Time Allocation Committee for Application No. MPG time at the ESO 2.2m-telescope c/o MPI f¨urAstronomie Observing period October 2014 K¨onigstuhl17 Received D-69117 Heidelberg / Germany

APPLICATION FOR OBSERVING TIME

from MPIA MPG institute X other

1. Telescope: 2.2-m X

2.1 Applicant Rolf Chini Ruhr-Universit¨atBochum Name Institute Universit¨atsstraße150 44801 Bochum street ZIP code - city [email protected] ESO User Portal username e-mail

2.2 Collaborators Klaus Fuhrmann Ruhr-Universit¨atBochum name(s) institute(s) R´egisLachaume MPI f¨urAstronomie, Heidelberg name(s) institute(s)

2.3 Observers R´egisLachaume name name By specifying the names under item 2.3 it is obligatory to also send out these observers to La Silla, if required. Correspondence on the rating of this application will be sent to the applicant (P.I.) as quoted under 2.1 above.

3. Observing programme: Category: E

Title : Multiplicity of as a function of Abstract : In the era of large Galactic surveys a major - yet mostly ignored - concern arises from the fact that up to one-third of the investigated samples will be subject to the polluting light of close and wide companion stars. To account for this circumstance, we aim at a thorough investigation of the stellar multiplicities as they are met around nearby stars in an unbiased, volume-complete sample and as a function of their primary . In analogy to our recent photometric search for distant companions to solar neighborhood stars, we do also expect to discover a number of stellar spectroscopic companions. We wish to finish our previous FEROS study in order to achieve a complete census of the spectroscopic binaries within 25 pc.

4. Instrument: WFI X FEROS GROND

5. Brightness range of objects to be observed: from 6 to 14 V-mag

6. Number of hours: applied for already awarded still needed 50 40 none no restriction grey dark

7. Optimum date range for the observations: ...... 01.01.15 – 31.12.15 Usable range in local sideral time LST: ...... 00:00h – 24:00h 8a. Description of the observing programme

Astrophysical context sphere is undoubtedly of general interest. By means of the FEROS spectrograph we intend complete the rel- The formation of stars has always been and continues evant observations of the final subsample of N∼ 100 to be one of the most diverse and complex topics in stars. modern astrophysics. Though, qualitatively, we known that stars are born in huge molecular gas clouds that can easily produce thousands of coeval objects, among Previous work the many unsolved questions is, what fraction of these Our previous work that includes all the nearby stars form in binaries or higher level systems, how much does in the Northern Hemisphere and down to this depend on the environment, the fraction of early- δ ≥ −15o is summarized in Fuhrmann (2011). More re- type stars, their quasi-instantaneous feedback, or the cently, we started the southern observations of mostly complex dynamical processes involved. With respect to bright, F-type stars with the BESO ´echelle spectro- the latter point, much of the theoretical work in this graph at Cerro Armazones (Fuhrmann & Chini 2012). field considers the formation of stars in terms of bina- Thus, at the current stage of the project an 85 per ries, part of which may then be disrupted or expelled cent volume-completeness of the N∼ 500 sample from a newly born cluster. However, the situation is is already achieved. very likely not that straightforward, since one must as- Not unexpectedly, it turned out that the inventory sume that more massive stars tend to create more com- of the stellar multiplicities at southern declinations is plex subunits, that is, hierarchical multiples consisting still fairly incomplete. Thus, in a very recent explo- of three, four, or even more components. Depending on rative survey, we found about a dozen new companion what stellar fraction is realized in terms of these mul- stars around FGK-type primaries within 25 pc from tiples, the general star formation process may proceed infrared photometry (Chini et al. 2014). We expect in a completely different manner. that part of these new companions will turn out to be In recent , astrophysics has seen a growing in- spectroscopic binaries on their own (which we intend terest in large-scale stellar surveys (e.g. APOGEE, to find out with FEROS). RAVE, GAIA-ESO) on the formation and evolution In Fuhrmann & Chini (2012) we have already shown of the . Among the basic science drivers is that there is a general decrease of the overall single- certainly the forthcoming launch of the GAIA satel- star fraction as a function of mass (cf. Fig. 1). But lite that aims at observations of about a billion stars even more, and as Fig. 2 demonstrates, there is also of our parent spiral. But on the other hand, there is a considerable lack of information on companion stars also the growing evidence that the merger-driven for- with the prospect that the importance of binary and mation scenario that one encounters in distant clusters higher-level systems may actually be much higher than of is eventually not realized in the Milky Way generally recognized. . Among the N∼ 40 stars observed in 2014 February A major, yet mostly ignored, concern for the am- the majority has by now been analyzed and will be part bitious Galactic surveys however arises from the cir- of a forthcoming comprehensive study (Fuhrmann & cumstance that about 30 per cent of the investigated Chini 2014). For one of the companions, HD 43162 B, stars will turn out to be multiple (in the sense that we already found an asymmetry in the FEROS cross- more than one component contributes in the spectra). correlation function, suggestive for an SB2 system, and Even more, and given the considerable distances, wide in line with Janson et al. (2012), who recently resolved companions may not be resolvable, meaning that in this star as an M3.5 V + M5 V pair. addition to the numerous SB2 stars, a non-negligible fraction will turn out to be SB3 and SB4 systems. To meet these objects, it is of considerable impor- Layout of observations tance to learn from unbiased samples of nearby stars (i) The objects are distributed over all sideral times. what number and kind of systems one must expect and Therefore the project can serve as a filler project when- (ii) how to deal with the non-single light sources. Evi- ever time is available. For the G- and K-type primary dently, there must be a general interest in these items, stars we aim at redundant observations, preferably sep- because otherwise the multiple stars will not contribute arated by a few days (or months). For the fainter com- to, but pollute, existing correlations that one intends panion stars, and depending on whether they are SB1 to find with the Galactic surveys. or SB2 systems, it would be reasonable to follow those with repeated observations. Immediate aim The Hipparcos astrometric observations have estab- Strategic importance for MPIA lished a volume-complete reference sample of about R´egisLachaume will be co-author on all future publi- half a thousand solar-type stars within 25 pc. A thor- cations in this project. ough account of the basic stellar parameters as well as the stellar multiplicities that are met in this local

