Astronomical Informant

2022-05-21 19:09:48 ATel 15389: Flaring activity from Mrk 421 observed by HAWC
https://www.astronomerstelegram.org/?read=15389

The HAWC Observatory has measured an increased gamma-ray activity from the direction of the BL Lac Markarian 421 (z=0.031) on the previous transit, May 20-21, 2022: Day: 2022-05-20, (MJD 59719) Duration: 6.2 hrs, from 2022-05-20 22:32:11 to 2022-05-21 04:48:09 (UT) Preliminary Flux level: (5.33 +/- 1.13) X 10-11 cm^-2s^-1 [ > 1 TeV] (2.76 +/- 0.58 CU) HAWC continuously monitors this source and will keep reporting in case that the enhance activity follows. ... Aprire / Come

2022-05-20 23:35:33 ATel 15387: OAUNI confirmation of optical flickering from RS Oph
https://www.astronomerstelegram.org/?read=15387

We report photometry post 2021 outburst of the recurrent nova RS Oph on 2022-05-02 (UT) gathered with the OAUNI 51cm telescope (Pereyra et al. 2015; arXiv:1512.03104) at Huancayo Observatory, Peru. ... Aprire / Come

2022-05-20 17:20:36 Starliner Launches to Space Station
http://www.nasa.gov/image-feature/starliner-launches-to-space-station

Boeing’s CST-100 Starliner spacecraft launched from Space Launch Complex 41, Thursday, May 19, 2022. Aprire / Come

2022-05-20 05:36:40 arXiv:We take advantage of exquisitely deep optical imaging data from HST/ACS in the F475W ($g_{F475W}$) and F606W ($V_{F606W}$) bands, to study the properties of the globular cluster (GC) population in the intermediate mass lenticular galaxy PGC 087327, in the Hydra I galaxy cluster. We inspect the photometric (magnitudes and color) and morphometric (compactness, elongation, etc.) properties of sources lying in an area of $\sim19\times19$ kpc centered on PGC 087327, and compare them with four neighbouring fields over the same HST/ACS mosaic. This allowed us to identify a list of GC candidates and to inspect their properties using a background decontamination method. Relative to the four comparison fields, PGC 087327 shows a robust overdensity of GCs, $N_{GC}=82\pm9$. At the estimated magnitude of the galaxy, this number implies a specific frequency of $S_N=1.8\pm0.7$. In spite of the short wavelength interval available with the $g_{F475W}$ and $V_{F606W}$ passbands, the color distribution shows a clear bimodality with a blue peak at $\langle g_{F475W}{-}V_{F606W} \rangle =0.47\pm0.05$ mag and a red peak at $\langle g_{F475W}{-}V_{F606W}\rangle =0.62\pm0.03$ mag. We also observe the typical steeper slope of the radial distribution of red GCs relative to blue ones. Thanks to the unique depth of the available data, we characterize the GC luminosity function (GCLF) well beyond the expected GCLF turn-over. We find $g^{TOM}_{F475W} = 26.54\pm0.10$ mag and $V^{TOM}_{F606W} = 26.08 \pm 0.09$ mag, which after calibration yields a distance of $D_{GCLF} = 56.7 \pm 4.3(statistical) \pm 5.2(systematic)$ Mpc.

