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- ID:
- ivo://CDS.VizieR/J/AJ/160/19
- Title:
- 827 ultracool dwarfs with K2
- Short Name:
- J/AJ/160/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The occurrence of planets orbiting ultracool dwarfs is poorly constrained. We present results from a guest observer program on NASA's K2 spacecraft to search for transiting planets orbiting a sample of 827 ultracool dwarfs. Having found no transiting planets in our sample, we determined an upper limit on the occurrence of planets. We simulated planets orbiting our sample for a range of orbital periods and sizes. For the simulated planets that transit their host, we injected the transit light curve into the real K2 light curves, then attempted to recover the injected planets. For a given occurrence rate, we calculated the probability of seeing no planets, and use the results to place an upper limit on planet occurrence as a function of planet radius and orbital period. We find that short-period, mini-Neptune and Jupiter-sized planets are rare around ultracool dwarfs, consistent with results for early and mid-type M dwarf stars. We constrain the occurrence rate {eta} for planets between 0.5 and 10 R{earth} with orbital periods between 1 and 26.3days.
- ID:
- ivo://CDS.VizieR/J/ApJ/923/257
- Title:
- Ultra-diffuse galaxies with spectroscopic obs.
- Short Name:
- J/ApJ/923/257
- Date:
- 14 Mar 2022 07:42:35
- Publisher:
- CDS
- Description:
- We present new redshift measurements for 19 candidate ultra-diffuse galaxies (UDGs) from the Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes) survey after conducting a long-slit spectroscopic follow-up campaign on 23 candidates with the Large Binocular Telescope. We combine these results with redshift measurements from other sources for 29 SMUDGes and 20 non-SMUDGes candidate UDGs. Together, this sample yields 44 spectroscopically confirmed UDGs (r_e_>=1.5kpc and {mu}_g_(0)>=24mag/arcsec^2^ within uncertainties) and spans cluster and field environments, with all but one projected on the Coma cluster and environs. We find no statistically significant differences in the structural parameters of cluster and noncluster confirmed UDGs, although there are hints of differences among the axis ratio distributions. Similarly, we find no significant structural differences among those in locally dense or sparse environments. However, we observe a significant difference in color with respect to projected clustercentric radius, confirming trends observed previously in statistical UDG samples. This trend strengthens further when considering whether UDGs reside in either cluster or locally dense environments, suggesting starkly different star formation histories for UDGs residing in high- and low-density environments. Of the 16 large (r_e_>=3.5kpc) UDGs in our sample, only one is a field galaxy that falls near the early-type galaxy red sequence. No other field UDGs found in low-density environments fall near the red sequence. This finding, in combination with our detection of Galaxy Evolution Explorer NUV flux in nearly half of the UDGs in sparse environments, suggests that field UDGs are a population of slowly evolving galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/160/44
- Title:
- Upper Scorpius spectroscopy and photometry
- Short Name:
- J/AJ/160/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have refined the census of stars and brown dwarfs in the Upper Sco association (~10Myr, ~145pc) by (1) updating the selection of candidate members from our previous survey to include the high-precision astrometry from the second data release of Gaia, (2) obtaining spectra of a few hundred candidate members to measure their spectral types and verify their youth, and (3) assessing the membership (largely with Gaia astrometry) of 2020 stars toward Upper Sco that show evidence of youth in this work and previous studies. We arrive at a catalog of 1761 objects that are adopted as members of Upper Sco. The distribution of spectral types among the adopted members is similar to those in other nearby star-forming regions, indicating a similar initial mass function. In previous studies, we have compiled mid-infrared photometry from the Wide-field Infrared Survey Explorer and the Spitzer Space Telescope for members of Upper Sco and used those data to identify the stars that show evidence of circumstellar disks; we present the same analysis for our new catalog of members. As in earlier work, we find that the fraction of members with disks increases with lower stellar masses, ranging from <~10% for >1M{sun} to ~22% for 0.01-0.3M{sun}. Finally, we have estimated the relative ages of Upper Sco and other young associations using their sequences of low-mass stars in M_G_RP__ versus G_BP_-G_RP_. This comparison indicates that Upper Sco is a factor of two younger than the {beta}Pic association (21-24Myr) according to both nonmagnetic and magnetic evolutionary models.
