A promising approach to decrease the uncertainties in the initial-final mass relationship, which is still poorly constrained, is to study white dwarfs for which external constraints are available, for instance, white dwarfs in common proper motion pairs (CPMPs). Important information of the white dwarf can be inferred from the study of the companion, since they were born at the same time and with the same initial chemical composition. In this contribution, we report new results obtained from spectroscopic observations of both members of several CPMPs composed of a F, G or K type star and a DA white dwarf

Catalan, Silvia

Garcia-Berro, E.

Isern, J.

Prieto, C. Allende

Ribas, I.

English

University of Hertfordshire Research Archive

15th European Workshop on White DwarfsASP Conference Series, Vol. 372, 2007R. Napiwotzki and M. R. BurleighThe Initial–Final Mass Relationship of White Dwarfs inCommon Proper Motion PairsS. Catala´n,1,2 I. Ribas,1,2 J. Isern,1,2 E. Garc´ıa–Berro,1,3 and C. AllendePrieto41Institut d’Estudis Espacials de Catalunya, c/ Gran Capita` 2–4, 08034Barcelona, Spain2Institut de Cie`ncies de l’Espai, CSIC, Facultat de Cie`ncies, CampusUAB, 08193 Bellaterra, Spain3Departament de F´ısica Aplicada, Escola Polite`cnica Superior deCastelldefels, Universitat Polite`cnica de Catalunya, Avda. del CanalOl´ımpic s/n, 08860 Castelldefels, Spain4McDonald Observatory and Department of Astronomy, University ofTexas, Austin, TX 78712, USAAbstract. A promising approach to decrease the uncertainties in the initial–ﬁnal mass relationship, which is still poorly constrained, is to study white dwarfsfor which external constraints are available, for instance, white dwarfs in commonproper motion pairs (CPMPs). Important information of the white dwarf canbe inferred from the study of the companion, since they were born at the sametime and with the same initial chemical composition. In this contribution, wereport new results obtained from spectroscopic observations of both members ofseveral CPMPs composed of a F, G or K type star and a DA white dwarf.1. Observations and AnalysisA preliminary list of targets was selected from the literature (Wegner & Reid1991; Silvestri et al. 2001) and is composed of 11 common proper motion pairs(CPMPs), composed of a DA white dwarf and a FGK star. The observationswere carried out using a suite of telescope/instrument conﬁgurations. The whitedwarf members were observed with the LCS spectrograph on the HJS (2.7 m)telescope at McDonald Observatory (Texas) and also with the TWIN spec-trograph on the 3.5 m telescope at Calar Alto Observatory (CAHA, Almeria,Spain), obtaining a FWHM resolving power of ∼ 4−5 A˚. The FGK companionswere observed with the FOCES echelle spectrograph on the 2.2 m telescope atCAHA and with the SARG echelle spectrograph at the TNG telescope in LaPalma (Canary Islands, Spain) with resolutions of R ∼ 47000 and R ∼ 57000,respectively. These spectroscopic observations have revealed that only 5 of the11 white dwarf components were in fact of the DA type, whereas the rest of thecandidates were misclassiﬁed.In principle, the total age of each system can be obtained from the analysisof the FGK star member as follows: ﬁrst, we derived the eﬀective tempera-ture, Teff , using the available V JHK photometry and following the method of6970 Catala´n et al.Table 1. Stellar parameters derived for the observed FGK starsName Teff (K) Z log(L/L⊙) Age (Gyr)G158−771 4387± 27 − − −BD+44◦1847 5627± 49 0.011± 0.003 −0.188± 0.059 −2BD+23◦25391 5666± 48 − − −BD+34◦2473 6268± 68 0.030± 0.008 0.369± 0.109 2.1± 1.5BD−8◦5980 5669± 52 0.012± 0.004 −0.151± 0.040 −21More observations are needed to complete the analysis of these stars.2Isochrone fits do not provide reliable ages. Other indicators are being considered.Figure 1. Fits of the observed spectra for the companion of WD 0913+442.The solid line is the ﬁt corresponding to the derived Z and the dotted anddashed lines are spectra computed for +3σ and −3σ from the average.Masana, Jordi, & Ribas (2006) — see Table 1. Then, we ﬁtted the observedspectra considering Teff and assuming a value for log g using the SYNSPEC pro-gram and Kurucz atmospheres to derive the metallicity, Z (Fig. 1). We focusedon those spectral windows where unblended lines of FeI, FeII and NiI are present:5800−5900 A˚, 6000−6150 A˚ and 6750−6850 A˚ for Fe and 6100−6200 A˚ and7700 − 7800 A˚ for Ni. When we know the distance and the apparent magni-tude of the star the calculation of the luminosity, L, is straightforward. Finally,using the stellar models of Schaller et al. (1992) we performed an