PAIRITEL NIR Supernova Follow Up Tutorial

Overview

Is the SN a good candidate?
Is the SN observable with PAIRITEL?
Setting the exposure time. (under construction).
Adding the SN to the PAIRITEL queue.
SN template observations.

Changing observational parameters.
Check remaining observations, cadence.
Deactivating / activating objects.
PAIRITEL mysql database.

Data Reduction at Berkeley (Mosaics). (under construction).
Data Reduction at the CfA (Mosaics). (under construction).
Bringing over the data to the CfA. (under construction).
Looking at the data (under construction).
Photometry pipeline (under construction).




Overview

PAIRITEL is a fully robotic 1.3m telescope at the Fred Lawrence Whipple Observatory on Mt. Hopkins, AZ. PAIRITEL uses the same telescope, camera, and filter system used by the now complete 2MASS project. PAIRITEL uses intelligent queue scheduling software guided by user input priorities and has been in operation as a robotic observatory since October 2004. For PAIRITEL specifications, see (http://www.pairitel.org/, Bloom et al. 2003, Science Case Document, Bloom et al. 2006, ASPC, 351, 751B).

The PAIRITEL SN Project is one of many PAIRITEL projects. It is second in global priority only to the Gamma-Ray Burst (GRB) project, which will override any SN observations. Since January 2005, the SN project has been fortunate to receive ~30% of the time (~2-4 hours / night) on this dedicated robotic telescope. We consistently observe 200-300 hours per semester and were granted 300 hours for each of the 2007-08 Semesters 2007B and 2008A. We also applied for 300 hours in Semester 2008B. Here are our proposals for 2008A and 2008B.

The Infrared Supernova Follow Up With PAIRITEL Page http://www.cfa.harvard.edu/pairitel/ is maintained by Andrew Friedman. For a table which lists all SN, SNTEMP names and ID numbers see /data/www/projects/pairitel/text/sncodes.txt. The IR SN Follow Up page is generated from a script which reads sncodes.txt. Web page updating will eventually be more automated by directly including queries to the PAIRITEL mysql database (See this section). It will also eventually have light curve plots and text files for some SNe, after Wood-Vasey et al. 2008 (arXiv:0711.2068v1 [astro-ph]) is refereed.

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Is the SN a good candidate?

We typically follow SNe with PAIRITEL 1.3m ONLY if they are also being followed in the optical by the Mt. Hopkins 1.2m.
See the Mt. Hopkins 1.2m Queue (Malcolm Hicken's List, Optical SN Follow Up Page).
PAIRITEL SN Candidates are prioritized by type and phase as follows.

1.) HIGHEST PRIORITY: Bright SNe Ia discovered before optical maximum (unfiltered KAIT < 18-19 mag)
2.) MEDIUM PRIORITY: Bright SNe Ib/c (unfiltered KAIT < 15 mag)
3.) LOWEST PRIORITY: Bright SNe II or II-P, (unfiltered KAIT < 15 mag)
SNe Ibc and SNe II are given higher priority if they are also being followed by Swift (Swift SN Follow Up Page)

We typically follow 80% SNe Ia, 15% SNe Ibc, and 5% SNe II (or unknown type) (See previous years of SNe observations: 04-05, 05-06, 06-07, 07-08). From 2005-2007, we've typically observed 2-3 hours per night, for 30% of the time on PAIRITEL (200-300 hours per semester).

If an object is bright enough (unfiltered KAIT < 15 mag), we ususally put it in the PTEL queue before spectroscopic typing / phase identification and remove later if needed.

If the SN is already being observed in the optical by the Mt. Hopkins 1.2m and we know it is a good PAIRITEL candidate based on the SN type and phase, then the question is whether the SN is bright enough in the NIR to be detected by PAIRITEL. IR SNe are typically ~1-2 mag fainter at peak than in the optical, so there are ~3-4 times as many SNe that are followed in the optical by the 1.2m but not in the NIR by the PAIRITEL 1.3m. PAIRITEL also does simultaneous JHK observing, so the S/N for a given band and exposure time is reduced by ~1/3 as compared observing a single band. For SNe with optical discovery brightness of < 18-19 unfiltered KAIT mag, PAIRITEL may be able to detect the SN, depending on the phase. (If you know the SN is up, skip to Setting the exposure time.)

