CONTINUATION OF: TYPES OF SPOTTED STARS BACKGROUND INFORMATION 2

SPECTRAL TYPES Subclasses: 0 - 9

e.g. B2, K9, A7 also B2.5

Peculiarities: many!

Examples: e… emission lines p… peculiarity n … nebulosity etc. „O Be A Fine Girl Kiss Me“ BACKGROUND INFORMATION 3

SPECTRAL TYPES BACKGROUND INFORMATION 4

SPECTRAL TYPE & LUMINOSITY CLASSES Absolute Magnitude TYPES 5

THE PHENOMENON OF STELLAR ACTIVITY

▸ Red Dwarfs and BY Dra phenomenon

▸ Solar-type stars

▸ T Tauri stars

▸ RS CVn stars

▸ FK Comae stars TYPES 6

RS CVn STARS

▸ close detached binaries with active chromospheres causing large stellar spots

▸ primary: more massive, G-K giant or subgiant

▸ secondary: subgiant or dwarf, G-M

▸ spots: optical variability outside of eclipses

▸ amplitudes of up to 0.6 mag in V

▸ cool spots on their surfaces

▸ low luminosity of the secondary lets many RS CVn systems appear as single-line binaries TYPES 7

RS CVn STARS

▸ Classification signatures (Hall 1976)

▸ binary systems

▸ subgiant component well within its Roche lobe

▸ photometric variability

▸ Ca II H & K emission lines

▸ fast rotation (orbital periods of a few days, almost synchronized)

▸ orbital period variations TYPES 8

RS CVn STARS: SUBGROUPS I

▸ Regular systems: 1d < Porbit < 14d ▸ hotter component: spectral type F or G, strong Ca II H and K emission outside eclipses

▸ Short period systems: Porbit < 1d ▸ hotter component: spectral type F or G, Ca II H and K emission in one or both components

▸ Long period systems: Porbit > 14d ▸ either component: spectral type G through K, strong Ca II H and K emission outside eclipses TYPES 9

RS CVn STARS: SUBGROUPS II

▸ Flare star systems

▸ hotter component: spectral type dKe or dMe, emission refers to strong Ca II H & K

▸ V 471 Tau systems

▸ hotter component: white dwarf

▸ cooler component: spectral type G through K & displays strong Ca II H & K emission A. J. Norton et al.: WASP/ROSAT variable stars 855

TYPES 10

RS CVn STARS: EXAMPLE

▸ GSC 02038-00293: short period RS CVn star

▸ Porbit = 0.4955 ± 0.0001d ▸ six-year cycle of star spot activity SuperWASP Project

Figure 3: Relative magnitude against phase, two cycles are shown with R band (top), V band (middle) and B band (bottom) Bruce et al. (2010) It can be seen from both figures 2 and 3 that the primary eclipse, shown at phase 1, is very well Norton et al. (2007) defined. The secondary eclipse, suspected at phase 0.5 is less well defined due in part to the increased scatter around phase 0.5-0.8 and the incompleteness of our B and R band curves and the asymmetry of the two maxima. The primary eclipse itself is slightly asymmetric with indications of a bell-shaped curve at the minimum as opposed to a sharp change. Both the R and B band curves show broadly the same features as in V. One notable difference is the sharp upturn in brightness at phase 0.6 following the secondary minimum, most notably in B. There is also a less pronounced shelf coming out of the primary minimum in B. Figure 4 shows a magnified section of the V band curve between phase 0.4 and 0.8 containing the increased scatter mentioned above. The data here are displayed according to the date the observations were made to better illustrate the observed changes. The evenings of the 10th May, 25th May and 13th June show a marked increase in scatter and brightness around phases ~0.55 and ~0.78. Over the period from the 13th May to 22nd May there seems to be a slight increase in overall brightness, perhaps a prelude to the subsequent high-scatter data on the 25th May but this is unclear.

6

TYPES 11

FK COMAE STARS

▸ first discovered in the early 1980’s (e.g. Bopp & Rucinski 1981)

▸ late type giants, G to K

▸ rotation periods of a few days only

▸ indicative for rapid rotation rates

▸ v sini ~50 - 150km/s

▸ most likely single stars TYPES 12

FK COMAE STARS

▸ rotationally modulated photometric variations with 0.1. - 0.3 mag in V

▸ caused by asymmetrically distributed spots on the surface

▸ strong and variable chromospheric emission in Ca II H & K and in the H Balmer lines TYPES 13

EXAMPLE: FK COMAE (ITSELF)

▸ single G5 III (giant) with vsini = 155 km/s

▸ photometric variability with P = 2.412 d first reported by Chugainov (1966)

▸ caused by spots ~600-800K cooler than the unspotted surface

▸ switch of activity between two active longitudes („activity flip-flop“) TYPES 14

EXAMPLE: FK COMAE (ITSELF)

