Archive for July, 2017

Visiting Universidad Catolica Observatory

Posted July 30, 2017 By grigoris

Only on the second day of my arrival in Chile (Jan 13, 2017) I found myself traveling from Valparaiso to Santiago to go to the Universidad Catolica Observatory (long title: Pontificia Universidad Católica de Chile), for spectroscopic observations (of bright Be stars).

Just in case you do not know where you are.

It is located about 50-60km from Santiago at an altitude of 1450m (and within the property of Hacienda Santa Martina – a private resort), so not in the darkest skies of Chile. It is a small facility which houses basically 2 telescopes, an instrument room, a control room, a small museum, a medium-sized seminar rooms, and a tiny kitchen with solely one bed to sleep. Practically people go overnight from Santiago to observe.

The front side of the UC Observatory.

The telescopes operating during the night (and… that’s why the extra noise in the photo!).

The main dome houses two telescopes, the ESO 50cm and the Tololo 40cm, and the main instrument is an echelle spectrograph (PUCHEROS) with a good outcome given the instrument and sight restrictions (see publications).

The telescopes inside the dome: the ESO 50cm in front and the Tololo 40cm in the back.

The ESO 50cm.

The ESO telescopes and part of the weight balance system.

The Tololo 40cm telescope, along with some accessories.

We came from Valparaiso for only one night of observations, so the dedication is more than obvious.

As I was not directly involved with the observations I had time to play around with my cameras. This resulted in this time-lapse video from inside the dome, that shows how the ESO telescope is slewing from one target to the next after each exposure. [Some details: GoPro 4 silver, set at 10s exposure, and running from 22:25:34 (Jan 13, 2017) up to 00:31:18 (Jan 14), video @25fps – edited with Blender.]

Universidad Catolica Observatory night sky time-lapse

However, I haven’t been fortunate enough to go to the big toys yet, and I hope that this will change in the near future (not much time is left anyways…).

Planets around A-type stars

Posted July 26, 2017 By grigoris

For an unknown reason I found this footnote from Menu et al. 2015 (A&A, 581A, 107) very interesting:

It is interesting to note that several of the few directly imaged planetary companions are found around A-type stars, which are descendants of Herbig Ae/Be stars. Examples of A-type exoplanet host stars are HR 8799 (e.g., Marois et al. 2008), HD 95086 (e.g., Rameau et al. 2013), κ And (e.g., Carson et al. 2013), β Pic (e.g., Lagrange et al. 2010), and HD 100546 (e.g., Quanz et al. 2013).

The (paper-)story of HD 87643

Posted July 25, 2017 By grigoris

A summary for HD 87643 (or MWC 198, Hen 3-365, V640 Car, … see also Simbad). That is a great number of papers (similar to the post for GG Car).

