arXiv subjects

D. Montes

Publications and source records attributed to D. Montes.

At least 217 records · Page 12Linked to original sources

arXiv2008

Low-resolution spectroscopy and spectral energy distributions of selected sources towards sigma Orionis

Aims: We investigated in detail nine sources in the direction of the young sigma Orionis cluster, which is considered a unique site for studying stellar and substellar formation. The nine sources were selected because of some peculiar properties, such as extremely red infrared colours or too strong Halpha emission for their blue optical colours. Methods: We took high-quality, low-resolution spectroscopy (R ~ 500) of the nine targets with ALFOSC at the Nordic Optical Telescope. We also re-analyzed [24]-band photometry from MIPS/Spitzer and compiled the best photometry available at the ViJHKs passbands and the four IRAC/Spitzer channels for constructing accurate spectral energy distributions covering from 0.55 to 24 mum. Results: The nine targets were classified into: one Herbig Ae/Be star with a scatterer edge-on disc, two G-type stars, one X-ray flaring, early-M, young star with chromospheric Halpha emission, one very low-mass, accreting, young spectroscopic binary, two young objects at the brown dwarf boundary with the characteristics of classical T Tauri stars, and two emission-line galaxies, one undergoing star formation, and another one whose spectral energy distribution is dominated by an active galactic nucleus. Besides, we discover three infrared sources associated to overdensities in a cold cloud in the cluster centre. Conclusions: Low-resolution spectroscopy and spectral energy distributions are a vital tool for measuring the physical properties and the evolution of young stars and candidates in the sigma Orionis cluster.

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arXiv2007

Multiwavelength optical observations of chromospherically active binary systems V. FF UMa (2RE J0933+624): a system with orbital period variation

This is the fifth paper in a series aimed at studying the chromospheres of active binary systems using several optical spectroscopic indicators to obtain or improve orbital solution and fundamental stellar parameters. We present here the study of FF UMa (2RE J0933+624), a recently discovered, X-ray/EUV selected, active binary with strong H_alpha emission. The objectives of this work are, to find orbital solutions and define stellar parameters from precise radial velocities and carry out an extensive study of the optical indicators of chromospheric activity. We obtained high resolution echelle spectroscopic observations during five observing runs from 1998 to 2004. We found radial velocities by cross correlation with radial velocity standard stars to achieve the best orbital solution. We also measured rotational velocity by cross-correlation techniques and have studied the kinematic by galactic space- velocity components (U, V, W) and Eggen criteria. Finally, we have determined the chromospheric contribution in optical spectroscopic indicators, from Ca II H & K to Ca II IRT lines, using the spectral subtraction technique. We have found that this system presents an orbital period variation, higher than previously detected in other RS CVn systems. We determined an improved orbital solution, finding a circular orbit with a period of 3.274 days. We derived the stellar parameters, confirming the subgiant nature of the primary component and obtained rotational velocities (vsini), of 33.57 km/s and 32.38 km/s for the primary and secondary components respectively. From our kinematic study, we can deduce its membership to the Castor moving group. Finally, the activity study has given us a better understanding of the possible mechanisms that produce the orbital period variation.

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arXiv2006

Analysis and modeling of high temporal resolution spectroscopic observations of flares on AD Leo

We report the results of a high temporal resolution spectroscopic monitoring of the flare star AD Leo. During 4 nights, more than 600 spectra were taken in the optical range using the Isaac Newton Telescope (INT) and the Intermediate Dispersion Spectrograph (IDS). We have observed a large number of short and weak flares occurring very frequently (flare activity > 0.71 hours-1). This is in favour of the very important role that flares can play in stellar coronal heating. The detected flares are non white-light flares and, though most of solar flares belong to this kind, very few such events had been previously observed on stars. The behaviour of different chromospheric lines (Balmer series from H_alpha to H_11, Ca II H & K, Na I D_1 & D_2, He I 4026 AA and He I D_3) has been studied in detail for a total of 14 flares. We have also estimated the physical parameters of the flaring plasma by using a procedure which assumes a simplified slab model of flares. All the obtained physical parameters are consistent with previously derived values for stellar flares, and the areas - less than 2.3% of the stellar surface - are comparable with the size inferred for other solar and stellar flares. Finally, we have studied the relationships between the physical parameters and the area, duration, maximum flux and energy released during the detected flares.

