Hi everyone,
Wow! Truly excellent to see these observations so far! These will be quite valuable (even necessary, in my opinion) in properly interpreting the TESS data for these stars. Seeing these first few datasets for the stars in the TESS observing list is especially important in deciding observational strategies going forward because they tell us critical information like whether or not there is a disk, its relative strength, inclination angle, whether or not there is variability, etc. I will try to keep this post as short as possible- my goal with this post is to comment on the observations in this thread, which I am using to update the TESS observing spreadsheet.
Please let me know if there is anything I can do to improve the spreadsheet or any questions about scientific priorities (and especially any disagreements with my interpretations of these data). In the next few days I will post more details about the observing strategies that I think will be most scientifically valuable in the context of this community and additional resources (along with some TESS light curves and other data as examples). I am still working on updating the spreadsheet to incorporate these recent observations.
I'm excited to work with you all and am confident that these observations will be important given that TESS is probably the best opportunity to study large numbers of bright Be stars with photometry from space, and that simultaneous spectra are very important in interpreting the photometric signals of these systems given how variable disks can be.
Addressing some comments:
"Very true. TESS has been observing the southern hemisphere for the past year and will observe the northern hemisphere for the next year
https://tess.mit.edu/science/observations
Not sure what plans there are for TESS beyond 2 years"
Especially these first 3 sectors of TESS (13,14,15) are very northern. The remaining 9 will still be northern, but will extend further south. about the future plans of TESS: Neither is anyone else! It is not known what the plans for TESS are beyond the next 10 months.
"I guess more northerly (or last year southerly) targets may also have the advantage of being observed by TESS for longer due to the increased overlap of segments near the poles."
Yes, these stars observed in multiple sectors are better to observe because of the 2x+ TESS data. It will be easier to identify pulsation and outburst/flicker variability in the photometry, which of course spectra will help with immensely in interpreting this variability.
Notes for observations in this thread so far:
BD+27_3970 = TIC 126756648
Observed in Halpha by Robin night of 2019/08/20. 2.5xContinuum, W-shape profile with small delta-Vp. FWHM = 6.7A. Observed by Christian Buil 2019/08/25 showing apparently single-peaked Halpha at 2.5xContinuum. Medium/low priority of 4 now because the Halpha line suggests this is nearly pole-on and the disk is relatively strong for a B6/8 star, and it will be difficult to detect spec. changes.
EM* MWC 1030/TYC 3178-815-1 = TIC 296771641
Observed in Halpha by Robin night of 2019/08/20. 27xContinuum! Single peaked Halpha. EW = -110A, FWHM 3.3A. unidentified emission line at ~6515A. There is a low resolution spectrum from 20180716 which also shows H alpha in emission at similar EW. Expired as classical Be star based on Halpha profile and SED that peaks in the NIR.
HD_194779 = TIC 15126043
- Spectra so far do not show signs of Halpha activity. Still interesting to monitor no more than once per night. If Halpha activity is seen then higher cadence will be requested.
V568_Cyg = TIC 100165164
- Observed by Robin on 2019/08/24 and Olivier on 2019/08/07. Both show the ~same single-peaked 4.5xContinuum Halpha. Priority slightly lowered since we are unlikely to see much activity in the remaining time TESS is observing this star (until Sept. 11) given the high strength of Halpha and near pole-on orientation.
V1362_Cyg = TIC 40478523
- Nice observations by Robin on 2019/08/24 and James Foster on 2018/09/20 that show double-peaked Halpha with large changes in V/R over just 5 days. Similar variability is seen in NRES spectra from Jon Bartz. Continue to monitor at 1+ observation per night. Jon will continue to monitor with NRES. This clearly has interesting Halpha variability on short timescales and is likely to be variable in TESS.
V2113_Cyg = TIC 202752748
- Observed by Robin on 2019/08/24 and Olivier Thizy on 2019/08/02. Both show similar strength 4-4.5xContinuum Halpha with mostly single-peaked shape. Some structure apparent in Olivier's spectrum. Priority level remains at 7. Despite the strong Halpha, we might be able to see variability near the line center on short timescales if this is in fact a binary.