Surface Temperature Maps obtained using Doppler Imaging (H. Korhonen - PhD thesis)

„Flip-Flop“ between July 1997 and January 1998 map TYPES 15

EXAMPLE: FK COMAE (ITSELF) H. Korhonen (PhD thesis) TYPES 16

FK COMAE: ORGIN ▸ First idea: they represent the further evolution of W UMa contact binaries into a single star

▸ Webbink (1976): mass ratio (secondary / primary) can decrease on an evolutionary time scale until the secondary is completely dissipated, during the primary’s initial ascent of the giant branch

▸ Fekel & Balachandran (1993): detection of Li is evidence against binary coalescence

▸ surface convection zone reaches the rapidly rotating core just as a star begins its first ascent on the giant branch and dredges both high angular momentum material and freshly synthesized Li to the surface IRREGULAR VARIABLES T TAURI STARS 18

T TAURI STARS

▸ discovered by Joy (1945)

▸ F, G, K, M pre-main sequence stars: few Myr old

▸ emission lines in spectra, high abundance of Lithium

▸ surrounded by circumstellar material

▸ magnetic fields play important role, similar to sunspots

▸ accretion processes

▸ stellar wind phenomena T TAURI STARS 19

T TAURI STARS: EMISSION 296LINES I. Appenzeller and R. Mundt

~ I ' ' ' ' l ' ' ' ' I ' r ' ' I ' ' '~ ' l

Variety of species in emission v...... v ', d

.3

I I + | I i ~ i i I , t i , I i- z , r J i i_ , , I 3~B 4 358 4 400 4 4.~1~ 4 5BI{} WAVELENGTH[~] Fig. 2. Section of the emission-line spectrum of the CTTS DR Tan illustrating the variety of emission lines occuring even in a small spectral range. Note the different profiles of the Balmer, He I, and Fe II lines. (from Appenzeller et al., 1988)

Part of the CTTSs with double-peaked Balmer line profiles are known to show (at least temporarily) at the higher Balmer lines (starting at HT) an additional absorption component redward of the redshifted emission peak. The radial velocity of this feature typically ranges between +200 and +400 km s -1. In rare cases this line component is also observed at Hfi. But it never occurs at Ha. Following Walker (1972), who first studied this phenomenon in a sample of Orion stars including YY Ori, TTSs showing this redward-displaced absorption component of the higher Balmer lines are called "YY Ori stars". At present about 30 TTSs are known to belong to this subclass. Those TTSs which do not have double-peaked Balmer-line profiles either show more or less symmetrical, approximately triangular profiles, or flat-topped profiles with weak multiple absorption reversals. Single-peaked profiles tend to occur more frequently among the weaker emission T Tauri stars. So far six TTSs (DR Tau, SU Ori, CO Ori, VV CrA, AS 353A, and LkHa 321) are known to exhibit (at least temporarily) classical (Beals Type I) P Cygni profiles (i.e. an absorption component reaching below the continuum blueward of the emission component) of their Balmer lines. Two of these six stars (DR Tau and SU Ori) belong to the YY Orionis subclass. DR Tau has been observed to exhibit sometimes blueward and redward-displaced Balmer absorption components simultaneously (Krautter and Bastian, 1980). Pronounced Type I P Cygni profiles are also present in the spectrum of the star V 1331 Cyg, which is listed as a TTS in the HBC. However, according to Chavarr[a-K. (1981) this star has a spectral type near F0 and therefore probably belongs to the Herbig-Ae/Be class, where such profiles seem to be more common (cf. Finkenzeller and Mundt, 1984) Helium lines: The He emission lines occurring in the optical emission line spectra of the TTSs originate from upper levels of considerably higher excitation T TAURI STARS 20

T TAURI STARS: EMISSION 296LINES I. Appenzeller and R. Mundt

~ I ' ' ' ' l ' ' ' ' I ' r ' ' I ' ' '~ ' l

Variety of species in emission v...... v ', d

.3

I I + | I i ~ i i I , t i , I i- z , r J i i_ , , I 3~B 4 358 4 400 4 4.~1~ 4 5BI{} WAVELENGTH[~] Fig. 2. Section of the emission-line spectrum of the CTTS DR Tan illustrating the variety of emission lines occuring even in a small spectral range. Note the different profiles of the Balmer, He I, and Fe II lines. (from Appenzeller et al., 1988)

