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Time evolution of cyclotron line of Her X-1: a detailed statistical analysis including new AstroSat data
Staubert, R.; Maitra, C.; Bhattacharya, D. +1 more
The cyclotron line feature in the X-ray spectrum of the accretion-powered pulsar Her X-1 has been observed and monitored for over three decades. The line energy exhibited a slow secular decline over the period 1995-2014, with a possible (not confirmed) indication of a reversal thereafter. Recent works have shown that the temporal evolution of the …
First spectroscopic study of ionised gas emission lines in the extreme low surface brightness galaxy Malin 1
Koda, J.; Chemin, L.; Boselli, A. +7 more
Context. Malin 1 is the largest known low surface brightness (LSB) galaxy, the archetype of so-called giant LSB galaxies. The structure and origin of such galaxies are still poorly understood, especially because of the lack of high-resolution kinematics and spectroscopic data.
Aims: We use emission lines from spectroscopic observations of Mal…
The origin of X-ray emission in the gamma-ray emitting narrow-line Seyfert 1 1H 0323+342
Fabian, A. C.; Reynolds, C. S.; Pinto, C. +7 more
We present the results of X-ray spectral and timing analyses of the closest gamma-ray emitting narrow-line Seyfert 1 (γ-NLS1) galaxy, 1H 0323+342. We use observations from a recent, simultaneous XMM-Newton/NuSTAR campaign. As in radio-quiet NLS1s, the spectrum reveals a soft excess at low energies (≲2 keV) and reflection features such as a broad i…
Carina High-contrast Imaging Project for massive Stars (CHIPS). I. Methodology and proof of concept on QZ Car (≡ HD 93206)
Absil, O.; De Ridder, J.; Zinnecker, H. +13 more
Context. Massive stars like company. However, low-mass companions have remained extremely difficult to detect at angular separations (ρ) smaller than 1″ (approx. 1000-3000 au, considering the typical distance to nearby massive stars) given the large brightness contrast between the companion and the central star. Constraints on the low-mass end of …
Explaining the chemical trajectories of accreted and in-situ halo stars of the Milky Way
Gibson, Brad K.; Kawata, Daisuke; Gallart, Carme +2 more
The Milky Way underwent its last significant merger ten billion years ago, when the Gaia-Enceladus-Sausage (GES) was accreted. Accreted GES stars and progenitor stars born prior to the merger make up the bulk of the inner halo. Even though these two main populations of halo stars have similar durations of star formation prior to their merger, they…
The H α star formation main sequence in cluster and field galaxies at z ∼ 1.6
Cooper, M. C.; Muzzin, Adam; Forrest, Ben +16 more
We calculate H α-based star formation rates and determine the star formation rate-stellar mass relation for members of three Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS) clusters at z ~ 1.6 and serendipitously identified field galaxies at similar redshifts to the clusters. We find similar star formation rates in cluster and field…
Collinder 135 and UBC 7: A physical pair of open clusters
Reffert, Sabine; Berczik, Peter; Just, Andreas +7 more
Context. Given the closeness of the two open clusters
Aims: We aim to recover the present-day stellar membership in the open clusters
A surprise in the updated list of stellar perturbers of long-period comet motion
Dybczyński, Piotr A.; Wysoczańska, Rita; Polińska, Magdalena
Context. The second Gaia data release (Gaia DR2) provided us with the precise five-parameter astrometry for 1.3 billion of sources. As stars passing close to the Solar System are thought to influence the dynamical history of long-period comets, we update and extend the list of stars that could potentially perturb the motion of these comets.
A…
The Gaia Ultra-Cool Dwarf Sample - III: seven new multiple systems containing at least one Gaia DR2 ultracool dwarf.
Caballero, J. A.; Sarro, L. M.; Marocco, F. +8 more
We present 10 new ultracool dwarfs in seven wide binary systems discovered using Gaia second data release data, identified as part of our Gaia Ultra-Cool Dwarf Sample project. The seven systems presented here include an L1 companion to the G5 IV star HD 164507, an L1: companion to the V478 Lyr AB system, an L2 companion to the metal-poor K5 V star…
The HSC-SSP Transient Survey: Implications from Early Photometry and Rise Time of Normal Type Ia Supernovae
Tominaga, Nozomu; Nomoto, Ken'ichi; Morokuma, Tomoki +9 more
With a booming number of Type Ia supernovae (SNe Ia) discovered within a few days of their explosions, a fraction of SNe Ia that show luminosity excess in the early phase (early-excess SNe Ia) have been confirmed. In this article, we report early-phase observations of seven photometrically normal SNe Ia (six early detections and one deep non detec…