Sunday, January 30, 2011
Module 5, Assignment 8
Post your spectral class and temperature for three of the stars, identified by the HD number, as well as the spectral type, B, and V from SIMBAD. Include a screen shot of at least one spectrum (send to Chris Martin) with the lines you have identified.Which technique do you think is more accurate for determining spectral class- temperature as determined by Wien’s Law or as determined by spectral lines?
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HD Peak(A) Temp(K) spectrum B V
ReplyDelete331085 6100 4900 K0 10.47 9.12
331241 4500 6700 F5 11.30 10.73
331246 3900 7700 B3V 9.00 9.00
332087 4000 7500 F0 9.53 9.18
I think that using Wien’s Law is much better for determining spectral-class and temperature. Using the spectral lines seems much more subjective. I found it difficult to differentiate spectral class just by looking at the spectral lines.
ReplyDeleteStar Temperature
ReplyDeleteHD331085 - 4800K – K0
HD331241 - 6400K – F5V
HD331246 - 7400K – B3V
B and V from SIMBAD
HD331085 - 10.47 and 9.12 - K0
HD331241 - 11.30 and 10.73 - F5
HD331246 - 9.00 and 9.00 - B3V
Some stars have peak radiation wavelength outside of the visible band so we cannot use Wien's law to determine the temperature. Wien’s law provides us an estimate temperature for stars since these are not a perfect blackbody radiator.
Stars have different strength and pattern of the absorption lines and these patterns will give the accurate temperature of the star’s photosphere and spectral type.
In this assignment, we want you to identify prominent absorption lines and from those suggest the spectral type. When you give the spectral class, list the identified absorption lines.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteHere is an example of what we are looking for. It was written by Sue Kamman from the summer 2010 astrobits course;
ReplyDeleteHD 332087: Temp 6900K from wavelength peak at 420nm. Borders split between A and F class stars; however, is in F class. Spectrum shows strong Hydrogen lines with a few strong metals, again border of A9 and F0 when compared to Jacoby Atlas. I went with F due to temperature match. SIMBAD says..F0 class with B value of 9.53 and V of 9.18...good call.
More information specific to absorption lines - take 2.
ReplyDeleteHD 331057 Peak Wavelength=4000 angstrom Temp=7200 K and Spectral Class=A (with Temp greater than 7000K, less than 9500K) Absorption Lines at (3753, 3772, 3799, 3838, 3889, 3972- out of visible light) and 4101, 4340, 4859 and 6563 (Matching a strong Hydrogen Balmer Seriers absorption that has lines at 4101 4341 4862 and 6564) –From SIMBAD Spectral Type=A0 B=9.20 V=9.20
HD 331059 Peak Wavelength=6300 angstrom Temp=4600 K and Spectral Class=K (with Temp greater than 3500K and less than 4900K) with Absorption Lines at 4309 (Magnesium), 5169 (Iron II), 5891 (Sodium) and 6870 (Oxygen) significantly there is not a strong Balmer Series Absorption– From SIMBAD Spectral Type=K5 B=10.82 V=9.73
HD 331061 Peak Wavelength=4000 angstrom Temp=7200 K and Spectral Class=A with Absorption Lines at (3753, 3775, 3802, 3836, 3892, 3972 – out of visible light) and 4104, 4340, 4862 and 6562 (Matching a strong Hydrogen Balmer Seriers absorption that has lines at 4101 4341 4862 and 6564) – From SIMBAD Spectral Type=A5 B=11.2 V=10.9
I think spectral classification is best done with help from both temperature and absorption data. The temperature gives you an idea of where to start, then the specific presence (or absence) of absorption lines can help you identify specific spectral class. The ranges (i.e. A0 versus A5) are difficult for me to specify, but I do know that the hotter stars have lower numbers - so for my two class A stars the HD331057 is hotter than the HD331061 - I must have estimated peak wavelength wrong as I came up with the same temperature for both.
ReplyDeleteI chose the following stars: HD331054, HD331055, HD331057
ReplyDeleteFrom SIMBAD: HD331054 -class KO (B=9.85 and V=8.91). The temperature using the simulator and filter (B-V) is 4280K (class K). Using the highest peak I got 5410K which indicates a class G star. I checked the spectral lines and the prominent line s are Ca+(strongest), neutral metals strong, H(weak) . Comparing the spectrum to the Jacobi. The star is classified as K not G
For HD331055 – class F8 (B=10.97 and V=10.39) (from SIMBAD). Using the same technique, my temperature is 6430K using the highest peak and 5440K using B-V. 6430 K denotes a F star and 5440K denotes a G star. After analyzing the prominent spectral lines (H(weaker), Ca+, ionized metals) and comparing it to Jacobi atlas. HD331055 is a class F star.
