- ID:
- ivo://CDS.VizieR/J/ApJS/247/11
- Title:
- RV photon limits of well-characterized F-M stars
- Short Name:
- J/ApJS/247/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The determination of extrasolar planet masses with the radial velocity (RV) technique requires spectroscopic Doppler information from the planet's host star, which varies with stellar brightness and temperature. We analyze the Doppler information in spectra from dwarfs of spectral types F-M utilizing empirical information from HARPS and CARMENES data and model spectra. We revisit the question of whether optical or near-infrared instruments are more efficient for RV observations in low-mass stars, and we come to the conclusion that an optical setup (BVR bands) is more efficient than a near-infrared one (YJHK) in dwarf stars hotter than 3200K. We publish a catalog of 46480 well-studied F-M dwarfs in the solar neighborhood, and we compare its distribution to more than 1 million stars from Gaia DR2. For all stars, we estimate the RV photon noise achievable in typical observations under the assumption of no activity jitter and slow rotation. We find that with an ESPRESSO-like instrument at an 8m telescope, a photon noise limit of 10cm/s or lower can be reached in more than 280 stars in a 5 minute observation. At 4m telescopes, a photon noise limit of 1m/s can be reached in a 10 minute exposure in approximately 10000 predominantly Sun-like stars with a HARPS-like (optical) instrument. The same applies to ~3000 stars for a red optical setup that covers the R and I bands and ~700 stars for a near-infrared instrument. For the latter two, many of the targets are nearby M dwarfs. Finally, we identify targets in which Earth-mass planets within the liquid water habitable zone can cause RV amplitudes comparable to the RV photon noise. Assuming the same exposure times as above, we find that an ESPRESSO-like instrument can reach this limit for 1M_{Earth}_ planets in more than 1000 stars. The optical, red optical, and near-infrared configurations reach the limit for 2M_{Earth}_ planets in approximately 500, 700, and 200 stars, respectively. An online tool is provided to estimate the RV photon noise as a function of stellar temperature and brightness and wavelength coverage.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/160/222
- Title:
- RVs and RI-photometry of HATS-37 and HATS-38
- Short Name:
- J/AJ/160/222
- Date:
- 09 Mar 2022 22:00:00
- Publisher:
- CDS
- Description:
- We report the discovery of two transiting Neptunes by the HATSouth survey. The planet HATS-37Ab has a mass of 0.099{+/-}0.042M_Jup_ (31.5{+/-}13.4M{Earth}) and a radius of 0.606{+/-}0.016R_Jup_, and is on a P=4.3315day orbit around a V=12.266{+/-}0.030mag, 0.843_-0.012_^+0.017^M{odot} star with a radius of 0.877_-0.012_^+0.019^R{odot}. We also present evidence that the star HATS-37A has an unresolved stellar companion HATS-37B, with a photometrically estimated mass of 0.654{+/-}0.033M{odot}. The planet HATS-38b has a mass of 0.074{+/-}0.011M_Jup_ (23.5{+/-}3.5M{Earth}) and a radius of 0.614{+/-}0.017R_Jup_, and is on a P=4.3750day orbit around a V=12.411{+/-}0.030mag, 0.890_-0.012_^+0.016^M{odot} star with a radius of 1.105{+/-}0.016 R{odot}. Both systems appear to be old, with isochrone-based ages of 11.46_-1.45_^+0.79^Gyr, and 11.89{+/-}0.60Gyr, respectively. Both HATS-37Ab and HATS-38b lie in the Neptune desert and are thus examples of a population with a low occurrence rate. They are also among the lowest-mass planets found from ground-based wide-field surveys to date.
