dynamical masses, orbital periods),
*inferred* for values derived through a model (dipole field
B = 3.2 × 10^19 (P Ṗ)^½ G, characteristic age P / 2Ṗ, dispersion-measure and
X-ray-absorption distances, association distances). The one-line
descriptions summarise the cited papers.