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4721. Optical & FeII sources in Supernova remnant with HST
ID:
ivo://CDS.VizieR/J/ApJ/899/14
Title:
Optical & FeII sources in Supernova remnant with HST
Short Name:
J/ApJ/899/14
Date:
14 Mar 2022 07:07:21
Publisher:
CDS
Description:
NGC6946 is a high-star-formation-rate, face-on, spiral galaxy that has hosted 10 supernovae since 1917. Not surprisingly, a large number of supernova remnants and candidates have been identified either as optical nebulae with high [SII]:H{alpha} line ratios (147) or as compact non-thermal radio sources (35). However, there are only seven overlaps between these two samples. Here, we apply [FeII] 1.644{mu}m emission as a new diagnostic to search for supernova remnants in an attempt to resolve this discrepancy. [FeII] is expected to be relatively strong in the radiative shocks of supernova remnants and almost absent in HII regions. It is less susceptible to the effects of absorption along the line of sight than the optical lines normally used to identify remnants. Using data from the WFC3 camera on Hubble Space Telescope (HST), we identify 132 [FeII] emission nebulae in NGC6946 as likely supernova remnants. Of these, 54 align with previously known optical supernova remnants. The remaining 78 objects are new; of these 44 are visible in new HST imagery in H{alpha} and [SII]. This brings the total number of supernova remnant candidates (from optical and/or IR data) in NGC6946 to 225. A total of 14 coincidences with radio supernova remnant candidates (out of 30 in our search area) are found in this expanded list. The identification of so many new remnant candidates validates the use of [FeII] imagery for finding remnants, and suggests that previous remnant searches in other galaxies may be far from complete.
4722. Optical flares on EV Lac in 1967-1977
ID:
ivo://CDS.VizieR/J/A+A/327/1114
Title:
Optical flares on EV Lac in 1967-1977
Short Name:
J/A+A/327/1114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on a large sample of homogeneous photoelectric data obtained by monitoring the red dwarf flare star EV Lac. The data were collected in 10 years (1967-77) at Catania Astrophysical Observatory on Mt. Etna. The peak luminosity, the total energy emitted, the rise and decay times were measured for each flare.
4723. Optical flux behaviour of Fermi blazars
ID:
ivo://CDS.VizieR/J/A+A/591/A21
Title:
Optical flux behaviour of Fermi blazars
Short Name:
J/A+A/591/A21
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim at investigating the time-behaviour of a sample of gamma-ray blazars. We present the results from a 13 month-long optical photometry monitoring campaign of the blazars PKS0048-097, PKS0754+100, [HB89] 0827+243, PKS0851+202, PKS1253-055, PKS1510-089, PKS1749+096, PKS2230+114 and PKS2251+158. We analyse the variability of each object, focusing on different time-scales (long term, short term, and microvariability), in an attempt to achieve a statistical comparison of the results. After applying a geometric model to explain the variability results, we found that it is possible that a slight change in the direction of the jet generates the variations detected in some objects during this campaign.
4724. Optical follow-up of ASAS-SN M dwarf flares
ID:
ivo://CDS.VizieR/J/ApJ/876/115
Title:
Optical follow-up of ASAS-SN M dwarf flares
Short Name:
J/ApJ/876/115
Date:
18 Jan 2022 15:06:46
Publisher:
CDS
Description:
The All-sky Automated Survey for Supernovae (ASAS-SN) is the only project in existence to scan the entire sky in optical light approximately every day, reaching a depth of g~18mag. Over the course of its first 4yr of transient alerts (2013-2016), ASAS-SN observed 53 events classified as likely M dwarf flares. We present follow-up photometry and spectroscopy of all 53 candidates, confirming flare events on 47 M dwarfs, one K dwarf, and one L dwarf. The remaining four objects include a previously identified T Tauri star, a young star with outbursts, and two objects too faint to confirm. A detailed examination of the 49 flare star light curves revealed an additional six flares on five stars, resulting in a total of 55 flares on 49 objects ranging in V-band contrast from {Delta}V=-1 to -10.2mag. Using an empirical flare model to estimate the unobserved portions of the flare light curve, we obtain lower limits on the V-band energy emitted during each flare, spanning log(E_V_/erg)=32-35, which are among the most energetic flares detected on M dwarfs. The ASAS-SN M dwarf flare stars show a higher fraction of H{alpha} emission, as well as stronger H{alpha} emission, compared to M dwarfs selected without reference to activity, consistent with belonging to a population of more magnetically active stars. We also examined the distribution of tangential velocities, finding that the ASAS-SN flaring M dwarfs are likely to be members of the thin disk and are neither particularly young nor old.
4725. Optical follow-up of Q0957+561 in 2005-2010
ID:
ivo://CDS.VizieR/J/A+A/540/A132
Title:
Optical follow-up of Q0957+561 in 2005-2010
Short Name:
J/A+A/540/A132
Date:
21 Oct 2021
Publisher:
CDS
Description:
The optical variability database of the two images (A and B) of the gravitationally lensed quasar Q0957+561 is based on frames taken with the Liverpool Robotic Telescope in the 2005-2010 period, as part of the Liverpool Quasar Lens Monitoring (LQLM) project (Goicoechea et al. 2010AdAst2010E..29G). A crowded-field photometry pipeline produced instrumental fluxes of both quasar images, and only frames with signal-to-noise ratio above 80 over Q0957+561A were passed through a transformation pipeline. This pipeline transformed instrumental magnitudes into SDSS magnitudes (the calibration-correction scheme is described in Appendix A of Shalyapin et al. (2008A&A...492..401S) and the main text of the paper). We also turned SDSS magnitudes into physical fluxes using suitable conversion equations (SDSS Photometric Flux Calibration 2007, http://www.sdss.org/dr7/algorithms/fluxcal.html). Table 1 contains g-band fluxes for 357 different nights, while Table 2 includes r-band fluxes for 371 observation nights.
