- ID:
- ivo://CDS.VizieR/J/AcA/52/129
- Title:
- DIA OGLE2 candidate variable stars catalog
- Short Name:
- J/AcA/52/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first edition of a catalog of variable stars from OGLE-II Galactic bulge data covering 3 years: 1997-1999. Typically 200-300 I band data points are available in 49 fields between -11 and +11 degrees in galactic longitude, totaling roughly 11 square degrees in sky coverage. Photometry was obtained using the Difference Image Analysis (DIA) software and tied to the OGLE data base with the DoPhot package. The present version of the catalog comprises 221801 light curves. In this preliminary work the level of contamination by spurious detections is still about 10%. Parts of the catalog have only crude calibration, insufficient for distance determinations. The next, fully calibrated, edition will include the data collected in year 2000. The data is accessible via ftp, at ftp://bulge.princeton.edu/ogle/ogle2/bulge_dia_variables
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- ID:
- ivo://CDS.VizieR/J/A+A/376/356
- Title:
- Diatomic molecules collisional rates
- Short Name:
- J/A+A/376/356
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A number of diatomic molecules have been found in vibrationally excited states in several cosmic objects. The molecules in vibrationally excited states provide valuable information about the physical conditions prevailing near star forming regions and in circumstellar envelopes of late-type stars. To analyze the spectrum of such molecules, some of the important parameters required are the collisional rate coefficients for vib-rotational transitions in the molecule. Currently, knowledge of collisional rate coefficients is very poor. Here, we discuss a method for calculating the collisional rate coefficients for vib-rotational transitions in a diatomic molecule, where the colliding partner H_2_ is considered as a structureless particle. This method is quite good for high temperatures (usually found in star-forming regions and in circumstellar envelopes of late-type stars), but may be questioned for low temperatures. As an example, calculations for the CS molecule at 500K for three vibrational states are presented.
- ID:
- ivo://CDS.VizieR/J/A+A/591/A20
- Title:
- DIB and NaD spectra of 3 nearby stars
- Short Name:
- J/A+A/591/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Diffuse interstellar absorption bands (DIBs) of largely unknown chemical origin are regularly observed primarily in distant early-type stars. More recently, detections in nearby late-type stars have also been claimed. These stars' spectra are dominated by stellar absorption lines. Specifically, strong interstellar atomic and DIB absorption has been reported in tau Boo. We test these claims by studying the strength of interstellar absorption in high-resolution TIGRE spectra of the nearby stars tau Boo, HD 33608, and alpha CrB. We focus our analysis on a strong DIB located at 5780.61{AA} and on the absorption of interstellar Na. First, we carry out a differential analysis by comparing the spectra of the highly similar F-stars, tau Boo and HD 33608, whose light, however, samples different lines of sight. To obtain absolute values for the DIB absorption, we compare the observed spectra of tau Boo, HD 33608, and alpha CrB to PHOENIX models and carry out basic spectral modeling based on Voigt line profiles.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/2653
- Title:
- 8620 DIB equivalent width and extinction
- Short Name:
- J/MNRAS/463/2653
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young stellar cluster Westerlund 1 (Wd 1: l=339.6, b=-0.4) is one of the most massive in the local Universe, but accurate parameters are pending on better determination of its extinction and distance. Based on our photometry and data collected from other sources, we have derived a reddening law for the cluster line-of-sight representative of the Galactic plane (-5{deg}<b<+5{deg}) in the window 0.4-4.8um. The power-law exponent alpha=2.13+/-0.08 is much steeper than those published a decade ago (1.6-1.8) and our index RV=2.50+/-0.04 also differs from them, but in very good agreement with recent works based on deep surveys in the inner Galaxy. As a consequence, the total extinction AKs=0.74+/-0.08 (AV=11.40+/-2.40) is substantially smaller than previous results (0.91-1.13), part of which (AKs=0.63 or AV=9.66) is from the interstellar medium. The extinction in front of the cluster spans a range of AV~8.7 with a gradient increasing from SW to NE across the cluster face, following the same general trend of warm dust distribution. The map of the J-Ks colour index also shows a trend of reddening in this direction. We measured the equivalent width of the diffuse interstellar band at 8620 A (the 'GAIA DIB') for Wd 1 cluster members and derived the relation AKs=0.612EW-0.191EW^2^. This extends the Munari et al. relation, valid for E(B-V)<1, to the non-linear regime (AV>4).