For HD331057 – class A0 (B=9.20 and V=9.20)(from SIMBAD). Using the filter (B-V) I got 9640K (class A) and using the highest peak I got 7390K (class F). The prominent spectral lines has H(strongest), Ca+, Mg+, Fe+. Com[paring it to the atlas, HD331057 is a class A star.
I think the spectral lines will help us identify the class or types of star and Wien's law, simulator, filter will give us the temperature.
From SIMBAD
ReplyDeleteHD332087- F0 (B=9.53 V=9.18)
HD331085- K0 (B=10.47 V=9.12)
HD331241- F5 (B=11.30 V=10.73)
Using Wien's law I got:
HD332087 -7210K
HD331085 -4770K
HD331241 -6430K
From the absorption analysis: HD332087 has the following prominent lines: Telluric, Ha, Na I, Hbeta, Hgamma, Hdelta, CaII, H8 and H9
This star has weak ionised Ca+, medium Balmer series. It has Hydrogen and other metals. Its temperature is between class F and A but is more on F...so its class is F0 (hottest among F stars). Comparing it to Jacobi atlas, this is really F0.
For HD331085: Telluric Na I. Mg I and H alpha
It has weak Balmer series. It has some metals metals and some molecular species. From Jacobi atlas, it suggests that this stars is K0. The temperature lies at the boundary but it is more on K.
For HD331241: Telluric, H alpha, NaI, MgI, Hbeta, Hgamma, TiII, Hdelta, CaII, Halpha
This star has medium Balmer series, metals and Hydrogen. The temperature is in the middle for temperatrure range of class F star. It is good call for this star as F5 star.
Using wien's law, we can compute for the temperature and analysis of the prominent absorption will determine the classification of the stars
For HD331066, I got a temperature of 7390K using Wien’s law which suggests a class F star. From SIMBAD, this star is classified as B8 and B=9.58 and V=9.59. It has neutral He absorption lines. H I Balmer lines in cooler types. Because of these He neutral lines, this star is classified as B star.
ReplyDeleteThese are the absorption lines:
7184-telluric
6870-Telluric
5895-Na I
4860-H-beta
4341-He II
4104-H-delta
3970-H-epsilon
3890-H8
3836-H9
3800-H10
HD331078 has a temperature of 7210K using Wien’s law. Its B= 10.39 and V= 10.05 and it is a F2 star. It has these prominent lines: Ca II stronger; H weaker; Ionized metal lines appearing. This suggests a class F star.
These are the absorption lines:
7194-Telluric
6871-Telluric
6559-H-alpha
5891-Na I
5270-Fe
5170-Mg I
4860-H-beta
4341-H-gamma
4105-H-delta
3971-Ca II
3934-Ca II
3890-H8
3839-H9
From SIMBAD, HD331083 is G5 star and using Wien’s law its temperature is 6430K. It is in the boundary of F and G star. Looking at the prominent absorption lines of strong Ca+, Fe, Na and other metals with neutral metal lines appearing and a weak balmer features. This star is really classified as G star.
These are the absorption lines
7185-telluric
6868-Telluric
6564-H-alpha
5893-Na I
5267-Fe
5172-Mg I
4860-H-beta
4341-H-gamma
4302-Ti II
4102-H-delta
3971-Ca II
3937-Ca II
3834-H9
For HD331085, the following are the prominent absorption lines in Angstroms:
ReplyDelete7185 - Telluric
6871 - Telluric
6559- H-alpha
5891- NaI
5269- Fe
5170- Mg I
The prominent lines of HD331085 are neutral metals, sodium. This suggests that this star is class K.
For HD331241, the following are the absorption lines in angstroms:
7188- Telluric
6871-Telluric
6561-H-alpha
5894- Na I
5267 - Fe
5172 Mg I
4863- H-beta
4339- H-gamma
4307- Ti II
4102 – H-delta
3971 – Ca II
3934- Ca II
3837- H-alpha
The prominent lines are Hydrogen, ionized calcium, iron and this suggest that this star is class F
For HD331246, the absorption lines in angstroms are:
7190-Telluric
6871-Telluric
6561-H-alpha
5896- Na I
4863-H-beta
4473-Mg II
4339- He II
4103- H-delta
3973- H-epsilon
3890- H8
3837-H9
3800-H10
The prominent lines are Helium and some hydrogen. This shows that HD331246 is B star
HD 331055 is class F, according to the spectral lines. It has a temperature of 6412 K. There are prominent absorption lines at 3934 angstroms (calcium) and 3963 angstroms (calcium).
ReplyDeleteHD 331059 is a M class. There are prominent lines at 5170 angstroms (magnesium) and 4300 angstroms (hydrogen). The max temperature is 4762 K.
HD 331061 is A class. It has prominent absorption lines at 4104 angstroms (hydrogen delta...I'm not sure what this means) 4343 angstroms (hydrogen gamma...I'm not sure what this means, either). The max temperature is 7187 K.