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arXiv2006

The nearest young moving groups

The latest results in the research of forming planetary systems have led several authors to compile a sample of candidates for searching for planets in the vicinity of the sun. Young stellar associations are indeed excellent laboratories for this study, but some of them are not close enough to allow the detection of planets through adaptive optics techniques. However, the existence of very close young moving groups can solve this problem. Here we have compiled the members of the nearest young moving groups, as well as a list of new candidates from our catalogue of late-type stars possible members of young stellar kinematic groups, studying their membership through spectroscopic and photometric criteria.

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arXiv2005

An illustrative experiment on electromagnetic oscillations

It is the purpose of this manuscript to place an illustrative demonstration on the measurement of damped electromagnetic oscillations for a RLC circuit that it is easy to set in any physics laboratory equipped with PASCO technologies and USB Electrical PASPort sensors together with standard electrical components. The results of recording the electrical voltage with DATA Studio software have a very good agreement with performed simulations from MULTISIM software and/or standard calculations from theory. Our students and instructors enjoy of the experiment for their simplicity set up in addition to the instructive oscillations.

physics.ed-ph↗

arXiv2003

Rotational modulation of the photospheric and chromospheric activity in the young, single K2-dwarf PW And

High resolution echelle spectra of PW And (HD~1405) have been taken during eight observing runs from 1999 to 2002. The detailed analysis of the spectra allow us to determine its spectral type (K2V), mean heliocentric radial velocity (V_hel = -11.15 km/s) rotational velocity (vsin{i} = 22.6 km/s), and equivalent width of the lithium line 6707.8 AA (EW(LiI) = 273 mAA). The kinematic (Galactic Velocity (U, V, W)) confirms its membership of the Local Association moving group, in agreement with the age (30 to 80 Myrs) inferred from the color magnitude diagram and the lithium equivalent width. Photospheric activity (presence of cool spots that disturb the profiles of the photospheric lines) has been detected as changes in the the bisectors of the cross correlation function (CCF) resulting of cross-correlate the spectra of PW And with the spectrum of a non active star of similar spectral type. These variations of the CCF bisectors are related to the variations in the measured radial velocities and are modulated with a period similar to the photometric period of the star. At the same time, chromospheric activity has been analyzed, using the spectral subtraction technique and simultaneous spectroscopic observations of the H_alpha, H_beta, NaI D_1 and D_2$, HeI D_3, MgI b triplet, CaII H&K, and CaII infrared triplet lines. A flare was observed during the last observing run of 2001, showing an enhancement in the observed chromospheric lines. A less powerful flare was observed on 2002 August 23. The variations of the chromospheric activity indicators seem to be related to the photospheric activity. A correlation between radial velocity, changes in the CCF bisectors and equivalent width of different chromospheric lines is observed with a different behaviour between epochs 1999, 2001 and 2002.

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arXiv2002

Simultaneous Optical and X-ray Observations of Flares and Rotational Modulation on the RS CVn Binary HR 1099 (V711 Tau) from the MUSICOS 1998 Campaign

We present simultaneous and continuous observations of the H$α$, H$β$, He {\sc i} D$_{3}$, Na {\sc i} D$_{1}$,D$_{2}$ doublet and the Ca {\sc ii} H & K lines for the RS CVn system HR 1099. The spectroscopic observations were obtained during the MUSICOS 1998 campaign involving several observatories and instruments, both echelle and long-slit spectrographs. During this campaign, HR 1099 was observed almost continuously for more than 8 orbits of $2\fd8$. Two large optical flares were observed, both showing an increase in the emission of H$α$, Ca {\sc ii} H & K, H$β$ and He {\sc i} D$_{3}$ and a strong filling-in of the Na {\sc i} D$_{1}$,D$_{2}$ doublet. {Contemporary photometric observations were carried out with the robotic telescopes APT-80 of Catania and Phoenix-25 of Fairborn Observatories. Maps of the distribution of the spotted regions on the photosphere of the binary components were derived using the Maximum Entropy and Tikhonov photometric regularization criteria}. Rotational modulation was observed in H$α$ and He {\sc i} D$_{3}$ in anti-correlation with the photometric light curves. Both flares occurred at the same binary phase (0.85), suggesting that these events took place in the same active region. Simultaneous X-ray observations, performed by ASM on board RXTE, show several flare-like events, some of which correlate well with the observed optical flares. Rotational modulation in the X-ray light curve has been detected with minimum flux when the less active G5 V star was in front. A possible periodicity in the X-ray flare-like events was also found.