- ID:
- ivo://CDS.VizieR/J/A+A/550/A108
- Title:
- DIB in VLT-FLAMES Tarantula Survey
- Short Name:
- J/A+A/550/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers of these enigmatic spectral features. Spectra of over 800 early-type stars from the Very Large Telescope Flames Tarantula Survey (VFTS) were analysed. Maps were created, separately, for the Galactic and LMC absorption in the DIBs at 4428 and 6614{AA} and - in a smaller region near the central cluster R 136 - neutral sodium (the NaI D doublet); we also measured the DIBs at 5780 and 5797{AA}.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/151
- Title:
- DIB Measurements in 25 atlas sightlines
- Short Name:
- J/ApJ/878/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aiming for a new and more comprehensive DIB catalog between 4000 and 9000{AA}, we revisited the Atlas Catalog based on the observations of HD 183143 and HD 204827. Twenty-five medium to highly reddened sight lines were selected, sampling a variety of spectral types of the background star and the interstellar environments. The median signal-to-noise ratio (S/N) of these spectra is ~1300 around 6400{AA}. Compared to the Atlas Catalog, 22 new DIBs were found, and the boundaries of 27 (sets of) DIBs were adjusted, resulting in an updated catalog containing 559 DIBs that we refer to as the Apache Point Observatory Catalog of Optical Diffuse Interstellar Bands. Measurements were then made based on this catalog. We found our survey most sensitive between 5500 and 7000{AA}, due largely to the local S/N of the spectra, the relative absence of interfering stellar lines, and the weakness of telluric residuals. For our data sample, the number of DIBs detected in a given sight line is mostly dependent on E_B-V_ and less on the spectral type of the background star. Some dependence on the molecular fraction f_H2_ is observed, but it is less well determined owing to the limited size of the data sample. The variations of the wavelengths of each DIB in different sight lines are generally larger than those of the known interstellar lines CH^+^, CH, and KI. Those variations could be due to the inherent error in the measurement, or to differences in the velocity components among sight lines.
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/839
- Title:
- DIB 661.3nm in Cepheid spectra
- Short Name:
- J/MNRAS/461/839
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated the diffuse interstellar band (DIB) at 661.3nm seen in the spectra of Cepheid stars. After removal of the blending lines of ionized yttrium and neutral iron, we determined the equivalent widths (EWs) of the DIB and used these values to investigate the E(B-V)-DIB EW relation. The relation found from Cepheids matches that found in B stars. This relation can help to find the reddening for newly discovered Cepheids without extensive photometric data, and thus determine their distances. The relation between E(B - V) and the DIB EW does not yield precise reddening values. It is not a substitute for better photometric or spectroscopic methods. At best, it is indicative, but it provides some information that may not be otherwise available. Defining R*=E(B-V)/DIB EW, which we consider to be the analogue of R=E(B-V)/A_V_, we investigated the Galactic longitudinal dependence of R* assuming that the DIB EW value is representative of the interstellar absorption A$_v$. We found that there is an apparent increase of the R* value that corresponds to the abnormal absorption seen towards Cygnus constellation. Finally, we constructed a 2D map of the DIB EW distribution in the Galactic disc basing on our rather limited sample of 253 spectra of 176 Cepheids.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A52
- Title:
- DIB properties in lines of sight to M17
- Short Name:
- J/A+A/620/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Diffuse interstellar bands (DIBs) are broad absorption features measured in sightlines probing the diffuse interstellar medium. Although large carbon-bearing molecules have been proposed as the carriers producing DIBs, their identity remains unknown. DIBs make an important contribution to the extinction curve; the sightline. to the young massive star-forming region M17 shows anomalous extinction in the sense that the total-to-selective extinction parameter (R_V_) differs significantly from the average Galactic value and may reach values R_V_>4. Anomalous DIBs have been reported in the sightline towards Herschel 36 (R_V_=5.5), in the massive star-forming region M8. Higher values of R_V_ have been associated with a relatively higher fraction of large dust grains in the line of sight. Given the high R_V_ values, we investigate whether the DIBs in sightlines towards young OB stars in M17 show a peculiar behaviour. We measure the properties of the most prominent DIBs in M17 and study these as a function of E(B-V) and R_V_. We also analyse the gaseous and