via astro-ph updates on arXiv.org https://ift.tt/DzkAbFL Aprire / Come

2022-03-03 06:37:05 arXiv:Red dwarf stars, which represent 75% of stars in the Milky Way, can be studied in great detail in the solar neighborhood where the sample is more complete. We intend to better characterize red dwarf candidates selected from the Gaia Catalog of Nearby Stars using optical and near-infrared photometry from the VVVX Survey, DECaPS, Pan-STARRS, and WISE. We performed a cross-matching procedure among the positions of a color-selected sample of M dwarfs in the VVVX Survey and the Gaia EDR3 sub-catalog of nearby stars. We explored their stellar parameters and spectral types using VOSA. Radii were also obtained using the Stefan-Boltzmann equation. Masses and ages were computed for some of the objects using evolutionary tracks and isochrones. Additional mass estimations were obtained with the MKs - M* relation. We then validated our results for the stellar parameters of two of our objects with spectra obtained with the TripleSpec instrument at the SOAR telescope, as well as those of our total amount of stars through a direct comparison with an independent sample from the literature. We revised the objects in our sample and compared their proper motion vectors with other sources within 30" to identify possible companions and probed their RUWE values to identify unresolved companions. We present a catalog of physical parameters for 99 low-mass objects with distances from 43.2 to 111.3 pc. Teffs range from 2500 to 3400 K, with the majority of stars in the sample compatible with being M4 dwarfs. We obtained a good agreement between the stellar parameters computed with VOSA and the estimations from observed spectra, also when comparing with an independent sample from the literature. The distribution of masses obtained with VOSA is concentrated toward the very low-mass regime. Eight objects present values of RUWE >= 1.4 and seven are consistent with being part of a binary system.

via astro-ph updates on arXiv.org https://ift.tt/gnkj4mi Aprire / Come

2022-03-02 19:14:43 Geostationary Operational Environmental Satellite-T Soars After Launch
http://www.nasa.gov/image-feature/geostationary-operational-environmental-satellite-t-soars-after-launch

A United Launch Alliance Atlas V 541 rocket, carrying NOAA's GOES-T, soars upward after lifting off from Space Launch Complex 41 on March 1, 2022. Aprire / Come

2022-03-02 07:36:33 arXiv:Electromagnetic follow-up of gravitational wave detections is very resource intensive, taking up hours of limited observation time on dozens of telescopes. Creating more efficient schedules for follow-up will lead to a commensurate increase in counterpart location efficiency without using more telescope time. Widely used in operations research and telescope scheduling, mixed integer linear programming (MILP) is a strong candidate to produce these higher-efficiency schedules, as it can make use of powerful commercial solvers that quickly and efficiently find globally optimal solutions to provided problems. We detail a new target of opportunity scheduling algorithm designed with Zwicky Transient Facility in mind that uses mixed integer linear programming. We compare its performance to \texttt{gwemopt}, the tuned heuristic scheduler used by the Zwicky Transient Facility and other facilities during the third LIGO-Virgo gravitational wave observing run. This new algorithm uses variable-length observing blocks to enforce cadence requirements and ensure field observability, along with having a secondary optimization step to minimize slew time. Our algorithm shows improvement over \texttt{gwemopt} in successfully scheduling observations for a simulated binary neutron star merger data set consistent with LIGO-Virgo's third observing run. We demonstrate the ability to achieve better efficiencies with this straightforward algorithm, highlighting the potential of mixed integer target of opportunity schedulers for future multimessenger follow-up surveys.

via astro-ph updates on arXiv.org https://ift.tt/t9rWBSj Aprire / Come

2022-03-02 07:36:32 arXiv:We present the final results of the Exploration of Local VolumE Satellites (ELVES) Survey, a survey of the dwarf satellites of a nearly volume-limited sample of Milky Way (MW)-like hosts in the Local Volume. Hosts are selected simply via a cut in luminosity ($M_{K_s}<-22.1$ mag) and distance ($D<12$ Mpc). We have cataloged the satellites of 25 of the 31 such hosts, with another five taken from the literature. All hosts are surveyed out to at least 150 projected kpc ($\sim R_\mathrm{vir}/2$) with the majority surveyed to 300 kpc ($\sim R_\mathrm{vir}$). Satellites are detected using a consistent semi-automated algorithm specialized for low surface brightness dwarfs. As shown through extensive tests with injected galaxies, the catalogs are complete to $M_V\sim-9$ mag and $\mu_{0,V}\sim26.5$ mag arcsec$^{-2}$. Candidates are confirmed to be real satellites through distance measurements including redshift, tip of the red giant branch, and surface brightness fluctuations. Across all 30 surveyed hosts, there are 338 confirmed satellites with a further 105 candidates awaiting distance measurement. For the vast majority of these, we provide consistent multi-band S\'{e}rsic photometry. We show that satellite abundance correlates with host mass, with the MW being quite typical amongst comparable systems, and that satellite quenched fraction rises steeply with decreasing satellite mass, mirroring the quenched fraction for the MW and M31. The ELVES survey represents a massive increase in the statistics of surveyed systems with known completeness, and the provided catalogs are a unique dataset to explore various aspects of small-scale structure and dwarf galaxy evolution.

