PoS(SSC2015)053 http://pos.sissa.it/ ∗ [email protected] Speaker. SALT has been usedhydrogen-deficient . to The greatest obtain challenge is amany posed have significant by exotic the surface number -rich compositions subdwarfs, of of andA which for second observations which strand has an of been evolutionary the hot origin studyof is of subdwarfs surface urgently pulsating motion sought. subdwarf and in B stars, an with effortevolved emphasis stars to on including use the the geometric -deficient detection binary methods DY Cen toon have measure also progress. been the observed. stellar We radius. report Other hot ∗ Copyright owned by the author(s) under the terms of the Creative Commons c ⃝ Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). SALT Science Conference 2015 -SSC2015- 1-5 June, 2015 Stellenbosch Institute of Advanced Study, South Africa C. Simon Jeffery Armagh Observatory, College Hill, Armagh BT61E-mail: 9DG, N.Ireland SALT Observations of Hot Subdwarfs andEvolved Other Stars PoS(SSC2015)053 (2.1) show 20 > Z C. Simon Jeffery ) and the relative amplitude of the angular . R δ δθ / ⟩ θ ⟨ 2 R δ = R ) can be measured for a given radial mode, then the radius follows from ⟩ θ ⟨ / δθ generally show sub-solar abundances (except for nitrogen), whilst those with These pulsations provide data for asteroseismological investigations of the internal structure In terms of internal structure, normal subdwarf B (sdB) stars may be thought of as extreme Armagh Observatory has been using the Southern African Large Telescope (SALT) in stud- The processes of destruction which dismantle stars as they age are just as important as those 20 < [7]. Potentially they canspecifically the also radius. provide If the data total radial for displacement ( more direct measurements of stellar dimensions, super-solar abundances (except for iron)radiatively-driven [4]. diffusion. Again, A these crucialsome patterns aid cases, can of to be multi-periodic the p- explained and interpretation inand g-mode of 3000–6000 terms pulsations, s these with of respectively periods [6]. stars in is the range the of presence, 100–600 s in [5] diameter variation ( The former can beby deduced combining by the integrating variation in thea effective radial temperature similar velocity, and approach whilst total allows flux. thetwo the latter Although observables radius less are may straightforward, necessary. to be High-time be deduced and deduced high-spectral resolution for spectroscopy low-degree is non-radial required to models. At least horizontal-branch stars; that is,lar they mass are with core amostly helium-burning very in low-mass stars binaries hydrogen of envelope ranging approximatelylong-period [1]. from half systems short-period a They containing systems so- have F containingsurfaces diverse M and are origins, helium-poor, dwarfs G being gravitational or found dwarfs, settlingor, white and and equivalently, dwarfs, radiative the also to levitation hydrogen sometimes causes toZ found the float helium singly [3]. to [2]. sink Amongst other Their elements, those with atomic number 2. Normal sdB stars ies of hot subdwarfs, bothbinary normal properties and (§ 2) their chemically and peculiar helium-richprecision surfaces. (§ spectroscopy A 3), particular of in goal pulsating order has hot to beenhelium to subdwarfs explore obtain their and BX high- Cir pulsation, of (§ 4). ahave related also Opportunities been object, to pursued the explore (§ 5). pulsating the extreme of other hydrogen-deficient systems associated with star formationa for function understanding of the mass, evolutionbe composition of better and the understoood. duplicity, cosmos. butof also They The reprocessed involve are outputs a material, clearly lead lot rates todegenerate of and mergers, the physics and types much final which more. of mass needs They can supernovae,pulsations, to function, be binaries the explored the by and compact-object observing surface mass highly-evolved chemistries. population, stars and using Theto double- diversity break composition of a the star hot far star outnumberas zoo the the tells ways formation us of to that common-envelopes make around the one, close ways the and binary physics helps stars, of the us radiatively-driven opacity explore diffusion. of diverse stellar phenomena material such and Hot Subdwarfs and other Evolved Stars 1. Introduction PoS(SSC2015)053 4 > H n / He is a known n C. Simon Jeffery 1123 ◦ can be established. 