interpolationconsidering Teff , Z and L to obtain the ages of these stars, that is, the total agesof the white dwarfs in the CPMPs. The value of log g was adjusted iterativelyfor self–consistency. We have found that some of the observed stars are fairlyunevolved and so, the use of isochrones to derive their ages with accuracy is notthe best option. In these cases we are currently studying other age indicatorssuch as chromospheric activity or X-ray luminosity.In Table 2, we list the atmospheric parameters derived from the ﬁtting of thetheoretical models of D. Koester to the Balmer lines using the package SPEC-FIT of IRAF, and following the procedure described in Bergeron, Wesemael, &Fontaine (1992) — see Fig. 2. This package is based on χ2 minimization usingthe method of Levenberg–Marquardt (Press et al. 1992). Once we have TeffWhite Dwarfs in Common Proper Motion Pairs 71Table 2. Stellar parameters derived for the observed white dwarfsWD name Teff (K) log g (dex) Mf (M⊙) tcool (Gyr) tms (Gyr) Mi (M⊙)0023+109 10377± 230 7.92± 0.08 0.56± 0.03 0.49± 0.08 − −0913+442 8918± 111 8.29± 0.02 0.78± 0.01 1.72± 0.06 − −1304+227 10798± 120 8.21± 0.05 0.73± 0.13 0.73± 0.06 − −1354+340 13650± 437 7.80± 0.15 0.49± 0.10 0.14± 0.02 2.03± 1.57 1.62+1.00−0.302253−081 7200± 170 8.40± 0.08 0.87± 0.03 3.75± 0.19 − −Figure 2. Fits of the observed Balmer lines for the case of WD 0913+442.Lines range from Hβ (bottom) to H8 (top).and log g of each star, we derive its mass, Mf , and cooling time, tcool, using thecooling sequences of Salaris et al. (2000). Since we already know the total age ofthe white dwarf (from the companion), we obtain the main–sequence lifetime ofthe white dwarf progenitor, tms, by subtracting its cooling time from the totalage, if this value is available. Finally, using the stellar models of Domı´nguez etal. (1999) we compute the mass of the progenitor in the main sequence, Mi.2. The Initial–Final Mass RelationshipIn Fig. 3 we show the ﬁnal mass versus the initial mass of the white dwarf in aCPMP for which the analysis has been completed. Also plotted are the resultsfor the white dwarfs in the open clusters M 35 (Williams, Bolte, & Koester 2004)and M 37 (Kalirai et al. 2005). We used the atmospheric parameters reportedby these authors and then, for the sake of internal consistency, we followed thesame procedure as for the white dwarfs in our list. The main drawback of usingCPMPs is the uncertainty in the determination of the age of the companion,which can be minimized by selecting evolved stars. However, the fact that thesesystems are potentially more abundant and closer to us makes them promisingtargets, since a better spectroscopic study of both members of the CPMPs canbe done. White dwarfs in CPMPs also allow a wide age coverage. This is not thecase for open clusters, which are younger and do not contribute to the low–massrange of the initial–ﬁnal mass relationship. A ﬁrst inspection of Fig. 3 reveals as72 Catala´n et al.Figure 3. Mf versusMi obtained for a white dwarf in a CPMP (circles) andfor white dwarfs in the open clusters M 35 (squares) and M 37 (triangles)well a large scatter in the distribution, which let us think that, maybe, the initial–ﬁnal mass relationship is not a single–valued function. More observational dataand improved theoretical stellar models (mainly in the AGB phase) will helpto better establish this function. In this sense, to further extend the sample,a cross–correlation of the SIMBAD database and the Villanova White DwarfCatalog has provided us with more pairs, which we expect to study shortly.Acknowledgments. This research was partially supported by the MCYTgrant AYA05-08013-C03-01 and 02, by the European Union FEDER funds andby the AGAUR. S.C. thanks the RAS for ﬁnancial help to attend this meeting.ReferencesBergeron, P., Wesemael, F., & Fontaine, G. 1992, ApJ, 387, 288Domı´nguez, I., Chieﬃ, A., Limongi, M., & Straniero, O. 1999, ApJ, 524, 226Kalirai, J. S., Richer, H. B., Reitzel, D., Hansen, B. M. S., Rich, R. M., Fahlman, G.G., Gibson, B. K., & von Hippel, T. 2005, ApJ, 618, L123Masana, E., Jordi, C., & Ribas, I. 2006, A&A, 450, 735Press, W. H., Flannery, B. P., & Teukolsky, S. A. 1986, Numerical Recipes (Cambridge:Cambridge Univ. Press)Salaris, M., Garc´ıa–Berro, E., Hernanz, M., Isern, J., & Saumon, D. 2000, ApJ, 544,1036Schaller, G., Schaerer, D., Meynet, G., & Maeder, A. 1992, A&AS, 96, 269Silvestri, N. M., Oswalt, T. D., Wood, M. A., Smith, J. A., Reid, I. N., & Sion, E. M.2001, AJ, 121, 503Wegner, G., & Reid, I. N. 1991, ApJ, 375, 674Williams, K. A., Bolte, M., & Koester, D. 2004, ApJ, 615, L49