via astro-ph updates on arXiv.org https://ift.tt/d17bSmT Aprire / Come

2022-03-02 07:36:31 arXiv:Contrary to many stereotypes about massive galaxies, observed brightest group galaxies (BGGs) are diverse in their star formation rates, kinematic properties, and morphologies. Studying how they evolve into and express such diverse characteristics is an important piece of the galaxy formation puzzle. We use a high-resolution cosmological suite of simulations Romulus and compare simulated central galaxies in group-scale halos at $z=0$ to observed BGGs. The comparison encompasses the stellar mass-halo mass relation, various kinematic properties and scaling relations, morphologies, and the star formation rates. Generally, we find that Romulus reproduces the full spectrum of diversity in the properties of the BGGs very well, albeit with a tendency toward lower than the observed fraction of quenched BGGs. We find both early-type S0 and elliptical galaxies as well as late-type disk galaxies; we find Romulus galaxies that are fast-rotators as well as slow-rotators; and we observe galaxies transforming from late-type to early-type following strong dynamical interactions with satellites. We also carry out case studies of selected Romulus galaxies to explore the link between their properties, and the recent evolution of the stellar system as well as the surrounding intragroup/circumgalactic medium. In general, mergers/strong interactions quench star-forming activity and disrupt the stellar disk structure. Sometimes, however, such interactions can also trigger star-formation and galaxy rejuvenation. Black hole feedback can also lead to a decline of the star formation rate but by itself, it does not typically lead to complete quenching of the star formation activity in the BGGs.

via astro-ph updates on arXiv.org https://ift.tt/kZSVXrQ Aprire / Come

2022-03-02 07:36:29 arXiv:We present the second catalog and data release of optical spectral line measurements and AGN demographics of the BAT AGN Spectroscopic Survey, which focuses on the of Swift-BAT hard X-ray detected AGNs. We use spectra from dedicated campaigns and publicly available archives to investigate spectral properties of most of the AGNs listed in the 70-month Swift-BAT all-sky catalog; specifically, 743 of the 746 unbeamed and unlensed AGNs (99.6%). We find a good correspondence between the optical emission line widths and the hydrogen column density distributions using the X-ray spectra, with a clear dichotomy of AGN types for NH = 10^22 cm-2. Based on optical emission-line diagnostics, we show that 48%-75% of BAT AGNs are classified as Seyfert, depending on the choice of emission lines used in the diagnostics. The fraction of objects with upper limits on line emission varies from 6% to 20%. Roughly 4% of the BAT AGNs have lines too weak to be placed on the most commonly used diagnostic diagram, [O III]{\lambda}5007/H\b{eta} versus [N II]{\lambda}6584/H{\alpha}, despite the high signal-to-noise ratio (S/N) of their spectra. This value increases to 35% in the [O III]{\lambda}5007/[O II]{\lambda}3727 diagram, owing to difficulties in line detection. Compared to optically-selected narrow-line AGNs in the Sloan Digital Sky Survey, the BAT narrow-line AGNs have a higher rate of reddening/extinction, with H{\alpha}/H\b{eta} > 5 (~ 36%), indicating that hard X-ray selection more effectively detects obscured AGNs from the underlying AGN population. Finally, we present a subpopulation of AGNs that feature complex broad-lines (34%, 250/743) or double-peaked narrow emission lines (2%, 17/743).

via astro-ph updates on arXiv.org https://ift.tt/nuocHYK Aprire / Come