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Register a new userM Dwarf Activity in the Pan-STARRS 1 Medium-Deep Survey: First Catalog and Rotation Periods
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We report on an ongoing project to investigate activity in the M dwarf stellar population observed by the Pan-STARRS 1 Medium Deep Survey (PS1-MDS). Using a custom-built pipeline, we refine an initial sample of $approx$ 4 million sources in PS1-MDS to a sample of 184,148 candidate cool stars using color cuts. Motivated by the well-known relationship between rotation and stellar activity, we use a multi-band periodogram analysis and visual vetting to identify 271 sources that are likely rotating M dwarfs. We derive a new set of polynomials relating M dwarf PS1 colors to fundamental stellar parameters and use them to estimate the masses, distances, effective temperatures, and bolometric luminosities of our sample. We present a catalog containing these values, our measured rotation periods, and cross-matches to other surveys. Our final sample spans periods of $lesssim$1-130 days in stars with estimated effective temperatures of $approx$ 2700-4000 K. Twenty-two of our sources have X-ray cross-matches, and they are found to be relatively X-ray bright as would be expected from selection effects. Our data set provides evidence that Kepler-based searches have not been sensitive to very slowly-rotating stars ($P_{rm rot} gtrsim 70$ d), implying that the observed emergence of very slow rotators in studies of low-mass stars may be a systematic effect. We also see a lack of low-amplitude ($<$2%) variability in objects with intermediate (10-40 d) rotation periods, which, considered in conjunction with other observational results, may be a signpost of a loss of magnetic complexity associated with a phase of rapid spin-down in intermediate-age M dwarfs. This work represents just a first step in exploring stellar variability in data from the PS1-MDS and, in the farther future, LSST.
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[abridged] We present the results of a pilot study for the extended MACS survey (eMACS), a comprehensive search for distant, X-ray luminous galaxy clusters at z>0.5. Our pilot study applies the eMACS concept to the 71 deg^2 area extended by the ten fields of the Pan-STARRS1 (PS1) Medium Deep Survey (MDS). Candidate clusters are identified by visual inspection of PS1 images in the g,r, i, and z bands in a 5x5 arcmin^2 region around X-ray sources detected in the ROSAT All-Sky Survey (RASS). To test and optimize the eMACS X-ray selection criteria, our pilot study uses the largest possible RASS database, i.e., all RASS sources listed in the Bright and Faint Source Catalogs (BSC and FSC) that fall within the MDS footprint. Scrutiny of PS1/MDS images for 41 BSC and 200 FSC sources combined with dedicated spectroscopic follow-up observations results in a sample of 11 clusters with estimated or spectroscopic redshifts of z>0.3. X-ray follow-up observations will be crucial in order to establish robust cluster luminosities for eMACS clusters. Although the small number of distant X-ray luminous clusters in the MDS does not allow us to make firm predictions for the over 20,000 deg^2 of extragalactic sky covered by eMACS, the identification of two extremely promising eMACS cluster candidates at z>0.6 (both yet to be observed with Chandra) in such a small solid angle is encouraging. Representing a tremendous gain over the presently known two dozen such systems from X-ray, optical, and SZ cluster surveys combined, the sample of over 100 extremely massive clusters at z>0.5 expected from eMACS would be invaluable for the identification of the most powerful gravitational lenses in the Universe, as well as for in-depth and statistical studies of the physical properties of the most massive galaxy clusters out to z~1.
