Measuring the distance to the black hole candidate X-ray binary MAXI J1348–630 using H i absorption

ABSTRACT We present neutral hydrogen (H i) absorption spectra of the black hole candidate X-ray binary (XRB) MAXI J1348–630 using the Australian Square Kilometre Array Pathfinder (ASKAP) and MeerKAT. The ASKAP H i spectrum shows a maximum negative radial velocity (with respect to the local standard of rest) of −31 ± 4 km s−1 for MAXI J1348–630, as compared to −50 ± 4 km s−1 for a stacked spectrum of several nearby extragalactic sources. This implies a most probable distance of $2.2^{+0.5}_{-0.6}$ kpc for MAXI J1348–630, and a strong upper limit of the tangent point distance at 5.3 ± 0.1 kpc. Our preferred distance implies that MAXI J1348–630 reached 17 ± 10 per cent of the Eddington luminosity at the peak of its outburst, and that the source transited from the soft to the hard X-ray spectral state at 2.5 ± 1.5 per cent of the Eddington luminosity. The MeerKAT H i spectrum of MAXI J1348–630 (obtained from the older, low-resolution 4k mode) is consistent with the re-binned ASKAP spectrum, highlighting the potential of the eventual capabilities of MeerKAT for XRB spectral line studies.

Precise mass measurements for the double neutron star system J1829+2456

ABSTRACT PSR J1829+2456 is a radio pulsar in a relativistic binary system with another neutron star. It has a rotational period of 41 ms and a mildly eccentric (e = 0.14) 28 h orbit. We have continued its observations with the Arecibo radio telescope and have now measured the individual neutron star masses of this system: The pulsar and companion masses are $1.306\, \pm \, 0.007\, \mathrm{M}_{\odot}$ and $1.299\, \pm \, 0.007\, \mathrm{M}_{\odot}$ ($2\sigma - 95{{\ \rm per\ cent}}$ confidence, unless stated otherwise), respectively. We have also measured the proper motion for this system and used it to estimate a space velocity of $49^{+77}_{-30}$$\, \mathrm{km}\, \mathrm{s}^{-1}$ with respect to the local standard of rest. The relatively low values for companion mass, space velocity, and orbital eccentricity in this system make it similar to other double neutron star systems in which the second-formed neutron star is thought to have formed in a low-kick, low mass-loss, symmetric supernova.

The environment of supernova remnant VRO 42.05.01 as probed with IRAM 30m molecular line observations

Context. The environment of supernova remnants (SNRs) is a key factor in their evolution, particularly at later stages of their existence. Mixed-morphology (MM) SNRs have a peculiar centre-filled X-ray shape that remains enigmatic. It is often assumed that they evolve in very dense environments, and that the X-ray morphology is due to interactions between the SNRs and their surroundings. Aims. We aim to determine whether VRO 42.05.01 is embedded in, and interacting with, a dense molecular environment. We also aim to understand the multi-wavelength emission from the environment of this SNR, and whether the interstellar material can be responsible for the the MM nature of the source, and for its strange radio and optical shape. Methods. We used the IRAM telescope in Pico Veleta, Spain, to search for signs of interaction between the SNR and neighbouring molecular clouds. We observed a region of 26′ × 14′ towards the west of VRO 42.05.01 and a region of 8′ × 4′ towards the north of the remnant in the 12CO J = 1−0, 13CO J = 1−0, and 12CO J = 2−1 transitions with the EMIR receiver. We made maps of the properties of the observed molecular clouds (peak temperatures, central velocities, velocity dispersions), as well as maps of column density along the line of sight, and ratio of the 12CO J = 2−1 to 12CO J = 1−0 transitions. We also analyse archival optical, infrared, and radio spectroscopic data for other hints on the nature of the medium. Results. We do not find conclusive physical proof that the SNR is interacting with the few, clumpy molecular clouds that surround it in the region of our observations, although there is some suggestion of such interaction (in a region outside our map) from infrared emission. We find that there is a velocity gradient in one of the molecular clouds that is consistent with a stellar wind blown by a 12−14 M⊙ progenitor star. We reassess the literature distance to VRO 42.05.01, and propose that it has a local standard of rest velocity of − 6 km s−1, and that it is located 1.0 ± 0.4 kpc away (the earlier distance value was 4.5 ± 1.5 kpc). We find that a dust sheet intersects VRO 42.05.01 and is possibly related to its double shell-shaped morphology.

The Stellar Age-Teff-Kinematical Asymmetry in the Solar Neighborhood from LAMOST

With the velocity de-projection technique, we derived the averaged 3 dimensional local velocity distribution using only the line-of-sight velocity for the 200,000 FGK type main-sequence stars from the LAMOST DR1 data. Taking the effective temperature as a proxy for age, we investigate the variation of the velocity distribution as a function of Teff and disk height within 100 < |z| < 500 pc. Using the mean velocities of the cool stars, we derive the solar motion of (U⊙, V⊙, W⊙)=(9.58±2.39, 10.52±1.96, 7.01±1.67) kms−1 with respect to the local standard of rest (LSR). Moreover, we find that the stars with Teff > 6000 K show a net asymmetric motion of 〈U〉~2 kms−1 and 〈W〉~3 kms−1 compared to the stars with Teff < 6000 K. And their azimuthal velocity increases when |z| increases. The asymmetric motion in the warmer stars is likely because they are too young and not completely relaxed.

A New Estimate of the Local Standard of Rest from Data on Young Objects

To estimate the peculiar velocity of the Sun with respect to the Local Standard of Rest (LSR), we use young objects in the Solar neighborhood with distance measurement errors within 10%–15%. These objects include the nearest