20 R − δ Accepted s No s Yes –s colours No – velocities s No s No s Yes –s noisy Yes –s velocities Yes – colours s Yes – colours 10 10 20 10 10 10 13 13 10 exp × × × × × × × × t ). × He-rich sdO/B stars with surface × 2% 106 220 185 98 102 148 105 180 342 n . 0 > He or less, from which n 1 Grating > intermediate − 8 . 3 0 ( ) and , and thus an origin in a double helium- 25 . 0 80% > single > H 2012 Jul 302012 Oct 13 0900 2012 Oct 2300 31 0900 2012 Dec 252012 3000 Dec 26 3000 2013 Apr 25 0900 n He / n He n > 4 He-rich sdO/B stars with surface helium-to-hydrogen ratios Observing log for SALT-RSS investigations of pulsating sdB stars. He-rich subdwarfs are considerably more diverse. CD 144 – 149 s 2012 Dec 02137 3000 – 159 s 2013 Apr 23 3000 Period Range Date 128 – 145 s 2012 Jun 30 0900 He-rich subdwarfs may be further divided into - and nitrogen-rich sub- extreme Table 1: extreme intermediate Some 90% of all hot subdwarfs have surfaces where the helium abundance is either normal Observations were attempted through 2012/13 for three stars, V4640 Sgr, PG 2303+019 and The The . Since p-mode pulsations in sdB stars have short periods, the relatively short observing runs θ 2M 0415+0154 V4640 Sgr PG 2303+019 Star (or fractional helium abundance or, in the case ofare sdB stars, either substantially partially below or normal.vided extremely However between some hydrogen-deficient. 10% have For surfaces convenience, which these can be roughly di- 3. Helium-rich sdO/B stars 2M 0415+0154. These stars were chosen1 for shows having the a number dominant of p-mode spectra pulsation andoscillations [8, exposure known, time 9, used 10]. and for Table each whether observinggratings the run, were the observations range used were of in p-mode accepted. effortsradial velocity, to respectively. Low- Observing obtain and conditions the generally medium-resolution conspired amplitudescases, against of the the the project. S/N In dominant was other modemeaningful substantially results in lower continue. both than colour anticipated and for an 11-m telescope; efforts to extract possible with the SALT Robert Stobieboth Spectrograph radial (RSS) velocity have and been colour used variations. in attempts to measure helium-to-hydrogen ratios measure amplitudes of a few km s Hot Subdwarfs and other Evolved Stars The amplitudes of light andin colour variations are also required in order to establish the variation binary [14]. More extraordinarily, three have quite extreme (4 dex) overabundances of exotic el- merger is plausible [11]. One,tuned PG binary 1544+488, is precursor a is doubleejection required extreme episode to [12, helium 13]. subdwarf; establish One a two question very helium is finely whether cores any following other such a systems common-envelope exist? groups. The majority are apparently PoS(SSC2015)053 , h ◦ 1 66 × − 24 . Owing to the C. Simon Jeffery 1 − km s 5 ≈ and a mean error of 1 4 − He-sdO star HE 0301–3039 to be a double He-sdO on extreme Coadded SALT RSS spectrum of the intermediate helium-rich subdwarf HE 0111–1526. One of the first hydrogen-deficient stars to be discovered was the bright A-type supergiant During 2015, we have embarked on an ambitious programme to use SALT-HRS to carry out Ströer et al. [17] reported the From previous observations, the He-rich sdOB star HE 0111–1526 had been identified as a SALT has been used to explore both groups of He-rich subdwarfs in an effort to (1) identify Figure 1: Sgr, which has an of 120 d [22]. Approximately five other hydrogen-deficient blocks completed. The data comprise some 275Reduction individual spectra and with analysis excellent are phase in distribution. progress. where SALT has a singlethe continuous SALT visibility High window Resolution Spectrograph lasting (HRS) over for six the hours. 