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Register a new userThe new carbon symbiotic star IPHAS J205836.43+503307.2
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Added by
Romano L. M. Corradi
Publication date
2011
fields
Physics
and research's language is
English
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We are performing a search for symbiotic stars using IPHAS, the INT Halpha survey of the northern Galactic plane, and follow-up observations. Candidate symbiotic stars are selected on the basis of their IPHAS and near-IR colours, and spectroscopy and photometry are obtained to determine their nature. We present here observations of the symbiotic star candidate IPHAS J205836.43+503307.2. The optical spectrum shows the combination of a number of emission lines, among which are the high-excitation species of [OIII], HeII, [Ca V], and [Fe VII], and a red continuum with the features of a star at the cool end of the carbon star sequence. The nebular component is spatially resolved: the analysis of the spatial profile of the [NII]6583 line in the spectrum indicates a linear size of ~2.5 arcsec along the east-west direction. Its velocity structure suggests an aspherical morphology. The near-infrared excess of the source, which was especially strong in 1999, indicated that a thick circumstellar dust shell was also present in the system. The carbon star has brightened in the last decade by two to four magnitudes at red and near-infrared wavelengths. Photometric monitoring during a period of 60 days from November 2010 to January 2011 reveals a slow luminosity decrease of 0.2 magnitudes. From the observed spectrophotometric properties and variability, we conclude that the source is a new Galactic symbiotic star of the D-type, of the rare kind that contains a carbon star, likely a carbon Mira. Only two other systems of this type are known in the Galaxy.
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We present and discuss the results of our photometric and spectroscopic monitoring of 2SXPS J173508.4-292958 carried out from April to August 2020. This X-ray source, in the foreground with respect to the Galactic center, brightened in X-rays during 2020, prompting our follow-up optical observations. We found the star to contain a K4III giant with a modest but highly variable Halpha emission, composed by a ~470 km/s wide component with superimposed a narrow absorption, offset by a positive velocity with respect to the giant. No orbital motion is detected for the K4III, showing an heliocentric radial velocity stable at -12(+/-1) km/s. No flickering in excess of 0.005 mag in B band was observed at three separate visits of 2SXPS J173508.4-292958. While photometrically stable in 2016 through 2018, in 2019 the star developed a limited photometric variability, that in 2020 took the form of a sinusoidal modulation with a period of 38 days and an amplitude of 0.12 mag in V band. We argue this variability cannot be ascribed to Roche-lobe filling by the K4III star. No correlation is observed between the photometric variability and the amount of emission in Halpha, the latter probably originating directly from the accretion disk around the accreting companion. While no emission from dust is detected at mid-IR wavelengths, an excess in U-band is probably present and caused by direct emission from the accretion disk. We conclude that 2SXPS J173508.4-292958 is a new symbiotic star of the accreting-only variety (AO-SySt).
In a previous paper [arXiv:0712.2391], we presented the selection criteria needed to search for symbiotic stars in IPHAS, the INT Halpha survey of the Northern Galactic plane. IPHAS gives us the opportunity to make a systematic, complete search for symbiotic stars in a magnitude-limited volume. Follow-up spectroscopy at different telescopes worldwide of a sample of sixty two symbiotic star candidates is presented. Seven out of nineteen S-type candidates observed spectroscopically are confirmed to be genuine symbiotic stars. The spectral type of their red giant components, as well as reddening and distance, were computed by modelling the spectra. Only one new D-type symbiotic system, out of forty-three candidates observed, was found. This was as expected (see discussion in our paper on the selection criteria). The object shows evidence for a high density outflow expanding at a speed larger than 65 km/s. Most of the other candidates are lightly reddened classical T Tauri stars and more highly reddened young stellar objects that may be either more massive young stars of HAeBe type or classical Be stars. In addition, a few notable objects have been found, such as three new Wolf-Rayet stars and two relatively high-luminosity evolved massive stars. We also found a helium-rich source, possibly a dense ejecta hiding a WR star, which is surrounded by a large ionized nebula.
As part of a systematic search programme of a 10-degree wide strip of the Northern Galactic plane we present preliminary evidence for the discovery of four (and possibly five) new supernova remnants (SNRs). The pilot search area covered the 19-20 hour right ascension zone sampling from +20 to +55 degrees in declination using binned mosaic images from the INT Photometric H-alpha Survey (IPHAS). The optical identification of the candidate SNRs was based mainly on their filamentary and arc-like emission morphologies, their apparently coherent, even if fractured structure and clear disconnection from any diffuse neighbouring HII region type nebulosity. Follow-up optical spectroscopy was undertaken, sampling carefully across prominent features of these faint sources. The resulting spectra revealed typical emission line ratios for shock excited nebulae which are characteristic of SNRs, which, along with the latest diagnostic diagrams, strongly support the likely SNR nature of these sources: G038.7-1.3 (IPHASX J190640.5+042819); G067.6+0.9 (IPHASX J195744.9+305306); G066.0-0.0 (IPHASX J195749.2+290259) and G065.8-0.5 (IPHASX J195920.4+283740). A fifth possible younger, higher density nebula SNR candidate, G067.8+0.5 (IPHASX J200002.4+305035) was discovered about 5 arcmins to the west of IPHASX J195744.9+305306, and warrants further study. A multi-wavelength cross-check from available archived data in the regions of these candidates was also performed with a focus on possible radio counterparts.
Faint high latitude carbon stars are rare objects commonly thought to be distant, luminous giants. For this reason they are often used to probe the structure of the Galactic halo; however more accurate investigation of photometric and spectroscopic surveys has revealed an increasing percentage of nearby objects with luminosities of main sequence stars. Aiming at clarifyin the nature of the ten carbon star candidates present in the General Catalog of the Second Byurakan Survey we analyzed new optical spectra and photometry and used astronomical databases available on the web. We verified that two stars are N-type giants already confirmed by other surveys. We found that four candidates are M type stars and confirmed the carbon nature of the remaining four stars; the characteristics of three of them are consistent with an early CH giant type. The fourth candidate, SBS1310+561 identified with a high proper motion star, is a rare type of dwarf carbon showing emission lines in its optical spectrum. We estimated absolute magnitudes and distances to the dwarf carbon and the three CH stars. Our limited sample confirmed the increasing evidence that spectroscopy or colour alone are not conclusive luminosity discriminants for CH$-$type carbon stars .
We present the first results of our search for new, extended Planetary Nebulae (PNe) based on careful, systematic, visual scrutiny of the imaging data from the INT Photometric H-alpha Survey of the Northern Galactic Plane (IPHAS). The newly uncovered PNe will help to improve the census of this important population of Galactic objects that serve as key windows into the late stage evolution of low to intermediate mass stars. They will also facilitate study of the faint end of the ensemble Galactic PN luminosity function. The sensitivity and coverage of IPHAS allows PNe to be found in regions of greater extinction in the Galactic Plane and/or those PNe in a more advanced evolutionary state and at larger distances compared to the general Galactic PN population. Using a set of newly revised optical diagnostic diagrams in combination with access to a powerful, new, multi-wavelength imaging database, we have identified 159 true, likely and possible PNe for this first catalogue release. The ability of IPHAS to unveil PNe at low Galactic latitudes and towards the Galactic Anticenter, compared to previous surveys, makes this survey an ideal tool to contribute to the improvement of our knowledge of the whole Galactic PN population
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