arXiv subjects

Daniel Majaess

Publications and source records attributed to Daniel Majaess.

At least 19 recordsLinked to original sources

arXiv2026

Concerns regarding recurrent fluorescence's impact on smaller diffuse ISM aromatics

Recent research implied that recurrent fluorescence (RF) could bolster smaller aromatics against fragmentation in the diffuse ISM, yet that hypothesis is contested by timescales for unrelenting dissociative recombination (electrons), and unceasing dissociating photons. Specifically, neutral cyanonaphthalene can sustain $13.6$ eV photoionization, and the ensuing cation's excess energy is channeled through intramolecular vibrational redistribution (IVR), with RF providing the radiative stabilization pathway ($\simeq7$ eV negligible survival limit). However, that cation endures dissociative recombination every $\tau\approx0.5^{+5.6}_{-0.4}$ years, which deposits $\simeq 8.6$ eV and exceeds the limit. Moreover, that is paired with $7-13.6$ eV photodestruction each $\tau\approx16^{+223}_{-14}$ years (total visual dust extinction $A_V=0-1$, and $\tau\approx4^{+7}_{-2}$ years for $A_V\approx0$). Recent laboratory characterizations of RF were seminal, but the mechanism may not overturn models indicating a gap in smaller $N_C\approx7-11$ diffuse ISM aromatics, nor support those molecules as viable diffuse interstellar band carriers.

astro-ph.GA↗

arXiv2026

The deepest color-magnitude diagrams for the benchmark open cluster NGC 2437 from Gaia and VVVX

Deep photometry of Galactic star clusters provides one of the most powerful tools for determining their physical properties. In particular, in low Galactic latitude regions that suffer from heavy extinction and crowding. NGC2437 is the most extended star cluster in the near-IR footprint of the VVV Extended Survey (VVVX), covering more than one degree on the sky. We aim to characterize its physical properties using Gaia DR3 in the optical and the VVVX in the near-IR. We use Gaia DR3 proper motions to select NGC2437 members in order to make optical and near-IR color-magnitude and color-color diagrams. We further exploited the newly constructed VVVX deep stack images to obtain the deepest near-IR color-magnitude diagram currently available for this cluster. We estimate the main physical parameters for NGC2437, including the mean parallax of 0.608 mas and PMs (-3.85, 0.41) mas/yr. The mean reddening E(J-Ks) = 0.059 mag and extinction of A_k = 0.034 mag for the cluster field, with no significant differential reddening spread. A distance modulus of 11.08 mag is estimated, equivalent to a distance of 1644 pc. This places NGC2437 at z=115 pc above the Galactic plane and at a galactocentric distance of 9.24 kpc. We measure the cluster structural parameters, obtaining a core radius of 10.79 arcmin. The estimated total absolute magnitudes are Mk = -4.91 mag and Mv = -3.70 mag. The cluster mean age is 350 Myr, using PARSEC-COLIBRI isochrones for solar metallicity. We measure a binary fraction of 28.6%. We also discuss the implications of the revised cluster parameters for the nearby open cluster NGC2425, the planetary nebula NGC2438, and the evolved OH/IR source OH231.8+04.2. The VVVX deep stacks increase the Ks photometric depth by 1.6 mag, nearly doubling the detected point sources and enabling significantly improved studies of stellar populations throughout the southern Galactic plane.

astro-ph.GA↗

arXiv2026

Ultracool and Brown Dwarf Candidates Identified via CatWISE-2MASS-Gaia DR3

Ultracool and brown dwarf candidates ($d_{\odot}\lesssim 125$ pc, $|b|>8^{\circ}$) were identified via multiband and astrometric data from CatWISE ($W_1W_2$), 2MASS ($JHK_s$), and Gaia DR3 ($G$, $G_{RP}$, $\pi$, $\mu_{\alpha}$, $\mu_{\delta}$). $N\approx 11.8 \times 10^3$ candidates emerged once simultaneously constrained by color and absolute magnitude criteria (e.g., $G-W_2 \ge 1.75(G-J)-2.25$), whereby $\simeq 350$ sources are absent from the Gaia Ultracool Dwarf (UCD) catalog. Spectral types were approximated using a hybrid $M_G-M_{W_1}$ sigmoid that offers additional temperature coverage in certain cases. Subsequent efforts may focus on extending sampling to the deeper NIR VVVX footprint that partly encompasses the Galactic plane, and over the long-term spectroscopically (in)validating candidates missing from the Gaia UCD database.