2015 season Observations have with concluded, with 5. Hydrogen-deficient binaries υ the basis of two VLT-UVES spectra obtainedtempts as to part obtain of repeat the observations Supernova atRSS Progenitor sufficiently in Survey high-resolution 2011/12 [18]. and have At- signal-to-noise so with far proved SALT- was unsuccessful. lower Again, than RSS expected. throughput at the time of observation a high-time and high-spectralperiod resolution of study 2.5 of hours the [19],have helium very demonstrated star similar the BX to Cir, that presence whichcontraction of of has of V652 the Her a a observable [20]. shock pulsation photosphere around at Recentcycle the observations is minimum pulsation of long cycle radius, the [21]. compared and latter Although with differential the most pulsation expansion SALT observing and windows, BX Cir has a of 4. Extreme helium stars potential binary. Follow-up RSSmeasurements with observations a were full obtained amplitudedistribution in of of eight 2012/13, 40 observations km over s giving some 10 radial-velocity months,period, it although has the proved data impossible to suggest deduce it a should unique be no longer than a few days. and characterize additional binaries and (2) pursue abundance studies of intermediate He-rich sdBs. Hot Subdwarfs and other Evolved Stars ements (zirconium, germanium, yttrium,another strontium, three show and similarly lead) large excesses on of iron-group their elements surfaces [16]. [15, 14], whilst PoS(SSC2015)053 C. Simon Jeffery show pulsations and variable 5 hydrogen-deficient binaries . Most of these 1 − Coadded SALT RSS spectrum of the hydrogen-deficient binary V1037 Sco. Figure 2: Thanks are due to the UK Salt Consortium, who enabled my attendance at the SALT Science SALT has offered the potential to make significant progress in understanding the late stages SALT-RSS and SALT-HRS observations have been attempted to address various questions Conference 2015, to Amy Holden whotroscopy, carried to out Pamela the Martin first for analysis reprocessinggenerous of much advice, the of and pulsating the to sdB RSS the star spectroscopy, Northern to spec- Ireland Steve Dept Crawford for for Culture Arts and Leisure for funding. of from synoptic studiesthan of expected pulsating efficiency in and RSS, binary a stars. sub-optimal distributiontion As of images, a observing windows, consequence many and of of poor lower calibra- thosework goals has await still realisation. to The be HRS donedeveloping data on robust look data-reduction the pipelines promising, data-reduction in but side. order substantial It to is exploit imperative its that full SALT potential. invest resources in Acknowledgments 6. Conclusion regarding the orbital periods and related emission ofof V1037 writing, Sco, V426 the Car HRS and DY data Cen.have have At proved still the impossible time to to be interpret. reduced.only A The major realised RSS problem during velocities encounterd for subsequent in DYwell-exposed Cen these data lines and early in analysis, V1037 observations, the Sco but is blue to that regularly the allow a RSS secure wavelength calibration calibration. lamp has insufficient Hot Subdwarfs and other Evolved Stars binaries are known. Only one,has KS a Per, reported has a period well-established ofBI period Lyn 52.1 are d, (360 unknown. d) and DY [23, Cen, an 24]. previously eccentric reputedhydrogen-deficient to V1037 binary Sco be [25]. a in hot The a RCrB orbital star,BI highly is Lyn periods apparently is eccentric of a the orbit carbon-rich V426 secondary Car of star and at identifiable period in a 39.7 the d rate visible [26]. of spectrum.emission, 250 The Only K surface the y in of latter DY the Cen uncorrelated is caseestimates heating (so suggest of some far) may with be potential either SN the Ib progenitors orbital [27, period 28]. or the pulsations. Mass PoS(SSC2015)053 aa , 383 , PG (July, 2005) (2014), no. 3 , A&A C. Simon Jeffery (Jan., 2003) A new class of 437 440 583 The origin of Structural parameters of , A&A , ApJ (Mar., 1997) 640–644. (Oct., 2002) 449–466, (Jan., 2012) 452–464. A new class of rapidly pulsating Discovery of A New Class of Studies of hot B subdwarfs. VI - 285 336 2M0415+0154: a new bright, 419 ]. MNRAS (Mar., 2009) 827–832. , , MNRAS , MNRAS 6 (Jan., 1986) 33–45. 496 155 (Sept., 1988) 964–983. , A&A 332 Spectroscopic orbital elements for the helium-rich subdwarf , A&A Evolutionary models for double helium white dwarf mergers and ]. , ApJ arXiv:1211.2689 Monthly Notices of the Royal Astronomical Society , ]. (Mar., 1997) 657–672. astro-ph/0 The atmosphere of subluminous B stars. II - Analysis of 10 helium poor subdwarfs 285 Hot subdwarf stars in close-up view. III. Metal abundances of subdwarf B stars (Jan., 2013) A110, [ astro-ph/0 2676–2683. short-period subdwarf B pulsator X. Zhang and C. S. Jeffery, the formation of helium-rich hot subdwarfs H. T. Sener and C. S.binary Jeffery, PG 1544+488 R. Oreiro, R. H. Østensen, E. M. Green, and S. Geier, the hot pulsating B subdwarf PG 1219+534 from asteroseismology D. O’Donoghue, A. E. Lynas-Gray, D.rapidly Kilkenny, pulsating R. star S. - Stobie, IV. and Oscillations C. inMNRAS Koen, EC 20117-4014 and atmospheric analyses R. Silvotti, R. Østensen, U. Heber,1325+101 J.