Part of the CTTSs with double-peaked Balmer line profiles are known to show (at least temporarily) at the higher Balmer lines (starting at HT) an additional absorption component redward of the redshifted emission peak. The radial velocity of this feature typically ranges between +200 and +400 km s -1. In normal absorption spectrumrare cases this line component is also observed at Hfi. But it never occurs at Ha. Following Walker (1972), who first studied this phenomenon in a sample of Orion stars including YY Ori, TTSs showing this redward-displaced absorption component of the higher Balmer lines are called "YY Ori stars". At present about 30 TTSs are known to belong to this subclass. Those TTSs which do not have double-peaked Balmer-line profiles either show more or less symmetrical, approximately triangular profiles, or flat-topped profiles with weak multiple absorption reversals. Single-peaked profiles tend to occur more frequently among the weaker emission T Tauri stars. So far six TTSs (DR Tau, SU Ori, CO Ori, VV CrA, AS 353A, and LkHa 321) are known to exhibit (at least temporarily) classical (Beals Type I) P Cygni profiles (i.e. an absorption component reaching below the continuum blueward of the emission component) of their Balmer lines. Two of these six stars (DR Tau and SU Ori) belong to the YY Orionis subclass. DR Tau has been observed to exhibit sometimes blueward and redward-displaced Balmer absorption components simultaneously (Krautter and Bastian, 1980). Pronounced Type I P Cygni profiles are also present in the spectrum of the star V 1331 Cyg, which is listed as a TTS in the HBC. However, according to Chavarr[a-K. (1981) this star has a spectral type near F0 and therefore probably belongs to the Herbig-Ae/Be class, where such profiles seem to be more common (cf. Finkenzeller and Mundt, 1984) Helium lines: The He emission lines occurring in the optical emission line spectra of the TTSs originate from upper levels of considerably higher excitation T Tauri Stars 297

potential (20 - 50 eV) than other emission features. It is thus not surprising that T theseTAURI lines STARSshow distinct properties. Most TTS which have been observed with 21 sufficient spectral resolution, show broad (FWHM ~ 150 • 50 km s -1) single- peaked He I emission lines. On high-resolution spectrograms of TTSs belonging to the YY Orionis subclass we find superimposed on the broad component a second (usually stronger) emission component of the He ! lines with a FWHM T ofTAURI <~ 50 km s -~STARS: (cf. Figures 2,EMISSION 3, and 6). These sharp 296LINES components have the same I. Appenzeller and R. Mundt radial velocities as the photospheric absorption spectrum. The gas producing these features must be essentially at rest with respect~ toI the' star.' 'The ' underlyingl ' ' ' ' I ' r ' ' I ' ' '~ ' l broad He I components are sometimes asymmetric and slightly displaced. Among the He II lines only the 4686 A line (probably enhanced by Lye fluorescence)Variety is detected of species in TTS spectra. Because of blending, its profile is not well known. In the high resolution spectrogram ofv...... DR vTau obtained by ', d Appenzellerin emission et al. (1988) the He II line shows the same low FWHM as the He I lines. But its emission peak is shifted to longer wavelengths by about 15 km s -1 and the line has an extended red wing which cannot be explained by blending alone. .3 I I + | oli [ I i ~ i i I , t i , I i- z , r J i i_ , , I 3~B 4 358 4 400 4 4.~1~ 4 5BI{} WAVELENGTH[~] v Fig. 2. Section of the emission-line spectrum of the CTTS DR Tan illustrating the variety of emission lines occuring even in a small spectral range. Note the different profiles of the Balmer, He I, and Fe II lines. (from Appenzeller et al., 1988) L Weakness of sharp Part of the CTTSs with double-peaked Balmer line profiles are known to show (at least temporarily) at the higher Balmerphotospheric lines (starting at HT) lines an additional absorption component redward of the redshifted emission peak. The radial velocity of this feature typically ranges between +200 and +400 km s -1. In <9 _J BUT: strong Li! rare cases this line component is also observed at Hfi. But it never occurs at I , T I , I T ,_~ z I , , , I I , , , L I t 6 680 6 650 6 788 Ha. Following6 758 Walker (1972),6 800 who first studied this phenomenon in a sample of WAVELENGTH [A] Orion stars including YY Ori, TTSs showing this redward-displaced absorption Fig. 3. Section of the red spectrum of the CTTS DR Tau. Notecomponent the weakness ofof the the sharp higher photospheric Balmer lines are called "YY Ori stars". At present absorption lines and the unusual relative strength of the Li I about(1) absorption. 30 TTSs (from are Appenzelter known to et belongal., to this subclass. 1988) Those TTSs which do not have double-peaked Balmer-line profiles either show more or less symmetrical, approximately triangular profiles, or flat-topped Metallic lines: The majority of the emission profileslines in withthe TTSweak spectra multiple corre- absorption reversals. Single-peaked profiles tend to spond to transitions from excited levels of neutraloccur or singly more ionized frequently metals. among These the weaker emission T Tauri stars. lines usually have rather uniform symmetric and triangularSo far six profile TTSs shapes.(DR Tau, The SU Ori, CO Ori, VV CrA, AS 353A, and LkHa observed FWHM values differ greatly between 321)different are knownobjects, to covering exhibit the(at least temporarily) classical (Beals Type I) P range 50 - 300 km s -t. Curve-of-growth studies Cygniof the profiles Fe I and (i.e. Fe anII absorptionlines of component reaching below the continuum several CTTSs indicate that (except for a few extremeblueward T Tauri of the stars, emission such as component) RU of their Balmer lines. Two of these six Lup; cf. Boesgaard, 1984) optical thickness effectsstars are negligible(DR Tau inand these SU lines.Ori) belongIn to the YY Orionis subclass. DR Tau has most cases the metallic lines show no or little dependencebeen observed of the to lineexhibit width sometimes on blueward and redward-displaced Balmer the line strength or the ionisation potential. Lessabsorption symmetric components Fe II profiles, simultaneously with (Krautter and Bastian, 1980). Pronounced Type I P Cygni profiles are also present in the spectrum of the star V 1331 Cyg, which is listed as a TTS in the HBC. However, according to Chavarr[a-K. (1981) this star has a spectral type near F0 and therefore probably belongs to the Herbig-Ae/Be class, where such profiles seem to be more common (cf. Finkenzeller and Mundt, 1984) Helium lines: The He emission lines occurring in the optical emission line spectra of the TTSs originate from upper levels of considerably higher excitation T TAURI STARS 22

