- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/880/32
- Title:
- Optical/{gamma}-ray flares for Fermi-LAT blazars
- Short Name:
- J/ApJ/880/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Even with several thousand Fermi-Large Area Telescope (LAT) blazar detections, the {gamma}-ray emission mechanism is poorly understood. We explore correlated optical/{gamma}-ray flux variations for 178 Fermi-LAT blazars regularly monitored by the Katzman Automatic Imaging Telescope, the Small and Moderate Aperture Research Telescope System, and the Steward Observatory. Out of the 178 sources, 121 show a measurable (>1{sigma}) discrete correlation function peak. Using the derived time lags and Bayesian block light-curve decompositions, we measure the fraction of common and orphan flares between the two bands. After accounting for sampling and sensitivity limitations we quantify for the first time the true orphan flare rates of optical and {gamma}-ray flares: 54.5% of optical and 20% of {gamma}-ray flares are orphan events. Both the intraband temporal relation and the small orphan {gamma}-ray flare fraction point toward leptonic processes as the likely mechanisms for the high-energy emission. Motivated to discriminate between synchrotron self-Compton (SSC) and external-Compton dominance in individual sources, we use the flux-flux variations to determine the slope m of the log fopt-log f{gamma} dependence. The slope distribution suggests a bimodal population with high and intermediate synchrotron peak objects showing larger m than low synchrotron peak objects. We find that m is naturally decreased through pollution from the orphan (typically optical) flares and develop a method to statistically recover, given the sources' measured orphan flare rate, the intrinsic m. While source classes show composite behavior, the majority of BL Lac objects favor m=2, indicating an SSC origin for the {gamma}-rays. No preference for either m is found in flat spectrum radio quasars.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/329/700
- Title:
- Optical IDs of JVAS using APM
- Short Name:
- J/MNRAS/329/700
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Files list1, list2, and list3 contain the lists of flat spectrum radio sources with their optical identifications from the APM (Automated Plate Measurement Facility at Cambridge) catalogue. List1 corresponds to the sources which are part of both the complete JVAS++ (a new complete sample constructed with selection criteria similar to those of JVAS -- Jodrell Bank VLA Astrometric Survey: S_5GHz_>200mJy, {alpha}_1.4-5GHz_>-0.5), and with the use of the more accurate GB6 and NVSS surveys) and original JVAS sample, List2 corresponds to sources which are only part of JVAS++, and List3 to sources which are only part of JVAS. The combination of List1 and List2 is a complete sample with S_6cm_>200mJy.
1876. Optical imaging for S4G
- ID:
- ivo://CDS.VizieR/J/A+A/569/A91
- Title:
- Optical imaging for S4G
- Short Name:
- J/A+A/569/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Spitzer Survey for Stellar Structure in Galaxies (S4G) and its more recently approved extension will lead to a set of 3.6 and 4.5um images for 2829 galaxies, which can be used to study many different aspects of the structure and evolution of local galaxies. We have collected and re-reduced optical images of 1768 of the survey galaxies, aiming to make these available to the community as ready-to-use FITS files to be used in conjunction with the mid-IR images. Our sky-subtraction and mosaicking procedures were optimised for imaging large galaxies. We also produce false-colour images of some of these galaxies to be used for illustrative and public outreach purposes. We collected and re-processed images in five bands from the Sloan Digital Sky Survey for 1657 galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/37
- Title:
- Optical interferometry of 6 O-type HD stars
- Short Name:
- J/ApJ/869/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present interferometric observations of six O-type stars that were made with the Precision Astronomical Visible Observations beam combiner at the Center for High Angular Resolution Astronomy (CHARA) Array. The observations include multiple brackets for three targets, {lambda} Ori A, {zeta} Oph, and 10 Lac, but there are only preliminary, single observations of the other three stars, {xi} Per, {alpha} Cam, and {zeta} Ori A. The stellar angular diameters range from 0.55mas for {zeta} Ori A down to 0.11mas for 10 Lac, the smallest star yet resolved with the CHARA Array. The rotational oblateness of the rapidly rotating star {zeta} Oph is directly measured for the first time. We assembled ultraviolet to infrared flux measurements for these stars, and then derived angular diameters and reddening estimates using model atmospheres and an effective temperature set by published results from analysis of the line spectrum. The model-based angular diameters are in good agreement with those observed. We also present estimates for the effective temperatures of these stars, derived by setting the interferometric angular size and fitting the spectrophotometry.
- ID:
- ivo://CDS.VizieR/J/MNRAS/238/1171
- Title:
- Optical/IR observ. of Radio Galaxies and QSOs
- Short Name:
- J/MNRAS/238/1171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog reports on an extensive optical and infrared study of the 178 radio sources in the Parkes Selected Regions (S > 100 mJy at 2.7 GHz). CCD observations have resulted in the essential completion (95 percent) of optical identifications and have provided B and R photometry. In addition, K photometry has been completed for four of the six selected regions.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A90
- Title:
- Optically bright post-AGB population of LMC
- Short Name:
- J/A+A/530/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct a catalogue of the optically bright post-AGB stars in the LMC. The sample forms an ideal testbed for stellar evolution theory predictions of the final phase of low- and intermediate-mass stars, because the distance and hence luminosity and also the current and initial mass of these objects is well constrained.
- ID:
- ivo://CDS.VizieR/J/AJ/139/390
- Title:
- Optically selected BL Lac objects from SDSS-DR7
- Short Name:
- J/AJ/139/390
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 723 optically selected BL Lac candidates from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) spectroscopic database encompassing 8250deg^2^ of sky; our sample constitutes one of the largest uniform BL Lac samples yet derived. Each BL Lac candidate has a high-quality SDSS spectrum from which we determine spectroscopic redshifts for ~60% of the objects. Redshift lower limits are estimated for the remaining objects utilizing the lack of host galaxy flux contamination in their optical spectra; we find that objects lacking spectroscopic redshifts are likely at systematically higher redshifts.