astro-ph.SR↗

arXiv2026

The potential broader complex linked to the key Cepheid SV Vul

A new distance was established to the Cepheid SV Vul ($P\simeq45^{d}$) and its host cluster Alicante 13, and is tied in part to deeper UKIDSS-DR6 photometry and Gaia DR3 observations ($d=2.30\pm0.13$ kpc). SV Vul and Alicante 13 possibly belong to a broader coeval stellar complex, which could include Liu-Pang 1738. The clusters and Cepheid share comparable astrometry (e.g., $\sigma_\pi\simeq0.02$ mas, $\sigma_{\mu_\delta}\simeq0.06$ mas yr$^{-1}$), and similar cluster turnoffs (ages) exist as indicated by ultraviolet UVEX color-color analyses, Gaia XP spectroscopically differentially dereddened color-magnitude diagrams, and Padova isochrones. Yet SV Vul may be comparatively overluminous. Robust radial velocities for both clusters could substantiate certain hypotheses.

astro-ph.SR↗

arXiv2026

Evaluating Cepheid Metallicity Effect Determinations via IC1613 and Gaia-independent Parallaxes

18 HST parallaxes for Galactic classical Cepheids are unified to establish a Gaia-independent IC1613 distance and evaluate metallicity effect determinations, since the Gaia zeropoint is debated. Recently proposed classical Cepheid metallicity corrections of $\gamma (W_{VI}) \simeq 0, -0.25, -0.50$ mag dex$^{-1}$ are benchmarked, and yield $\mu_{0,{W_{VI}}} \simeq 24.39, 24.16, 23.93$ ($\pm0.07$). Larger corrections are disfavored relative to a weighted mean of IC1613 TRGB and TRGB/JAGB distances of $24.39^{+0.07}_{-0.04}$ (EDD) and $24.36\pm0.06$/$24.45\pm0.11$ (CCHP). A more expansive metallicity baseline is desirable to scrutinize smaller corrections (e.g., $\gamma (W_{VI}) \lesssim -0.1$ mag dex$^{-1}$), while concurrently acquiring additional non-Gaia parallaxes since published concerns exist regarding DR3 (e.g., critical long-period Cepheids S Vul, SV Vul).

astro-ph.SR↗

arXiv2026

Benchmarking Astrochemistry Paradigms: Relative Absence of C6H5CN+ in the Diffuse ISM

The detectability of C6H5CN+ (benzonitrile cation) in the diffuse ISM is re-evaluated. A holistic evidentiary framework suggests C6H5CN+ is relatively absent in the diffuse ISM owing to the following concurrently: a marginal intramolecular vibrational energy redistribution (IVR) favoring fragmentation, recurrent fluorescence being an improbable mechanism in this case to prevent dissociation, unceasing photon strikes, mismatches between observed DIBs and experimental results, and the hitherto absence of DIBs matching any similarly sized cations. The putative gap in bottom-up synthesis is reaffirmed (diffuse ISM), and although DIB sources are largely unknown, within a broader approach the lines can help benchmark astrochemistry paradigms. The results relied on new advantageous Daly et al. experimental spectra, an expanded observational DIB analysis (APO catalog), and complementary $\omega$B97X-D/cc-pVTZ computations.

astro-ph.GA↗

arXiv2025

Doubly Discordant SH0ES NGC4258 Cepheid Relations (HVI), and Impactful Extinction Laws