  • 1909 /
    Object of the Henry Draper catalog.
  • 1933 / Merrill, P. W.; Burwell, C. G. 1933 (ApJ, 78, 87)
    First reference as a Be star.
  • 1968 / Hiltner, W. A.; Stephenson, C. B.; Sanduleak, N. 1968 (ApL, 2, 153H)
    They identified Balmer lines with their absorption borders to be similar to those of P Cygni. They identified also FeII lines in emission. They argued that the star has changed significantly from a P Cygni star (in 1909) and as a emission line star with WR characteristics (referring to Münch Luis 1953; Boletin los Obs. de Ton. y Tae., No 8, 27) to a nova like object, similar to Nova Delphini 1967.
  • 1971 / Crampton, D. 1971 (AJ, 76, 260)
    Identifying it within an HII region (KCW 47).
  • 1972 / van den Bergh, S. 1972 (PASP, 84, 594)
    A nebula is identified. A suggestion of a B2 V star with Av=2.5 mad and Vo=6.0, at a distance of 500 pc is proposed.
  • 1973 / Allen, D. A. 1973 (MNRAS, 161, 145), Sanduleak, N.; Stephenson, C. B. 1973 (ApJ, 185, 899)
    Allen: H,K,L ir observations show excess which is accounted to “reradiation from circumstellar dust clouds” (the star belongs to Dn category, which means “D”ust and presence of “n”ebulosity). See also section 4 (explanation). Sanduleak: Identified as a peculiar Be star.
  • 1974 / Stephenson, C. B. 1974 (ApJ, 191, 685), Albers, H. 1974 (ApJ, 189, 463), Swings J. P. 1974 (A&A, 34, 333)
    Stephenson: A nova-like nature is proposed. There is “a diffuse absorption spectrum violet-displaced from the corresponding emission lines by many hundreds of km/s”. In Hiltner+ 1968 that was ~850 km/s while in the current work is ~900 km/s. Moreover, the P Cygni absorption, present in 1968, is gone in 1973 (current work). Other than that the spectrum is similar to Hiltner’s, but very different than the original observation in HD catalog (1909). Albers: Identification of the CaII triplet and the OI 8446 lines (with a strong presence). Swings: Similar spectrum to GG Car. Balmer lines with P Cygni profiles, FeII (double-peaked with ~30km/s) and [FeII] (diffuse) lines present.
  • 1976 / Williams, P. M.; Beattie, D. H.; Stewart, J. M. 1976 (Obs, 96, 184), Allen, D. A. 1976 (MNRAS, 174P, 29), Henize, K. G. 1976 (ApJS, 30, 491), Allen, D. A.; Swings, J. P. 1976 (A&A, 47, 293)
    Williams: First SED for HD 87643. Mid-r observations indicative of a dust shell presence. Allen: Deriving reddening parameters: Teff = 11000 K, Av=1.9 mag, B(B-V)/Av = 0.35. Henize: Catalog of emission line stars, object 365 (or MWC 198). Comments: “Hβ is seen in emission and a P Cygni profile is suspected at Hα. Classified as P Cyg in HDE and as W-R by Münch (1953). Mount Stromlo slit spectra show a peculiar nova-like spectrum (Henize 1962; Carlson 1968). A direct plate with the Mount Stromlo 74 inch (1.9 m) reflector shows the star to be centered in a peculiar nebula (Henize 1962). Recent observations of this star have been reported by Hiltner, Stephenson, and Sanduleak (1968) and by van den Bergh (1972).” Allen+Swings: Member of Group 2 of peculiar Be stars with IR excess (see paper for more).
  • 1979 / 1979 / Carlson, E. D.; Henize, K. G. 1979 (VA, 23, 213)
    Included in the catalog of southern peculiar emission-line stars. [Note: I couldn’t access the paper though!]
  • 1981 / Surdej, A.; Surdej, J.; Swings, J. P.; Wamsteker, W. 1981 (A&A, 93, 285)
    The Reflection Nebula Surrounding HD87643: Imaging of HD 87643 shows a filamentary structured nebula (already mentioned in previous works) but more careful examination of Hα, [OIII], [SII] images showed that the nebula is not emitting, and the authors conclude towards a reflection nature of the nebula (at about 1 kpc). A spectrum of this nebula reveals strong P Cygni profiles (from Hβ to Hε) and many diffuse FeII lines. Expansion velocity ~1200 km/s
  • 1982 / Barbier, R.; Swings, J. P. 1982 (IAUS, 98, 103), de Freitas Pacheco, J. A.; Gilra, D. P.; Pottasch, S. R. 1982 (A&A, 108, 111)
    Barbier: Polarization measurements (in UBV). de Freitas Pacheco: Using UV spectra they estimated the mass loss ~7×107 M/year, evidence of a strong wind. See also the explanation of line formation (physics).
  • 1983 / Surdej, J.; Swings, J. P. 1983 (A&A, 117, 359)
    A non-isotropic and/or homogeneous environment is suggested based also in their previous work (Surdej+ 1981).
  • 1985 / de Freitas Pacheco, J. A.; Faria Lopes, D.; Landaberry, S. C.; Selvelli, P. L. 1985 (A&A, 152, 101)
    High-resolution UV spectra revealed a large number of lines. They discuss the excitation mechanism for FeII and provide a sketch of the circumstellar environment with: regions of ionized elements closer to the star, a region of neutral H, and a cold shell. The presence of a strong low ionization wind is mentioned. The wind velocity is estimated to ~800 km/s, with a mass loss of ~107 M/year, and the NaI doublet suggests a distance of 2 kpc.
  • 1986 / Olnon, F. M.; Raimond, E.; Neugebauer, G.; van Duinen, R. J.; Habing, H. J.; Aumann, H. H.; Beintema, D. A.; Boggess, N.; Borgman, J.; Clegg, P. E.; Gillett, F. C.; Hauser, M. G.; Houck, J. R.; Jennings, R. E.; de Jong, T.; Low, F. J.; Marsden, P. L.; Pottasch, S. R.; Soifer, B. T.; Walker, R. G.; Emerson, J. P.; Rowan-Robinson, M.; Wesselius, P. R.; Baud, B.; Beichman, C. A.; Gautier, T. N.; Harris, S.; Miley, G. K.; Young, E. 1986 (A&AS, 65, 607)
    Identified in the IRAS catalog.
