A PHOTOMETRIC VARIABILITY SURVEY OF FIELD K AND M DWARF STARS WITH HATNet

By Joel D. Hartman, Gáspár Á. Bakos, R. W. Noyes, Brigitta M. Sipocz, G. Kov'acs, T. Mazeh, Avi Shporer, A. P'al, Cfa, Elte and 2 more. 2009

141 citations recorded by the source corpus.

Using light curves from the HATNet survey for transiting extrasolar planets we investigate the optical broadband photometric variability of a sample of 27, 560 field K and M dwarfs selected by color and proper motion (V − K ≳ 3.0, μ > 30 mas yr−1, plus additional cuts in J − H versus H − KS and on the reduced proper motion). We search the light curves for periodic variations and for large-amplitude, long-duration flare events. A total of 2120 stars exhibit potential variability, including 95 stars with eclipses and 60 stars with flares. Based on a visual inspection of these light curves and an automated blending classification, we select 1568 stars, including 78 eclipsing binaries (EBs), as secure variable star detections that are not obvious blends. We estimate that a further ∼26% of these stars may be blends with fainter variables, though most of these blends are likely to be among the hotter stars in our sample. We find that only 38 of the 1568 stars, including five of the EBs, have previously been identified as variables or are blended with previously identified variables. One of the newly identified EBs is 1RXS J154727.5+450803, a known P = 3.55 day, late M-dwarf SB2 system, for which we derive preliminary estimates for the component masses and radii of M1 = M2 = 0.258 ± 0.008 M☉ and R1 = R2 = 0.289 ± 0.007 R☉. The radii of the component stars are larger than theoretical expectations if the system is older than ∼200 Myr. The majority of the variables are heavily spotted BY Dra-type stars for which we determine rotation periods. Using this sample, we investigate the relations between period, color, age, and activity measures, including optical flaring, for K and M dwarfs, finding that many of the well-established relations for F, G, and K dwarfs continue into the M dwarf regime. We find that the fraction of stars that is variable with peak-to-peak amplitudes greater than 0.01 mag increases exponentially with the V − KS color such that approximately half of field dwarfs in the solar neighborhood with M ≲ 0.2 M☉ are variable at this level. Our data hint at a change in the rotation–activity–age connection for stars with M ≲ 0.25 M☉.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/7d93ced84ba3602d1d7965cd3aeb8d272f573495

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In Astronomy and Astrophysics

1. D. Charbonneau
2. Nuno C. Santos
3. E. Gaidos
4. S. Udry
5. M. Mayor
6. A. Mann
7. J. Southworth
8. Michael C. Liu

Citations in the corpus

• PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS (2014, methodology): “A rotational period of 0.562 days for the unresolved system was measured in the HATNet survey (Hartman et al. 2011).”
• THE CATALINA SURVEYS PERIODIC VARIABLE STAR CATALOG (2014, background): “Survey for planetary transits have also discovered periodic variable stars (e.g., HATNet, Hartman et al. 2011; BOKS, Feldmeier et al. 2011).”
• A SPECTROSCOPIC CATALOG OF THE BRIGHTEST (J < 9) M DWARFS IN THE NORTHERN SKY, (2012, background): “Some M dwarfs have significant photometric variability (flares, spots) which are affecting transit searches (Hartman et al. 2011); some display chromospheric emission affecting Doppler searches (Isaacson & Fischer 2010).”
• The stellar rotation–activity relationship in fully convective M dwarfs (2018, background): “These were complemented by additional rotation periods for nearby fully convective stars from Benedict et al. (1998), Hartman et al. (2011), and Kiraga (2012).”
• THE Hα EMISSION OF NEARBY M DWARFS AND ITS RELATION TO STELLAR ROTATION (2016, background): “For 2MASS J08175130+3107455 (G 90-52), Hartman et al. (2011) report a period of 0.97 days, and flag it as a possible blend.”
• THE STELLAR-ACTIVITY–ROTATION RELATIONSHIP AND THE EVOLUTION OF STELLAR DYNAMOS (2011, background): “This included 218 stars from Hartman et al. (2011), 23 stars from Kiraga & Stepien (2007), 6 stars from Xing et al. (2007), 8 stars from Bouvier et al. (1997) 3 and 79 stars were added from the compilation of Mamajek & Hillenbrand (2008).”
• The HARPS search for southern extra-solar planets - XXXI. The M-dwarf sample (2011, background): “On the one hand solar-type stars are brighter and have a lower jitter level (e.g. Hartman et al. 2011), but on the other hand they are more massive and the reflex motion induced by a given planet is weaker.”
• ROTATION PERIODS OF 34,030 KEPLER MAIN-SEQUENCE STARS: THE FULL AUTOCORRELATION SAMPLE (2014, background): “Previous studies have suggested a typical increase in variability with rotation rate (e.g., Pizzolato et al. 2003; Hartman et al. 2011), although this was not seen by Basri et al. (2011).”
• ON THE ANGULAR MOMENTUM EVOLUTION OF FULLY CONVECTIVE STARS: ROTATION PERIODS FOR FIELD M-DWARFS FROM THE MEarth TRANSIT SURVEY (2010, background): “Hartman et al. (2009b) also report a number of long rotation periods for field M-dwarfs from the HATNet transit survey.”