TYPES OF T TAURI STARS (CTTS) ▸ Weak lined T Tauri stars (CTTS)

▸ no evidence for disk accretion Image: NASA/JPL-Caltech/R. Hurt (SSC)

▸ Classical T Tauri Stars (CTTS)

▸ broad emission lines

▸ sometimes forbidden emission lines

▸ spectroscopic & photometric variability

▸ UV, optical & IR excess

▸ strong magnetic fields (~2 kG) that regulates accretion

▸ X-ray emitters No. 6, 2003 131 HERBIG Ae/Be CANDIDATE STARS 2979

TABLE 3 TABLE 4 Rotational Velocities for Herbig Ae/Be Candidates Distribution of the Forbidden Lines among Different Spectral v sin i Types and H Line-Profile Types Object (km sÀ1) Type Sp. Type Distribution PDS 225...... 225 I B3 Type (%) PDS 514...... 58 I A0 V PDS 002...... 175 I B0 V Spectral Type PDS 564...... 88 I A3 V B ...... 54 PDS 395...... 52 I A8 V A...... 30 HD 52721 ...... 456 I B2 Vn F ...... 8 PDS 174...... 144 II B3 O...... 8 PDS 180...... 125 II A8 V PDS 327...... 132 II B1 H Profile PDS 361...... 190 II B3 PDS 398A ...... 281 II A0 V I ...... 29 PDS 545...... 238 II B2 II...... 41 PDS 076...... 97 II F0 V III ...... 18 PDS 080...... 120 II F1 III IV ...... 12 HBC 282 ...... 142 II B+sh HD 95881 ...... 74 II A0 HBC 552 ...... 128 II F+sh HD 76534 ...... 116 II B2 profile stars. Corcoran & Ray (1997, 1998), however, found PDS 069N...... 158 III B3 that forbidden lines were more common among type II line PDS 339...... 100 III A9 V profiles, while our results point to an equal distribution HBC 551 ...... 245 III B5 among all profile types. Selection effects may explain their HD 53367 ...... 55 III B4 results, since the majority of their stars belong to group II in PDS 183...... 59 IV A8 V PDS 315...... 44 IV O8 the work of Hillenbrand et al. (1992), which generally PDS 172...... 90 IV A3 V presents H line profiles of types II and III. PDS 201...... 119 IV A7 V HD 98922 ...... 52 IV B9 HBC 078 ...... 85 IV A5 V 5. DISCUSSION AND ANALYSIS HD 150193...... 103 IV A0 V 5.1. Circumstellar Environment The Balmer line profiles and the presence of forbidden forbidden lines in the low- and medium-resolution observ- lines are strongly connected with the circumstellar environ- ations. In some cases, however, forbidden lines detected in ment. To check this correlation, we use SEDs calculated for low- and medium-resolution spectra were not present inBACKGROUND the 62 HAeBe stars in our sample by M. Sartori & J. Gregorio- 23 high-resolution observations (taken at a different epoch), Hetem (private communication), using the disk model of suggesting that those lines also present variable intensities. Gregorio-Hetem & Hetem (2002). In this model the star is The distribution of the detected forbidden lines among surrounded by an extended and flat disk and a thin dust different spectral types and H line-profile types can beSPECTRAL seen ENERGY DISTRIBUTION in Table 4. We have an almost equal number of A (40%) and B (45%) stars in our sample; therefore, the results in Table 4 point to a significantly higher occurrence of forbidden lines among B stars. The forbidden line distribution among dif- observations ferent H profile types is nearly identical to the H profile distribution in our sample (see x 4.1), indicating that forbidden lines are evenly distributed among each H line-profile type. In a previous work Bo¨hm & Catala (1994) detected [O i] in stars with H line profiles of types II, III and IV and did not detect it in stars with type I profiles. Since types II, III, total and IV are characteristic of stars with stellar winds and [O i] disk star is expected to originate in jet/outflow regions associated with mass-loss processes, they suggested that objects with type I profiles do not present stellar winds or have very low envelope mass-loss rates. As can be seen in Table 4, 29% of the [O i] lines detected by us belong to type I stars, leading us to believe that the Bo¨hm & Catala (1994) sample is strongly Vieira et al. (2003) affected by selection effects in this aspect. The distribution in our sample of [O i] and [S ii] forbidden Fig. 8.—Example of SED fitting using the model of Gregorio-Hetem & Hetem (2002). The solid thick line is the resulting total emission, and lines supports the results of Corcoran & Ray (1997, 1998), different lines are used to show contributions from the star (dashed line), the who also found that the forbidden lines are concentrated disk (solid line), and the envelope (dotted line). The observed data are among B type stars and are observed among type I H line- represented by open squares. T TAURI STARS 24