S$H_0$ES 2016-2022 $HVI$ data for classical Cepheids in the keystone galaxy NGC4258 yield doubly discordant Wesenheit Leavitt functions:~$\Delta W_{0,H-VI} = -0.13\pm0^{m}.02$ ($-0^{m}.17$ unweighted) and that is paired with a previously noted $\Delta W_{0,I-VI}\simeq-0^{m}.3$, which in concert with complimentary evidence suggest the 2016 S$H_0$ES NGC4258-anchored $H_0 \pm \sigma_{H_0}$ warrants scrutiny (i.e., $\sigma_{H_0}/{H_0}\gtrsim 6$\%). Cepheid distance uncertainties are further exacerbated by extinction law ambiguities endemic to such Leavitt relations (e.g., NGC4258), particularly for comparatively obscured variables (e.g., $\Delta d \gtrsim 4$\%, reddened Cepheid subsamples in the Milky Way, M31, NGC2442, NGC4424, NGC5643, NGC7250). Lastly, during the analysis it was identified that the 2022 S$H_0$ES database relays incorrect SMC Cepheid photometry.

astro-ph.GA↗

arXiv2025

Near-infrared photometry of the central stars of planetary nebulae with the VVVX survey

Achieving accurate photometric characterizations of central stars of planetary nebulae (CSPNe) toward the galactic plane is significantly hindered by the high levels of interstellar extinction in these regions. However, near-infrared (NIR) observations offer a more effective alternative, as extinction is substantially reduced at these wavelengths. By mitigating the effects of interstellar extinction via NIR observations of the Galactic disk and bulge, we seek to improve the identification and characterization of CSPNe in these regions, enabling a deeper understanding of their properties and evolutionary status. We used NIR photometry from the VISTA Variables in the V\'ia L\'actea (VVV) survey and its extension VVVX to define the NIR photometry of a large sample of CSPNe recently identified with Gaia EDR3 data. We explored the optical and NIR properties of all CSPNe in our sample and searched for eclipsing binary candidates among them by employing relevant catalogs. We present a homogeneous catalog of 1274 CSPNe, including their Z, Y, H, J, and K NIR magnitudes and errors. We also include our findings on the photometric properties of our sample. We report 14 CSPNe with a large IR excess indicating cool companions and/or surrounding discs and 56 eclipsing binary candidates. Based on the present VVVX CSPN catalog, we conclude that NIR photometry can prove valuable for further and in-depth studies of CSPNe. Subsequent studies ought to focus on exploring the true nature of the CSPNe that present IR excess as well as eclipsing-binary CSPNe candidates.

astro-ph.SR↗

arXiv2025

The Critical 9365 {\AA} Diffuse Interstellar Band and C$_{60}^{+}$ Association

The detection of interstellar C$_{60}^{+}$ has been debated for 30 years. The contested attribution of a weaker DIB at 9365 {\AA} was re-evaluated here on the basis of a Pearson correlation relative to 9577 {\AA}, which was previously tied to C$_{60}^{+}$ by diverse collaborations. An assessment of 11 sightlines revealed a high correlation amongst 9365$-$9577 {\AA} equivalent widths ($r=0.93 \pm 0.05$), after contamination from an adjacent line was mitigated using both numerical integration and Gaussian fits. In tandem with a recent separate study's high-$r$ evaluation linking 9577$-$9632 {\AA} across a sizable baseline: three interrelated DIBs matching C$_{60}^{+}$ laboratory findings were independently reaffirmed (9365, 9577, 9632 {\AA}). Yet further investigations are required to strengthen the case via two other weak DIBs disputedly linked to C$_{60}^{+}$, particularly owing to potential overlapping lines arising from an expansive chemical space (PAHs).

astro-ph.GA↗

arXiv2025

Potential Vibrational Modes Tied to Diffuse Interstellar Bands

Potential vibrational modes associated with diffuse interstellar bands (DIBs) could be discerned by examining energy differences between correlated DIBs. Consequently, $\approx 10^3$ higher correlated DIB pairs ($r-\sigma_r \ge 0.8$, $\ge 12$ sightlines) were extracted from the Apache Point Observatory DIB catalog, and their energy spacings computed. In this first macro exploratory step, a histogram possibly reveals chemical bond signatures of C$\equiv$C, C$\equiv$N, S$-$H, C$-$O, C$=$O, Si$-$H, N$-$H, C$-$H (aliphatic), C$\mathbf{^{\underline{...}}}$C (in-ring), and aromatics (C$-$H stretch, C$\mathbf{^{\underline{...}}}$C in-ring, oop C$-$H bending, and overtones). Continued research is required to (in)validate the histogram approach, mitigate noise, scrutinize maxima, break degeneracies, and converge upon an optimal framework.