- ID:
- ivo://CDS.VizieR/J/AJ/160/151
- Title:
- RVs of 5 cataclysmic variable candidates
- Short Name:
- J/AJ/160/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report follow-up observations of five cataclysmic variable candidates from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) published by Hou et al. LAMOSTJ024048.51+195226.9 is the most unusual of the five; an early-M type secondary star contributes strongly to its spectrum, and its spectral and photometric behavior are strikingly reminiscent of the hitherto-unique propeller system AE Aqr. We confirm that a 7.34hr period discovered in the Catalina survey data is orbital. Another object, LAMOSTJ204305.95+341340.6, appears to be a near twin of the novalike variable V795Her, with an orbital period in the so-called 2-3hr "gap." LAMOSTJ035913.61+405035.0 is evidently an eclipsing, weakly outbursting dwarf nova with a 5.48hr period. Our spectrum of LAMOSTJ090150.09+375444.3 is dominated by a late-type secondary and shows weak, narrow Balmer emission moving in phase with the absorption lines, but at lower amplitude; we do not see the HeII {lambda}4686 emission evident in the published discovery spectrum. We again confirm that a period from the Catalina data, in this case 6.80hr, is orbital. LAMOSTJ033940.98+414805.7 yields a radial-velocity period of 3.54hr, and its spectrum appears to be typical of novalike variables in this period range. The spectroscopically selected sample from LAMOST evidently includes some interesting cataclysmic variables that have been unrecognized until now, apparently because of the relatively modest range of their photometric variations.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A4
- Title:
- RVs of 18 Galactic luminous blue variable stars
- Short Name:
- J/A+A/657/A4
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Luminous blue variables (LBVs) are characterised by strong photometric and spectroscopic variability. They are thought to be in a transitory phase between O-type stars on the main sequence and the Wolf-Rayet stage. Recent studies also evoked the possibility that they might be formed through binary interaction. Only a few are known in binary systems so far, but their multiplicity fraction is still uncertain. We derive the binary fraction of the Galactic LBV population. We combine multi-epoch spectroscopy and long-baseline interferometry to probe separations from 0.1 to 120mas around confirmed and candidate LBVs. We used a cross-correlation technique to measure the radial velocities of these objects. We identified spectroscopic binaries through significant radial velocity variability with an amplitude larger than 35km/s. We also investigated the observational biases to take them into account when we established the intrinsic binary fraction. We used candid to detect interferometric companions, derive their flux fractions, and their positions on the sky. From the multi-epoch spectroscopy, we derive an observed spectroscopic binary fraction of 26-10+16%. Considering period and mass ratio ranges from log(Porb)=0-3 (i.e. from 1 to 1000days), q=0.1-1.0, and a representative set of orbital parameter distributions, we find a bias-corrected binary fraction of 62_-24_^+38^%. Based on data of the interferometric campaign, we detect a binary fraction of 70+/-9% at projected separations between 1 and 120mas. Based on the derived primary diameters and considering the distances of these objects, we measure for the first time the exact radii of Galactic LBVs to be between 100 and 650R_{sun}_. This means that it is unlikely that short-period systems are included among LBV-like stars. This analysis shows for the first time that the binary fraction in the Galactic LBV population is large. If they form through single-star evolution, their orbit must be large initially. If they form through a binary channel, the implication is that either massive stars in short binary systems must undergo a phase of fully non-conservative mass transfer to be able to sufficiently widen the orbit to form an LBV, or that LBVs form through merging in initially binary or triple systems. Interferometric follow-up would provide the distributions of orbital parameters at more advanced stages and would serve to quantitatively test the binary evolution in massive stars.
- ID:
- ivo://CDS.VizieR/J/AJ/159/290
- Title:
- RVs of 12 spectroscopic binaries M-dwarfs
- Short Name:
- J/AJ/159/290
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the spectroscopic orbits of 11 nearby, mid-to-late M dwarf binary systems in a variety of configurations: 2 single-lined binaries (SB1s), 7 double-lined binaries (SB2s), 1 double-lined triple (ST2), and 1 triple-lined triple (ST3). Eight of these orbits are the first published for these systems, while five are newly identified multiples. We obtained multi-epoch, high-resolution spectra with the TRES instrument on the 1.5m Tillinghast Reflector at the Fred Lawrence Whipple Observatory located on Mt. Hopkins in AZ. Using the TiO molecular bands at 7065-7165{AA}, we calculated radial velocities for these systems, from which we derived their orbits. We find LHS 1817 to have in a 7hr period a companion that is likely a white dwarf, due to the ellipsoidal modulation we see in our MEarth-North light-curve data. We find G123-45 and LTT11586 to host companions with minimum masses of 41MJup and 44MJup with orbital periods of 35 and 15days, respectively. We find 2MA0930+0227 to have a rapidly rotating stellar companion in a 917 day orbital period. GJ268, GJ1029, LP734-34, GJ1182, G258-17, and LTT7077are SB2s with stellar companions with orbital periods of 10, 96, 34, 154, 5, and 84days; LP655-43 is an ST3 with one companion in an 18day orbital period and an outer component in a longer undetermined period. In addition, we present radial velocities for both components of L870-44AB and for the outer components of LTT11586 and LP655-43.