CTTS LIGHT CURVES sinusoidal, stable shape AA Tauri like non-periodical

Alencar et al. (2010) T TAURI STARS 25

PHASE PLOTS OF CTTS LIGHT CURVES Alencar et al. (2010) T TAURI STARS 26

PROPERTIES OF CTTS

Alencar et al. (2010)

�IRAC < +0.50 m

μ �IRAC < -0.50

�IRAC < -1.80

�IRAC < -2.56 : slope of SED relation IRAC � between 3.6 and 8

NGC 2264 CTTS observed with CoRoT & Spitzer: Diamonds: spot-like LCs, triangles: AA Tau like; squares: non-periodical LCs larger symbols: 5 stars with fast rotation (P < 2 days) No. 6, 2003 131 HERBIG Ae/Be CANDIDATE STARS 2979

TABLE 3 TABLE 4 Rotational Velocities for Herbig Ae/Be Candidates Distribution of the Forbidden Lines among Different Spectral v sin i Types and H Line-Profile Types Object (km sÀ1) Type Sp. Type Distribution PDS 225...... 225 I B3 Type (%) PDS 514...... 58 I A0 V PDS 002...... 175 I B0 V Spectral Type PDS 564...... 88 I A3 V B ...... 54 PDS 395...... 52 I A8 V A...... 30 HD 52721 ...... 456 I B2 Vn F ...... 8 PDS 174...... 144 II B3 O...... 8 PDS 180...... 125 II A8 V PDS 327...... 132 II B1 H Profile PDS 361...... 190 II B3 PDS 398A ...... 281 II A0 V I ...... 29 PDS 545...... 238 II B2 II...... 41 PDS 076...... 97 II F0 V III ...... 18 PDS 080...... 120 II F1 III IV ...... 12 HBC 282 ...... 142 II B+sh HD 95881 ...... 74 II A0 HBC 552 ...... 128 II F+sh HD 76534 ...... 116 II B2 profile stars. Corcoran & Ray (1997, 1998), however, found PDS 069N...... 158 III B3 that forbidden lines were more common among type II line PDS 339...... 100 III A9 V profiles, while our results point to an equal distribution HBC 551 ...... 245 III B5 among all profile types. Selection effects may explain their HD 53367 ...... 55 III B4 results, since the majority of their stars belong to group II in PDS 183...... 59 IV A8 V PDS 315...... 44 IV O8 the work of Hillenbrand et al. (1992), which generally PDS 172...... 90 IV A3 V presents H line profiles of types II and III. PDS 201...... 119 IV A7 V HD 98922 ...... 52 IV B9 HBC 078 ...... 85 IV A5 V 5. DISCUSSION AND ANALYSIS HD 150193...... 103 IV A0 V 5.1. Circumstellar Environment The Balmer line profiles and the presence of forbidden forbidden lines in the low- and medium-resolution observ- lines are strongly connected with the circumstellar environ- ations. In some cases, however, forbidden lines detected in ment. To check this correlation, we use SEDs calculated for low- and medium-resolution spectra were not present inBACKGROUND the 62 HAeBe stars in our sample by M. Sartori & J. Gregorio- 27 high-resolution observations (taken at a different epoch), Hetem (private communication), using the disk model of suggesting that those lines also present variable intensities. Gregorio-Hetem & Hetem (2002). In this model the star is The distribution of the detected forbidden lines among surrounded by an extended and flat disk and a thin dust different spectral types and H line-profile types can beSPECTRAL seen ENERGY DISTRIBUTION in Table 4. We have an almost equal number of A (40%) and B (45%) stars in our sample; therefore, the results in Table 4 point to a significantly higher occurrence of forbidden lines among B stars. The forbidden line distribution among dif- observations ferent H profile types is nearly identical to the H profile distribution in our sample (see x 4.1), indicating that forbidden lines are evenly distributed among each H line-profile type. In a previous work Bo¨hm & Catala (1994) detected [O i] in stars with H line profiles of types II, III and IV and did not detect it in stars with type I profiles. Since types II, III, total and IV are characteristic of stars with stellar winds and [O i] disk star is expected to originate in jet/outflow regions associated with mass-loss processes, they suggested that objects with type I profiles do not present stellar winds or have very low envelope mass-loss rates. As can be seen in Table 4, 29% of the [O i] lines detected by us belong to type I stars, leading us to believe that the Bo¨hm & Catala (1994) sample is strongly Vieira et al. (2003) affected by selection effects in this aspect. The distribution in our sample of [O i] and [S ii] forbidden Fig. 8.—Example of SED fitting using the model of Gregorio-Hetem & Hetem (2002). The solid thick line is the resulting total emission, and lines supports the results of Corcoran & Ray (1997, 1998), different lines are used to show contributions from the star (dashed line), the who also found that the forbidden lines are concentrated disk (solid line), and the envelope (dotted line). The observed data are among B type stars and are observed among type I H line- represented by open squares. CTTS CLASSIFICATION 28