astro-ph.GA↗

arXiv2025

Strengthening the Link Between Fullerenes and a Subset of Diffuse Interstellar Bands

A debate persists regarding the correlation between the DIBs 9577 and 9632 \r{A}, and whether they share a common molecular carrier (i.e., C$_{60}^{+}$). A robust high correlation determination emerges after bridging the baseline across an order of magnitude ($\simeq 50 - 700$ m\r{A}, $r=0.93\pm0.02$), and nearly doubling the important higher equivalent width domain by adding new Mg II-corrected sightlines. Moreover, additional evidence is presented of possible DIB linkages to fullerenes, whereby attention is drawn to DIBs at 7470.38, 7558.44, and 7581.47 \r{A}, which match the Campbell experimental results for C$_{70}^{+}$ within 1 \r{A}, and the same is true of 6926.48 and 7030.26 \r{A} for C$_{70}^{2+}$. Yet their current correlation uncertainties are unsatisfactory and exacerbated by expectedly low EWs (e.g., $\overline{EW}=4$ m\r{A} for 6926.48 \r{A}), and thus further observations are required to assess whether they represent a bona fide connection or numerical coincidence.

astro-ph.GA↗

arXiv2025

Variable stars in the VVV globular clusters III. RR Lyrae stars in the inner Galactic globular clusters

High reddening near the Galactic plane hampers observations and proper characterization of the globular clusters (GCs) located toward the inner regions of the Milky Way. The VISTA Variables in the Via Lactea (VVV) survey observed the Galactic bulge and adjacent disk for several years, providing multi-epoch, near-infrared images for 41 Galactic GCs. Detecting RRLyrae variables belonging to these GCs will aid in their accurate parameterization. By fully leveraging the astrometric, photometric, and variability VVV catalogs, we searched for RRLyrae stars associated with GCs. Our selection criteria, based on proper motions, proximity to the cluster centers, and distances inferred from their period-luminosity-metallicity relations, enable us to accurately identify the RRLyrae population in these GCs and determine color excesses and distances in a homogeneous manner. Since the VVV catalogs cover from the innermost regions of the GCs to their outskirts, we can provide a comprehensive picture of the entire RRLyrae population in these GCs. We have discovered significant RRLyrae populations in two highly reddened Galactic GCs: UKS1 and VVV-CL160, previously unknown to host RRLyrae stars. Additionally, we have detected one RRLyrae candidate in each of Terzan4 and Terzan9, also new to RRLyrae detection. We further confirm and increase the number of RRLyrae stars detected in 22 other low-latitude Galactic GCs. The RRLyrae distances place most of these GCs within the Galactic bulge, aligning well with the few GCs in our sample with reliable Gaia or Hubble Space Telescope measurements. However, most of the VVV GCs lack accurate Gaia distances, and literature distances are generally significantly smaller than those derived in this work. As a byproduct of our analysis, we have obtained the proper motions for all the VVV GCs, independently confirming Gaia results, except for UKS1 and 2MASS-GC02.

astro-ph.GA↗

arXiv2025

The Gaia parallax discrepancy for the cluster Pismis 19, and separating $\delta$ Scutis from Cepheids

Pre-Gaia distances for the open cluster Pismis 19 disagree with Gaia parallaxes. A 2MASS $JK_s$ red clump distance was therefore established for Pismis 19 ($2.90\pm0.15$ kpc), which reaffirms that zero-point corrections for Gaia are required (e.g., Lindegren et al.~2021). OGLE GD-CEP-1864 is confirmed as a member of Pismis 19 on the basis of DR3 proper motions, and its 2MASS+VVV color-magnitude position near the tip of the turnoff. That $0^{\rm d}.3$ variable star is likely a $\delta$ Scuti rather than a classical Cepheid. The case revealed a pertinent criterion to segregate those two populations in tandem with the break in the Wesenheit Leavitt Law ($\simeq 0^{\rm d}.5$). Just shortward of that period discontinuity are $\delta$ Scutis, whereas beyond the break lie first overtone classical Cepheids mostly observed beyond the first crossing of the instability strip.

