Studying the black widow pulsars PSR J0312–0921 and PSR J1627+3219 in the optical and X-rays

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Table 1.

J0312 and J1627 parameters.

PSR	J0312	J1627
Right ascension α (J2000)	03^h12^m06 $.^{s}$ $.\!\!^\mathrm{s}$ 21465615(2)	16^h27^m52 $.^{s}$ $.\!\!^\mathrm{s}$ 9985(5)
Declination δ (J2000)	−09°21′56 $.^{″}$ $.\!\!^{\prime \prime }$ 55324461(5)	+32°18′26 $.^{″}$ $.\!\!^{\prime \prime }$ 643(8)
Galactic longitude l, deg	191.510	52.970
Galactic latitude b, deg	−52.378	43.209
Spin period P, ms	3.7043355330862(3)	2.1828338203418(5)
Spin period derivative Ṗ, s s⁻¹	1.9723(6) × 10⁻²⁰	5.478(4) × 10⁻²¹
Orbital period P_b, d	0.0974588765(11)	0.165880827(4)
Dispersion measure (DM) pc cm⁻³	20.5	–
Distance D_YMW, kpc	0.82	4.47
Characteristic age $τ_{c} \equiv P / 2 \dot{P}$ $\tau_c\equiv P/2\dot{P}$ , Gyr	3.0	6.3
Observed spin-down luminosity Ė, erg s⁻¹	1.5 × 10³⁴	2.1 × 10³⁴
Minimum companion mass M_{c, min}, M_⊙	0.009	0.022
Mass function f_M, M_⊙	3.9 × 10⁻⁷	6 × 10⁻⁶
P.m. in RA direction μ_αcosδ, mas yr⁻¹	31.7 ± 1.2	1.6 ± 1.4
P.m. in Dec direction μ_δ, mas yr⁻¹	8.9 ± 3.0	−2.8 ± 1.5

Notes. Parameters are taken from the web page of the Third Fermi LAT catalogue of γ-ray pulsars (https://fermi.gsfc.nasa.gov/ssc/data/access/lat/3rd_PSR_catalog/3PC_HTML/) and the Australia Telescope National Facility Pulsar catalogue (Manchester et al. 2005; https://www.atnf.csiro.au/people/pulsar/psrcat/). Numbers in parentheses denote 1σ uncertainties relating to the last significant digit quoted. P.m. ≡ proper motion. D_YMW is the DM distance calculated using the YMW16 (Yao et al. 2017) model for the distribution of free electrons in the Galaxy. For J1627, the value is taken from Smith et al. (2023). The spin-down luminosity is calculated assuming the canonical moment of inertia of 10⁴⁵ g cm². The minimum companion mass is calculated assuming a system inclination of i = 90° and a canonical pulsar mass of M_p = 1.35 M_⊙ (similarly to e.g. Koljonen & Linares 2025). The mass function for J0312 is calculated from the orbital parameters.

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