Numerical Recipes (Cambridge: Cambridge Univ.

The initial-final mass relationship of white dwarfs in common proper motion pairs

We have studied white dwarfs in common proper motion pairs (CPMPs) to improve
the semi-empirical initial–final mass relationship of white dwarfs. In this contribution, we re-
port new results obtained from spectroscopic observations of both members of several CPMPs
composed of a F, G or K type star and a DA white dwarf.Peer Reviewe

Catalán, S.

Ribas Vila, Immaculada

Isern Vilaboy, Jordi

García-Berro Montilla, Enrique

Allende Prieto, C.

UPCommons. Portal del coneixement obert de la UPC

Proceedings Title IAU SymposiumProceedings IAU Symposium No. 240, 2006A.C. Editor, B.D. Editor & C.E. Editor, eds.c© 2006 International Astronomical UnionDOI: 00.0000/X000000000000000XThe initial–final mass relationship of whitedwarfs in common proper motion pairs andopen clustersS. Catala´n1,2, I. Ribas1,2, J. Isern1,2,E. Garc´ıa–Berro1,3 and C. Allende Prieto41Institut d’Estudis Espacials de Catalunya, c/ Gran Capita` 2–4, 08034 Barcelona, Spainemail: catalan@ieec.uab.es2Institut de Cie`ncies de l’Espai, CSIC, Facultat de Cie`ncies, UAB, 08193 Bellaterra, Spain3Departament de F´ısica Aplicada, Escola Polite`cnica Superior de Castelldefels, UniversitatPolite`cnica de Catalunya, Avda. del Canal Ol´ımpic s/n, 08860 Castelldefels, Spain4McDonald Observatory and Dep. of Astronomy, University of Texas, Austin, TX 78712, USAAbstract. We have studied white dwarfs in common proper motion pairs (CPMPs) to improvethe semi-empirical initial–final mass relationship of white dwarfs. In this contribution, we re-port new results obtained from spectroscopic observations of both members of several CPMPscomposed of a F, G or K type star and a DA white dwarf.Keywords. stars: white dwarfs, stars: abundances, stars: evolution, binaries: visual1. Introduction and observationsThe initial–final mass relationship connects the properties of a white dwarf with thoseof its main-sequence progenitor. This function is important for determining the ages ofglobular clusters and their distances, for studying the chemical evolution of galaxies,and also for understanding the properties of the galactic population of white dwarfs.Despite its relevance, this relationship is still poorly constrained. A promising approachto decrease the uncertainties is to study white dwarfs for which external constraints areavailable. This is the case of white dwarfs in common proper motion pairs (CPMPs). Im-portant information of the white dwarf can be inferred from the study of the companion,since they were born at the same time and with the same initial chemical composition.The list of CPMPs under study was selected from the available literature (Wegner &Reid 1991, Silvestri et al. 2001). Each CPMP (11 in total) is composed of a white dwarfclassified as DA and a F, G or K type star. The observations were carried out using a suiteof telescope/instrument configurations. The white dwarf members were observed with theLCS spectrograph of the HJS (2.7 m) telescope at McDonald Observatory (Texas, USA)and with the TWIN spectrograph of the 3.5 m telescope at Calar Alto Observatory(CAHA, Almer´ıa, Spain), obtaining a FWHM resolving power of ∼ 4 − 5 A˚. The FGKcompanions were observed with the FOCES echelle spectrograph of the 2.2 m telescopeat CAHA and with the SARG echelle spectrograph at the TNG telescope in la Palma(Canary Islands, Spain) with resolutions of R ∼ 47000 and R ∼ 57000, respectively.These spectroscopic observations have revealed that only 5 of the 11 white dwarfs werein fact of the DA type, whereas the rest were misclassified.119120 S. Catala´n et al.Table 1. Stellar parameters derived for the observed FGK stars.Name Teff (K) Z log(L/L⊙) Age (Gyr)G158-771 4387± 27 − − −BD+441847 5627± 49 0.011± 0.003 −0.188± 0.059 −2BD+2325391 5666± 48 − − −BD+342473 6268± 68 0.030± 0.008 0.369± 0.109 2.1± 1.5BD-085980 5669± 52 0.012± 0.004 −0.151± 0.040 −21Not analyzed because of low S/N . More observations are underway.2The ages obtained from isochrone fits are not reliable (see text).Table 2. Stellar parameters derived for the observed white dwarfs.Name Teff (K) log g Mf (M⊙) tcool (Gyr) tms (Gyr) Mi (M⊙)WD0023+109 10377± 230 7.92± 0.08 0.56± 0.03 0.49± 0.08 − −WD0913+442 8918± 111 8.29± 0.02 0.78± 0.01 1.72± 0.06 − −WD1304+227 10798± 120 8.21± 0.05 0.73± 0.13 0.73± 0.06 − −WD1354+340 13650± 437 7.80± 0.15 0.49± 0.10 0.14± 0.02 2.03± 1.57 1.62+1.00−0.30WD2253-081 7200± 170 8.40± 0.08 0.87± 0.03 3.75± 0.19 − −2. Analysis and resultsTo determine the total age of each system, we analyzed the spectra of the FGK starsfollowing this procedure: first, we derived the effective temperatures, Teff , using the avail-able V JHK photometry and following the method of Masana et al. (2006). Then, wefitted the observed spectra using the SYNSPEC program and synthetic spectra basedon Kurucz atmospheres to derive their metallicities, Z, focusing on spectral windowswhere unblended lines of FeI, FeII and NiI are present. If the distance and the apparentmagnitude are known the calculation of the luminosity, L, is straightforward. Finally, weinterpolated the stellar models of Schaller et al. 1992 using Teff , Z and L to obtain theages of these stars, and, consequently, the total ages of the CPMPs — see Table 1. Wehave found that some of the observed stars are fairly unevolved and so, isochrone fitsdo not provide reliable ages. Other age indicators such as the chromospheric activity orX-ray luminosity are currently being considered.The atmospheric parameters of each white dwarf, Teff and log g, were derived from thefitting of the theoretical models of D. Koester to the observed Balmer lines using thepackage SPECFIT of IRAF following the procedure described in Bergeron et al. (1992)— see Table 2. Then, we derived its mass, Mf , and cooling time, tcool, using the coolingsequences of Salaris et al. (2000). Since we know the total age of the white dwarf (from thecompanion), we obtain the main sequence lifetime of the progenitor, tms, by subtractingits cooling time to the age of the system. Finally, using the stellar models of Domı´nguezet al. (1999) we compute the mass of the progenitor in the main sequence, Mi.In Fig. 1 we show the final mass versus the initial mass of the white dwarf in a CPMPfor which the analysis has been completed. Also plotted are the results for the whitedwarfs in the open clusters M 35 (Williams et al. 2004) and M 37 (Kalirai et al. 2005).We