studying the pair wds 01487+7528 = hj 2075 ab … · the binary system hj 2075 with ... this method...

Vol. 14 No. 1 January 1, 2018 Page 93 Journal of Double Star Observations

Introduction The GAIA satellite was launched by European

Space Agency (ESA) on December 19, 2013. It is an astrometric mission, which is a successor of the Hip-parcos satellite (also launched by ESA). GAIA will pro-duce a catalog of 1 billion stars (up to 20 magnitude) with an astrometric solution of 5 parameters (AR and DEC, proper motion, parallax and radial velocity). The accuracy of the astrometric data will be much greater than any existing catalog.

GAIA will publish its final results after year 2020. Until then, intermediate data releases, with less accurate results, will be published. The first of these releases, GAIA DR1 (Lindegren et al., 2016), was published in September 2016. This release lists complete astrometric solutions for most Hipparcos and Tycho-2 stars (about 2 million stars). This subset of data is called TGAS (Tycho-Gaia Astrometric Solutions). The mean accura-cies for the positions and parallaxes are 0.32 milli-arcsecond (mas). In addition to this, the parallax has a systematic error of ±0.3 mas. The mean errors in the proper motions are 1.3 mas/yr.

A previous work using GAIA data was published in the OED magazine (Rica 2017). I wanted to re-analyze those double stars studied by LIADA Double Star Sec-tion in 2003 (Rica 2006). For the 103 double stars stud-

ied in Rica (2006) I only found TGAS data for both components in 10 of these double stars (many double stars are composed of faint stars). For these 10 pairs, 80% (8 double stars) are optical and only 2 are physi-cal (with common parallaxes and proper motions). If we take into account the double stars studied by LI-ADA in 2002, only 21% (3 of 14 systems) of the pairs are physical.

In this work I focus on WDS 01487+7528( = HJ 2075 AB). HJ 2075 AB consists of stars of 10.0 and 11.3 magnitudes separated by 31". See Figure 1.

Study of HJ 2075 AB in 2003 In Rica (2006, Figure 2) we classified HJ 2075 AB

as a high common proper motion pair with spectral types of G8V and K6V (based on the B-V Tycho-2 col-or). The WDS catalog lists 10 measures, the first in 1897 (229º and 31.1") and the last in 2015 (231º and 30.7").

The New Study Using TGAS TGAS lists the components A (TYC 4494-160-1)

and B (TYC 4494-349-1) (Figure 3). This data confirms the common parallax (listed as Plx) for A and B and in addition to the high common proper motion (listed as

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Studying the Pair WDS 01487+7528 = HJ 2075 AB Using the GAIA-DR1 Data

Francisco Rica Romero

Astronomical Forum of Extremadura (Spain) [email protected]

Abstract: In September 2016, the European Space Agency (ESA) released GAIA-DR1. ESA also published TGAS, a subset of Gaia source comprising those stars in the Hipparcos and Tycho-2 catalogs for which a full 5-parameters astrometric solution have been achieved. After publication of TGAS, the author decided to use the parallaxes and proper motions to review the double stars studied by LIADA’s Double Star Section during 2003. This year LIADA measured and studied 103 pairs of which only 10 have both stellar components listed in TGAS. Of those 10 pairs, 80% (8 double stars) are optical and only 2 are physical (with common parallaxes and proper motions).The main object of this work is a new study of HJ 2075 AB (WDS 01487+7528), located at 60 pc and composed of stars of 10.0 and 11.3 magnitudes with spectral types G8V and K4V separated by 31". This is a physical pair according to TGAS data (common parallaxes and proper motions).

mailto:[email protected]



Figure 1. The binary system HJ 2075 with the components A, B and C. Digitized Sky

Survey Image from Aladin.

Figure 2. Study published in Rica (2006).

Figure 3. Data listed in TGAS for A and B components.



pmRA and pmDEC) clearly suggests a physical relation. Table 1 lists the photometric and astrophysical data

obtained from the literature. From the trigonometric parallax, we determine the

reddening for the system using the Galactic dust extinc-tion determined by Schlafly & Finkbeiner (2011) and implemented in the “Galactic Dust Reddening”

† web

site. This method calculates the reddening in the line of sight (that is, for an object located outside our Galaxy) and needs to be scaled to obtain the initial reddening for distance. For this, I use the exponential law of Anthony-Twarog & Twarog (1994). I estimated a reddening of E(B-V) = 0.04 (Av = 0.15).

Spectral types for both components were deter-mined in two ways: 1) Based on the multi-photometric information (and

their errors) obtained from literature. I used the ex-cel tool Mamajek tool v1.3.xlsm, designed by me. This tool contains the table of the astrophysicist Eric Mamajek

†† (Figure 4). This table relates pho-

tometric colors with astrophysical data (spectral

types, mass, absolute magnitude) for the main se-quence. The interstellar reddening is also estimated. The best fit entry from the table is chosen accord-

ing to 2. 2) Using the absolute magnitude (determined from

TGAS parallax) and the relation of absolute magni-tude-spectral type listed in the table of Eric Mamajek.

