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Your search keyword '"Calchi Novati, Sebastiano"' showing total 2 results
Start Over Author "Calchi Novati, Sebastiano" Topic astrophysics - solar and stellar astrophysics
2 results on '"Calchi Novati, Sebastiano"'

1. Radii of 88 M Subdwarfs and Updated Radius Relations for Low-Metallicity M Dwarf Stars

Author

Kesseli, Aurora Y., Kirkpatrick, J. Davy, Fajardo-Acosta, Sergio B., Penny, Matthew T., Gaudi, B. Scott, Veyette, Mark, Boeshaar, Patricia C., Henderson, Calen B., Cushing, Michael C., Calchi-Novati, Sebastiano, Shvartzvald, Yossi, and Muirhead, Philip S.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

M subdwarfs are low-metallicity M dwarfs that typically inhabit the halo population of the Galaxy. Metallicity controls the opacity of stellar atmospheres; in metal poor stars, hydrostatic equilibrium is reached at a smaller radius, leading to smaller radii for a given effective temperature. We compile a sample of 88 stars that span spectral classes K7 to M6 and include stars with metallicity classes from solar-metallicity dwarf stars to the lowest metallicity ultra-subdwarfs to test how metallicity changes the stellar radius. We fit models to Palomar Double Spectrograph (DBSP) optical spectra to derive effective temperatures ($T_\mathrm{eff}$) and we measure bolometric luminosities ($L_\mathrm{bol}$) by combining broad wavelength-coverage photometry with Gaia parallaxes. Radii are then computed by combining the $T_\mathrm{eff}$ and $L_\mathrm{bol}$ using the Stefan-Boltzman law. We find that for a given temperature, ultra-subdwarfs can be as much as five times smaller than their solar-metallicity counterparts. We present color-radius and color-surface brightness relations that extend down to [Fe/H] of $-$2.0 dex, in order to aid the radius determination of M subdwarfs, which will be especially important for the WFIRST exoplanetary microlensing survey., Comment: Accepted to AJ

Published
2018
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2. OGLE-2009-BLG-092/MOA-2009-BLG-137: A Dramatic Repeating Event with the Second Perturbation Predicted by Real-time Analysis

Author

Ryu, Y. H., Han, C., Hwang, K. H., Street, R., Udalski, A., Sumi, T., Fukui, A., Beaulieu, J. P., Gould, A., Dominik, M., Abe, F., Bennett, D. P., Bond, I. A., Botzler, C. S., Furusawa, K., Hayashi, F., Hearnshaw, J. B., Hosaka, S., Itow, Y., Kamiya, K., Kilmartin, P. M., Korpela, A., Lin, W., Ling, C. H., Makita, S., Masuda, K., Matsubara, Y., Miyake, N., Muraki, Y., Nishimoto, K., Ohnishi, K., Perrott, Y. C., Rattenbury, N., Saito, T. o., Skuljan, L., Sullivan, D. J., Suzuki, D., Sweatman, W. L., Tristram, P. J., Wada, K., Yock, P. C. M., Szymański, M. K., Kubiak, M., Pietrzyński, G., Poleski, R., Soszyński, I., Szewczyk, O., Wyrzykowski, Ł., Ulaczyk, K., Bos, M., Christie, G. W., Depoy, D. L., Gal Yam, A., Gaudi, B. S., Kaspi, S., Lee, C. U., Maoz, D., Mccormick, J., Monard, B., Moorhouse, D., Pogge, R. W., Polishook, D., Shvartzvald, Y., Shporer, A., Thornley, G., Yee, J. C., Albrow, M. D., Batista, V., Brillant, S., Cassan, A., Cole, A., Corrales, E., Coutures, C. h., Dieters, S., Fouque, P., Greenhill, J., Menzies, J., Allan, A., Bramich, D. M., Browne, P., Horne, K., Kains, N., Snodgrass46, C., Steele, I., Tsapras, Y., Bozza, Valerio, Burgdorf, M. J., CALCHI NOVATI, Sebastiano, Dreizler, S., Finet, F., Glitrup, M., Grundahl, F., Harpsøe, K., Hessman, F. V., Hinse, T. C., Hundertmark, M., Jørgensen, U. G., Liebig, C., Maier, G., Mancini, Luigi, Mathiasen, M., Rahvar, S., Ricci, D., Scarpetta, Gaetano, Skottfelt, J., Surdej, J., Southworth, J., Wambsganss, J., and Zimmer, F.

Subjects
Physics, 010504 meteorology & atmospheric sciences, FOS: Physical sciences, Binary number, Perturbation (astronomy), Astronomy and Astrophysics, Astrophysics, Light curve, Gravitational microlensing, 01 natural sciences, Stars, Settore FIS/05 - Astronomia e Astrofisica, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Bulge, 0103 physical sciences, Orbital motion, Real time analysis, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences
Abstract

We report the result of the analysis of a dramatic repeating gravitational microlensing event OGLE-2009-BLG-092/MOA-2009-BLG-137, for which the light curve is characterized by two distinct peaks with perturbations near both peaks. We find that the event is produced by the passage of the source trajectory over the central perturbation regions associated with the individual components of a wide-separation binary. The event is special in the sense that the second perturbation, occurring $\sim 100$ days after the first, was predicted by the real-time analysis conducted after the first peak, demonstrating that real-time modeling can be routinely done for binary and planetary events. With the data obtained from follow-up observations covering the second peak, we are able to uniquely determine the physical parameters of the lens system. We find that the event occurred on a bulge clump giant and it was produced by a binary lens composed of a K and M-type main-sequence stars. The estimated masses of the binary components are $M_1=0.69 \pm 0.11\ M_\odot$ and $M_2=0.36\pm 0.06\ M_\odot$, respectively, and they are separated in projection by $r_\perp=10.9\pm 1.3\ {\rm AU}$. The measured distance to the lens is $D_{\rm L}=5.6 \pm 0.7\ {\rm kpc}$. We also detect the orbital motion of the lens system., 18 pages, 5 figures, 1 table

Published
2010

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