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arXiv2002

Multiwavelength optical observations of chromospherically active binary systems. IV. The X-ray/EUV selected binary BK Psc (2RE J0039+103)

We present high resolution echelle spectra taken during four observing runs from 1999 to 2001 of the recently X-ray/EUV selected chromospherically active binary BK Psc (2RE J0039+103). Our observations confirm the single-lined spectroscopic binary(SB1) nature of this system and allow us to obtain, for the first time,the orbital solution of the system as in the case of a SB2 system. We have determined precise radial velocities of both components: for the primary by using the cross correlation technique, and for the secondary by using its chromospheric emission lines. We have obtained a circular orbit with an orbital period of 2.1663 days, very close to its photometric period of 2.24 days (indicating synchronous rotation). The spectral type (K5V) we determined for our spectra and the mass ratio (1.8) and minimum masses (Msin^{3}i) resulting from the orbital solution are compatible with the observed K5V primary and an unseen M3V secondary. Using this spectral classification, the projected rotational velocity (vsini, of 17.1 km/s}) obtained from the width of the cross-correlation function and the data provided by Hipparcos, we have derived other fundamental stellar parameters. The kinematics and the non-detection of the LiI line indicate that it is an old star. The analysis of the optical chromospheric activity indicators from the CaII H & K to CaII IRT lines, by using the spectral subtraction technique, indicates that both components of the binary system show high levels of chromospheric activity. H_alpha emission above the continuum from both components is a persistent feature of this system during the period 1999 to 2001 of our observations as well as in previous observations.

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arXiv2001

MUSICOS 1998: Optical and X-rays Observations of Flares on the RS CVn Binary HR 1099

We present simultaneous and continuous observations of H_alpha, H_beta, NaI D_1, D_2 and HeI D_3 lines of the chromospherically active binary HR 1099. We have observed HR 1099 for more than 3 weeks almost continuously and monitored two flares. An increase in H_alpha, CaII H & K, H_beta, HeI D_3 and HeI lambda6678 and a strong filling-in of the NaI D_1, D_2 and MgI b triplet during one of the flares are observed. We have found that the flares took place at the same phase (0.85) of the binary orbit, and both of them seems to occur near the limb. Several X-rays flares were also detected by ASM on board RXTE. Rotational modulation in the X-rays light curve has been detected with maximum flux when the active K1IV star is in front.

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arXiv2001

Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups

We present here high resolution echelle spectra taken during three observing runs of 14 single late-type stars identified in our previous studies (Montes et al. 2001b, hereafter Paper I) as possible members of different young stellar kinematic groups (Local Association (20 - 150 Myr), Ursa Major group (300 Myr), Hyades supercluster (600 Myr), and IC 2391 supercluster (35 Myr)). Radial velocities have been determined by cross correlation with radial velocity standard stars and used together with precise measurements of proper motions and parallaxes taken from Hipparcos and Tycho-2 Catalogues, to calculate Galactic space motions (U, V, W) and to apply Eggen's kinematic criteria. The chromospheric activity level of these stars have been analysed using the information provided for several optical spectroscopic features (from the Ca II H & K to Ca II IRT lines) that are formed at different heights in the chromosphere. The Li I 6707.8 AA line equivalent width (EW) has been determined and compared in the EW(Li I) versus spectral type diagram with the EW(Li I) of stars members of well known young open clusters of different ages, in order to obtain an age estimation. All these data allow us to analyse in more detail the membership of these stars in the different young stellar kinematic groups. Using both kinematic and spectroscopic criteria we have confirmed PW And, V368 Cep, V383 Lac, EP Eri, DX Leo, HD 77407, and EK Dra as members of the Local Association and V834 Tau, pi^{1} UMa, and GJ 503.2 as members of the Ursa Major group. A clear rotation-activity dependence has been found in these stars.