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Is the SN observable with PAIRITEL?

A.) Calculate the Hourly Airmass Table on the web with John Thorstensten's skycalc
      It takes RA (hh mm ss), DEC (hh mm ss), Epoch (i.e. 2000.0) as inputs

      You can also run skycalc on the CfA unix command line, or with Andrew Friedman's script, reqirsn.pro

      IDL> reqirsn, 'sn2008A', /SKY
      which calls skycalc and calculates the airmass table for tonight and the seasonal observability of the object.
      Read the documentation for reqirsn.pro here.

B.) Make sure DEC > -30 (or else it's only visible in the southern hemisphere)
      (if you're taking a SN template, you know the DEC is ok, since it's already been observed before)

C.) Check if it is up (i.e. above the horizon) from the Hourly Airmass Table

D.) Make sure the Airmass is < 2.5 during the time it's up

E.) -4 < HA < 4 (see if HA from Hourly Airmass table is within the hour angle limit of telescope)

F.) Normally you'd check the proximity to the moon, but in the near-IR JHK bands it's not so important

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Setting the exposure time.


The PAIRITEL 10-sigma point source sensitivity (S/N = 10) is better than Ks = 14.3 mag, H = 15.1 mag, and J = 15.8 mag using six 1.3 second exposures (or one 7.8s exposure). PAIRITEL can detect point sources with S/N = 5 down to ~18, 17.5, 17 mag in the JHKs bands respectively with an 1800 second (half hour) mosaic that includes simultaneous JHK observing. With 3600 second (1 hour exposures) we can push down to ~19, 18.5, 18 in JHKs, respectively. 10-sigma point source sensitivities of Ks = 18.0 mag, H = 18.5 mag, and J = 19.4 mag should be achievable in 1.5 hours of dithered imaging. Exposure times for individual SNe will rarely exceed 1.5 hours. The sky brightness is the biggest source of error and is worst in the K band.

IR SNe are typically ~1-2 mag fainter than in the optical, so information about the optical discovery magnitude and the latest real time optical magnitudes from the Rochester Latest Supernovae Page, and eye checking the latest mosaics can inform your choice to observe and/or continue observing the object, changing the exposure time as needed depending on whether the SN is rising or declining in brightness.

Here are some links to useful NIR exposure time calculators for telescopes and instruments similar to PAIRITEL. PAIRITEL uses the same telescope, camera, and filter system as 2MASS (http://www.ipac.caltech.edu/2mass/)

VISTA Exposure Time Calculator (ESO)
ISAAC Exposure Time Calculator (ESO)
NACO Exposure Time Calucator (ESO)
NICMOS Imaging ETC (On HST in space, so sky properties are much different, but PAIRITEL also uses NICMOS arrays)

Some relevant parameters for PAIRITEL are.

Telescope diameter: 1.3m
Typical seeing: 1.8"-2.0" (PAIRITEL seeing is limited by the dome seeing and is roughly constant in time)
Allowed airmass: < 2.5

Typical Exposure Times
These numbers include total time on the sky including dithering, slew overhead. Mosaics are comprised of ~100-200 x 7.8s second pointings, 3 at each dither position. The table below assumes the SN is ~1 mag fainter in J than in unfiltered KAIT discovery mag but this assumption depends on the SN phase so is VERY approximate. Furthermore, the bolometric contribution in the NIR increases with time for SN of all types. For SNe Ia, there is a second peak in the LC which is comparable in brightness to the first. The exposure time should be adjusted based on whether SN is rising or declining in brightness by checking images visually or doing real time photometry.

!!! UNDER CONSTRUCTION !!!

Optical discovery magnitude
(V mag or KAIT unfiltered)
PAIRITEL JHKs Exposure Time (seconds)
For S/N = 10
PAIRITEL JHKs Exposure Time (seconds)
For S/N = 5
< 13
1200
14
1800
15
2100
16
2400
17
3000
18
3600
19
3900
20
4200
!!! UNDER CONSTRUCTION !!!


Saturation for point sources in the individual 7.8s exposures will occur for sources brighter than ~10-11 mag in JHKs. The final check to see if the given exposure time is sufficient is to look at the images and/or perform photometry if the SN is buried within the host galaxy.

