A Dust-scattering Halo of 4U 1630–47 Observed with Chandra and Swift: New Constraints on the Source Distance

Abstract

We have observed the Galactic black hole transient 4U 1630−47 during the decay of its 2016 outburst with Chandra and Swift to investigate the properties of the dust scattering halo created by the source. The scattering halo shows a structure that includes a bright ring between 80 ′′ and 240 ′′ surrounding the source, and a continuous distribution beyond 250 ′′ . An analysis of the 12 CO J = 1 − 0 map and spectrum in the line of sight to the source indicate that a molecular cloud with a radial velocity of -79 km s −1 (denoted MC −79) is the main scattering body that creates the bright ring. We found additional clouds in the line of sight, calculated their kinematic distances and resolved the well known "near" and "far" distance ambiguity for most of the clouds. At the favored far distance estimate of MC −79, the modeling of the surface brightness profile results in a distance to 4U 1630−47 of 11.5 ± 0.3 kpc. If MC −79 is at the near distance, then 4U 1630−47 is at 4.7 ± 0.3 kpc. Future Chandra, Swift, and sub-mm radio observations not only can resolve this ambiguity, but also would provide information regarding properties of dust and distribution of all molecular clouds along the line of sight. Using the results of this study we also discuss the nature of this source and the reasons for the anomalously low soft state observation observed during the 2010 decay.

Chandrahigh-resolution spectra of 4U 1630-47: the disappearance of the wind

“…Finally, we have considered the effect of dust scattering in the spectra of 4U 1630-47, which has been reported previously (Hori et al 2014;Neilsen et al 2014;Kalemci et al 2018). The overall effect of the scattering in the spectra (and therefore in the SEDs) consist of the hardening of the continuum due to the E −2 dependence of the dust model.…”

“…In Section 5, we discuss the possible launching mechanisms present in this system and Section 6 summarizes the main results of our analysis. We assume a value of 10 kpc throughout this paper, as previous authors (Abe et al 2005;Tomsick et al 2005;Díaz Trigo et al 2014) but note that Kalemci et al (2018) have recently reported two potential distances of 4.7 ± 0.3 kpc and 11.5 ± 0.3 kpc to the source based on an analysis of the dust scattering halo around the source. Table 1 shows the specifications, including IDs, dates, exposure times and count rates, of the LMXB 4U 1630-47 Chandra observations analyzed in this paper.…”

Investigating state transition luminosities of Galactic black hole transients in the outburst decay

“…The complete list of the sources investigated in this study is given in Table 1 alongside with relevant observational properties. We have excluded 4U 1630-47 because of its erratic outburst behaviour (Abe et al 2005;Tomsick et al 2005), contaminated background by the Galactic ridge and a dust scattering halo (Kalemci, Tomsick & Maccarone 2018). For the sources without a mass measurement we have adopted a general value of 8 ± 1.5 M (shown in blue in Table 1) based on work ofÖzel et al (2010) and Kreidberg et al (2012).…”

The X-Ray Variable Sky as Seen by MAXI: The Future of Dust-echo Tomography with Bright Galactic X-Ray Bursts

“…The algorithm flags the intervals when LMC X-3 is in a bright state. The next two panels show Cir X-1 and 4U 1630-47 during the flares leading to dust echoes study by Heinz et al (2015) and Kalemci et al (2018), respectively. The calculated fluences are 0.023 erg cm −2 over 85 days (Cir X-1) and 0.021 erg cm −2 over 171 days (4U 1630-47).…”

“…The blue, red, and green circles show data points from the flares observed from Cir X-1, 4U 1630-47, and LMC X-3, respectively. The flares that led to dust echoes studied by Heinz et al (2015) and Kalemci et al (2018) are highlighted by the large blue and red circles, respectively. Middle: Plot of the dust echo 2-4 keV fluence versus the ring sharpness metric, (t f /tq).…”