  • 1987 / Volk, K.; Kwok, S. 1987 (ApJ, 315, 654)
    Identifying dust at 10 micron (~162 K).
  • 1988 / Shore, S. N.; Sanduleak, N.; Brown, D. N.; Sonneborn, G.; Bopp, B. W.; Robinson, C. R. 1988 (ESASP, 281a, 417), McGregor, P. J.; Hyland, A. R.; Hillier, D. J. 1988 (ApJ, 324, 1071)
    Shore: Similarities between Galactic and Magallanic Cloud stars, ie. HD 87643 (Hen3-365) to S22 in LMC. McGregor: IR spectra with HI lines present, but no first-overtone CO emission (in contrast to others lines GG Car, CPD-529243, CPD-572874). Estimating E(B-V)=1.0, 2.5 kpc, Teff~16000 K, L=4.9 L. Hot (T(K-L)=1190 K) and cold (T(25-60)=125 K) dust present for this star (they give other properties like radii and masses).
  • 1989 / Gaylard, M. J.; West, M. E.; Whitelock, P. A.; Cohen, R. J. 1989 (MNRAS, 236, 247)
    IR measurements and detection of OH.
  • 1990 / Deguchi, S.; Nakada, Y.; Sahai, R. 1990 (A&A, 230, 339), Shore, S. N.; Brown, D. N.; Bopp, B. W.; Robinson, C. R.; Sanduleak, N.; Feldman, P. D. 1990 (ApJS, 73, 461)
    Deguchi: No detection of CO or SiO in radio observations (HD 87643 is referred as SAO 237672). Shore: UV spectra for HD 87643, with P Cygni profiles. They assign a tentative B3 type with Teff~15000 K, L=3.7 L. Discussing the shell and how it affects the optical photometry. Identifying ~10% variation in the Fe II lines. Note from Section IIIb: “Van den Bergh (1972) attempted to determine the distance to He 3-365, assuming it to be a B2 V star. The derived distance of 0.5 kpc is certainly an underestimate. De Freitas Pacheco, Gilra, and Pottasch (1982) have analyzed the optical and UV pectrum of this star, concluding that it is a B supergiant at a distance of about 2-3 kpc. In a subsequent paper, de Freitas Pacheco, Gilra, and Pottasch (1985) refer to it as a B[e] star with a cool wind. They reported Mg II P Cygni profiles at high dispersion and suggested that the mass-loss rate is about M~lO-7 M/yr. Surdej and Swings (1983) detected a reflection nebula in the vicinity of the star. MHH88 report the detection of hot dust emission.”
  • 1992 / Gnedin, Yu. N.; Kiselev, N. N.; Pogodin, M. A.; Rosenbush, A. E.; Rosenbush, V. K. 1992 (SvAL, 18, 182), Lopes, D. F.; Damineli Neto, A.; de Freitas Pacheco, J. A. 1992 (A&A, 261, 482)
    Gndedin: A small polarization ~0.6% was observed, but without any variation reported. Lopes:Optical and ir spectroscopy, and short discussion of the the observed lines/features. Extracting physical properties: B3I, E(B-V)=1.3, d= 2.9 kpc, Mv=-7.6, Mbol=-8.9, M=34 M, Vwind=1300 km/s, MassLoss=1.2×10-5 M/year (a good physics paper also!).
  • 1994 / The, P. S.; de Winter, D.; Perez, M. R. 1994 (A&AS, 104, 315)
    Object refer to the catalog as “extreme emission line object”
  • 1998 / Lamers, H. J. G. L. M.; Zickgraf, F.-J.; de Winter, D.; Houziaux, L.; Zorec, J. 1998 (A&AS, 131, 401), Oudmaijer, R. D.; Proga, D.; Drew, J. E.; de Winter, D. 1998 (MNRAS, 300, 170)
    Lamers: It is not considered a definite SG since “show some characteristics of pre-main sequence stars (e.g. forbidden emission lines, evidence for disks, nebulosity) but there is no evidence for infall.” They provide a B4II[e] type classification for HD 87643. Noting: “HD 87643 is embedded in a reflecting nebula (Henize 1962, van den Bergh 1972, Surdej et al. 1981). The star was originally classified as a P Cygni type star and even a nova-like star (Carlson & Henize 1979). From IUE spectra McGregor et al. (1988a) and Shore et al. (1990) assigned an effective temperature of 15000 K to HD 87643. A distinctive peculiarity of HD 87643 is the presence of a strong, low ionization wind (de Freitas Pacheco et al. 1985, L ́opes et al. 1992). P Cygni line profiles are observed in many species, indicating outflows up to 1400 km s −1 (Surdej et al. 1981, Shore et al. 1990) and 1800 km s −1 (Oudmaijer et al. 1998). The estimated bolometric luminosity indicates that this star should be a bright giant (Zorec 1998; Oudmaijer et al. 1998).”. Yudin: Polarimteric observations show an increase of the polarization (compared to Barbier & Swings 1982 and Gnedin 1992) to ~1%, as well as some variability within a few days, consistent with HAeBe stars with Algol-like minima. Oudmaijer: A focused study on HD 87643, with high-resolution spectroscopy and medium-resolution spectropolarimetric data. Good intro. Imaging show nebulosity in V, R but not in Ha and [SII] (consistent with Surdej et al. 1981). Suggesting an evolved SG nature, with an “optically thick disk where irradiation pressure is sufficient to power mass loss from both the star and the disk”. Three different line-forming regions at ~1800 km/s (Ha and HeI), ~150km/s (H and FeII lines), and ~40km/s (forbidden lines, FeI, weaker FeII lines), with a disk-like structure. Commenting on the fainting magnitude of the system.
  • 1999 / Oudmaijer, R. D.; Drew, J. E. 1999 (MNRAS, 305, 166), Voors, R. H. M. 1999 (Ph.D. Thesis, Universiteit Utrecht, The Netherlands)
    Oudmaijer:Hα spectropolarimetry “indicates that the polarization profile can be best reproduced with a circumstellar disc that is both rotating and expanding”. Voors: Proposed a circumbinary disk.