4726. Optical identification of ROSAT-FSC sources
ID:
ivo://CDS.VizieR/J/A+A/449/425
Title:
Optical identification of ROSAT-FSC sources
Short Name:
J/A+A/449/425
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Byurakan/Hamburg/ROSAT Catalogue (BHRC) of the optical identifications of X-ray sources is presented. The BHRC includes all 2791 sources from the ROSAT-FSC (<IX/29>) with |b|>30, DEC>0 and ROSAT count rate CR>0.04cts/s. The optical identifications were carried out by means of the Hamburg Quasar Survey (HQS) digitized spectroscopic plates, the DSS1 and DSS2 (blue, red, and IR) images, and other available data. We managed to identify 97% of sources (2696 sources) that are associated with 3202 optical objects. 2248 X-ray sources have a single optical counterpart, 144 have a double or multiple optical counterpart (binaries, galaxy groups etc.), and 304 have ambiguous identifications. The table gives all available multiwavelength data for the identified sources.
4727. Optical identification of XMM-LSS sources
ID:
ivo://CDS.VizieR/J/MNRAS/401/294
Title:
Optical identification of XMM-LSS sources
Short Name:
J/MNRAS/401/294
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present optical spectroscopic identifications of X-ray sources in ~3deg^2^ of the XMM-Large Scale Structure survey (XMM-LSS), also covered by the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS), obtained with the AAOmega instrument at the Anglo-Australian Telescope. In a flux-limited sample of 829 point-like sources in the optical band with g'<=22mag and the 0.5-2keV flux (f_0.5-2keV_)>10^-15^erg/cm^2^/s, we observed 693 objects and obtained reliable spectroscopic identification for 487 sources, approximately 59 per cent of the overall sample.
4728. Optical identifications of Molonglo sources
ID:
ivo://CDS.VizieR/J/MNRAS/227/607
Title:
Optical identifications of Molonglo sources
Short Name:
J/MNRAS/227/607
Date:
21 Oct 2021
Publisher:
CDS
Description:
Optical identifications have been sought for 304 radio sources from the declination -20{deg} region of the first Molonglo deep survey. Optical objects have been measured using the Palomar sky survey to an accuracy of 1 arcsec and magnitude estimates are to 0.4mag. Finding charts are given for all fields with optical objects within +/-2{sigma} of the radio position. Sixteen QSOs have been confirmed (details have been reported elsewhere) amongst the blue stellar-like objects and spectroscopy is complete to m_o_=19.5. The mean magnitude of the QSOs is 19.2 and the mean redshift is 1.34. A study of the background densities of objects indicates that about half of the remaining blue stellar-like objects are QSOs and about 80 per cent of the galaxies are associated with the radio emission. The QSOs are amongst the fainter and the bluer of the blue stellar-like objects. There is no evidence for any average offset between the radio and optical positions.
4729. Optical Imaging of 57 spiral galaxies
ID:
ivo://CDS.VizieR/VI/112
Title:
Optical Imaging of 57 spiral galaxies
Short Name:
VI/112
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present optical observations of a sample of 57 spiral galaxies and describe the procedures followed to reduce the data. We have obtained images in the optical B and I broad bands, as well as in H{alpha}, with moderate spatial resolution and across wide enough fields to image the complete disks of the galaxies. In addition, we observed 55 of our sample galaxies in the R and eight in the V band, and imaged a subset through a dedicated narrow continuum filter for the H{alpha} line. We describe the data reduction procedures we developed in the course of this work to register, combine and photometrically calibrate each set of images for an individual galaxy. We describe in some detail the procedure used to subtract the continuum emission from our H{alpha} images. In companion papers, we describe near-infrared imaging of the galaxy sample, and present analyses of disk scale lengths, and of properties of bars, rings, and HII regions in the sample galaxies. The images described here will be made available for use by other researchers through the CDS.
4730. Optical-infrared colors of CORALS QSOs
ID:
ivo://CDS.VizieR/J/AJ/130/1345
Title:
Optical-infrared colors of CORALS QSOs
Short Name:
J/AJ/130/1345
Date:
21 Oct 2021
Publisher:
CDS
Description:
The presence of dust in quasar absorbers, such as damped Ly{alpha} (DLA) systems, may cause the background QSO to appear reddened. We investigate the extent of this potential reddening by comparing the optical-to-infrared colors of QSOs with and without intervening absorbers. Our QSO sample is based on the Complete Optical and Radio Absorption Line System (CORALS) survey of Ellison and coworkers. The CORALS data set consists of 66 radio-selected QSOs at z_em_>=2.2 with complete optical identifications. We have obtained near-simultaneous B- and K-band magnitudes for a subset of the CORALS sample and supplemented our observations with further measurements published in the literature. In total, we have B-K colors for 42 of the 66 QSOs, of which 14 have intervening DLA systems. To account for redshift-related color changes, the B-K colors are normalized using the Sloan Digital Sky Survey QSO composite.