I think it is more accurate to use Wien's Law to determine the temperature of a star.
HD 331072 is an M star. It has a very distinctive spectra with a peak wavelength to the right of the wavelength range. CaI and CaII lines are clearly present. Absent in this spectra is the Hydrogen Balmer Series. The upper limit for my temperature estimate is 4000 degrees. Since the peak isn’t visible, the temp is most likely lower. Simbad also classifies this star as an M star and it has a B magnitude of 11.7 and a V magnitude of 10.17.
ReplyDeleteHD 331078 is an F star. The Hydrogen Balmer lines are clearly present, but I can also identify lines for calcium. I estimate the peak wavelength at 4019 which puts the temperature around 7460 degrees. Simbad agrees and the B magnitude is 10.39 and V is 10.05
HD 331083 was a tricky one. I thought it might be a K star, but Simbad classifies it as a G5 star. H and Ca lines are both present, although the Ca lines are stronger. The peak wavelength is around 4682 which yields a temp of 6407. The temperature definitely seems more like a G star temp, but I’m still having troubles seeing the difference in the spectral lines between G and K. Simbad lists the B magnitude as 10 and no V magnitude is listed.
All the spectra exhibit the telluric absorption band which I read was an artifact of the earth’s atmosphere. But I am wondering what causes it?
I find it easier to identify spectra by their peak wavelength. I probably wouldn’t have misidentified the third spectra if I had used the temp instead of the spectral lines, but that might also be because I’m not totally sure what lines are supposed to be present in each stellar type. I also found there is a lot of error in measuring the wavelength. Moving the cursor one pixel resulted in a change of 7 Angstroms which could be several different elements.
HD 331066 – peak at 3914 A, temperature calculated at 7401 K, implying A, possibly F type
ReplyDeleteAbsorptions at 3838 (H9)
3894 (H8)
3975 (Heps)
4101 (Hsig)
4338 (Hgamm)
4857 (Hbeta)
The all-Hydrogen pattern indicates that A is the correct type
SIMBAD shows B8. B 9.58; V 9.59
HD 331078 – peak at 4019, temperature calculated at 7208 K, implying A or F type
Absorptions at 3836 (H9)
3895 (H8)
3931 (CaII?)
3968 (Heps)
4099 (Hsig)
4338 (Hgamm)
4857 (Hbeta)
6561 (Halph)
6873 (Telluric)
Strong Hydrogen with some (possible) metals indicates A again.
SIMBAD shows F2. B 10.39; V 10.05 And I’m starting to feel pretty stupid.
HD 331083 – peak at 4509, temperature calculated at 6424 K, implying F or G type
Absorptions at 3834 (H9)
3932 (CaII)
3968 (Heps)
4102 (Hsig)
4307 (TiII?)
4338 (Hgamm)
4860 (Hbet)
5172 (MgI?)
5891 (NaI)
6559 (Halph)
6871 (Telluric?)
Weaker hydrogen and many metals indicates G type.
SIMBAD shows G5. B 10, no V given.
Apparently my temperature estimates STINK! I’d better stick to using the spectral lines!
HD 332087
ReplyDeletePeak = 4020 A
Temp = 7210 K
By identifying some prominent absorption lines and comparing them to data given here: http://www.noao.edu/education/astrobits/files/Spectroscopy-GA3-Abits.pdf I concluded that the lines were characteristic of He 1. I don’t know how to transfer that to a spectral class, and looking at the Jacoby examples further confused me. So, I’ll just defer to what Simbad said:
Spectral type: F0 D
B flux: 9.53
V flux: 9.18
HD 331246
Peak = 3900 A
Temp = 7400 K
H-epsilon lines
Simbad:
Spectral type: B3V D
B flux: 9.00
V flux: 9.00
HD 331241
Peak = 4500 A
Temp = 6400 K
metal lines
Simbad:
Spectral type: F5 D
B flux: 11.30
V flux: 10.73
Since you can get more data by examining the spectral lines, that's probably the best way to classify a star's type (although I'm still unsure how to connect the type of elements to the type of star).
From John Webster
ReplyDeleteModule 5 Assignment 8
My data for the 3Stars is as follows:
HD 331085
Max λ- 6071Å, Temp-6071°K, K0 D, B- 10.47, V-9.12
HD 331241
Maxλ-4268Å, Temp- 6787.7°K, F5 D, B-11.3, V-10.73
HD 331246
Maxλ- 3914Å, Temp-7401.6°K, B3 V, B-9.0, V-9.0
I think the spectral lines are a more accurate method to determine spectral class. The wavelength determination for use in the calculations for Wien’s Law is just based on one piece of data, and an estimation at that. The spectral lines will give you multiple data lines to examine in helping you determine the class.
