Professor of Mathematics
Paata Ivanisvili
Department of Mathematics, University of California, Irvine
Candidate 23: a reddened star whose orbit does not fix the companion’s mass
Why this estimate. The fit leaves the companion’s mass almost entirely open, the dust in front of the star makes its own mass uncertain, the orbit comes from Gaia’s less reliable alternative solutions, and no measurements along the line of sight confirm it.
How to read the pictures. The orbit figure has three panels. On the left is the small ellipse that Gaia’s orbit traces on the sky, measured in thousandths of an arcsecond, with grey orbits that fit the data about equally well. In the middle is the mass the unseen companion would need for each possible mass of the visible star; the shaded band is the likely range, the red line marks the star’s estimated mass, and the dotted and dashed lines mark 3 and 1.4 solar masses, roughly where black holes begin and where a typical neutron star lies. On the right, the star (red) sits among other stars in Gaia’s diagram of colour against brightness. The finder chart shows a patch of sky two arcminutes across, about a fifteenth of the Moon’s width, with north up and east to the left; the star sits between the two yellow ticks, and the white bar is 30 arcseconds long.
What Gaia found. This star is seen through thick dust, about 1.4 magnitudes of dimming in Gaia’s G band, some 1,350 parsecs away in the Milky Way in Vela. One of Gaia’s alternative orbit-fitting methods found a nearly circular 705-day wobble.
Why the estimate is low. The fit leaves the companion’s mass open: its likely range runs from 2.6 to 117 solar masses, and the upper end is unphysical. The dust makes the star’s own mass uncertain, the solution comes from Gaia’s less reliable alternative solutions, and there are no measurements of the star’s speed along the line of sight.
No record of a dark companion for this star could be found. The star is too far south for Pan-STARRS1 and ZTF, so there is no light curve.
- Star
- Gaia DR3 5329908767714982400, a star seen through thick dust
- Location
- RA 132.40037°, Dec −45.93832° (J2000), in Vela, in the Milky Way
- Distance
- about 1,350 parsecs (4,400 light-years)
- Brightness
- Gaia G = 15.8
- Probability
- This candidate is unconfirmed. The percentage under the title is an estimate of the chance that it is a real, previously unrecorded case of the kind described. The estimate has not been checked by outside experts. See the introduction to all fifty-eight candidates.
- Caveat
- The companion’s mass is unconstrained, the star’s own mass is uncertain, the orbit is a less reliable kind of Gaia solution, and no measurements along the line of sight confirm it.