The spectral type determined from the two methods

show similar conclusions. The adopted spectral types are G8V and K4V for primary and secondary compo-nents.

According to Jao, Wei-Chun et al., (2016), TGAS parallax has a systematic error of -0.06" (sample of 11592 stars) for stars with parallaxes between 10 and 20 mas. In Table 1, I combined the error terms by sum-ming in quadrature for the total TGAS error. The abso-lute magnitude is corrected by reddening. The listed error is a quadrature sum of the V error, reddening error and the error due to the parallax.

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A Component Source B Component Source

V1 9.98 ± 0.03 Tycho-2 11.27 ± 0.05 APASS

B - V +0.78 ± 0.04 Tycho-2 +1.13 ± 0.09 APASS

g --- --- 11.86 ± 0.08 APASS

r --- --- 10.83 ± 0.07 APASS

i --- --- 10.46 ± 0.06 APASS

J 8.44 ± 0.03 2MASS 9.23 ± 0.02 2MASS

H 8.00 ± 0.05 2MASS 8.64 ± 0.03 2MASS

Ks 7.94 ± 0.03 2MASS 8.53 ± 0.02 2MASS

(mas) 16.60 ± 0.26 TGAS 16.91 ± 0.32 TGAS

Distance (pc)4 60.24 ± 0.9 This work 59.14 ± 1.1 This work

(Mv)o 5.93 ± 0.05 This work 7.26 ± 0.07 This work

Spectral Type G8V This work K4V This work

Mp(RA) [mas/yr] 144.3 ± 0.4 This work 143.4 ± 0.6 This work

Mp(DEC) [mas/yr] -45.0 ± 0.6 This work -43.8 ± 0.8 This work

Table 1. Astrophysical Data for Stellar Componenets of HJ 2075

Figure 4. Fragment of the Eric Mamajek’s table within the excel tool “Mamajek Tool v1.3”.

† http://irsa.ipac.caltech.edu/applications/DUST/. †† “A Modern Mean Stellar Color and Effective Temperature Sequence for O9V-Y0V Dwarf Stars”, version of 2013 February, http://www.pas.rochester.edu/~emamajek/EEM_dwarf_UBVIJHK_colors_Teff.dat

http://irsa.ipac.caltech.edu/applications/DUST/

http://www.pas.rochester.edu/~emamajek/EEM_dwarf_UBVIJHK_colors_Teff.dat



Using Evolutionary Isochrones I use a CMD (Color Magnitude Diagram) 2.8

† evo-

lutionary isochrones, using PARSEC isochrones (Bressan et al. 2012) version 1.2S with the photometric system UBVRIJHK (Bessell 1990; Maíz-Apellániz 2006). In Figure 5, I plot three isochrones with solar age and metallicity ([Fe/H]) of 0.0, -0.3 and -0.5. Error bars are showed for Mv and B-V. The best fit is ob-tained for [Fe/H] = -0.3 and in this paper I adopted a metallicity of -0.3 ± 0.1.

X-Ray Source Close to the Primary Star The ROSAT satellite observed during 1990 August

and 1991 February an X-ray source (1RXS J014826.2+752835) at 11.6 arcsecond from the primary component (see Figure 6). The positional error of this X-ray source is 13 arcseconds (typical for ROSAT satel-lite sources). The B and C components are located about 33” from the X-ray source. I cannot reject these stars as the X-ray source because there are cases where the optical counterparts are located some distance from the X-ray position (see Figure 2 of Agüeros and Marcel (2009)). The flux ratio fx/fopt (in V and J band) are typi-

cal for F/G stars. It is likely the primary star is the counterpart of the X-ray source.

My conclusion is reinforced by the WGACAT ver-sion of ROSAT sources (White, Giommi & Angelini 2000) that points out that the primary component is the optical counterpart of the X-ray source. If I assumed the primary star is the X-ray counterpart, then the primary could have an age of 0.8 Gyr

††.

Acknowledgments This research work makes use of data from the Two

Micron All Sky Survey (2MASS), which is a joint pro-ject of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foun-dation. The study here presented also uses the Washing-ton Double Star Catalog, maintained at the U.S. Naval Observatory and the SIMBAD astronomical database and VizieR astronomical catalogs service, both main-tained and operated by the Center de Données As-tronomiques de Strasbourg (http://cdsweb.u-strasbg.fr/).

Figure 5. Isochrones obtained using the web interface CMD for a solar age and metallicity of 0.0, -0.3 and -0.5. The filled circles are the A and B components. The errors bars are shown.