-E. and Solheim, PG S. 2303+019: Dreizler, Two and new M.(Jan., large Altmann, 2002) amplitude 239–243. subdwarf B pulsators S. Charpinet, G. Fontaine, P. Brassard, E. M. Green, and P. Chayer, Detailed calculations of radiative forces onhydrogen-rich metals subdwarfs in the envelopes and atmospheres of D. Kilkenny, C. Koen, D. O’Donoghue,star and - R. I. S. EC Stobie, 14026-2647, the class prototype E. M. Green, G. Fontaine, M.Hyde, D. R. Reed, Østensen, K. O. Callerame, Cordes, I. P.M. R. Brassard, Giovanni, Seitenzahl, S. H. B. Falter, Edelmann, A. E. J. White, J. Rigby, E. Jeffery, and S. A. A. Dreizler, Bronowska, S. L. Schuh, and the birthrate of sdB stars Z. Han, P. Podsiadlowski, P. F. L.subdwarf Maxted, B T. R. stars Marsh, - and I. N. The Ivanova, formation channels P. Bergeron, F. Wesemael, G. Michaud, and G. Fontaine, S. Geier, 549 Pulsating Stars: Gravity-Mode Pulsators among Subdwarf B Stars 575–597, [ U. Heber, [ L31–L34. [9] [7] [8] [5] [6] [4] [2] [3] [1] [12] [10] [11] Hot Subdwarfs and other Evolved Stars References PoS(SSC2015)053 , ]. ]. (Sept., , (Nov., 434 Hydrogen The 760 ]. C. Simon Jeffery , ApJ ]. , MNRAS Lick Observatory , arXiv:1204.4387 ]. arXiv:1412.8672 (Sept., 1995) 383. astro-ph/0 (Mar., 1950) 333. arXiv:1008.1584 Discovery of extremely lead-rich 276 . PhD thesis, astro-ph/0 111 , ApJ , MNRAS 7 On the formation of single and binary helium-rich (July, 2012) 3031–3038, [ ]. 423 (Mar., 2015) 2836–2851, [ ]. 447 (Dec., 2001) 411–418, [ (Jan., 2011) 984–993, [ Search for progenitors of supernovae type Ia with SPY (July, 1995) 327–330. (Jan., 2007) 269–280, [ 322 410 The orbital elements of the hydrogen-poor spectroscopic binary , MNRAS The detection of small-amplitude variations in the extreme helium 275 462 , MNRAS arXiv:1407.7668 Subaru and Swift observations of V652 Herculis: resolving the (June, 1955) 162. , A&A , MNRAS The Peculiar Star HD 30353. 60 On the optical variability of the helium stars HD 160641 and BD +13 3224. Spectroscopic analyses of subluminous B stars: observational constraints for The Hot R Coronae Borealis Star DY Centauri is a Binary The orbit of the spectroscopic binary upsilon Sagittarii. , MNRAS arXiv:1210.4199 , AJ (1915) 132–133. (Mar., 1975) 789–790. 8 196 Deficient Binaries - Photometry and Orbits D. J. Frame, P. L. Cottrell, A. C. Gilmore, P. M. Kilmartin, and W. A. Lawson, N. Kameswara Rao, D. L. Lambert,B. D. McArthur, A. García-Hernández, C. S. Jeffery, V. M. Woolf, and W. P. Bidelman, J. F. Heard and O. Boshko, HD 30353. Astronomische Nachrichten ApJ C. S. Jeffery, D. Kurtz, H.and Shibahashi, J. R. McCormac, L. C. Starling, V. Elkin, P. Montañés-Rodríguez, R. E. Wilson, Bulletin 2012) L3, [ A. U. Landolt, photospheric pulsation R. Napiwotzki, N. Christlieb, H. Drechsel,D. H.-J. Koester, Hagen, B. U. Leibundgut, Heber, T. R. D.A. Marsh, Homeier, Renzini, S. C. and Moehler, Karl, L. G. Yungelson, Nelemans, E.-M. Pauli, D. Reimers, D. Kilkenny and C. Koen, A. Ströer, U. Heber, T. Lisker,Hot R. subdwarfs Napiwotzki, from S. the Dreizler, ESO N. supernova Christlieb,subdwarf Ia and O progenitor D. stars survey. Reimers, II. Atmospheric parameters of star LSS 3184 2013) 1920–1929, [ N. Naslim, S. Geier, C. S.helium-rich Jeffery, subdwarf N. CPD–20 T. 1123: Behara, V. a M. post-common-envelopeextended Woolf, binary and horizontal evolving L. branch on Classen, to the H. Edelmann, the theory of stellar evolutio, pulsation and diffusion N. Naslim, C. S. Jeffery, A. Hibbert, and N. T. Behara, S. Justham, P. Podsiadlowski, and Z. Han, subdwarf O stars subdwarfs: does heavy metal signal the formation of subdwarf B stars? Friedrich-Alexander-Universität Erlangen-Nürnberg, 2003. [26] [24] [25] [22] [23] [20] [21] [18] [19] [17] [16] [14] [15] Hot Subdwarfs and other Evolved Stars [13] PoS(SSC2015)053 C. Simon Jeffery (Nov., 1986) 310 , ApJ 8 The Mass Ratio of Upsilon-Sagittarii from Ultraviolet Radial (Dec., 1990) 400. 247 What stars become peculiar type I supernovae? , MNRAS R. E. Dudley and C. S. Jeffery, A. Uomoto, Velocities L35–L37. [28] Hot Subdwarfs and other Evolved Stars [27]