- ID:
- ivo://CDS.VizieR/J/MNRAS/475/1609
- Title:
- RV variability in NGC 2516 and NGC 2422
- Short Name:
- J/MNRAS/475/1609
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-epoch, high-dispersion, optical spectra obtained with the Michigan/Magellan Fiber System of 126 and 125 Sun-like stars in the young clusters NGC 2516 (141Myr) and NGC 2422 (73Myr). We determine stellar properties including radial velocity (RV), Teff, [Fe/H], [{alpha}/Fe], and the line-of-sight rotation rate, v_r_sin(i), from these spectra. Our median RV precision of 80m/s on individual epochs that span a temporal baseline of 1.1yr enables us to investigate membership, stellar binarity, and search for sub-stellar companions. We determine membership probabilities and RV variability probabilities for our sample along with candidate companion orbital periods for a select subset of stars. We identify 81 RV members in NGC 2516, 27 spectroscopic binaries (17 previously identified as photometric binaries), and 16 other stars that show significant RV variability after accounting for average stellar jitter found to be at the 74m/s level. In NGC 2422 we identify 57 members, 11 spectroscopic binaries, and 3 other stars that show significant RV variability after accounting for an average jitter of 138m/s. We use Monte Carlo simulations to verify our stellar jitter measurements, determine the proportion of exoplanets and stellar companions to which we are sensitive, and estimate companion mass limits for our targets. We also report mean cluster metallicity, velocity, and velocity dispersion based on our member targets and identify 58 non-member stars as RV variables - 24 of which have RV amplitudes that imply stellar or brown-dwarf mass companions. Finally, we note the discovery of a separate RV clustering of stars in our NGC 2422 sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/877/44
- Title:
- RV variability in SDSS dwarf carbon stars
- Short Name:
- J/ApJ/877/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dwarf carbon (dC) stars (main-sequence stars showing carbon molecular bands) were initially thought to be an oxymoron because only asymptotic giant branch (AGB) stars dredge carbon into their atmospheres. Mass transfer from a former AGB companion that has since faded to a white dwarf seems the most likely explanation. Indeed, a few types of giants known to show anomalous abundances- notably, the CH, Ba and CEMP-s stars-are known to have a high binary frequency. The dC stars may be the enhanced-abundance progenitors of most, if not all of these systems, but this requires demonstrating a high binary frequency for dCs. Here, for a sample of 240 dC stars targeted for repeat spectroscopy by the SDSS-IV's Time Domain Spectroscopic Survey, we analyze radial velocity (RV) variability to constrain the binary frequency and orbital properties. A handful of dC systems show large velocity variability (>100km/s). We compare the dCs to a control sample with a similar distribution of magnitude, color, proper motion, and parallax. Using Markov chain Monte Carlo methods, we use the measured {Delta}RV distribution to estimate the binary fraction and the separation distribution assuming both a unimodal and bimodal distribution. We find the dC stars have an enhanced binary fraction of 95%, consistent with them being products of mass transfer. These models result in mean separations of less than 1 au corresponding to periods on the order of 1 yr. Our results support the conclusion that dC stars form from close binary systems via mass transfer.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A128
- Title:
- S abundances for 1301 stars from GES
- Short Name:
