Type Ia supernovae (SNe Ia) are securely understood to come from the thermonuclear explosion of a white dwarf as a result of binary interaction, but the nature of that binary interaction and the secondary object is uncertain. Recently, a double white dwarf model known as the dynamically driven double-degenerate double-detonation (D6) model has become a promising explanation for these events. One realization of this scenario predicts that the companion may survive the explosion and reside within the remnant as a fast moving (Vpeculiar > 1000 km s−1), overluminous (L > 0.1 Le) white dwarf. Recently, three objects that appear to have these unusual properties have been discovered in the Gaia survey. We obtained photometric observations of the SN Ia remnant SN 1006 with the Dark Energy Camera over four years to attempt to discover a similar star. We present a deep, high-precision astrometric proper-motion survey of the interior stellar population of the remnant. We rule out the existence of a high-proper-motion object consistent with our tested realization of the D6 scenario (Vtransverse > 600 km s−1 with mr < 21 corresponding to an intrinsic luminosity of L > 0.0176 L_sun). We conclude that such a star does not exist within the remnant or is hidden from detection by either strong localized dust or the unlikely possibility of ejection from the binary system almost parallel to the line of sight.
Searching for a Hypervelocity White Dwarf SN Ia Companion: A Proper-motion Survey of SN 1006
- Article by Josh Shields
- 10th Jul, 2022
2017 DECam imagery of the SN 1006 remnant. The contours are CHANDRA X-ray data (0.5-0.9 keV) showing the position of the remnant. The circles indicate the search region (red) and the the likely maximum displacement of a D6 star (blue), as well as the physical transverse velocity of a star corresponding to the angular distance assuming a distance of the remnant. The larger search region allows for ambiguity on the center of the remnant.
Results of proper motion survey showing apparent r-band magnitude against proper motion measurement and calculated transverse velocities assuming a distance of 2.17 kpc for DECam sources. The three Shen et al. 2018 stars have corrected apparent magnitudes as they would appear at the same distance with uncertainties and including foreground extinction. A surviving white dwarf companion in accordance with the predictions of the D6 scenario was expected to lie in the shaded region with the previously discovered D6 stars. The four Gaia stars in the analyzed region are shown in Table 1 and Figure 6, and are discussed in Section 4 along with the high proper motion objects fainter than 21
Color-Magnitude Diagram of 150 000 secure parallax (parallax over error > 30), Gaia stars around SN 1006. The blue dots show the three D6 candidates discovered in the field by (Shen et al. 2018) far off the main sequence. The red dots show the high proper motion (> 500 km s−1) Gaia objects inside SN 1006 in our search. They lie on or close to the main sequence with ordinary colors
