A standard stellar spectral sequence in the red/near-infrared - Classes K5 to M9

We present the first dynamical determination of the binary parameters of an eclipsing SW Sextantis star in the 3-4 hour orbital period range during a low state. We obtained time-resolved optical spectroscopy and photometry of HS 0220+0603 during its 2004-2005 low brightness state, as revealed in the combined SMARTS, IAC80 and M1 Group long-term optical light curve.The optical spectra taken during primary eclipse reveal a secondary star spectral type of M5.5±0.5 as derived from molecular band-head indices. The spectra also provide the first detection of a DAB white dwarf in a cataclysmic variable. By modelling its optical spectrum we estimate a white dwarf temperature of 30 000 ± 5 000 K.By combining the results of modelling the white dwarf eclipse from ULTRA-CAM light curves with those obtained by simultaneously fitting the emission-and absorption-line radial velocity curves and I-band ellipsoidal light curves, we measure the stellar masses to be M 1 = 0.87 ± 0.09 M and M 2 = 0.47 ± 0.05 M for the white dwarf and the M dwarf, respectively, and an inclination of the orbital plane of i ≈ 79 o . A radius of 0.0103 ± 0.0007 R is obtained for the white dwarf. The secondary star in HS 0220+0603 is likely too cool and undersized for its mass.

Section: Secondary Star Molecular-band Indicesmentioning

confidence: 91%

Dynamical masses of a nova-like variable on the edge of the period gap

Rodríguez‐Gil

Shahbaz

Marsh

et al. 2015

“…Stars could mimic having an emission line if they have extremely red or a broad absorption feature, which would lead to a strong colour between the two NB filters. We expect the line emitters selected in the NB2 filter to be particularly contaminated with a population of (L, M) dwarf stars (Kirkpatrick et al 1991(Kirkpatrick et al , 1999. They will be selected as having excess in NB2 because their continuum has a broad absorption feature falling within the NB1 filter, leading to an underestimation of the continuum emission.…”

Section: Star Removalmentioning

confidence: 99%

A large narrow-band Hα survey at z∼ 0.2: the bright end of the luminosity function, cosmic variance and clustering across cosmic time

Stroe

Sobral

2015

We carried out the largest (> 3.5 × 10 5 Mpc 3 , 26 deg 2 ) Hα narrow band survey to date at z ∼ 0.2 in the SA22, W2 and XMMLSS extragalactic fields. Our survey covers a large enough volume to overcome cosmic variance and to sample bright and rare Hα emitters up to an observed luminosity of ∼ 10 42.4 erg s −1 , equivalent to ∼ 11M yr −1 . Using our sample of 220 sources brighter than > 10 41.4 erg s −1 (> 1M yr −1 ), we derive Hα luminosity functions, which are well described by a Schechter function with φ * = 10 −2.85±0.03 Mpc −3 and L * Hα = 10 41.71±0.02 erg s −1 (with a fixed faint end slope α = −1.35). We find that surveys probing smaller volumes (∼ 3 × 10 4 Mpc 3 ) are heavily affected by cosmic variance, which can lead to errors of over 100 per cent in the characteristic density and luminosity of the Hα luminosity function. We derive a star formation rate density of ρ SFRD = 0.0094 ± 0.0008 M yr −1 , in agreement with the redshift-dependent Hα parametrisation from Sobral et al. (2013). The two-point correlation function is described by a single power law ω(θ ) = (0.159 ± 0.012)θ (−0.75±0.05) , corresponding to a clustering length of r 0 = 3.3 ± 0.8 Mpc/h. We find that the most luminous Hα emitters at z ∼ 0.2 are more strongly clustered than the relatively fainter ones. The L * Hα Hα emitters at z ∼ 0.2 in our sample reside in ∼ 10 12.5−13.5 M dark matter haloes. This implies that the most star forming galaxies always reside in relatively massive haloes or group-like environments and that the typical host halo mass of star-forming galaxies is independent of redshift if scaled by L Hα /L * Hα (z), as proposed by Sobral et al. (2010).

“…Kirkpatrick et al 1991;Gizis 1997;Lépine et al 2013) so we relied instead on the overall shape of the spectrum.…”

Section: Spectral Typingmentioning

confidence: 99%

“…To find the best match, we performed a χ 2 minimization over two different wavelength ranges. First for the twenty later type stars we used the range λ=6500-9000 Å, as most of the flux and spectral features of interest are in that region, also the templates from Kirkpatrick et al (1991) that we used do not cover bluer wavelengths. For the four hotter objects we minimize over a broader wavelength region, λ=3500-9500 Å as they have more flux towards the bluer regions.…”

Section: Spectral Typingmentioning

confidence: 99%

Spectrophotometric characterization of high proper motion sources fromWISE

Beamín

Ivanov

Minniti

et al. 2015

The census of the solar neighborhood is almost complete for stars and becoming more complete in the brown dwarf regime. Spectroscopic, photometric and kinematic characterization of nearby objects helps us to understand the local mass function, the binary fraction, and provides new targets for sensitive planet searches. We aim to derive spectral types and spectro-photometric distances of a sample of new high proper motion sources found with the WISE satellite, and obtain parallaxes for those objects that fall within the area observed by the Vista Variables in the Vía Láctea survey (VVV). We used low resolution spectroscopy and template fitting to derive spectral types, multiwavelength photometry to characterize the companion candidates and obtain photometric distances. Multi-epoch imaging from the VVV survey was used to measure the parallaxes and proper motions for three sources. We confirm a new T2 brown dwarf within ∼15 pc. We derived optical spectral types for twenty four sources, mostly M dwarfs within 50 pc. We addressed the wide binary nature of sixteen objects found by the WISE mission and previously known high proper motion sources. Six of these are probably members of wide binaries, two of those are new, and present evidence against the physical binary nature of two candidate binary stars found in the literature, and eight that we selected as possible binary systems. We discuss a likely microlensing event produced by a nearby low mass star and a galaxy, that is to occur in the following five years.