2 8b. Figures and tables

Figure 1: Multiplicities of solar neighborhood stars as a function of their primary masses. The percentages of single, binary and higher level systems are presented in steps of 0.10 M , but as a running mean of bin width 0.20 M , with the number of stars per bin as indicated in the top of the figure. Average projected rotational velocities < v sin i > are depicted with a light blue shading. Except for the highest mass bins – which are mostly subject to Poisson noise (denoted by error bars) and high rotational velocities – there is a steady decline of the single-star fraction as a function of mass. (from Fuhrmann & Chini 2012) Figure 2: Same as Fig. 1, but with companion candi- dates included. Provided these candidates can be con- firmed, there is the prospect that the single-star frac- tion already converges to zero at the M ' 1.70 M transition to the A-type stars. (from Fuhrmann & Chini 2012)

3 9. Objects to be observed

(Objects to be observed with high priority should be marked in last column)

magnitude in Designation α (2000) δ (2000) spectral range priority to be observed

HD 145825 16h 14m 11s.9 −31◦ 390 4900 6.55 1 HD 148704 A 16h 31m 30s.0 −39◦ 000 4400 7.24 1 HD 149612 16h 39m 04s.1 −58◦ 150 2900 7.03 1 HD 154088 17h 04m 27s.8 −28◦ 340 5700 6.59 1 HD 156274 A 17h 19m 03s.8 −46◦ 380 1000 5.47 1 HD 156274 B 17h 19m 02s.9 −46◦ 380 1300 8.70 1 HD 156897 A 17h 21m 00s.3 −21◦ 060 4600 4.40 1 HD 156897 B 17h 21m 00s.3 −21◦ 060 4600 8.90 1 HD 165185 A 18h 06m 23s.7 −36◦ 010 1100 5.95 1 HD 165185 B 18h 06m 23s.7 −36◦ 010 2300 13.0 1 HD 167425 A 18h 19m 40s.1 −63◦ 530 1100 6.16 1 HD 167425 B 18h 19m 39s.9 −63◦ 530 0400 10.8 1 HD 181321 19h 21m 29s.7 −34◦ 590 0000 6.47 1 HD 189567 20h 05m 32s.7 −67◦ 190 1500 6.49 1 HD 190422 20h 07m 35s.0 −55◦ 000 5700 6.25 1 HD 194640 20h 27m 44s.2 −30◦ 520 0400 6.62 1 HD 196761 20h 40m 11s.7 −23◦ 460 2500 6.38 1 HD 197214 A 20h 43m 15s.9 −29◦ 250 2600 6.95 1 HD 197214 B 20h 43m 14s.6 −29◦ 250 2200 13.0 1 HD 199288 20h 57m 40s.0 −44◦ 070 4500 6.52 1 HD 199509 21h 09m 20s.7 −82◦ 010 3800 7.00 1 HD 200525 AB 21h 09m 22s.5 −73◦ 100 2300 5.67 1 HD 200525 C 21h 09m 23s.7 −73◦ 100 2700 13.5 1 HD 202628 21h 18m 27s.2 −43◦ 200 0400 6.76 1 HD 202940 A 21h 19m 45s.6 −26◦ 210 1000 6.55 1 HD 202940 B 21h 19m 45s.6 −26◦ 210 1900 9.55 1 HD 203244 21h 24m 40s.6 −68◦ 130 4000 6.97 1 HD 203985 A 21h 27m 01s.3 −44◦ 480 3000 7.48 1 HD 203985 B 21h 26m 52s.8 −44◦ 480 4600 14.0 1 HD 205536 21h 40m 29s.7 −74◦ 040 2700 7.06 1 HD 210918 22h 14m 38s.6 −41◦ 220 5300 6.22 1 HD 211415 22h 18m 15s.6 −53◦ 370 3700 5.39 1 HD 212168 A 22h 25m 51s.1 −75◦ 000 5600 6.13 1 HD 212168 B 22h 25m 56s.3 −75◦ 000 5200 8.72 1 HD 212330 A 22h 24m 56s.3 −57◦ 470 5000 5.32 1 HD 212330 B 22h 24m 53s.5 −57◦ 480 0000 11.0 1 HD 212697/8 22h 26m 34s.2 −16◦ 440 2900 5.57 1 HD 213845 A 22h 34m 41s.6 −20◦ 420 2900 5.20 1 HD 213845 B 22h 34m 41s.9 −20◦ 420 3200 11.0 1 HD 214953 A 22h 42m 36s.8 −47◦ 120 3800 5.99 1 HD 214953 B 22h 42m 37s.4 −47◦ 120 4200 11.1 1 HD 218687 A 23h 09m 57s.1 +14◦ 250 3500 6.55 1 HD 218687 B 23h 09m 55s.0 +14◦ 250 3500 10.1 1 HD 222335 23h 39m 51s.3 −32◦ 440 3600 7.19 1 HD 870 00h 12m 50s.2 −57◦ 540 4500 7.22 1 HD 1237 00h 16m 12s.6 −79◦ 510 0400 6.60 1 HD 1273 00h 16m 53s.8 −52◦ 390 0400 6.83 1 HD 2151 00h 25m 45s.0 −77◦ 150 1500 2.81 1 HD 2262 00h 26m 12s.2 −43◦ 400 4700 3.93 1