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arXiv2001

MUSICOS 1998: Observations of Rotational Modulation and Flares on the RS CVn Binary HR 1099

We present simultaneous and continuous observations of H_alpha, H_beta, NaI D_1, D_2, HeI D_3 and CaII H & K lines of the chromospherically active binary HR 1099. We have observed HR 1099 for more than 3 weeks almost continuously and monitored two flares. An increase in H_alpha and CaII H & K, H_beta and HeI D_3 and a strong filling-in of the NaI D_1, D_2 during the flares are observed. We have found that the flares took place at the same phase (0.85) of the binary orbit, and both of them seems to occur near the limb.

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arXiv2001

Late-type stars members of young stellar kinematic groups - I. Single stars

This is the first paper of a series aimed at studying the properties of late-type stars members of young stellar kinematic groups. We concentrate our study on classical young moving groups as: Local Association (Pleiades moving group, 20 - 150 Myr), IC 2391 supercluster (35 Myr), Ursa Major group (Sirius supercluster, 300 Myr), and Hyades supercluster (600 Myr); as well as on recently identified groups as: Castor moving group (200 Myr). In this paper we have compiled a preliminary list of single late-type stars possible members of some of these young stellar kinematic groups. Stars have been selected from previously established members of stellar kinematic groups based on photometric and kinematic properties as well as from candidates based on other criteria as their level of chromospheric activity, rotation rate, lithium abundance. Precise measurements of proper motions and parallaxes taken from Hipparcos Catalogue, as well as from Tycho-2 Catalogue, and published radial velocity measurements are used to calculate the Galactic space motions (U, V, W) and to apply the Eggen's kinematic criteria in order to determine the membership of the selected stars to the different groups. Additional criteria using age-dating methods for late-type stars will be applied in forthcoming papers of this series. A further study of the list of stars compiled here could lead to a better understanding of the chromospheric activity and their age evolution as well as of the star formation history in the solar neighbourhood. In addition, these stars are also potential search targets for direct imaging detection of sub-stellar companions.

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arXiv2000

Multiwavelength optical observations of chromospherically active binary systems. III. High resolution echelle spectra from Ca II H&K to Ca II IRT

This is the third paper of a series aimed at studying the chromosphere of active binary systems using the information provided for several optical spectroscopic features. High resolution echelle spectra including all the optical chromospheric activity indicators from the Ca II H & K to Ca II IRT lines are analysed here for 16 systems. The chromospheric contribution in these lines has been determined using the spectral subtraction technique. Very broad wings have been found in the subtracted H_alpha profile of the very active star HU Vir. These profiles are well matched using a two-component Gaussian fit (narrow and broad) and the broad component can be interpreted as arising from microflaring. Red-shifted absorption features in the H_alpha line have been detected in several systems and excess emission in the blue wing of FG UMa was also detected. These features indicate that several dynamical processes, or a combination of them, may be involved. Using the E(H_alpha)/E(H_beta) ratio as a diagnostic we have detected prominence-like extended material viewed off the limb in many stars of the sample, and prominences viewed against the disk at some orbital phases in the dwarfs OU Gem and BF Lyn. The He I D_3 line has been detected as an absorption feature in mainly all the giants of the sample. Total filling-in of the He I D_3, probably due to microflaring activity, is observed in HU Vir. Self-absorption with red asymmetry is detected in the Ca II H & K lines of the giants 12 Cam, FG UMa and BM CVn. All the stars analysed show clear filled-in Ca II IRT lines or even notable emission reversal. The small values of the E(8542)/E(8498) ratio we have found indicate Ca II IRT emission arises from plage-like regions.