b NEW RESULTS a NGC 2264 CTTS observed with CoRoT in 2011/12 a) + b) variable extinction c d c) unstable accretion or accretion bursts d) cold spots e) hot spots f) stochastic light curve e f

Stauffer et al. (2016) HERBIG AE/BE STARS 29

HERBIG AE/BE STARS Herbig (1960), Thé et al. (1994) Leiden University ▸ intermediate masses

▸ spectral types B, A, early F

▸ located in obscured region

▸ fairly bright nebulosity in its vicinity

▸ anomalous extinction law

▸ circumstellar matter

▸ emission lines (e.g., Hα), UV & IR excesses

▸ photometrically variable on different time scales HERBIG AE/BE STARS 30

HERBIG AE/BE STARS: Hα EMISSION Reipurth et al. (1996) ▸ Classification scheme:

▸ Type I: symmetric profiles without absorption features

▸ Type II: double-peaked, secondary peak has more than half the strength of the primary

▸ Type III: double-peaked, secondary peak has less than half the strength of the primary

▸ Type IV: P Cygni characteristics Vieira et al. (2003) P CYGNI PROFILE 31

P CYGNI PROFILE

▸ presence of absorption and emission in spectral line profile

▸ indicates presence of gaseous envelope expanding away from star

▸ emission line: from dense stellar wind

▸ blueshifted absorption: radiation passes through circumstellar material and expands rapidly towards observer

▸ used to study stellar winds in many types of stars

Image: By Sailsbystars - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17555995 HERBIG AE/BE STARS 32

