Search Publications
Photometric variations from stellar activity as an age indicator for solar-twins
Yana Galarza, Jhon; Lorenzo-Oliveira, Diego; Valio, Adriana +2 more
Stellar ages are elusive to measure, albeit being very important for understanding stellar evolution. We investigate the impact of photospheric activity on 2-min cadence light curves from the TESS/NASA mission of a selected sample of 30 solar-twins with well-determined ages. The photometric variability, $\mathcal {A}_{ {{TESS}}}$, of the light cur…
The magnetic fields around the cometary globules L328, L323, and L331
Soam, Archana; Roy, Nirupam; Kumar, Siddharth
This work presents the magnetic field geometry in a complex of three cometary (with head-tail morphology) globules, namely LDN 323, LDN 328, and LDN 331, using R-band polarization measurements of background stars. These observations were combined with a Planck sky survey to study the large-scale morphology of the magnetic fields in the region. The…
Solar coronal magnetic field measurements using spectral lines available in Hinode/EIS observations: strong and weak field techniques and temperature diagnostics
Chen, Yajie; Tian, Hui; Bai, Xianyong +4 more
Recently, it has been proposed that the magnetic-field-induced transition (MIT) in Fe X can be used to measure coronal magnetic field strengths. Several techniques, the direct line ratio technique and the weak and strong magnetic field techniques, are developed to apply the MIT theory to spectroscopic observations taken by EUV Imaging Spectrometer…
Radial velocity confirmation of a hot super-Neptune discovered by TESS with a warm Saturn-mass companion
McLeod, K. K.; Dai, F.; Gandolfi, D. +59 more
We report the discovery and confirmation of the planetary system TOI-1288. This late G dwarf harbours two planets: TOI-1288 b and TOI-1288 c. We combine TESS space-borne and ground-based transit photometry with HARPS-N and HIRES high-precision Doppler measurements, which we use to constrain the masses of both planets in the system and the radius o…
The MOSDEF survey: probing resolved stellar populations at z 2 Using a new bayesian-defined morphology metric called patchiness
Siana, Brian; Shapley, Alice E.; Reddy, Naveen A. +12 more
We define a new morphology metric called 'patchiness' (P) that is sensitive to deviations from the average of a resolved distribution, does not require the galaxy centre to be defined, and can be used on the spatially resolved distribution of any galaxy property. While the patchiness metric has a broad range of applications, we demonstrate its uti…
Astrometry via close approach events: applications to main-belt asteroid (702) Alauda
Vienne, A.; Peng, Q. Y.; Guo, B. F. +1 more
The release of Gaia catalogue is revolutionary to the astronomy of Solar system objects. After some effects such as atmospheric refraction and CCD geometric distortion have been taken into account, the astrometric precision for ground-based telescopes can reach the level of tens of milli-arcseconds (mas). If an object approaches a reference star i…
The first evidence of tidally induced activity in a brown dwarf-M dwarf pair: a Chandra study of the NLTT 41135/41136 system
Stelzer, Beate; Poppenhaeger, Katja; Wolk, Scott J. +3 more
The magnetic activity of low-mass stars changes as they age. The primary process decreasing the stellar activity level is the angular momentum loss via magnetized stellar wind. However, processes like tidal interactions between stars and their close companions may slow down the braking effect and the subsequent decrease of the activity level. Unti…
Environmental effects on associations of dwarf galaxies
Gottlöber, Stefan; Libeskind, Noam I.; Yepes, Gustavo +5 more
We study the properties of associations of dwarf galaxies and their dependence on the environment. Associations of dwarf galaxies are extended systems composed exclusively of dwarf galaxies, considering as dwarf galaxies those galaxies less massive than $M_{\star , \rm max} = 10^{9.0}$${\rm M}_{\odot }\, h^{-1}$. We identify these particular syste…
Did Kepler-444 have a long-lived convective core?
Stokholm, Amalie; Verma, Kuldeep; Aguirre Børsen-Koch, Víctor +2 more
With the greater power to infer the state of stellar interiors provided by asteroseismology, it has become possible to study the survival of initially convective cores within stars during their main-sequence evolution. Standard theories of stellar evolution predict that convective cores in subsolar mass stars have lifetimes below $1\, {\rm Gyr}$. …
Type II and anomalous Cepheids in the Kepler K2 mission
Bódi, Attila; Szabó, Róbert; Molnár, László +4 more
We present the results of the analysis of Type II and anomalous Cepheids using the data from the Kepler K2 mission. The precise light curves of these pulsating variable stars are the key to study the details of their pulsation, such as the period-doubling effect or the presence of additional modes. We applied the Automated Extended Aperture Photom…