Extension of the C star rotation curve of the Milky Way to 24 kpc

Demers and Battinelli published, in 2007 the rotation curve of the Milky Way based on the radial velocity of carbon stars outside the Solar circle. Since then we have established a new list of candidates for spectroscopy. The goal of this paper is to determine the rotation curve of the galaxy, as far as possible from the galactic center, using N type carbon stars. The stars were selected from their dereddened 2MASS colours, then the spectra were obtained with the Dominion Astrophysical Observatory and Asiago 1.8 meter telescopes. This publication adds radial velocities and Galactrocentric distances of 36 carbon stars, from which 20 are new confirmed. The new results for stars up to 25 kpc from the galactic center, suggest that the rotation curve shows a slight decline beyond the Solar circle.Comment: 13 pages, 3 figures, 1 table; accepted for publication in Astrophysic

Cool carbon stars in the halo II. A study of 25 new objects

We present new results from an ongoing survey of carbon-rich asymptotic giant (AGB) stars in the halo of our Galaxy. After selecting candidates primarily through their 2MASS colours, slit spectroscopy was achieved at the ESO NTT telescope. Twenty-one new AGB carbon stars were discovered, increasing the total of presently known similar AGB C stars to about 120. A further four were observed again in order to confirm their carbon-rich nature and measure radial velocities. Two main findings emerge from this work. First, we found a C star located at about 130 kpc from the Sun and at b = -62 degrees. This distant star is remarkably close (5 kpc) to the principal plane of the Stream of the Sagittarius dwarf galaxy, and is likely to be a tracer of a distant poorly populated southern warp of the Stream. etc etcComment: accepted by Astronomy and Astrophysic

Serendipitous discovery of seven new southern L-dwarfs

We report the discovery of seven hitherto unknown L-dwarfs found as a result of a spectroscopic search for distant AGB stars. Their far-red and near-infrared colours are very similar to known dwarfs of the same spectral type. One new object is among the ~30 brightest L-dwarfs, with K_s=12.12, and is nearby, ~20pc. Using low resolution spectroscopy from the Danish 1.54 m ESO telescope, spectral types in the range L0.5 - L5 are derived for these seven L-dwarfs by direct comparison to L-type standards taken from Kirkpatrick et al. (1999). Distances are determined from existing calibrations, and together with measured proper motions, yield kinematics for the seven new dwarfs consistent with that expected for the solar neighbourhood disk population.Comment: 8 pages, 11 figures, accepted by A&

Cool carbon stars in the halo: new very red or distant objects

The goal of this paper is to present and analyse a new sample of cool carbon (C)stars located in the halo. Twenty three new C stars were discovered. Spectra are typical of N-type stars with C2 and CN bands and sometimes Halpha in emission. ... Four objects are particularly red with J-K > 3, with 2 located at more than 5 kpc. from the Galactic plane. Eight additional objects with similar properties are found in the literature and our previous works. These 12 C stars could be useful to study mass loss at low metallicity. Two objects are at distances of 95 and 110 kpc. They are located in the region with galactocentric Z < -60 kpc in which the model of Law et al. predicts the Sgr stream to have a loop. (Abstact abridged)Comment: 16 pages, 12 figures, accepted by A

Cool carbon stars in the halo: a new survey based on 2MASS

We present the first results of a new survey for finding cool N-type carbon (C) stars in the halo of the Galaxy. Candidates were first selected in the 2MASS Second Incremental Release database with JHKs colours typical of red AGB C stars and Ks < 13, and susequently checked through slit spectroscopy. 27 new halo C stars were discovered, and a detailed study of their properties are given (distance, radial velocity, variablility, proper motion, colors etc). It is found that most probably all these stars are true luminous AGB stars, rather than C dwarfs. It is finally found that about half of these stars belong to the Sgr Stream. (this abstract was shortened)Comment: 21 pages, 12 figs, accepted by Astron. & Astrophysic

The Digitized First Byurakan Survey Data Base. Late-Type Stars Candidates. New Confirmations. I

International audienceThe Digitized First Byurakan Survey (DFBS) is the digitized version of the First Byurakan Survey (FBS, or Markarian survey). The FBS was the first systematic survey of the extragalactic sky. This objective-prism survey was carried out in 1965-1980 by B.E.Markarian and his colleagues using the 1 m Schmidt telescope of the Byurakan Astrophysical Observatory and resulted in discovery of 1517 UVX-excess (Markarian) galaxies. FBS low-resolution spectral plates have been used for a long time to search and study faint Late-Type Stars (LTS, M-type and C stars) at high Galactic latitudes. A total of 18 lists of the FBS LTS were published between 1990 and 2016. We report newly confirmed C and M giants, and also large amount of M dwarfs based on the Gaia DR3 BP/RP low-resolution spectroscopic data base. Some of the newly confirmed M dwarfs presents binary systems. Some of them are new eclipsing binaries. In our previous studies of the DFBS spectral plates, all were presented as LTS candidates. Gaia high-accuracy astrometric and photometric data and Transiting Exoplanet Survey Satellite (TESS) data are used to characterize these new confirmed LTS. TESS phase-dependent light curves show rotational modulations and flares for many new M dwarfs. This confirmations of the large number of completely new objects represents a very significant extension in the census of M giants, faint N-type Asymptotic Giant Branch C stars, CH-type C giants at high Galactic latitudes, and M dwarfs in the solar vicinity. Some objects are located more than 7 kpc from the Galactic plane. Ultimately, we aim to present value-added catalog and update the FBS LTS catalog. Note that a large amount of the blue stellar objects with UVX-excess and numerous of emission line objects were also detected

TYC 1417-891-1 and TYC 1478-742-1: Eclipsing Variable Stars. The Gaia EDR3 and TESS Photometric Data

International audienceBased on the TESS (Transiting Exoplanet Survey Satellite) phase dependent light curves, we confirm the eclipsing type variability nature for two G-type dwarfs: TYC 1417-891-1 and TYC 1478-742-1. Both objects show EA (Algol-type) light curves morphology. Orbital period for TYC 1417-891-1 is P ≈ 8.0 day and for TYC 1478-742-1, P ≈ 13.6 day. We present Gaia EDR3 and TESS catalogue important physical parameters as well as LAMOST spectra. Both objects are relatively bright and are located at a distance of 260.59 (±3.21) pc (TYC 1417-891-1) and 117.42 (±0.74) pc (TYC 1478-742-1). The TESS light curve of TYC 1478-742-1 shows also flares as well. We discuss possible nature of the secondary and faint objects around these stars