V2162_Cyg = TIC 240258004
- Interesting behavior in many observables (too tedious to name them all). High priority. Possible SB2. Very likely to be active on short timescales with TESS. Likely has a dense inner disk.
HD_175511 = TIC 236785664
Robin: "HD175511 - He 6678 is present in absorption 20190322 but is absent currently. Does anyone know the astrophysical significance of this ?"
Interesting observation + question. From Halpha, this is practically a shell star. My first guess is that an enhanced density in the inner disk could obscure the photosphere to a degree that would make the apparent depth of He lines smaller. But this would also presumably make the Halpha line core deeper, which we do not see in the observation. Non-radial pulsation can change the depth/shape of photospheric lines, but I don't think the effect would be so strong as to wash the line out completely. Or, maybe the photospheric Teff is variable. I don't have a good answer for this, but it's definitely interesting.
- This is one of the 3 Be stars that is being observed in 10+ sectors with TESS. Continued monitoring at a low cadence of 1 spectrum per week or so is ideal for now.
V374_Cep = EM* AS 505 = TIC 434972921
- Apparently a Herbig Ae/Be star according to Simbad. The SED peaks in the NIR and there seems to be dust excess. Probably not interesting for Classical Be star work, but this could still be interesting if its visible TESS light curve is variable (which would not be surprising).
V421_Cep = TIC 314576961
Robin: "H alpha looks similar to the spectrum in BeSS taken 2 days earlier but there are some strange differences in the continuum on the red side of H alpha and the 6678 He absorption line has shifted to the blue and possibly changed shape. Are these differences real ?"
- Interesting find! The He variability looks real to my eye. This could be consistent with pulsation changing the line profile shape. This is certainly worth continued monitoring especially since it will be visible for TESS sectors 15,16,17.
HD_175863 = TIC 233613741
- Observed by Robin and ChK on 2019/08/26 and 2019/08/22 respectively. No obvious difference in Halpha- pure absorption down to 0.72xContinuum. This star is in the TESS continuous viewing zone. In that respect, I think it is good there is no disk right now. Continue to monitor once every few days. If any change in Halpha, we want higher cadence observations. Good chance to observe a disk build-up from a purely photospheric level in both TESS and spectroscopy.
HD_183339 = TIC 284563819
Observed by Robin and Houpert 2019/08/26, 2019/03/20. narrow Halpha absorption with no variability. I don't think this is a classical Be star. Priority is lowered. Still, since it is in the TESS continuous viewing zone, a spectra every few weeks might still prove interesting.
HD_203356 = TIC 63318608
- Robin, 2019/08/25, and Charbonnel 2019/07/10 both see double-peaked weak Halpha in a wide absorption profile. No change between the two spectra. Based on the late spectral type and consistent line profile I doubt we'll see much variability over TESS timescales.
V2153_Cyg = TIC 373819241
- Robin, 2019/08/25, and vdesnoux 2019/08/08 both see ~4.5xContinuum mostly single-peaked Halpha. Some variation present. Halpha profile is somewhat distorted. Obviously not a shell star from the spectrum. Could be a binary based on observables. Will be interesting to continue to monitor. Nice target.
V420_Cep = TIC 313986452
Robin, 2019/08/25, vdesnoux 2018/07/14 both see single-peaked Halpha at 2.4xContinuum. Since older spectra from BeSS show up to 6xContinuum, we are probably seeing the disk at a relatively low state. Continued monitoring at low cadence is a good strategy since this is in 3 TESS sectors and we may see some disk growth from flickers.
BD+50_3188 = TIC 364925342
Christian Buil, 2019/08/25, apparently single-peaked Halpha at 2xContinuum. Not known in BeSS. APOGEE spectrum show Br11 double-peaked 1.2xContinuum with variable central depression. Priority lowered since the KELT light curve is exceptionally flat for a Be star. Still, one more spectrum couldn't hurt to see if there is variability in hydrogen lines.