PESSTO OBs information

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Background info on PESSTO - EFOSC2 SPECTROSCOPY OBs

Exptimes and S/Ns have been computed with the following assumptions: Tbb = 8000 K, airmass = 1.2, seeing = 1”, grism #13, slit 1”; phase from full moon = 7d.

Standard stars

- 1 exp. of 70s with 1” (or 1.5” ) to remove telluric bands;

SN monitoring spectra (S/N > 50)

- very bright objects (V<13) => t = 100s (V=12 => S/N~290)

- bright sources (13<V<14.5) => t = 600s (V=14 => S/N~280)

- relatively bright sources (14.5<V<16) => t = 900 s (V=15.5=> S/N~170)

- intermediate mag source (16<V<17.5) => t = 1500 s (V=17 => S/N~105)

- faintish sources (17.5<V<18.5) => t = 2 x 1800 s (V=18=> S/N~95)  Note the OBs now have 1 exposure. You must repeat the whole OB twice. 

- faint sources (18.5<V<19.5) => t = 2 x 2700 s (V=19=> S/N~65) Note the OBs now have 1 exposure. You must repeat the whole OB twice. 

- very faint sources (19.5<V<20.5) => t = 3 x 2700 s (V=20 => S/N~40) Note the OBs now have 1 exposure. You must repeat the whole OB three times. 

SN classification spectra (S/N > 20)

- very bright objects (V<13) => t = 40 s (V=12 => S/N~180)

- bright sources (13<V<14.5) => t = 120 s (V=14 => S/N~120)

- relatively bright sources (14.5<V<16) => t = 180 s (V=15.5=> S/N~70)

- intermediate mag. sources (16<V<17.5) => t = 300 s (V=17 => S/N~45)

- faintish sources (17.5<V<18.5) => t = 600 s (V=18 => S/N~35)

- faint sources (18.5<V<19.5) => t = 900 s (V=19 => S/N~25)

- very faint sources (19.5<V<20.5) => t = 1500 s (V=20 => S/N~15)



PESSTO - EFOSC2 PHOTOMETRY OBs

- Landolt Fields and very bright sources (V<13): U (10 s), B (2 s), V=R=i (1 s); although we suggest to degradate the telescope focus and use the same OBs as bright sources (see below).

- Bright sources (13<V<14.5): U (20 s); B (5 s); V=R=i (3 s)

- Relatively bright sources (14.5<V<16): U (150 s), B (20 s), V (10 s), R (5 s), i (8 s)

- Intermediate mag sources (16<V<17.5): U (300s), B (45s), V (30s), R=I (20s)

- Faint sources (17.5<V<19): B (200 s), V (90 s), R=i (60 s); if the object is UV-luminous (e.g. ultra-bright SNe Ic), add U (3x200s)

- Extremely faint sources: B (3x300 s), V=R=i (3x200s)


NOTE: with poor seeing (>2”) exposure times should be modified accordingly, and only bright targets (brighter than mag ~ 17.5 should be observed!



PESSTO - SOFI PHOTOMETRY OBs

The details of our standard SOFI dither sequences are in the OBs. And summarised here :

JHK_*_target_ on_source: 20 arcsec dithers. This should be used when we have an extended host galaxy and the SN is in a very peripheral position, or the SN is in a very small host galaxy (i.e. less than about 10 arcsec diameter).
JHK_*_target_ gal_less90sec: 60 arcsec dithers. This should be used when we have a medium-small host galaxy, with a semi-major diameter < 90 arcsec. The dither patter in this template is also usable for standard stars/fields, but note that we rarely take those (see above).
JHK_*_target_ on_off: 60 arcsec dithers and off-galaxy sky taken at 300 arcsec from the centering position. This should be used for a large, extended host galaxy with semi-major diameter > 90 arcsec and the SN is embedded in the galaxy light. The difference between this and the “on_source” case is the position of the SN - in this case we are trying to subtract of all, or most, of the host galaxy and need off-target sky frames to do this cleanly.


The * in the OB names above stands for verybright, bright, intermediate, faint, veryfaint. Guidelines fo the mags are :

Very bright sources (transients with mag <13 and/or standards):

- dit=1.5 s, ndit=4 => texp = 6 s (for all bands! J=12 => S/N~930)


bright sources: (13<mag<14.5)

- dit = 4 s, ndit = 2 => texp = 32 s (J, H; for J=14 => S/N~690)

- dit = 3 s, ndit = 5 => texp = 60 s (Ks; for Ks=14 => S/N~260)


intermediate mag sources: (14.5<mag<16)

- dit = 15 s, ndit = 1 => texp = 60 s (J band; for J=15 => S/N~480)

- dit = 12 s, ndit = 3 => texp = 144 s (H band; for H=15 => S/N~350)

- dit = 10 s, ndit = 4 => texp = 160 s (Ks band; Ks=15 => S/N~180)


faint sources: (16<mag<17.5)

- dit = 20 s, ndit = 4 => texp = 320 s (J band; for J=17 => S/N~220)

- dit = 15 s, ndit = 6 => texp = 360 s (H band; for H=17 => S/N~90)

- dit = 10 s, ndit = 9; 2 cycl => texp = 720 s (Ks band; Ks=17 => S/N~60)


Very faint sources: (17.5<mag<19)

- dit = 30 s, ndit = 3, Ncycles = 3 => texp = 1080 s (J band; for J=18 => S/N~160)

- dit = 20 s, ndit = 6, Ncycles = 3 => texp = 1440 s (H band; for H=18 => S/N~75)

- dit = 10 s, ndit = 9; Ncycles = 4 => texp = 1440 s (Ks band; for Ks=18 => S/N~35)


PESSTO - SOFI SPECTROSCOPY OBs

Telluric standards and flux standard BD+174708 (J~7-8)

- BLUE GRISM: dit = 1.5 s, ndit = 4, AB cycles = 1 => texp = 12 s (for J = 7.5 => S/N~410)

- RED GRISM: dit = 2 s, ndit = 4, AB cycles = 1 => texp = 16 s (Ks = 7.5 => S/N~320)


Very bright SNe and flux standards GD71 & GD153 (11<J<13)

- BLUE GRISM: dit = 20 s, ndit = 3, ABBA cycles = 1 => texp = 240 s (for J = 12 => S/N~220)

- RED GRISM: dit = 30 s, ndit = 4, ABBA cycles = 1 => texp = 480 s (for Ks = 12 => S/N~180)


Bright SNe (13<J<14.5)

- BLUE GRISM: dit = 120 s, ndit = 2, ABBA cycles = 1 => texp = 960 s (for J = 14 => S/N~170)

- RED GRISM: dit = 125 s, ndit = 3, ABBA cycles = 1 => texp = 1500 s (for Ks = 14 => S/N~85)


Intermediate mag SNe (14.5<J<16)

- BLUE GRISM: dit = 90 s, ndit = 3, ABBA cycles = 2 => texp = 2160 s (for J = 15 => S/N~150)

- RED GRISM: dit = 90 s, ndit = 5, ABBA cycles = 2 => texp = 3600 s (for Ks = 15 => S/N~55)


Faint targets (16<J<17)

- BLUE GRISM: dit = 90 s, ndit = 3, ABBA cycles = 3 => texp =  3240 s (for J = 16.5 => S/N~70)
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