- ID:
- ivo://CDS.VizieR/J/AJ/159/187
- Title:
- First RVs with the EXPRES spectrograph: 51Peg
- Short Name:
- J/AJ/159/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The EXtreme-PREcision Spectrograph (EXPRES) is an environmentally stabilized, fiber-fed, R=137500, optical spectrograph. It was recently commissioned at the 4.3m Lowell Discovery Telescope near Flagstaff, Arizona. The spectrograph was designed with a target radial-velocity (RV) precision of 30cm/s. In addition to instrumental innovations, the EXPRES pipeline, presented here, is the first on-sky, optical, fiber-fed spectrograph to employ many novel techniques-including an "extended flat" fiber used for wavelength-dependent quantum efficiency characterization of the CCD, a flat-relative optimal extraction algorithm, chromatic barycentric corrections, chromatic calibration offsets, and an ultra-precise laser frequency comb for wavelength calibration. We describe the reduction, calibration, and RV analysis pipeline used for EXPRES and present an example of our current sub-meter-per-second RV measurement precision, which reaches a formal, single-measurement error of 0.3m/s for an observation with a per-pixel signal-to-noise ratio of 250. These velocities yield an orbital solution on the known exoplanet host 51Peg that matches literature values with a residual rms of 0.895m/s.
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- ID:
- ivo://CDS.VizieR/J/AJ/151/142
- Title:
- Five years of blazar observations with VERITAS
- Short Name:
- J/AJ/151/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as very-high-energy (VHE; E>100 GeV) {gamma}-ray sources. In this work, we present the analysis results of a sample of 114 undetected objects. The observations constitute a total live-time of ~570 hr. The sample includes several unidentified Fermi-Large Area Telescope (LAT) sources (located at high Galactic latitude) as well as all the sources from the second Fermi-LAT catalog (Nolan et al. 2012, J/ApJS/199/31) that are contained within the field of view of the VERITAS observations. We have also performed optical spectroscopy measurements in order to estimate the redshift of some of these blazars that do not have spectroscopic distance estimates. We present new optical spectra from the Kast instrument on the Shane telescope at the Lick observatory for 18 blazars included in this work, which allowed for the successful measurement or constraint on the redshift of four of them. For each of the blazars included in our sample, we provide the flux upper limit in the VERITAS energy band. We also study the properties of the significance distributions and we present the result of a stacked analysis of the data set, which shows a 4{sigma} excess.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/39
- Title:
- Fluxes of NGG7793 & NGC4945 with GMOS-S
- Short Name:
- J/ApJ/812/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gas-phase abundances in HII regions of two spiral galaxies, NGC7793 and NGC4945, have been studied to determine their radial metallicity gradients. We used the strong-line method to derive oxygen abundances from spectra acquired with GMOS-S, the multi-object spectrograph on the 8m Gemini South telescope. We found that NGC7793 has a well-defined gas-phase radial oxygen gradient of -0.321+/-0.112dexR_25_^-1^ (or -0.054+/-0.019dex/kpc) in the galactocentric range 0.17<R_G_/R_25_<0.82, not dissimilar from gradients calculated with direct abundance methods in galaxies of similar mass and morphology. We also determined a shallow radial oxygen gradient in NGC 4945, -0.253+/-0.149dexR_25_^-1^ (or -0.019+/-0.011dex/kpc) for 0.04<R_G_/R_25_<0.51, where the larger relative uncertainty derives mostly from the larger inclination of this galaxy. NGC 7793 and NGC 4945 have been selected for this study because they are similar, in mass and morphology, to M33 and the Milky Way, respectively. Since at zeroth order we expect the radial metallicity gradients to depend on mass and galaxy type, we compared our galaxies in the framework of radial metallicity models best suited for M33 and the Galaxy. We found a good agreement between M33 and NGC7793, pointing toward similar evolution for the two galaxies. We notice instead differences between NGC 4945 and the radial metallicity gradient model that best fits the Milky Way. We found that these differences are likely related to the presence of an active galactic nucleus combined with a bar in the central regions of NGC 4945, and to its interacting environment.
