The Hamburg/RASS Catalogue of optical identifications

Zickgraf, F. J.; Engels, D.; Hagen, H. J.; Reimers, D.; Voges, W.

doi:10.1051/0004-6361:20030679

Cited by 88 publications

(132 citation statements)

References 42 publications

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“…The very soft X-ray spectrum (HR1 = −1.0) clearly points towards the white dwarf PG 1232+238 as the counterpart, consistent with the identification by Zickgraf et al (2003).…”

Section: Sdss Spectrasupporting

confidence: 82%

“…38a: classified as QSO in Zickgraf et al (2003); too faint on Sonneberg plates for variability assessment. The SDSS-III spectrum classifies it as broadline QSO at z = 0.5471.…”

Section: Sdss Spectramentioning

confidence: 99%

“…Possibly an optically faint X-ray binary or an X-ray bright AGN, based on f X / f opt . Zickgraf et al (2003) report "BLUE-WK", a moderately blue continuum, weak point-like object. The SDSS-III spectrum classifies it as broadline QSO at z = 0.1606.…”

Section: Sdss Spectramentioning

confidence: 99%

“…132a: galaxy (by extent). Zickgraf et al (2003) reports "BLUE-WK", a moderately blue continuum, weak point-like object. The f X / f opt ratio suggests an AGN nature.…”

Section: Sdss Spectramentioning

confidence: 99%

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Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes

Greiner

Richter

2015

A&A

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Context. The optical identification of large number of X-ray sources such as those from the ROSAT All-Sky Survey is challenging with conventional spectroscopic follow-up observations. Aims. We investigate two ROSAT All-Sky Survey fields of size 10 • × 10 • each, one at galactic latitude b = 83 • (26 Com), the other at b = −5 • (γ Sge), in order to optically identify the majority of sources. Methods. We used optical variability, among other more standard methods, as a means of identifying a large number of ROSAT All-Sky Survey sources. All objects fainter than about 12 mag and brighter than about 17 mag, in or near the error circle of the ROSAT positions, were tested for optical variability on hundreds of archival plates of the Sonneberg field patrol.Results. The present paper contains probable optical identifications of altogether 256 of the 370 ROSAT sources analysed. In particular, we found 126 active galactic nuclei (some of them may be misclassified cataclysmic variables, CVs), 17 likely clusters of galaxies, 16 eruptive double stars (mostly CVs), 43 chromospherically active stars, 65 stars brighter than about 13 mag, 7 UV Cet stars, 3 semiregular resp. slow irregular variable stars of late spectral type, 2 DA white dwarfs, 1 Am star, 1 supernova remnant and 1 planetary nebula. As expected, nearly all active galactic nuclei are found in the high-galactic latitude field, while the majority of CVs is located at low galactic latitudes. We identify in total 72 new variable objects. Conclusions. X-ray emission is, expectedly, tightly correlated with optical variability, and thus our new method for optically identifying X-ray sources is demonstrated to be feasible. Given the large number of optical plates used, this method was most likely not more efficient than e.g. optical spectroscopy. However, it required no telescope time, only access to archival data.

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“…The very soft X-ray spectrum (HR1 = −1.0) clearly points towards the white dwarf PG 1232+238 as the counterpart, consistent with the identification by Zickgraf et al (2003).…”

Section: Sdss Spectrasupporting

confidence: 82%

“…38a: classified as QSO in Zickgraf et al (2003); too faint on Sonneberg plates for variability assessment. The SDSS-III spectrum classifies it as broadline QSO at z = 0.5471.…”

Section: Sdss Spectramentioning

confidence: 99%

Section: Sdss Spectramentioning

confidence: 99%

“…132a: galaxy (by extent). Zickgraf et al (2003) reports "BLUE-WK", a moderately blue continuum, weak point-like object. The f X / f opt ratio suggests an AGN nature.…”

Section: Sdss Spectramentioning

confidence: 99%

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Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes

Greiner

Richter

2015

A&A

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“…It is listed in the ROSAT all-sky survey (Schwope et al 2000) and identified in the Hamburg/RASS bright source identification catalogue (Zickgraf et al 2003). A study of the X-ray selected Seyfert galaxies by Vaughan et al (2001) listed HD 123351 in their Galactic sample with a Galactic column density of 1.25 × 10 20 cm −2 .…”

Section: Introductionmentioning

confidence: 99%

Binary-induced magnetic activity?

