Δμ binaries among stars with large proper motions

Abstract

Based on observations performed with the Pulkovo normal astrograph in 2008-2015 and data from sky surveys (DSS, 2MASS, SDSS DR12, WISE), we have investigated the motions of 1308 stars with proper motions larger than 300 mas/yr down to magnitude 17. The main idea of our search for binary stars based on this material is reduced to comparing the quasi-mean (POSS2-POSS1; an epoch difference of ≈50 yr) and quasi-instantaneous (2MASS, SDSS, WISE, Pulkovo; an epoch difference of ≈10 yr) proper motions. If the difference is statistically significant compared to the proper motion errors, then the object may be considered as a ∆µ-binary candidate. One hundred and twenty one stars from among those included in the observational program satisfy this requirement. Additional confirmations of binarity for a number of stars have been obtained by comparing the calculated proper motions with the data from several programs of stellar trigonometric parallax determinations and by analyzing the asymmetry of stellar images on sky-survey CCD frames. Analysis of the highly accurate SDSS photometric data for four stars (J0656+3827, J0838+3940, J1229+5332, J2330+4639) allows us to reach a conclusion about the probability that these ∆µ binaries are white dwarf + M dwarf pairs.

The Field Substellar Mass Function Based on the Full-sky 20 pc Census of 525 L, T, and Y Dwarfs

“…We nonetheless still note these as binaries in Table 4, and we split out those cases here for individual discussion. Khovritchev & Kulikova (2015) have identified likely accelerators by comparing the proper motion measured between the first and second Palomar Observatory Sky Surveys (POSS-I and POSS-II; Minkowski & Abell 1963;Reid et al 1991;Lasker & STSCI Sky-Survey Team 1998) to a motion derived using first-epoch data from other sky surveys (2MASS, SDSS, WISE) and their own second-epoch follow-up astrometry. With these two independent measurements, they can compare a long-baseline motion over 50 yr to one derived more instantaneously, over only ∼10 yr. Brandt (2021) have similarly intercompared the near-instantaneous Hipparcos-measured proper motion from the early 1990's, the near-instantaneous Gaia-measured motion from the midto late-2010's, and a long-baseline motion constructed from the Hipparcos-to-Gaia baseline.…”

“…The Khovritchev & Kulikova (2015) list of ∼2400 objects covers only a portion of the northern sky (30 • < Dec < 70 • ) for bright (V < 17 mag), high motion (µ > 300 mas yr −1 ) stars. Within 20 pc of the Sun, nine such accelerators are identified, only two of which -BD+66 34 and G 96-29 (Capella HL) -were already identified as known multiples in Table 4.…”

An astronegatives digitization method in the Pulkovo observatory glass library

“…Для глубокого анализа астрономических изображений на цифровых носителях хорошо зарекомендовал себя метод Шейплет-декомпозиции (Refregier, 2003). Он позволяет получать высокоточные положения звезд (Khovritchev, Kulikova, 2015) и анализировать форму изображений (Khovrichev et al, 2018). Этот метод позволяет представить изображение согласно соотношениям (1).…”

Detection of the binarity of the star J1158+4239

“…This idea was applied by Wielen et al (1999) to bright stars from the FK6 catalog. When implementing the Pulkovo program of research on stars with large proper motions, this technique was adapted to reveal astrometric binaries among the low-luminosity stars in the solar neighborhood (Khrutskaya et al (2011);Khovritchev&Kulikova (2015)). …”

“…Such stars are being actively investigated within the Pulkovo observational program (Khrutskaya et al (2011); Khovritchev et al (2013)). Some of the program stars have turned out to exhibit evidence for nonlinearity of their motion over the celestial sphere (astrometric binary candidates; see Khovritchev&Kulikova (2015)). …”