- ID:
- ivo://CDS.VizieR/J/ApJ/826/144
- Title:
- Follow-up observations of SNIa ASASSN-14lp
- Short Name:
- J/ApJ/826/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On 2014 December 9.61, the All-sky Automated Survey for SuperNovae (ASAS-SN or "Assassin") discovered ASASSN-14lp just ~2 days after first light using a global array of 14cm diameter telescopes. ASASSN-14lp went on to become a bright supernova (V=11.94mag), second only to SN 2014J for the year. We present prediscovery photometry (with a detection less than a day after first light) and ultraviolet through near-infrared photometric and spectroscopic data covering the rise and fall of ASASSN-14lp for more than 100 days. We find that ASASSN-14lp had a broad light curve ({Delta}m_15_(B)=0.80+/-0.05), a B-band maximum at 2457015.82+/-0.03, a rise time of 16.94_-0.10_^+0.11^days, and moderate host-galaxy extinction (E(B-V)_host_=0.33+/-0.06). Using ASASSN-14lp, we derive a distance modulus for NGC 4666 of {mu}=30.8+/-0.2, corresponding to a distance of 14.7+/-1.5Mpc. However, adding ASASSN-14lp to the calibrating sample of Type Ia supernovae still requires an independent distance to the host galaxy. Finally, using our early-time photometric and spectroscopic observations, we rule out red giant secondaries and, assuming a favorable viewing angle and explosion time, any nondegenerate companion larger than 0.34R_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/126
- Title:
- Follow-up obs. of the PSJ0147+4630 lens system
- Short Name:
- J/ApJ/887/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Because follow-up observations of quadruple gravitational lens systems are of extraordinary importance for astrophysics and cosmology, we present single-epoch optical spectra and r-band light curves of PS J0147+4630. This recently discovered system mainly consists of four images ABCD of a background quasar around a foreground galaxy G that acts as a gravitational lens. First, we use long-slit spectroscopic data in the Gemini Observatory Archive and a multi-component fitting to accurately resolve the spectra of A, D, and G. The spectral profile of G resembles that of an early-type galaxy at a redshift of 0.678+/-0.001, which is about 20% higher than the previous estimate. Additionally, the stellar velocity dispersion is measured to ~5% precision. Second, our early r-band monitoring with the Liverpool Telescope leads to accurate light curves of the four quasar images. Adopting time delays predicted by the lens model, the new lens redshift, and a standard cosmology, we report the detection of microlensing variations in C and D as large as ~0.1mag on timescales of a few hundred days. We also estimate an actual delay between A and B of a few days (B is leading), which demonstrates the big potential of optical monitoring campaigns of PS J0147+4630.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/131
- Title:
- Follow-up of candidate counterparts of S190814bv
- Short Name:
- J/ApJ/890/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On 2019 August 14, the Advanced LIGO and Virgo interferometers detected the high-significance gravitational wave (GW) signal S190814bv. The GW data indicated that the event resulted from a neutron star-black hole (NSBH) merger, or potentially a low-mass binary BH merger. Due to the low false-alarm rate and the precise localization (23deg^2^ at 90%), S190814bv presented the community with the best opportunity yet to directly observe an optical/near-infrared counterpart to an NSBH merger. To search for potential counterparts, the GROWTH Collaboration performed real-time image subtraction on six nights of public Dark Energy Camera images acquired in the 3 weeks following the merger, covering >98% of the localization probability. Using a worldwide network of follow-up facilities, we systematically undertook spectroscopy and imaging of optical counterpart candidates. Combining these data with a photometric redshift catalog, we ruled out each candidate as the counterpart to S190814bv and placed deep, uniform limits on the optical emission associated with S190814bv. For the nearest consistent GW distance, radiative transfer simulations of NSBH mergers constrain the ejecta mass of S190814bv to be M_ej_<0.04M_{sun}_ at polar viewing angles, or M_ej_<0.03M_{sun}_ if the opacity is {kappa}<2cm^2^g^-1^. Assuming a tidal deformability for the NS at the high end of the range compatible with GW170817 results, our limits would constrain the BH spin component aligned with the orbital momentum to be {chi}<0.7 for mass ratios Q<6, with weaker constraints for more compact NSs.
- ID:
- ivo://CDS.VizieR/J/ApJ/863/109
- Title:
- Follow-up optical observations of the SNIc SN2014L
- Short Name:
- J/ApJ/863/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical spectroscopic and photometric observations of the nearby type Ic supernova (SN Ic) SN 2014L. This SN was discovered by the Tsinghua-NAOC Transient Survey (TNTS) in the nearby type-Sc spiral galaxy M99 (NGC 4254). Fitting to the early-time light curve indicates that SN 2014L was detected at only a few hours after the shock breakout, and it reached a peak brightness of M_V_=-17.73+/-0.28mag (L=[2.06+/-0.50]x10^42^erg/s) approximately 13 days later. SN 2014L shows a close resemblance to SN 2007gr in the photometric evolution, while it shows stronger absorption features of intermediate-mass elements (especially CaII) in the early-time spectra. Based on simple modeling of the observed light curves, we derived the mass of synthesized ^56^Ni as M_Ni_=0.075+/-0.025M_{sun}_, and the mass and total energy of the ejecta as M_ej_=1.00+/-0.20M_{sun}_ and E_ej_=1.45+/-0.25 foe, respectively. Given these typical explosion parameters, the early detection, and the extensive observations, we suggest that SN 2014L could be a template sample for the investigation of SNe Ic.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/82