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arXiv1999

Chromospheric activity of the double-lined spectroscopic binary BF Lyn

We present simultaneous spectroscopic observations taken during four observing runs (1996 to 1999) of H_alpha, H_beta, H_epsilon, Ca II H & K, and Ca II IRT lines of the chromospherically active binary BF Lyn. Both components have strong emission in the H_epsilon, Ca II H & K and Ca II IRT lines and a strong filling-in of the H_alpha and H_beta lines have been observed after the application of the spectral subtraction technique. We have found that the hot component (K2 V) is always the most active of the system. The different activity indicators of the hot and cool components show anticorrelated variations with the orbital phase.

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arXiv1999

Multiwavelength optical observations of the chromospherically active binary system OU Gem

We have analysed several multiwavelength optical observations (H_alpha, H_beta, H_epsilon, Ca II H & K, Ca II IRT lines) of chromospherically active binary system OU Gem, taken in three observation runs: March 1996, April 1998 (using the SOFIN spectrograph and the Nordic Optical Telescope) and January 1999 (using the ESA-MUSICOS spectrograph and the Isaac Newton Telescope). The spectra show double H_alpha and H_beta absorption lines, but after applying the spectral subtraction technique, clear excess emission is seen in both components. The two stars have the Ca II IRT lines in emission, strong emission in the Ca II H & K lines and small emission in the H_epsilon line. Although they have very similar spectral types, the cool one is more active than the hot one in all runs, except for MUSICOS run, and in all spectral lines, except for Ca II IRT lines.

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arXiv1999

Chromospherically active binaries members of young stellar kinematic groups

We present a kinematic study of a large sample of chromospherically active binaries (CAB) in order to determine their membership to representative young disk stellar kinematic groups: the Local Association (Pleiades moving group, 20 - 150 Myr), Ursa Mayor group (Sirius supercluster, 300 Myr), Hyades supercluster (800 Myr), IC 2391 supercluster (35 Myr) and Castor moving group (200 Myr). Precise measurements of proper motions and parallaxes taken from Hipparcos Catalogue and published radial velocity measurements are used to calculate Galactic space motions (U, V, W) in order to determine the membership of the selected stars to the different stellar kinematic groups.

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arXiv1999

Young stellar kinematic groups and their relation with young open clusters, star forming regions and the Gould Belt

Stellar kinematic groups (SKG) are kinematically coherent groups of stars that share a common origin. We have compiled (Montes et al. 1999; 2000) a sample of late-type stars of previously established members and possible new candidates to different young SKG (Local Association (20 - 150 Myr), Ursa Mayor group (300 Myr), Hyades supercluster (600 Myr), IC 2391 supercluster (35 Myr) and Castor Moving Group (200 Myr)). In order to better understand the origin of these young SKG, and to be able to identify late-type stars members of the classical and the recently identified SKG, we also need to study the kinematic properties of nearby young open clusters and star forming regions. With this aim we have taken the most recent data available in the literature (including astrometric data from Hipparcos Catalogue) of the nearby young open clusters, OB associations, T associations, and other associations of young stars as TW Hya. We use these data to calculate their Galactic space motions (U, V, W) and space coordinates (X, Y, Z) and study their possible association with the different SKG as well as with the young flattened and inclined Galactic structure known as the Gould Belt.

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arXiv1999

Late-type stars members of young stellar kinematic groups

We have compiled a catalog of late-type stars (F5-M) member of representative young disk stellar kinematic groups: the Local Association (Pleiades moving group, 20 - 150 Myr), Ursa Mayor group (Sirius supercluster, 300 Myr), and Hyades supercluster (600 Myr). Other moving groups as IC 2391 supercluster (35 Myr) and Castor Moving Group (200 Myr) have been also included. Stars have been selected from previously established member of stellar kinematic groups based in photometric and kinematic properties as well as from candidates based in other criteria as their level of chromospheric activity, rotation rate, lithium abundance. Precise measurements of proper motions and parallaxes taken from Hipparcos Catalogue, and published radial velocity measurements are used to calculate Galactic space motions (U, V, W) in order to determine the membership of the selected stars to the different stellar kinematic groups. In addition to kinematic properties we also give for each star photometric, spectroscopic and physical properties as well as information about activity indicators and Li abundance. Some chromospherically active binaries results to be also members of some of these stellar kinematic groups.

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