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Adding the SN to the PAIRITEL queue.

http://dbadjust.pairitel.org/ ("Add observations to database":)

To add objects to the PTEL queue, you need to past a line into the above web page with a valid format like:

SN, sn2008A, 24.572417, 35.370472, 1, 1.0, 50.0, 12.0, 12.0, 70, 1800.0, 2.5, 2.5, 0.3, -1, 50, 20.0, self

Multiple objects can be added by pasting multiple lines.
The format of this entry is as follows:

Project ID: String identifier of Project, SN in example
Object Name: String name of the object to be observed, sn2008A in example
RA: Right Ascension in decimal degrees, 24.572417 in example
DEC: Declination in decimal degrees, 33.370472 in example
Dither Type: 1 or 4 for right now. Type 1 is a tight dither, 4 is a wide dither, 1 in example
Dither Param 1: set to 1.0
Dither Param 2: set of 50.0
RA Size: Requested size of resulting mosaic in arc-minutes, 12 in example
DEC Size: Requested size of resulting mosaic in arc-minutes, 12 in example
Priority: A user priority between 0.0 and 100., 70 in example
Exposure Time: Requested exposure time in seconds, 1800.0 in example
Seeing Limit: worst acceptable seeing in arc-seconds, 2.5 in example
Airmass Limit: worst acceptable airmass, 2.5 in example
Transmission Limit: worst acceptable transmission between 0.0 and 1.0, 0.3 in example
Place Holder: Set this to -1
Number of Obs: number of sequenced observations of length Exposure Time you would like, 50 in example, can be 1
Spacing: Hours between sequenced observations, 20.0 in example
Darktype: Sky subtraction method for mosaics (self in example, can be bankit, (darktype='self': sky subtraction done with science images, darktype='bankit': sky subtraction done from bank of dark images)

Explainations of each of the variables can also be found on the db adjust page http://dbadjust.pairitel.org/ ("Add observations to database":). You can type each line like this by hand for each new SN or you can use Andrew Friedman's reqirsn.pro script. A tarball of all the relevant files needed to run reqirsn.pro can be found here (reqirsn.tar). Further documentation for reqirsn.pro is included in the reqirsn.pro file, but here is an overview and some examples.

IDL> reqirsn

will also print some basic syntax documentation and several examples.

reqirsn.pro requires that the RA, DEC for the SN are in either of these two textfiles, maintained by Stephane and Andrew, respectively:

   /data/www/projects/supernova/SNrequests.txt
   /data/www/projects/pairitel/text/SN_SNTEMP_requests.txt

If neither file has an entry, you will receive an error message from reqirsn.pro. Add the appropriate line to Andrew's file (/data/www/projects/pairitel/text/SN_SNTEMP_requests.txt)


EXAMPLE 1


For SN observations - we generally request 50 images at a time.

IDL> reqirsn, 'sn2005am', '', '50', '1800.0', '70', ' 20.0'
Will output request line for 50 observations of sn2005am, each 1800 second exposures at priority 70 (out of 100), with cadence of a minimum of 20 hours between observations. The blank string following 'sn2005am' defaults to today's date.

IDL> reqirsn, 'sn2005am'
This line is equivalent to the above line due to the SN defaults

SCREEN OUTPUT:
Today's date
2008 11 17

Date entered by user
2008 11 17

Date 6 months from the date entered by user (or default date 6 months from today)
2009 6 17

The coords for sn2005am
RA: 09:16:12.47
DEC: -16:18:16.0
are from the text file maintained by Andrew:
/data/www/projects/pairitel/text/SN_SNTEMP_requests.txt

To add this SN to the PAIRITEL queue, paste the following into the web-based request page
http://dbadjust.pairitel.org/ ("Add observations to database")
SN, sn2005am, 139.05196, -16.304444, 1, 1.0, 50.0, 12.0, 12.0, 70, 1800.0, 2.5, 2.5, 0.3, -1, 50, 20.0, self


EXAMPLE 2

For templates, we generally request 2 images at a time.

IDL> reqirsn, 'sn2005am', '', '2', '1800.0', '100', '20.0'
Will output request line for 2 observations of sn2005am, each 1800 second exposures at priority 100 (out of 100), with cadence of a minimum of 20 hours between observation.s The blank string following 'sn2005am' defaults to today's date.