For HD 331085 some of the spectral lines detected were-Ti,MgI,Na I, N IV, and TelluricBands.
For HD 331241 some of the spectral lines were- Ca II, Hβ, Na I,and Hα.
For HD 331246 some of the lines detected were H8, CN, Fe II, Hγ, Hβ, and Hα.
Using SIMBAD query
ReplyDeleteHD331059- K5 (B=10.82 V=9.73)
HD331057- A0 (B=9.20 V=9.20)
HD331061- A5 (B=11.2 V=10.9)
Using Wien's law I got:
HD331059 =4440K
HD331057 =7380K
HD331061 = 7200K
From the absorption analysis, I chose at least 4 prominent absorption lines,
HD331059 has the following prominent absorption lines: Telluric (6873-7199), CaII (3933), MgI(5167), NaI(5890). This star is classified as class K, it has weak hydrogen and neutral metals usually orange in color.
HD331057 has the following prominent absorption lines; Telluric(6870-7186), violet H delta (4101), H gamma (4340), blue H beta (4861) and red H alpha (6563). This star is classified as class A, it has strong hydrogen and ionized metals usually white in color.
HD331061 has the following prominent absorption lines: Telluric (6562-7199), H gamma (4338), blue H beta(4862), and red H alpha (6874). This star is classified as class A, it has strong hydrogen and ionized metals usually white in color.
Oh my!
ReplyDeleteI'm very confused at the moment. I can find the spectral lines and determine which element is represented, but I do not know how to translate that to a spectral class. This all is very new to me (and I'm really enjoying learning this) but I think I need to go back to the beginning and read everything again. I will be glad to submit on this again after I figure it out.
HD331241
Spectral lines in Angstroms (major – not all)
4338 He II
4860 H Beta
5891 H Alpha
6562 H Alpha
Spectral lines indicate strong Hydrogen and some Helium
Maximum is at 4505 Angstroms which corresponds to a temperature of 6700K
From looking at the Jacoby Atlas, I would say that the graph most closely resembles F8 based on the shape and the maximum.
From SIMBAD
Spectral type F5, B = 11.30 and V = 10.73
HD331246
Maximum is at 3915 Angstroms which corresponds to a temperature of 7400K
From looking at the Jacoby Atlas, graph most closely resembles B1
From SIMBAD
Spectral type B3, B = 9.00 and V = 9.00
HD332087
Maximum is at 4021 Angstroms which corresponds to a temperature of 7200K
From the Jacoby Atlas, I thought that the graph most resembled A1
From SIMBAD
Spectral type F0, B = 9.53 and V = 9.18
I choose HD 331072, HD 331078, and HD 331081 for my stars.
ReplyDeleteHD 331072 is an M5 V type star and I calculated its temperature as 4,000 K. I see absorption lines from He I but I don't believe that there are absorption lines from He II, which would make some sense for a star that isn't too hot. I think I've picked out some sodium and magnesium lines as well as some C_2 lines.
HD 331078 doesn't appear (to me) to closely match any of the stars in the Jacoby catalog. I guess I shall go with an F type star, but I'm having difficulty picking within that list. F 6, I guess is what I go with...but it seems almost like an arbitrary choice between the various examples of F type stars there. If I could zoom in on the Jacoby atlas I might be able to make a better determination. Anyway I calculate the temperature of that star as being 7455 K, give or take.
Spectral lines in this are the Balmer series of Hydrogen, which are extremely prominent. I'm curious as to why the Hydrogren absorption spectra should be so strong in this star and so weak in the previous star? Is that because in a M5 type star the hydrogen near the outside is hot enough to be providing an emission spectra but in a F type star the outer shell is cool enough that the hydrogen instead provides an absorption spectra?
HD331081 appears to me to be another M5 V type star and I calculate it's temperature as 4,013 K.
Noticeable absorption lines include sodium, magnesium, neon, and nitrogen IV (at least the second absorption line in that series).
A couple of thoughts before I look up the correct values and get egg on my face. I think that looking at the absorption lines may be a more accurate method of determining temperature than Wien's law simply because sometimes the peak can be outside the range of the telescope.
However one thing that occurs is that stars are seldom at rest with respect to our telescopes. I'm assuming that most of these starts are nearby and close to at rest relative to us so there are few blue or redshift effects however I wondered about that some, especially as some of the prominent absorption lines I found weren't in exactly the right place.
Anyway: Actual results from SIMBAD
HD331072: Spectral type: M D ~ (Is MD and M5 V the same or did I miscategorize?)
B 11.7
V 10.17
HD331078: Spectral type: F2 D (Quite a bit off from my not very confident estimate of F6)
B 10.39
V 10.05
HD331081 Spectral type M1 D ~
B 11.5
V 9.81