HERBIG AE/BE STARS

HD 142666 MOST

MOST

Kepler K2 134 G. Meeus et al.: HD 139614, HD 142666 and HD 144432: evidence for circumstellar disks 134 G. Meeus et al.: HD 139614, HD 142666 and HD 144432: evidence for circumstellar disks 3.2. Optical photometric variability 3.2. Optical photometric variability The Geneva photometric data obtained for HD 139614 and The Geneva photometric data obtainedHD 144432for HD do 139614 not show and any significant variability; on the other HD 144432 do not show any significant variability; on the other hand, HD 142666 displays large (> 1m.2) brightness varia- hand, HD 142666 displays large (> 1m.2) brightness varia- tions. The visual magnitude (mV ) of this star as a function of tions. The visual magnitude (mV ) ofthe this Julian star as Date a function (JD) is of shown in Fig. 2. It should be noted that the Julian Date (JD) isHERBIG shown in Fig. the 2.AE/BE It star should is most STARS be noted frequently that in its bright state. A period analysis 33 the star is most frequently in its brightfor state. this Astar period was performed, analysis but no period was found. Therefore for this star was performed, but no periodit can was be found. concluded Therefore that the variations are irregular. it can be concluded that the variations are irregular. In Fig. 2, the color-magnitude diagram mV [U B] for In Fig. 2, the color-magnitude diagramHD 142666mV is[U shown.B] for It can be seen that, for this star, there is HD 142666 is shown. It can be seen that, for this star, there is 134 G. Meeus et al.: HD 139614, HD 142666 and HDSPECTROSCOPIC 144432: evidencea linear for relation circumstellar between disks EVIDENCEmV and the color-index OF [U BCIRCUMSTELLAR]: the DISKS a linear relation between mV and thestar color-index becomes [U redderB]: as the the apparent magnitude decreases. This star becomes redder as the apparent magnitude decreases. This 3.2. Optical photometric variability shows that HD 142666 is a member of class R (Red behaviour), shows that HD 142666 is a member ofas class definedR (Red by behaviour), Bibo & The´ (1991), in their study of the photo- as defined by Bibo & The´ (1991), in their study of the photo- The Geneva photometric data obtained for HD 139614 and metric variability of Herbig Ae/Be stars in a color-magnitude- metric variability of Herbig Ae/Be stars in a color-magnitude- HD 144432 do not show any significant variability; on the other diagram. The slope of the (mV , [U B]) curve is similar to diagram. The slope of the (m , [U B]) curve is similar to hand, HD 142666 displays large (> 1m.2) brightness varia- V that of the IS extinction law by Savage & Mathis (1979). This that of the IS extinction law by Savage & Mathis (1979). This tions. The visual magnitude (m ) of this star as a function of suggests that, like the Herbig Ae star HR 5999 (Bibo & The´ V suggests that, like the Herbig Ae star HR 5999 (Bibo & The´ the Julian Date (JD) is shown in Fig. 2. It should be noted that 1991), the brightness variations of HD 142666 can be ascribed 1991), the brightness variations of HD 142666 can be ascribed the star is most frequently in its bright state. A period analysis to variable obscuration by CS dust. It can be concluded that the to variable obscuration by CS dust. It can be concluded that the for this star was performed, but no period was found. Therefore star HD 142666 shows nonperiodic Algol-like minima, and can star HD 142666 shows nonperiodic Algol-like minima, and can it can be concluded that the variations are irregular. be considered as a member of the UXor class. be considered as a member of the UXor class. In Fig. 2, the color-magnitude diagram mV [U B] for HD 142666 is shown. It can be seen that, for this star, there is a linear relation between mV and the color-index [U B]: the 4. Spectral observations star becomes redder as the apparent magnitude4. Spectral decreases. observations This shows that HD 142666 is a member of class R (Red behaviour), 4.1. Optical spectroscopy as defined by Bibo & The´ (1991), in their4.1. study Optical of the spectroscopy photo- metric variability of Herbig Ae/Be stars in a color-magnitude- In Fig. 3 the optical high-resolution spectra of the three stars in In Fig. 3 the optical high-resolution spectra of the three stars in diagram. The slope of the (mV , [U B]) curve is similar to the spectral regions around 5885 A,˚ 6563 A,˚ and 8685 A˚ ˚ ˚ ˚ that of the IS extinction law by Savage &the Mathis spectral (1979). regions This around 5885 A,are 6563 shown.A, andThe following8685 A features should be noted. suggests that, like the Herbig Ae star HRare 5999 shown. (Bibo The & following The´ features should be noted. In HD 139614, H displays a single-peaked emission pro- 1991), the brightness variations of HD 142666In can HD be 139614, ascribed H displays a single-peaked emission pro-↵ ↵ file; the 5876 A˚ HeI line is seen as a broad CS emission profile; to variable obscuration by CS dust. It can befile; concluded the 5876 thatA˚ the HeI line is seen as a broad CS emission profile; the NaI D and D lines are in absorption, with a width which star HD 142666 shows nonperiodic Algol-like minima, and can 1 2 the NaI D1 and D2 lines are in absorption,is similar with to a that width of the which NI lines at 8680 and 8688 A;˚ the Paschen be considered as a member of the UXor class.is similar to that of the NI lines at 8680 and 8688 A;˚ the Paschen 13 line of HI ( 8665 A)˚ appears in absorption. 13 line of HI ( 8665 A)˚ appears in absorption. Meeus et al. (1998) HD 142666 shows a H↵ double-peaked emission profile HD 142666 shows a H↵ double-peakedwith a deep emission absorption profile reversal reaching well below the adja- with a deep absorption reversal reaching well below the adja- 4. Spectral observations cent continuum; a broad HeI 5876 A˚ absorption is observed; cent continuum; a broad HeI 5876 A˚ absorption is observed; the NaI D profile consists of a narrow, strong component, su- 4.1. Optical spectroscopy the NaI D profile consists of a narrow, strong component, su- 1 perimposed1 on a broader (v = 56 km s ) component; P13 is Fig. 3. Normalised spectra of the three program stars around 5885 A,˚ perimposed on a broader (v = 56 km s ) component; P13 is ˚ seen in absorption. Fig. 3. Normalised spectra of the three program 6563 starsA,˚ around and 8685 5885A.˚ A, The star HD 142666 shows CS absorption In Fig. 3 the optical high-resolution spectraseen of the in three absorption. stars in 6563 A,˚ and 8685 A.˚ The star HD 142666 shows CS absorption HD 144432 also shows a double-peaked H↵ profile, with a lines, while the stars HD 139614 and HD 144432 show CS emission the spectral regions around 5885 A,˚ 6563 A,HD˚ and 144432 8685 alsoA˚ shows a double-peaked H↵ profile, with a lines, while the stars HD 139614 and HDlines. 144432 show CS emission deep absorption reversal goinglines. below the continuum, but here are shown. The following features should bedeep noted. absorption reversal going belowthe the red continuum, component but is here much stronger than the blue component; a the red component is much stronger than the blue component; a 4.2. Near-IR spectroscopy In HD 139614, H↵ displays a single-peaked emission pro- broad HeI 5876 A˚ emission4.2. line Near-IR is observed; spectroscopy the sodium lines ˚ file; the 5876 A˚ HeI line is seen as a broadbroad CS emission HeI 5876 profile;A emission line is observed;appear in the emission, sodium with lines two narrow IS absorption components; In Fig. 4 the obtained near-IR spectra around the HeI 1.08 µm appear in emission, with two narrow IS absorption components; In Fig. 4 the obtained near-IR spectra around the HeI 1.08 µm the NaI D1 and D2 lines are in absorption, with a width which P13 is now seen in emission. line are shown. The observed features are summarised in Ta- is similar to that of the NI lines at 8680 and 8688P13 isA;˚ now the seen Paschen in emission. line are shown. The observed featuresble are 4. summarised in Ta- A value for v sin i was derivedble 4. from other spectra showing 13 line of HI ( 8665 A)˚ appears in absorption.A value for v sin i was derived from other spectra showing 1 photospheric1 lines and a values of 13 km s for HD 139614, HD 142666 shows a H double-peakedphotospheric emission profilelines and a values of 13 km s for1 HD 139614, 1 ↵ 1 56 km1 s for HD 142666 and 54 km s for HD 144432 were with a deep absorption reversal reaching well56 km belows for the HD adja- 142666 and 54 km found.s for HD 144432 were cent continuum; a broad HeI 5876 A˚ absorptionfound. is observed; the NaI D profile consists of a narrow, strong component, su- 1 perimposed on a broader (v = 56 km s ) component; P13 is Fig. 3. Normalised spectra of the three program stars around 5885 A,˚ seen in absorption. 6563 A,˚ and 8685 A.˚ The star HD 142666 shows CS absorption HD 144432 also shows a double-peaked H↵ profile, with a lines, while the stars HD 139614 and HD 144432 show CS emission deep absorption reversal going below the continuum, but here lines. the red component is much stronger than the blue component; a 4.2. Near-IR spectroscopy broad HeI 5876 A˚ emission line is observed; the sodium lines appear in emission, with two narrow IS absorption components; In Fig. 4 the obtained near-IR spectra around the HeI 1.08 µm P13 is now seen in emission. line are shown. The observed features are summarised in Ta- A value for v sin i was derived from other spectra showing ble 4. 1 photospheric lines and a values of 13 km s for HD 139614, 1 1 56 km s for HD 142666 and 54 km s for HD 144432 were found. PULSATING STARS ASTEROSEISMOLOGY 35