  • 2000 / Valenti, J. A.; Johns-Krull, C. M.; Linsky, J. L. 2000 (ApJS, 129, 399), Clark, J. S.; Miroshnichenko, A. S.; Larionov, V. M.; Lyuty, V. M.; Hynes, R. I.; Pooley, G. G.; Coe, M. J.; McCollough, M.; Dieters, S.; Efimov, Yu. S.; Fabregat, J.; Goranskii, V. P.; Haswell, C. A.; Metlova, N. V.; Robinson, E. L.; Roche, P.; Shenavrin, V. I.; Welsh, W. F. 2000 (A&A, 356, 50)
    Valenti: Treated as Herbig Ae/Be star (id 89). A spectral type of B3.5 is given and a Av=1.88 mag. Clark: “HD 87643 (which faded by ∼1 mag since the 1960’s), and MWC 342 (∆V∼0.6 mag). Of these, only HD 87643 showed a long term trend in colour with brightness, becoming redder as it faded (Miroshnichenko 1998).” (Miroshnichenko A.S., 1998, In: Jaschek C., Hubert A.M. (eds.), B[e] stars, Kluwer Academic Publishers, p. 145)
  • 2001 / de Winter, D.; van den Ancker, M. E.; Maira, A.; Thé, P. S.; Djie, H. R. E. Tjin A.; Redondo, I.; Eiroa, C.; Molster, F. J. 2001 (A&A, 380, 609)
    Previously unpublished photometry from data “obtained between 1978 and 1997 in the Walraven (WULBV), Johnson/Cousins (UBV(RI)c) and ESO and SAAO near-infrared (JHKLM) photometric systems”.
  • 2003 / Zickgraf, F.-J. 2003 (A&A, 408, 257)
    Detailed work on the spectral features observed on many galactic objects, including HD 87643 (simply put… must see paper!).
  • 2005 / Greaves, J. 2005 (IBVS, 5699, 18), Cool, Richard J.; Howell, Steve B.; Peña, Maria; Adamson, Andy J.; Thompson, Robert R. 2005 (PASP, 117, 462)
    Greaves: Assigning an SDOR type of variability for HD 87643 (V=8.68 – 9.83mag). Cool: They show UV spectra for HD 87643 as a comparison but they say they have been published previously (de Freitas Pacheco et al. 1982). The star is considered a similar source to the ones studied (iron stars) and the discussion about the nature is interesting. E.g. “hot Be star with an evolved late‐type secondary. The hydrogen emission features arise in the hot wind from the Be star, while the corresponding P‐Cygni absorption lines are produced from dense material in the expanding, radiation‐driven wind around each system.”
  • 2006 / Baines, D.; Oudmaijer, R. D.; Porter, J. M.; Pozzo, M. 2006 (MNRAS, 367, 737)
    They treat HD 87643 are a Herbig Ae/Be star (although its supergiant nature is not excluded, as it stands out from all others), plus they do not detect binarity. Hα emission is considered as an outflow, which consists of a high- and low-velocity components.
  • 2007 / Groh, J. H.; Damineli, A.; Jablonski, F. 2007 (A&A, 465, 993)
    Comment: “HD 87643 (Fig. 11) is thought to be an evolved B[e] star (Oudmaijer et al. 1998) and appears to be related to the LBV class, although the link is not clear yet. This object has an optical spectrum dominated by emission lines of Fe II and P Cygni profiles in the Balmer series, together with low excitation forbidden lines. The spectrum is produced by a fast polar wind combined with a slow disk wind (Oudmaijer et al. 1998). The ultraviolet and optical spectra of HD 87643 was previously discussed by de Freitas Pacheco et al. (1985,1982), who reported a strong spectral line variability. HD 87643 has a bright reflection nebula, which was analyzed by Surdej et al. (1981) and Surdej & Swings (1983). Its 2001 near infrared spectrum shows prominent Fe II, CI lines and Pa γ emission, compatible with the presence of a cold wind. He I 10 830 A presents a P-Cygni profile, with a weak emission and a strong absorption that goes up to -1750 km s-1, which is probably formed in the fast polar wind.”
  • 2007 / Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. 2007 (IBVS, 5863, 1)
    Included in the catalog of Variable stars (as V0640 Car).
  • 2009 / Millour, F.; Chesneau, O.; Borges Fernandes, M.; Meilland, A.; Mars, G.; Benoist, C.; Thiébaut, E.; Stee, P.; Hofmann, K.-H.; Baron, F.; Young, J.; Bendjoya, P.; Carciofi, A.; Domiciano de Souza, A.; Driebe, T.; Jankov, S.; Kervella, P.; Petrov, R. G.; Robbe-Dubois, S.; Vakili, F.; Waters, L. B. F. M.; Weigelt, G. 2009 (A&A, 507, 317), Kraus, M. 2009 (A&A, 494, 253)
    Millour: Just read this paper! 🙂 They identify a companion (much fainter). Their separation is ~51 AU, and the corresponding orbital period 20-50 years. The structure of the nebula may be the result of periastron passages. The suggested picture is: i. a giant/supergiant with a dusty disk (contributes mainly to the IR emission, which originates from the inner and hotter rim of the disk, 2.5-3 AU), ii. a much fainter companion star (probably not hot) embedded in a dusty envelope, iii. a cooler circumbinary envelope. Comment on the continuous fainting of the system.Kraus: Simple commenting on HD 87643 in Table A.1 with some physical parameters and further references.
  • 2011 / Carmona, A.; van der Plas, G.; van den Ancker, M. E.; Audard, M.; Waters, L. B. F. M.; Fedele, D.; Acke, B.; Pantin, E. 2011 (A&A, 533A, 39)
    They include HD 87643 as a Herbig Ae/Be object, although they mention its controversial nature. They do not detect any H2 (in IR spectra of R~90000 resolution CRIRES data)
  • 2015 / Menu, J.; van Boekel, R.; Henning, Th.; Leinert, Ch.; Waelkens, C.; Waters, L. B. F. M. 2015 (A&A, 581A, 107)
    They treat HD 87643 as a Herbig Be star. They find that T=Tsub( R/Rsub)^q with q=0.72 (for the temperature of the molecular disk at 10.7 um) and a half-light radius of 37.3 mas corresponding to 56 au. However, they do not detect any H2 (as found in other pre-main sequence objects) or report any gap presence, although a number of objects studied do show gaps.