- ID:
- ivo://CDS.VizieR/J/AJ/126/1208
- Title:
- UVBI magnitudes and redshifts in HDF-South
- Short Name:
- J/AJ/126/1208
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 97 (*) spectroscopic redshifts of z<1 galaxies in the Hubble Deep Field South (HDF-S) and its flanking fields (FFs). In the HDF-S proper we observed approximately half the galaxies brighter than I_814_(AB)=24 and obtained redshifts for 76% of them. Targets in our HDF-S sample were preselected to be at z<1 based on photometric redshifts, while in the FFs a simple magnitude cut was used. The photometric redshift preselection in the HDF-S resulted in a spectroscopic success rate that is significantly higher than in the FFs, where no preselection was applied. The rms precision of our redshift measurements, determined from repeat observations, is {delta}z=0.0003. We present the photometry and redshifts for the 97 objects for which we secured spectroscopic redshifts and describe the basic properties of this sample. The photometry was derived from the HST observations; the spectroscopy was obtained at the VLT using the FORS2 spectrograph on the Kueyen (UT2) and Yepun (UT4) 8.2m telescopes. (*) Actually, 103 redshifts in table1.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/147
- Title:
- UV-NIR LCs of the energetic H-stripped SN2016coi
- Short Name:
- J/ApJ/883/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present comprehensive observations and analysis of the energetic H-stripped SN 2016coi (a.k.a. ASASSN-16fp), spanning the {gamma}-ray through optical and radio wavelengths, acquired within the first hours to ~420 days post explosion. Our observational campaign confirms the identification of He in the supernova (SN) ejecta, which we interpret to be caused by a larger mixing of Ni into the outer ejecta layers. By modeling the broad bolometric light curve, we derive a large ejecta-mass-to-kinetic-energy ratio (M_ej_~4-7M_{sun}_, E_k_~(7-8)x10^51^erg). The small [CaII]{lambda}{lambda}7291,7324 to [OI]{lambda}{lambda}6300,6364 ratio (~0.2) observed in our late-time optical spectra is suggestive of a large progenitor core mass at the time of collapse. We find that SN 2016coi is a luminous source of X-rays (L_X_>10^39^erg/s in the first ~100 days post explosion) and radio emission (L_8.5GHz_~7x10^27^erg/s/Hz at peak). These values are in line with those of relativistic SNe (2009bb, 2012ap). However, for SN 2016coi, we infer substantial pre-explosion progenitor mass loss with a rate dM/dt~(1-2)x10^-4^M_{sun}_/yr and a sub-relativistic shock velocity v_sh_~0.15c, which is in stark contrast with relativistic SNe and similar to normal SNe. Finally, we find no evidence for a SN- associated shock breakout {gamma}-ray pulse with energy E_{gamma}_>2x10^46^erg. While we cannot exclude the presence of a companion in a binary system, taken together, our findings are consistent with a massive single-star progenitor that experienced large mass loss in the years leading up to core collapse, but was unable to achieve complete stripping of its outer layers before explosion.
- ID:
- ivo://CDS.VizieR/J/ApJ/898/56
- Title:
- UVOT, ZTF gri LCs and spectra of the SN Ia 2019yvq
- Short Name:
- J/ApJ/898/56
- Date:
- 16 Mar 2022 00:53:53
- Publisher:
- CDS
- Description:
- Early observations of Type Ia supernovae (SNe Ia) provide essential clues for understanding the progenitor system that gave rise to the terminal thermonuclear explosion. We present exquisite observations of SN 2019yvq, the second observed SN Ia, after iPTF 14atg, to display an early flash of emission in the ultraviolet (UV) and optical. Our analysis finds that SN 2019yvq was unusual, even when ignoring the initial flash, in that it was moderately underluminous for an SN Ia (M_g_~-18.5mag at peak) yet featured very high absorption velocities (v~15000km/s for SiII{lambda}6355 at peak). We find that many of the observational features of SN 2019yvq, aside from the flash, can be explained if the explosive yield of radioactive 56Ni is relatively low (we measure M_56Ni_=0.31+/-0.05M_{sun}_) and it and other iron-group elements are concentrated in the innermost layers of the ejecta. To explain both the UV/optical flash and peak properties of SN 2019yvq we consider four different models: interaction between the SN ejecta and a nondegenerate companion, extended clumps of ^56^Ni in the outer ejecta, a double-detonation explosion, and the violent merger of two white dwarfs. Each of these models has shortcomings when compared to the observations; it is clear additional tuning is required to better match SN 2019yvq. In closing, we predict that the nebular spectra of SN 2019yvq will feature either H or He emission, if the ejecta collided with a companion, strong [CaII] emission, if it was a double detonation, or narrow [OI] emission, if it was due to a violent merger.
