VERY LONG BASELINE INTERFEROMETRY MEASURED PROPER MOTION AND PARALLAX OF THE γ-RAY MILLISECOND PULSAR PSR J0218+4232

Journal Article · Thu Feb 20 04:00:00 EST 2014 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/782/2/L38· OSTI ID:22363969

Du, Yuanjie; Chen, Ding ^[1]; Yang, Jun; Campbell, Robert M. ^[2]; Janssen, Gemma; Stappers, Ben ^[3]

---

1. National Space Science Center, Chinese Academy of Sciences, No. 1 Nanertiao, Zhongguancun, Haidian district, Beijing 100190 (China)
2. Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo (Netherlands)
3. University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire, SK11 9DL (United Kingdom)

PSR J0218+4232 is a millisecond pulsar (MSP) with a flux density ∼0.9 mJy at 1.4 GHz. It is very bright in the high-energy X-ray and γ-ray domains. We conducted an astrometric program using the European VLBI Network (EVN) at 1.6 GHz to measure its proper motion and parallax. A model-independent distance would also help constrain its γ-ray luminosity. We achieved a detection of signal-to-noise ratio S/N >37 for the weak pulsar in all five epochs. Using an extragalactic radio source lying 20 arcmin away from the pulsar, we estimate the pulsar's proper motion to be μ{sub α}cos δ = 5.35 ± 0.05 mas yr{sup –1} and μ{sub δ} = –3.74 ± 0.12 mas yr{sup –1}, and a parallax of π = 0.16 ± 0.09 mas. The very long baseline interferometry (VLBI) proper motion has significantly improved upon the estimates from long-term pulsar timing observations. The VLBI parallax provides the first model-independent distance constraints: d=6.3{sub −2.3}{sup +8.0} kpc, with a corresponding 3σ lower-limit of d = 2.3 kpc. This is the first pulsar trigonometric parallax measurement based solely on EVN observations. Using the derived distance, we believe that PSR J0218+4232 is the most energetic γ-ray MSP known to date. The luminosity based on even our 3σ lower-limit distance is high enough to pose challenges to the conventional outer gap and slot gap models.

• OSTI ID: 22363969
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 782; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COSMIC GAMMA SOURCES
DETECTION
DISTANCE
FLUX DENSITY
GHZ RANGE
INTERFEROMETRY
LIMITING VALUES
LUMINOSITY
PROPER MOTION
PULSARS
SIGNAL-TO-NOISE RATIO
X RADIATION