Strassmeier

Carroll

Weber

et al. 2011

A&A

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Context. Multi-wavelength time-series observations with high cadence and long duration are needed to resolve and understand the many variations of magnetically active late-type stars, which is an approach often used to observe the Sun. Aims. We present a first and detailed study of the bright and active K0IV-III star HD 123351. Methods. We acquired a total of 955 high-resolution STELLA echelle spectra during the years 2006-2010 and a total of 2260 photometric VI C data points during 1998-2010. These data are complemented by some spectra from CFHT and KPNO. Results. The star is found to be a single-lined spectroscopic binary with a period of 147.8919 ± 0.0003 days and a large eccentricity of e = 0.8086 ± 0.0001. The rms of the orbital solution is just 47 m s −1 , making it the most precise orbit ever obtained for an active binary system. The rotation period is constrained from long-term photometry to be 58.32 ± 0.01 days. It shows that HD 123351 is a very asynchronous rotator, rotating five times slower than the expected pseudo-synchronous value. Two spotted regions persisted throughout the 12 years of our observations. We interpret them as active longitudes on a differentially rotating surface with a ΔP/P of 0.076. Four years of Hα, Ca ii H&K and He i D3 monitoring identifies the same main periodicity as the photometry but dynamic spectra also indicate that there is an intermittent dependence on the orbital period, in particular for Ca ii H&K in 2008. Line-profile inversions of a pair of Zeeman sensitive/insensitive iron lines yield an average surface magnetic-flux density of 542 ± 72 G. The time series for 2008 is modulated by the stellar rotation as well as the orbital motion, such that the magnetic flux is generally weaker during times of periastron and that the chromospheric emissions vary in anti-phase with the magnetic flux. We also identify a broad and asymmetric lithium line profile and measure an abundance of log n(Li) = 1.70 ± 0.05. The star's position in the H-R diagram indicates a mass of 1.2 ± 0.1 M and an age of 6-7 Gyr. Conclusions. We interpret the anti-phase relation of the magnetic flux with the chromospheric emissions as evidence that there are two magnetic fields present at the same time, a localized surface magnetic field associated with spots and a global field that is oriented towards the (low-mass) secondary component. We suggest that the inter-binary field is responsible for the magnetic-flux dilution at periastron. It is also likely to be responsible for the unexpected slow and asynchronous rotation of the primary star.

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Spectroscopic and photometric confirmation of chromospheric activity in four stars

Özdarcan

Dal

2018

Astron Nachr

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We present analysis of medium resolution optical spectra and long term V band photometry of four cool stars, BD+13 5000, BD+11 3024, TYC 3557-919-1 and TYC 5163-1764-1. Our spectroscopic analysis reveals that the stars are giant or sub-giant from K0 or K1 spectral type, and all of them exhibit emission features in their Ca ii H& K lines. These features appear to be modulated with the rotation of the stars. Except BD+11 3024, we observe that the radial velocities of the target stars are not stable, which suggests that each of them might be a member of a binary system. Global analysis of photometric data indicates clear cyclic variation for BD+13 5000 and TYC 5163-1764-1 with a period of 8.0±0.3 and 5.04±0.04 year, respectively. Besides that, we observe a dramatic increase (∼0. m 7) in the mean brightness of BD+11 3024, accompanied with a 2.87 ± 0.12 cyclic variation, embedded into the global brightening trend, which indicates possible multiple cycles on this star.

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The Hamburg/RASS Catalogue of optical identifications

Cited by 88 publications

References 42 publications

Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes

Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes

Binary-induced magnetic activity?

Spectroscopic and photometric confirmation of chromospheric activity in four stars

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