- ID:
- ivo://CDS.VizieR/J/ApJ/898/166
- Title:
- UV to NIR obs. of SN 2019ehk
- Short Name:
- J/ApJ/898/166
- Date:
- 21 Mar 2022 09:18:33
- Publisher:
- CDS
- Description:
- We present panchromatic observations and modeling of the Calcium-rich supernova (SN) 2019ehk in the star-forming galaxy M100 (d~16.2Mpc) starting 10hr after explosion and continuing for ~300days. SN 2019ehk shows a double-peaked optical light curve peaking at t=3 and 15days. The first peak is coincident with luminous, rapidly decaying Swift-XRT-discovered X-ray emission (L_x_~10^41^erg/s at 3days; Lx{propto}t^-3^), and a Shane/Kast spectral detection of narrow H{alpha} and HeII emission lines (v~500km/s) originating from pre-existent circumstellar material (CSM). We attribute this phenomenology to radiation from shock interaction with extended, dense material surrounding the progenitor star at r<10^15^cm and the resulting cooling emission. We calculate a total CSM mass of ~7x10^-3^M_{sun}_ (M_He_/M_H_~6) with particle density n~10^9^cm^-3^. Radio observations indicate a significantly lower density n<10^4^cm^-3^ at larger radii r>(0.1-1)x10^17^cm. The photometric and spectroscopic properties during the second light-curve peak are consistent with those of Ca-rich transients (rise-time of t_r_=13.4!+/-0.210days and a peak B-band magnitude of M_B_=-15.1+/-0.200mag). We find that SN 2019ehk synthesized (3.1+/-0.11)x10^-2^M_{sun}_ of ^56^Ni and ejected M_ej_=(0.72+/-0.040)M_{sun}_ total with a kinetic energy E_k_=(1.8+/-0.10)x10^50^erg. Finally, deep HST pre-explosion imaging at the SN site constrains the parameter space of viable stellar progenitors to massive stars in the lowest mass bin (~10M_{sun}_) in binaries that lost most of their He envelope or white dwarfs (WDs). The explosion and environment properties of SN 2019ehk further restrict the potential WD progenitor systems to low-mass hybrid HeCO WD+CO WD binaries.
- ID:
- ivo://CDS.VizieR/J/ApJ/900/47
- Title:
- UV to NIR spectra of the QSO 2MASS J15165323+1900482
- Short Name:
- J/ApJ/900/47
- Date:
- 21 Mar 2022 09:27:00
- Publisher:
- CDS
- Description:
- We present detailed studies of the partially obscured quasar 2MASSJ151653.23+190048.2 with continuous broadband spectrophotometry from near-infrared (NIR) through optical to ultraviolet (UV). The NIR and optical spectra show strong broad emission lines, while the UV spectrum is dominated by a set of rich intermediate-width emission lines (IELs). These IELs, unshifted with respect to the quasar systemic velocity measured by narrow emission lines, share a common profile of about 1900km/s in FWHM, in contrast to the Balmer and Paschen broad emission lines of FWHM ~6300km/s observed in the optical and NIR. The intermediate width of these lines indicates that the emitting gas may come from the dusty torus region. However, the observed peculiar IEL intensity ratios, such as NV{lambda}1240/Ly{alpha}, indicate that the emitting gas has a very high density, up to ~10^13^cm^-3^. Such a high density is unusual for gas around the dusty torus region, except that we consider mechanisms such as shocks that can produce local ultradense gas. We speculate that these emission lines could originate from the shock region, possibly induced by the quasar outflow colliding with the inner wall of the dusty torus. If true, this may give us an opportunity to peep at the quasar outflows at the scale of the dusty torus that have so far been elusive due to the limited resolving powers of existing facilities.
- ID:
- ivo://CDS.VizieR/J/A+A/402/37
- Title:
- UV to radio SED of galaxies in Virgo cluster
- Short Name:
- J/A+A/402/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multifrequency dataset for an optically-selected, volume-limited, complete sample of 118 late-type galaxies (>=S0a) in the Virgo cluster. The database includes UV, visible, near-IR, mid-IR, far-IR, radio continuum photometric data as well as spectroscopic data of H{alpha}, CO and HI lines, homogeneously reduced, obtained from our own observations or compiled from the literature. Assuming the energy balance between the absorbed stellar light and that radiated in the IR by dust, we calibrate an empirical attenuation law suitable for correcting photometric and spectroscopic data of normal galaxies. The data, corrected for internal extinction, are used to construct the spectral energy distribution (SED) of each individual galaxy, and combined to trace the median SED of galaxies in various classes of morphological type and luminosity.