- Title:
- Follow-up photometry & spectroscopy of PTF14jg
- Short Name:
- J/ApJ/874/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the outbursting source PTF 14jg, which, prior to the onset of its late 2013 eruption, was a faint, unstudied, and virtually uncataloged star. The salient features of the PTF 14jg outburst are (i) projected location near the W4 HII region and radial velocity consistent with physical association; (ii) a light curve that underwent an ~6-7mag optical (R-band) through mid-infrared (L-band) brightening on a timescale of a few months, peaked and then faded by ~3mag, but plateaued still >3.5mag above quiescence by ~8 months post-peak, lasting to at least 4yr after eruption; (iii) strong outflow signatures with velocities reaching -530km/s; (iv) a low-gravity and broad (~100-150km/s FWHM) optical absorption-line spectrum that systematically changes its spectral type with wavelength; (v) lithium; and (vi) ultraviolet and infrared excess. We tentatively identify the outburst as exhibiting characteristics of a young star FU Ori event. However, the burst would be unusually hot, with an absorption spectrum exhibiting high-excitation (~11000-15000K) lines in the optical and no evidence of CO in the near-infrared, in addition to exhibiting an unusual light curve. We thus also consider alternative scenarios-including various forms of novae, nuclear-burning instabilities, massive star events, and mergers-finding them all inferior to the atypically hot FU Ori star classification. The source eventually may be interpreted as a new category of young star outburst with a larger amplitude and shorter rise time than most FU Ori-like events.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/8
- Title:
- Follow-up spectroscopy of SDSS changing-look QSOs
- Short Name:
- J/ApJ/874/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Active galactic nuclei (AGNs) that show strong rest-frame optical/UV variability in their blue continuum and broad line emission are classified as changing-look AGN, or at higher luminosities, changing-look quasars (CLQs). These surprisingly large and sometimes rapid transitions challenge accepted models of quasar physics and duty cycles, offer several new avenues for study of quasar host galaxies, and open a wider interpretation of the cause of differences between broad and narrow-line AGN. To better characterize extreme quasar variability, we present follow-up spectroscopy as part of a comprehensive search for CLQs across the full Sloan Digital Sky Survey (SDSS) footprint using spectroscopically confirmed quasars from the SDSS DR7 catalog. Our primary selection requires large-amplitude (|{Delta}g|>1mag, |{Delta}r|>0.5mag) variability over any of the available time baselines probed by the SDSS and Pan-STARRS 1 surveys. We employ photometry from the Catalina Sky Survey to verify variability behavior in CLQ candidates where available, and confirm CLQs using optical spectroscopy from the William Herschel, MMT, Magellan, and Palomar telescopes. For our adopted signal-to-noise ratio threshold on variability of broad H{beta} emission, we find 17 new CLQs, yielding a confirmation rate of >~20%. These candidates are at lower Eddington ratio relative to the overall quasar population, which supports a disk-wind model for the broad line region. Based on our sample, the CLQ fraction increases from 10% to roughly half as the continuum flux ratio between repeat spectra at 3420{AA} increases from 1.5 to 6. We release a catalog of more than 200 highly variable candidates to facilitate future CLQ searches.
- ID:
- ivo://CDS.VizieR/J/ApJ/901/134
- Title:
- Foreground galaxies toward FRB 190608 from SDSS
- Short Name:
- J/ApJ/901/134
- Date:
- 21 Feb 2022 09:50:38
- Publisher:
- CDS
- Description:
- Fast radio burst (FRB) 190608 was detected by the Australian Square Kilometre Array Pathfinder (ASKAP) and localized to a spiral galaxy at z_host_=0.11778 in the Sloan Digital Sky Survey (SDSS) footprint. The burst has a large dispersion measure (DM_FRB_=339.8pc/cm^3^) compared to the expected cosmic average at its redshift. It also has a large rotation measure (RM_FRB_=353rad/m^2^) and scattering timescale ({tau}=3.3ms at 1.28GHz). Chittidi+ (2021ApJ...922..173C) perform a detailed analysis of the ultraviolet and optical emission of the host galaxy and estimate the host DM contribution to be 110+/-37pc/cm^3^. This work complements theirs and reports the analysis of the optical data of galaxies in the foreground of FRB 190608 in order to explore their contributions to the FRB signal. Together, the two studies delineate an observationally driven, end-to-end study of matter distribution along an FRB sightline, the first study of its kind. Combining our Keck Cosmic Web Imager (KCWI) observations and public SDSS data, we estimate the expected cosmic dispersion measure DM_cosmic along the sightline to FRB 190608. We first estimate the contribution of hot, ionized gas in intervening virialized halos (DM_halos_~7-28pc/cm^3^). Then, using the Monte Carlo Physarum Machine methodology, we produce a 3D map of ionized gas in cosmic web filaments and compute the DM contribution from matter outside halos (DM_IGM_~91-126pc/cm^3^). This implies that a greater fraction of ionized gas along this sightline is extant outside virialized halos. We also investigate whether the intervening halos can account for the large FRB rotation measure and pulse width and conclude that it is implausible. Both the pulse broadening and the large Faraday rotation likely arise from the progenitor environment or the host galaxy.