IDL> reqirsn, 'sn2005am', /TEMPLATE
This line is equivalent to the above line due to the SN defaults

SCREEN OUTPUT:
Today's date
2008 11 17

Date entered by user
2008 11 17

Date 6 months from the date entered by user (or default date 6 months from today)
2009 6 17

The coords for sn2005am
RA: 09:16:12.47
DEC: -16:18:16.0
are from the text file maintained by Andrew:
/data/www/projects/pairitel/text/SN_SNTEMP_requests.txt

To add this SN to the PAIRITEL queue, paste the following into the web-based request page
http://dbadjust.pairitel.org/ ("Add observations to database")
SNTEMP, tsn2005am, 139.05196, -16.304444, 1, 1.0, 50.0, 12.0, 12.0, 100, 1800.0, 2.5, 2.5, 0.3, -1, 2, 20.0, self


EXAMPLE 3

;;;to check current and seasonal observability with skycalc, use /SKY
IDL> reqirsn, 'sn2008J', /SKY

SCREEN OUTPUT:
skycalc hourly airmass table, almanac, seasonal variablity table, and line to paste into PTEL dbadjust page.

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SN template observations.

We observe SN template images of the host galaxy about 6 months - 1 year after the SN has faded, depending on whether the SN field is up. Generally, we put templates as priority 100 and request at least 2 and as many as 5 template images depending on how populated the queue is. The SNTEMP observations have a different ProjID ="SNTEMP" and ObjID in the PAIRITEL databases. The SNTEMPimage names thus have *SNTEMP.* and not *SN.* in them.

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Changing observational parameters.

http://dbadjust.pairitel.org/ ("Change Observation Parameters for objects in database")
Can change the following parameters:
Object Name:
New RA:
New Dec:
New Exposure Time:
New Priority:
New Airmass Limit:
New Mosaic Size (arc.min):
New Observation Spacing( hours):

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Check remaining observations, cadence.


http://pteld.sao.arizona.edu/sked/datasked/tablmgr/remaining.html

Enter a Project ID like SN or SNTEMP and select "list" to see a list of currently active objects, the number of observations taken, and the number of remaining observations.

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Deactivating / activating objects.


http://dbadjust.pairitel.org/ ("Change the active status of objects")
Objects are active by default when added to the PTEL queue. This is mainly used to de-activate SNe that have faded or set, or re-activate SNe or templates that are rising above the horizon again.

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PAIRITEL mysql database.

http://pteld.sao.arizona.edu/sked/datasked/tablmgr/index.php
Host: localhost
User Name:
Password:

The User Name and Password should have been provided to you. Each semester's database has 2 tables, the object and obs tables that contain information about the individual objects and observations, respectively. The current database is Mt_Hopkins. Others include Sem 2007A, Sem2006B, Sem2006A, Sem2005B, preMar_12_2005, and preSep_13_2005. You can search each mysql database table through the GUI or enter mysql queries through the GUI directly.

For example:

   SELECT * from object where ProjID='SN' and IsActive='Yes'
   SELECT * from object where ProjID='SNTEMP' and IsActive='Yes'

will return all information for Active SNe and SNTEMP, respectively. The mysql table column names for the object table: ObjID, ProjID, IsActive, Name, ra, decl, user_priority,last_observed, percent_complete, total_hours_complete, epoch_user.

Using the obs database, for example, the query:

   SELECT * from obs where Name='sn2007le' and IsDone=1'

will return all rows for the object named 'sn2007le' for where the sequenced observation has been completed. The mysql table column names for the obs table include: ObsID, ObjID, ProjID, IsActive, IsDone, Name, ExpTime_req, Exp_Start, Exp_Stop, worst_air, worst_seeing, worst_trans, time_sensitive, is_in_sequence, override, offset_n, seq_after_id, seq_after_constraint, time_constraint_opt, time_constraint_min, time_constraint_max, dither_pattern, frame_overlap, ra_sz, dec_sz, step_size_arcsec, num_steps, d4_num_tight, DataPath, XMLout, mosaic, darktype, quickr, ALTNAME, COMMENTS, EXPIRE

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Data Reduction at Berkeley (Mosaics).

http://lyra.berkeley.edu/~jbloom/dstarr/pipeline_status.html
... (under construction).

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Bringing over the data to the CfA.
... (under construction).

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Looking at the data
... (under construction).

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Photometry pipeline
...(under construction).


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WJH


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