† http://stev.oapd.inaf.it/cgi-bin/cmd †† Figure 5 of Damiani et al. (1995) was used to estimate the age.

http://cdsweb.u-strasbg.fr/



The author thanks Frank Smith for his review of the English version of this work.

References

Agüeros M. A. et al., 2009, ApJS, 181, 444.

Anthony-Twarog B. J., Twarog B. A., 1994, AJ, 107, 1577.

Bessell, M. S., 1990, PASP, 102, 1181.

Bressan, A., Marigo, P., Girardi, L., et al., 2012, MNRAS, 427, 127.

Damiani, F., Micela, G., Sciortino, S., Harnden, F. R., Jr., 1995, ApJ, 446, 331.

Jao, Wei-Chun; Henry, Todd J.; Riedel, Adric R.; Win-ters, Jennifer G.; Slatten, Kenneth J.; Gies, Douglas R., 2016, ApJ, 832L, 18J.

Lindegren, L., Lammers, U., Bastian, U., et al., 2016, ArXiv e-prints, arXiv:1609.04303.

Maíz-Apellániz, J., 2006, AJ, 131, 1184.

Rica, F., 2006, JDSO, 2, 118.

Rica, F., 2017, OED, 18, 37.

Schlafly, E. F., and Finkbeiner, D.P., 2011, ApJ, 737, 103.

Vogt, N., et al., 2012, A&A, 546A, 63V.

White N. E., Giommi P., Angelini L. Laboratory for High Energy Astrophysics (LHEA/NASA), Green-belt (2000).

Figure 6. X-Ray source as the yellow circle close to the primary component.



APPENDIX I. OPTICAL PAIRS In Table 2, I list the pairs of stars, studied by LIADA in 2003, for which the stellar components have no physi-

cal relation. Both stellar components in these pairs are listed in TGAS and I analyze their trigonometric parallaxes and proper motion to determine in their status.

HDS 1595: flagged as “U” in WDS: “Proper motion or other technique indicates that this pair is non-physical”. The proper motion listed in Tycho-2 has large errors (20 mas/yr). The proper motion listed for B com-ponent in PPMXL: -11.9 ± 3.5 and -5.2 ± 3.5 mas/yr.

HJ 29: TGAS lists small and nearly identical parallaxes, but the proper motions of the components are incom-patible. This object is flagged with “U” in WDS:.

HJ 2450: A and B have different proper motions in AR and Dec. Following the method of Vogt, et al. (2012) , I derived a significance of 2.8 and 2.9 for not being a background object and for orbital motion. These significanc-es indicate an unrelated pair.

WDS Componente Mag. WDS (º) (") year (mas) ()

(mas/yr)

() mas/yr)

11119-5312 HDS1595 A 8.99 345 23.70 2010 3.24 ± 0.26 -26.75 ± 0.08 +6.62 ± 0.08

11119-5312 HDS1595 B 10.78 2.11 ± 0.39 -6.48 ± 0.71 -7.24 ± 0.76

04537-0618 HJ 29 A 10.8 300 31.1 2013 2.95 ± 0.23 +14.73 ± 0.57 -9.45 ± 0.56

04537-0618 HJ 29 B 11.8 2.96 ± 0.31 +0.82 ± 0.92 +33.00 ± 0.84

08171+3348 HJ 780 A 11.2 208 14.6 2005 1.52 ± 0.32 +8.76 ± 1.33 -19.07 ± 1.32

HJ 780 B 12.1 0.49 ± 0.36 -0.87 ± 1.48 -6.92 ± 1.39

19251+3511 HJ1394 A 10.6 29 17.4 2010 1.16 ± 0.35 -8.31 ± 1.13 -35.23 ± 1.25

HJ1394 B 11.6 0.85 ± 0.50 -3.16 ± 1.60 +2.14 ± 1.85

03314+0131 HJ 2194 A 11.4 121 34.3 2011 2.62 ± 0.31 -8.97 ± 1.28 -18.02 ± 0.76

HJ 2194 B 11.8 3.50 ± 0.28 +42.53 ± 1.23 -35.06 ± 0.72

08292+1343 HJ 2450 A 10.4 172 27.9 2014 1.60 ± 0.58 -10.93 ± 1.95 -13.01 ± 0.94

HJ 2450 B 11.0 1.84 ± 0.87 -0.50 ± 3.14 -18.18 ± 1.50

03378+4943 WFC 250 A 11.3 68 11.1 2015 1.85 ± 0.27 -6.29 ± 0.91 -5.48 ± 0.51

WFC 250 B 11.1 1.41 ± 0.25 +0.61 ± 1.53 +0.61 ± 0.79

Table 2. Optical Pairs Studied by LIADA in 2003

studying the pair wds 01487+7528 = hj 2075 ab … · the binary system hj 2075 with ... this method...

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