And the list is not exhaustive.

A novel method to automatically detect and measure the ages of star clusters in nearby galaxies: Application to the Large Magellanic Cloud

T. Bitsakis, P. Bonfini, R. A. Gonzalez-Lopezlira, V. H. Ramirez-Siordia, G. Bruzual, S. Charlot, G. Maravelias, D. Zaritsky

We present our new, fully-automated method to detect and measure the ages of star clusters in nearby galaxies, where individual stars can be resolved. The method relies purely on statistical analysis of bservations and Monte-Carlo simulations to define stellar overdensities in the data. It decontaminates the cluster color-magnitude diagrams and, using a revised version of the Bayesian isochrone fitting code of Ramirez-Siordia et al., estimates the ages of the clusters. Comparisons of our estimates with those from other surveys show the superiority of our method to extract and measure the ages of star clusters, even in the most crowded fields. An application of our method is shown for the high-resolution, multi-band imaging of the Large Magellanic Cloud. We detect 4850 clusters in the 7 deg2 we surveyed, 3451 of which have not been reported before. Our findings suggest multiple epochs of star cluster formation, with the most probable occurring ~310 Myr ago. Several of these events are consistent with the epochs of the interactions among the Large and Small Magellanic Clouds, and the Galaxy, as predicted by N-body numerical simulations. Finally, the spatially resolved star cluster formation history may suggest an inside-out cluster formation scenario throughout the LMC, for the past 1 Gyr.

arXiv: 1707.02311