ESO New Technology Telescope Research Articles

Near-infrared and optical observations of the failed outbursts of black hole binary XTE J1550−564

A number of low mass X-ray binaries (LMXBs) undergo "failed outbursts" in which, instead of evolving through the canonical states, they remain in a hard state throughout the outburst. While the sources of X-ray and radio emission in the hard state are relatively well understood, the origin of the near infrared (NIR) and optical emission is more complex though it likely stems from an amalgam of different emission processes, occurring as it does, at the intersecting wavelengths of those processes. We aim to identify the NIR/optical emission region(s) during a number of failed outbursts of one such low mass X-ray binary and black hole candidate, XTE J1550-564, in order to confirm or refute their classification as hard-state, failed outbursts. We present unique NIR/optical images and spectra, obtained with the ESO-New Technology Telescope, during the failed outbursts of 2001 and 2000. We compare the NIR/optical photometric, timing, and spectral properties with those expected for the different emission mechanisms in the various LMXB states. The NIR/optical data are consistent with having come from reprocessing of X-rays in the accretion disk, with no evidence of direct thermal emission from the disk itself. However, the observed variability in high-cadence NIR light curves suggest that the radio jet extends and contributes to the NIR wavelengths. We find that these failed outbursts did not transition to an intermediate state but remained in a true, hard state where there was no sign of jet quenching or deviation from the observed hard state correlations.

Disentangling the NIR/optical emission of the black hole XTE J1650−500 during outburst

While the sources of X-ray and radio emission in the different states of low-mass X-ray binaries are relatively well understood, the origin of the near-infrared (NIR) and optical emission is more often debated. It is likely that the NIR/optical flux originates from an amalgam of different emission regions, because it occurs at the intersecting wavelengths of multiple processes. We aim to identify the NIR/optical emission region(s) of one such low-mass X-ray binary and black hole candidate, XTE J1650-500, via photometric, timing, and spectral analyses. We present unique NIR/optical images and spectra, obtained with the ESO-New Technology Telescope, during the peak of the 2001 outburst of XTE J1650-500. The data suggest that the NIR/optical flux is due to a combination of emission mechanisms including a significant contribution from X-ray reprocessing and, at early times in the hard state, a relativistic jet that is NIR/radio dim compared to similar sources.The jet of XTE J1650-500 is relatively weak compared to that of other black hole low-mass X-ray binaries, possibly because we observe as it is being "turned off" or quenched at the state transition. While there are several outliers to the radio--X-ray correlation of the hard state of low-mass X-ray binaries, XTE J1650-500 is the first example of an outlier to the NIR/optical--X-ray correlation.

Observations and properties of candidate high-frequency GPS radio sources in the AT20G survey

We used the Australia Telescope Compact Array (ATCA) to obtain 40 GHz and 95 GHz observations of a number of sources that were selected from the Australia Telescope Compact Array 20 GHz (AT20G) survey . The aim of the observations was to improve the spectral coverage for sources with spectral peaks near 20 GHz or inverted (rising) radio spectra between 8.6 GHz and 20 GHz. We present the radio observations of a sample of 21 such sources along with optical spectra taken from the ANU Siding Spring Observatory 2.3m telescope and the ESO-New Technology Telescope (NTT). We find that as a group the sources show the same level of variability as typical GPS sources, and that of the 21 candidate GPS sources roughly 60% appear to be genuinely young radio galaxies. Three of the 21 sources studied show evidence of being restarted radio galaxies. If these numbers are indicative of the larger population of AT20G radio sources then as many as 400 genuine GPS sources could be contained within the AT20G with up to 25% of them being restarted radio galaxies.

Near-infrared photometry of carbon stars in the Sagittarius dwarf irregular galaxy and DDO 210

Aims. We investigate the intermediate-age asymptotic giant branch stellar population of two Local Group dwarf irregular galaxies to characterize their carbon star population in near-infrared (IR). Methods. Our work is based on near-IR photometry complemented with optical ground based and Hubble Space Telescope (HST) photometry. Near-IR photometry is based on our and archival J and Ks-band images from SOFI near-IR array of the ESO New Technology Telescope (NTT). Optical photometry for DDO 210 is from the EMMI optical imager of ESO NTT, while the SagDIG optical data come from Momany et al. (2005, A&A, 439, 111). Results. We show that near-IR photometry is a very powerful tool for carbon star detection. We recovered two out of three previouslyknown carbon stars in DDO 210 and discovered six additional objects in this galaxy which have optical and near-IR colors consistent with carbon giants. This brings the total number of bona fide C-star candidates in DDO 210 to nine. However, to confirm the nature of these objects additional higher spatial resolution imaging or spectroscopic data are necessary. We detected a large population of C-star candidates in SagDIG, 18 of which were previously identified in Demers & Battinelli (2002, AJ, 123, 238) and Cook (1987, Ph.D. Thesis), and six new bona fide carbon stars. We present their optical and near-IR colors and use their luminosity function to put constraints on the star formation history (SFH) in this dwarf irregular galaxy.

High-resolution optical imaging of the Large Magellanic Cloud plerion 0540 - 69

view Abstract Citations (48) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-Resolution Optical Imaging of the Large Magellanic Cloud Plerion 0540-69 Caraveo, P. A. ; Bignami, G. F. ; Mereghetti, S. ; Mombelli, M. Abstract The Crab-like SNR 0540-69 in the LMC has been investigated using the ESO NTT (New Technology Telescope) equipped with SUSI (SUperb Seeing Imager). B, V, O III, S II, and Hα images were collected under very good seeing conditions, yielding unprecedented detail on the picture of the expanding shell as well as of the synchrotron nebula, which is shown to harbor two maxima of emission. Both of these are seen to have magnitudes comparable to that of the optical pulsar reported by Middleditch et al. (1987), the northern one appearing more compact. The Hα image shows previously unseen structures, apparently unrelated to the expanding shell as well as to the synchrotron nebula. The Hα extent of the remnant is significantly smaller than that at other wavelengths and shows a symmetric pattern centered on the northern maximum of continuum emission which could very well be the optical counterpart of PSR 0540-69. Publication: The Astrophysical Journal Pub Date: August 1992 DOI: 10.1086/186498 Bibcode: 1992ApJ...395L.103C Keywords: Magellanic Clouds; Pulsars; Supernova Remnants; Astronomical Spectroscopy; Emission Spectra; H Alpha Line; Line Spectra; Synchrotron Radiation; Astronomy full text sources ADS | data products SIMBAD (4) NED (2)

Active optics and the new technology telescope (NTT): The key to improved optical quality at lower cost in large astronomical telescopes

Abstract The first fully ‘active’ telescope, the ESO NTT, produced its first astronomical images (‘First Light’) in March 1989. The spectacular results and the background work leading to them are described. The origins of the development of the active optics concept are reviewed and a description of the NTT system is given. Recent operational results and limitations to optical quality are discussed, as well as the steps taken to establish a fully automatic correction system. Finally, the optical efficiency of telescopes is considered in the light of the NTT experience and the implications for future ground- and space-based telescopes summarized.