astro-ph.SR↗

arXiv2024

The Valuable Long-period Cluster Cepheid KQ Scorpii and other Calibration Candidates

The classical Cepheid KQ Sco is a valuable anchor for the distance scale because of its long pulsation period ($28^{\rm d}.7$) and evidence implying membership in the open cluster UBC 1558. Analyses tied to Gaia DR3 astrometry, photometry, spectroscopy, radial velocities, and 2MASS-VVV photometry indicate a common distance of $2.15\pm0.15$ kpc (\citealt{lin21} DR3 corrections applied). Additional cluster Cepheid candidates requiring follow-up are identified, and it's suggested that a team of international researchers could maintain a cluster Cepheid database to guide the broader community to cases where consensus exists.

astro-ph.SR↗

arXiv2024

A suite of classical Cepheids tied to the binary cluster Berkeley 58 \& NGC 7790

The classical Cepheids CE Cas A, CE Cas B, CF Cas, and CG Cas are likely members of the binary open cluster comprising NGC 7790 and Berkeley 58. The clusters are of comparable age and in close proximity, as deduced from differentially dereddened $UuB_PBVGR_P$ photometry, and Cepheid period-age relations. Gaia DR3 astrometric and spectroscopic solutions for the clusters are likewise consistent. Conversely, the seemingly adjacent open cluster NGC 7788 is substantially younger and less distant.

astro-ph.SR↗

arXiv2024

Concerning S$H_0$ES Data: Discrepant $W_{0,VI}$ Absolute Magnitudes for Cepheids in the Keystone Galaxy NGC4258

S$H_0$ES $VI$-band photometry for classical Cepheids in the keystone galaxy NGC4258 yield discrepant absolute magnitudes. Specifically, the 2016 and 2022 published S$H_0$ES Cepheid data for NGC4258 exhibit a substantial offset of $\Delta W_{0,VI}\simeq0^{\rm m}.3$. That adds to a suite of existing concerns associated with the S$H_0$ES analysis, which in sum imply that their relatively non-changing Hubble constant for nearly twenty years warrants scrutiny.

astro-ph.CO↗

arXiv2024

The Concerning S$H_0$ES Hubble Constant

Concerns are raised regarding the S$H_0$ES results, and the present $H_0$ controversy. The S$H_0$ES $H_0 \simeq 73$ km/s/Mpc has remained relatively unaltered across $18$ years (2005-2023), despite marked shifts in maser and Cepheid distances to the keystone galaxy NGC4258 (M106), and changes in the slope, zeropoint, metallicity, and extinction terms tied to the Leavitt Law, and notwithstanding uncertain photometry for remote Cepheids spanning galaxies with highly inhomogeneous crowding and surface brightness profiles. Concerns raised regarding the S$H_0$ES findings by fellow researchers are likewise highlighted. An independent blind assessment of the entire suite of raw HST Cepheid images is warranted, while being mindful of \textit{a priori} constraints and confirmation bias that unwittingly impact conclusions.

astro-ph.CO↗

arXiv2023

Roman Early-Definition Astrophysics Survey Opportunity: Galactic Roman Infrared Plane Survey (GRIPS)

A wide-field near-infrared survey of the Galactic disk and bulge/bar(s) is supported by a large representation of the community of Galactic astronomers. The combination of sensitivity, angular resolution and large field of view make Roman uniquely able to study the crowded and highly extincted lines of sight in the Galactic plane. A ~1000 deg2 survey of the bulge and inner Galactic disk would yield an impressive dataset of ~120 billion sources and map the structure of our Galaxy. The effort would foster subsequent expansions in numerous dimensions (spatial, depth, wavelengths, epochs). Importantly, the survey would benefit from early defintion by the community, namely because the Galactic disk is a complex environment, and different science goals will require trade offs.

astro-ph.GA↗