used the Teff and log g reported by these authors and then, for internal consistency,we followed the same procedure as for the white dwarfs in our list. By comparing theobservational data it can be noted that the error obtained for the Mi in the case of thewhite dwarf in a CPMP is higher than those obtained for white dwarfs in open clusters.In fact, the uncertainty in the determination of the ages is the main drawback of usingCPMPs, but it can be minimized by selecting the pairs with evolved companions.The IFMR of white dwarfs in common proper motion pairs 121Figure 1. Final masses versus the initial masses obtained for one of the CPMPs in our sample(circle) and for white dwarfs in the open clusters M 35 (squares) and M 37 (triangles).However, the fact that these systems are potentially more abundant and closer tous makes this a promising approach to improve the semi–empirical initial–final massrelation, since a better spectroscopic study of both members of the pairs can be done.White dwarfs in CPMPs also provide a wider age coverage of this relation, in contrastwith open clusters, which are younger and do not contribute to its low–mass range.A thorough comparison of the semi–empirical data with different theoretical relation-ships is currently underway and reveals a large scatter in the distribution (Fig. 1). Thiscould be due to the fact that maybe the initial–final mass relationship is not a single–valued function. More observational data and improved theoretical stellar models (mainlyin the AGB phase) will help to better establish this function. In this sense, to furtherextend the sample, a cross–correlation of the SIMBAD database and the Villanova WhiteDwarf Catalog has provided us with more pairs, which we expect to study shortly.AcknowledgementsThis research was partially supported by the MCYT grant AYA05–08013–C03–01 and02, by the European Union FEDER funds and by the AGAUR.ReferencesBergeron, P., Wesemael, F. & Fontaine, G. 1992, ApJ, 387, 288Domı´nguez, I., Chieffi, A., Limongi, M., & Straniero, O. 1999, ApJ, 524, 226Kalirai, J.S., Richer, H.B., Reitzel, D., Hansen, B.M.S., Rich, R.M., Fahlman, G.G., Gibson,B.K. & von Hippel, T. 2005, ApJ, 618, L123Masana, E., Jordi, C. & Ribas, I. 2006, A&A, 450, 735Salaris, M., Garc´ıa–Berro, E., Hernanz, M., Isern, J. & Saumon, D. 2000, ApJ, 544, 1036Schaller, G., Schaerer, D., Meynet, G. & Maeder, A. 1992, A&AS, 96, 269Silvestri, N.M., Oswalt, T.D., Wood, M.A., Smith, J.A., Reid, I.N. & Sion, E.M. 2001, AJ, 121,503Wegner, G. & Reid, I.N. 1991, ApJ, 375, 674Williams, K.A., Bolte, M. & Koester, D. 2004, ApJ, 615, L49

The initial–final mass relationship of white dwarfs in common proper motion pairs and open clusters

We have studied white dwarfs in common proper motion pairs (CPMPs) to improve

the semi-empirical initial–final mass relationship of white dwarfs. In this contribution, we re-

port new results obtained from spectroscopic observations of both members of several CPMPs

composed of a F, G or K type star and a DA white dwarf.Peer Reviewe

UPCommons

https://upcommons.upc.edu/bitstream/2117/1379/1/send.pdf

The initial-final mass relationship of white dwarfs in common proper motion pairs

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