4 10. Justification of the amount of observing time requested:

The total sample consists of 112 G- and K-type primaries, mostly in the magnitude range 6 ≤ V ≤ 8 mag, and 32 faint companion stars with 8 < V ≤ 14 mag. For the latter, S/N ratios of about 50 are sufficient, whereas for the G- and K-type primaries we need S/N ratios ≥ 200. We also aim at redundant observations of the primaries – preferably separated by a few days, weeks, or months. In addition, there are a some bright calibration stars. Experience during the 2014 February observing run has shown that the total required telescope time is about 75 hours. In 2014 February we were granted 40 hours, but on account of GROND triggers and weather constraints, observations we done for only about 25 hours, meaning that only one-third of the stars could be observed. 11. Constraints for scheduling observations for this application:

The targets are distributed over all siderial times, meaning that this project is a ideal filler project. However, we want to emphasize that due to accuracy requirements at least one (better two) calibration stars are required. These calibration stars are bright and require only integration times of 1 minute 12. Observational experience of observer(s) named under 2.3: (at least one observer must have sufficient experience) R´egisLachaume is an expert for FEROS observations at the 2.2 m telescope. Both R.C. and K.F. have observational experience with the BESO high-resolution ´echelle spectrograph of the Universit¨atssternwarte Bochum near Cerro Armazones in Chile. BESO is a twin of the FEROS spectrograph. 13. Observing runs at the ESO 2.2m-telscope (preferably during the last 3 years) and publications resulting from these

Telescope instrument date hours success rate publications 2.2m FEROS Feb 14 40 60% Fuhrmann & Chini (2014, in preparation)

5 14. References for items 8 and 13: Chini R., Fuhrmann K., Barr A., Pozo F., Westhues C., Hodapp K. (2014): New visual companions of solar-type stars within 25 pc MNRAS 437, 879

Fuhrmann K. (2011): Nearby stars of the Galactic disc and halo – V MNRAS 414, 2893

Fuhrmann K., Chini R. (2012): Multiplicity among F-type stars ApJS 203, 30

Fuhrmann K., Chini R. (2014): Multiplicity among F- and G-type stars in preparation

Janson M., Hormuth F., Bergfors C., et al. (2012): The Astralux large M-dwarf multiplicity survey ApJ 754, 44

6 Tolerance limits for planned observations: maximum seeing: 300 minimum transparency: 30% maximum airmass: 2 photometric conditions: no moon: max. phase / 6 : 1.0/10◦ min. / max. lag: 0/365 nights