Using the first 18 months of the Pan-STARRS 1 survey we have identified 33 candidate high-amplitude objects for follow-up observations and carried out observations of 22 asteroids. 4 of the observed objects were found to have observed amplitude $A_{obs}geq 1.0$ mag. We find that these high amplitude objects are most simply explained by single rubble pile objects with some density-dependent internal strength, allowing them to resist mass shedding even at their highly elongated shapes. 3 further objects although below the cut-off for high-amplitude had a combination of elongation and rotation period which also may require internal cohesive strength, depending on the density of the body. We find that none of the high-amplitude asteroids identified here require any unusual cohesive strengths to resist rotational fission. 3 asteroids were sufficiently observed to allow for shape and spin pole models to be determined through light curve inversion. 45864 was determined to have retrograde rotation with spin pole axes $lambda=218pm 10^{circ}, beta=-82pm 5^{circ}$ and asteroid 206167 was found to have best fit spin pole axes $lambda= 57 pm 5^{circ}$, $beta=-67 pm 5^{circ}$. An additional object not initially measured with $A_{obs}>1.0$ mag, 49257, was determined to have a shape model which does suggest a high-amplitude object. Its spin pole axes were best fit for values $lambda=112pm 6^{circ}, beta=6pm 5^{circ}$. In the course of this project to date no large super-fast rotators ($P_{rot} < 2.2$ h) have been identified.
A large sample of white dwarfs is selected by both proper motion and colours from the Pan-STARRS 1 3{pi} Steradian Survey Processing Version 2 to construct the White Dwarf Luminosity Functions of the discs and halo in the solar neighbourhood. Four-parameter astrometric solutions were recomputed from the epoch data. The generalised maximum volume method is then used to calculate the density of the populations. After removal of crowded areas near the Galactic plane and centre, the final sky area used by this work is 7.833 sr, which is 83% of the 3{pi} sky and 62% of the whole sky. By dividing the sky using Voronoi tessellation, photometric and astrometric uncertainties are recomputed at each step of the integration to improve the accuracy of the maximum volume. Interstellar reddening is considered throughout the work. We find a disc-to-halo white dwarf ratio of about 100.
We present a spectroscopic catalog of 67082 M dwarfs from the LAMOST pilot survey. For each spectrum of the catalog, spectral subtype, radial velocity, equivalent width of H${alpha}$, a number of prominent molecular band indices and the metal sensitive parameter $zeta$ are provided . Spectral subtype have been estimated by a remedied Hammer program (Original Hammer: Covey et al. 2007), in which indices are reselected to obtain more accurate auto-classified spectral subtypes. All spectra in this catalog have been visually inspected to confirm the spectral subtypes. Radial velocities have been well measured by our developed program which uses cross-correlation method and estimates uncertainty of radial velocity as well. We also examine the magnetic activity properties of M dwarfs traced by H${alpha}$ emission line. The molecular band indices included in this catalog are temperature or metallicity sensitive and can be used for future analysis of the physical properties of M dwarfs. The catalog is available on the website url{http://sciwiki.lamost.org/MCatalogPilot/}.
We present rotation period measurements for 107 M dwarfs in the mass range $0.15-0.70 M_odot$ observed within the context of the APACHE photometric survey. We measure rotation periods in the range 0.5-190 days, with the distribution peaking at $sim$ 30 days. We revise the stellar masses and radii for our sample of rotators by exploiting the Gaia DR2 data. For $sim 20%$ of the sample, we compare the photometric rotation periods with those derived from different spectroscopic indicators, finding good correspondence in most cases. We compare our rotation periods distribution to the one obtained by the Kepler survey in the same mass range, and to that derived by the MEarth survey for stars in the mass range $0.07-0.25 M_odot$. The APACHE and Kepler periods distributions are in good agreement, confirming the reliability of our results, while the APACHE distribution is consistent with the MEarth result only for the older/slow rotators, and in the overlapping mass range of the two surveys. Combining the APACHE/Kepler distribution with the MEarth distribution, we highlight that the rotation period increases with decreasing stellar mass, in agreement with previous work. Our findings also suggest that the spin-down time scale, from fast to slow rotators, changes crossing the fully convective limit at $approx0.3 M_odot$ for M dwarfs. The catalogue of 107 rotating M dwarfs presented here is particularly timely, as the stars are prime targets for the potential identification of transiting small planets with TESS and amenable to high-precision mass determination and further atmospheric characterization measurements.
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