dust components contributing to the interstellar extinction. The DIB strengths in M17 concur with the observed relations between DIB equivalent width and reddening E(B-V) in Galactic sightlines. For several DIBs we discover a linear relation between the normalised DIB strength EW/A_V_ and R_V_^-1^. These trends suggest two groups of DIBs: (i) a group of ten moderately strong DIBs that show a sensitivity to changes in R_V_ that is modest and proportional to DIB strength, and (ii) a group of four very strong DIBs that react sensitively and to a similar degree to changes in R_V_, but in a way that does not appear to depend on DIB strength. DIB behaviour as a function of reddening is not peculiar in sightlines to M17. Also, we do not detect anomalous DIB profiles like those seen in Herschel 36. DIBs are stronger, per unit visual extinction, in sightlines characterised by a lower value of R_V_, i.e. those sightlines that contain a relatively large fraction of small dust particles. New relations between extinction normalised DIB strengths, EW/A_V_, and R_V_ support the idea that DIB carriers and interstellar dust are intimately connected. Furthermore, given the distinct behaviour of two groups of DIBs, different types of carriers do not necessarily relate to the dust grains in a similar way.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A62
- Title:
- DIBs from Baade's window bulge clump giants
- Short Name:
- J/A+A/550/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Interstellar (IS) absorption lines or diffuse bands are usually extracted from early-type star spectra because they are characterized by smooth continua. However, this introduces a strong limitation on the number of available targets, and reduces potential studies of the IS matter and the use of absorptions for cloud mapping. We have developed a new and automated fitting method appropriate to interstellar (IS) absorptions in the spectra of cool stars that possess stellar atmospheric parameters. We applied this method to the extraction of three diffuse interstellar bands (DIBs) in high resolution VLT FLAMES/GIRAFFE spectra of red-clump stars from the bulge. By combining all stellar synthetic spectra, HITRAN-LBLRTM atmospheric transmission spectra and diffuse band empirical absorption profiles, we determined the 6196.0, 6204.5, and 6283.8{AA} DIB strength toward the 219 target stars and discuss the sources of uncertainties. To test the sensitivity of the DIB extraction, we compared all three results and compared the DIB equivalent widths (EWs) with the reddening derived from an independent extinction map based on OGLE photometric data. We also derived the three independent color excess estimates based on the DIB strengths and average linear correlation coefficients previously established in the solar neighborhood and compared with the OGLE photometric results.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A129
- Title:
- DIBs in APOGEE telluric standard star spectra
- Short Name:
- J/A+A/600/A129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Information on the existence and properties of diffuse interstellar bands (DIBs) outside the optical domain is still limited. Additional infra-red (IR) measurements and IR-optical correlative studies are needed to constrain DIB carriers and locate various absorbers in 3D maps of the interstellar matter. We extended our study of H-band DIBs in Apache Point Observatory Galactic Evolution Experiment (APOGEE) Telluric Standard Star (TSS) spectra. We used the strong {lambda}15273 band to select the most and least absorbed targets. We used individual spectra of the former subsample to extract weaker DIBs, and we searched the two stacked series for differences that could indicate additional bands. High-resolution NARVAL and SOPHIE optical spectra for a subsample of 55 TSS targets were additionally recorded for NIR/optical correlative studies. From the TSS spectra we extract a catalog of measurements of the poorly studied {lambda}{lambda}15617, 15653, and 15673 DIBs in ~300 sightlines, we obtain a first accurate determination of their rest wavelength and constrained their intrinsic width and shape. In addition, we studied the relationship between these weak bands and the strong {lambda}15273 DIB.We provide a first or second confirmation of several other weak DIBs that have been proposed based on different instruments, and we add new constraints on their widths and locations. We finally propose two new DIB candidates. We compared the strength of the {lambda}15273 15273 absorptions with their optical counterparts {lambda}{lambda}5780, 5797, 6196, 6283, and 6614. Using the 5797-5780 ratio as a tracer of shielding against the radiation field, we showed that the {lambda}15273 DIB carrier is significantly more abundant in unshielded ({sigma}-type) clouds, and it responds even more strongly than the {lambda}5780 band carrier to the local ionizing field.