STELLAR OSCILLATIONS

radial oscillations

non-radial oscillations ASTEROSEISMOLOGY 36

INTERNAL BEHAVIOUR OF THE OSCILLATIONS

▸ The oscillation pattern at the surface propagates in a continuous way towards the stellar center

▸ Study of the surface patterns hence allows to characterize the oscillation throughout the star ASTEROSEISMOLOGY 37

ASTEROSEISMOLOGY: WHAT DOES IT MEAN?

astero ⇒ star seismos ⇒ oscillations logos ⇒ discourse

The analysis of stellar oscillations enables the study of the stellar interior because different modes penetrate into different depths inside the star. ASTEROSEISMOLOGY 38

HISTORY OF ASTEROSEISMOLOGY

▸ Periodic large-amplitude variables known for a long time, e.g., Cepheids & RR Lyrae stars

▸ Multiperiodicity at low amplitude found in many different kinds of variables

▸ Cause: non-radial oscillations

▸ Idea: every body “sounds” according to its internal structure ⇒ different oscillation frequencies tell us something about the stellar interior

▸ Between 1900 and 1990: mainly inventories of variables

▸ Since 1990: use frequency content to derive internal structure parameters and try to improve stellar structure and evolution models ASTEROSEISMOLOGY 39

OSCILLATIONS, SOUND, PRESSURE WAVES

▸ Sound speed: e.g., in air 343 m/s at 20° C temperature

▸ Sound speed increases

▸ with temperature e.g., air at 40°C: 355 m/s

▸ lighter gas e.g. Helium: 965 m/s

▸ higher density z.B.: granite: 6000 m/s ASTEROSEISMOLOGY 40

1-D OSCILLATIONS

Fundamental 1st Overtone 2nd Overtone

nodes

modes ASTEROSEISMOLOGY 41

2D OSCILLATIONS

radial fundamental radial 1st overtone radial 2nd overtone

non-radial dipole non-radial quadrupole TEXT 42

2D OSCILLATIONS - TACOMA BRIDGE

Inauguration 1 July 1940

With little wind… TEXT 43

2D OSCILLATIONS - TACOMA BRIDGE 7 November 1940: collaps with 68km/h wind ASTEROSEISMOLOGY 44

PULSATING STARS ARE EVERYWHERE