- J/A+A/604/A128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Due to their volatile nature, when sulphur and zinc are observed in external galaxies, their determined abundances represent the gas-phase abundances in the interstellar medium. This implies that they can be used as tracers of the chemical enrichment of matter in the Universe at high redshift. Comparable observations in stars are more difficult and, until recently, plagued by small number statistics. We wish to exploit the Gaia ESO Survey (GES) data to study the behaviour of sulphur and zinc abundances of a large number of Galactic stars, in a homogeneous way. By using the UVES spectra of the GES sample, we are able to assemble a sample of 1301 Galactic stars, including stars in open and globular clusters in which both sulphur and zinc were measured. We confirm the results from the literature that sulphur behaves as an alpha-element. We find a large scatter in [Zn/Fe] ratios among giant stars around solar metallicity. The lower ratios are observed in giant stars at Galactocentric distances less than 7.5kpc. No such effect is observed among dwarf stars, since they do not extend to that radius. Given the sample selection, giants and dwarfs are observed at different Galactic locations, and it is plausible, and compatible with simple calculations, that Zn-poor giants trace a younger population more polluted by SN Ia yields. It is necessary to extend observations in order to observe both giants and dwarfs at the same Galactic location. Further theoretical work on the evolution of zinc is also necessary.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/58
- Title:
- Sagittarius stream stars with APOGEE obs.
- Short Name:
- J/ApJ/872/58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey provides precise chemical abundances of 18 chemical elements for ~176000 red giant stars distributed over much of the Milky Way Galaxy (MW), and includes observations of the core of the Sagittarius dwarf spheroidal galaxy (Sgr). The APOGEE chemical abundance patterns of Sgr have revealed that it is chemically distinct from the MW in most chemical elements. We employ a k-means clustering algorithm to six-dimensional chemical space defined by [(C+N)/Fe], [O/Fe], [Mg/Fe], [Al/Fe], [Mn/Fe], and [Ni/Fe] to identify 62 MW stars in the APOGEE sample that have Sgr-like chemical abundances. Of the 62 stars, 35 have Gaia kinematics and positions consistent with those predicted by N-body simulations of the Sgr stream, and are likely stars that have been stripped from Sgr during the last two pericenter passages (<2Gyr ago). Another 20 of the 62 stars exhibit chemical abundances indistinguishable from the Sgr stream stars, but are on highly eccentric orbits with median rapo ~25kpc. These stars are likely the "accreted" halo population thought to be the result of a separate merger with the MW 8-11 Gyr ago. We also find one hypervelocity star candidate. We conclude that Sgr was enriched to [Fe/H]~-0.2 before its most recent pericenter passage. If the "accreted halo" population is from one major accretion event, then this progenitor galaxy was enriched to at least [Fe/H]~-0.6, and had a similar star formation history to Sgr before merging.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/60
- Title:
- SAMI Galaxy Survey: early-type gal. in A119 & A168
- Short Name:
- J/ApJ/875/60
- Date:
- 08 Mar 2022 13:03:14
- Publisher:
- CDS
- Description:
- We investigate the kinematic alignments of luminous early-type galaxies (M_r_<=-19.5mag) in A119 and A168 using the kinematic position angles (PA_kin_) from the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) survey data, motivated by the implication of the galaxy spin alignment in a cosmological context. To increase the size of our sample for statistical significance, we also use the photometric position angles (PA_phot_) for galaxies that have not been observed by SAMI, if their ellipticities are higher than 0.15. Our luminous early-type galaxies tend to prefer the specific position angles in both clusters, confirming the results of Kim+ (2018ApJ...860L...3K), who recently found the kinematic alignment of early-type galaxies in the Virgo cluster based on the ATLAS3D integral-field spectroscopic data. This alignment signal is more prominent for galaxies in the projected phase-space regions dominated by infalling populations. Furthermore, the alignment angles are closely related to the directions of the filamentary structures around clusters. The results lead us to conclude that many cluster early-type galaxies are likely to be accreted along filaments while maintaining their spin axes, which are predetermined before cluster infall.
