ROBIN'S ASTRONOMY PAGE spectra_46 ALPY 200 asassn 15fa 15fz

SPECTROSCOPY

ALPY 200 - Spectra of two magnitude 17.5 Supernovae

The ALPY 200 concept was developed in early 2014 to explore the potential magnitude limits at THO for producing very low resolution (R~100) spectra for supernova identification for example. See here for more information on the equipment and initial test results. Further tests in April 2015 described below show the potential of the system to reach mag 17

ASASSN 15fa in NGC 6319

ASASSN 15fa was discovered by the All Sky Automated Survey for Supernovae on 2015-03-17 (ATel 7245) and identified from a spectrum taken by the Asiago Transient Classification Program as a type 1a supernova (ATel 7253).

An R~100 spectrum was taken using the ALPY 200 at THO on 2105-04-17 at ~ mag 17.5

ASASSN 15fz in NGC 5227

ASASSN 15fz was discovered by the All Sky Automated Survey for Supernovae on 2015-03-31 (ATel 7320) and identified from a spectrum taken by the Asiago Transient Classification Program as a young type II supernova (ATel 7323).

An R~100 spectrum was taken using the ALPY 200 at THO on 2105-04-26 at ~ mag 17.5

Guide camera image (15x20sec)

Guide camera image (40x20sec)

A field star was used for guiding (stars down to ~mag 12 can be used with the ATK16IC-S camera). The offset of the guide star from the target was measured from the long exposure guide camera image and applied to the slit coordinates to calculate the coordinates for the guiding position. (The targets were invisible in the 1 sec guider images) Test spectra at +-1 pixel in x were taken to verify the correct location of the target on the slit.

Raw spectrum image (6x1200sec)

Raw spectrum image (6x1200sec)

Recorded at an altitude of 60 deg. The SN spectrum is ~1/3 from the top of the slit. The bright line on the left is the zero order. The spectrum at the bottom is the edge of a " bright" (~mag 11 ) star caught in the slit. (Note the OH molecular airglow bands in the IR)

Recorded at an altitude of 35 deg with gibbous moon. The SN spectrum is ~1/3 from the top of the slit. The bright line on the left is the zero order. (Note the high sky continuum, particularly in the blue, from the moonlight )

Calibrated spectra with and without sky background

Calibrated spectra with and without sky background

The spectrum was corrected for instrument response and approximately for atmospheric extinction using MILES star HD137391. Note the high sky background relative to the signal. The SNR is ~15 (estimated from the variation in the spectra between the individual exposures ) The spectrum was corrected for instrument response and approximately for atmospheric extinction using MILES star HD141851. Note the high sky background relative to the signal, particularly in the blue due to the moonlight. The SNR is ~20 (estimated from the variation in the spectra between the individual exposures )

GELATO CLASSIFICATION OF THO SPECTRA

The spectrum taken at THO (black) and corrected for the galaxy velocity (z= 0.0274) was compared with a spectrum of the same reference supernova used to classify asassn 15fa soon a fter discovery (1998es) but recorded 29 days later (blue). Although the spectrum has evolved significantly since the original classification (shown below), there is still good correspondance with the similarly evolved reference spectrum from the GELATO on line supernova identification system library. The spectrum taken at THO (black) was compared with a type IIp spectrum from the GELATO on line supernova identification system library recorded at 20 days. The spectrum is rather featureless except for the broad H alpha line with a hint of a P Cygni profile, characteristic of type II supernovae (slightly redshifted due the velocity of the galaxy at z= 0.0175)

GELATO CLASSIFICATION OF DISCOVERY SPECTRA

This shows the earlier spectrum produced by the Asiago Transient Classification Program (black) taken using the 1.82m Copernico Telescope compared with the best fit library spectrum selected by the GELATO on line supernova identification system (blue). There has been significant redenning between the dates of the Asiago and THO spectra which was also seen in the reference supernova This shows the earlier spectrum produced by the Asiago Transient Classification Program (black) taken using the 1.82m Copernico Telescope compared with an early (4 days) spectrum of the same type IIp supernova from GELATO (blue) The spectrum is similarly rather featureless except for the features at H alpha (and H beta). The redenning between the Asiago and THO spectra is clear and is similar to that seen in the reference supernova.

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ASASSN 15fa in NGC 6319 ASASSN 15fa was discovered by the All Sky Automated Survey for Supernovae on 2015-03-17 (ATel 7245) and identified from a spectrum taken by the Asiago Transient Classification Program as a type 1a supernova (ATel 7253). An R~100 spectrum was taken using the ALPY 200 at THO on 2105-04-17 at ~ mag 17.5		ASASSN 15fz in NGC 5227 ASASSN 15fz was discovered by the All Sky Automated Survey for Supernovae on 2015-03-31 (ATel 7320) and identified from a spectrum taken by the Asiago Transient Classification Program as a young type II supernova (ATel 7323). An R~100 spectrum was taken using the ALPY 200 at THO on 2105-04-26 at ~ mag 17.5
Guide camera image (15x20sec)		Guide camera image (40x20sec)

A field star was used for guiding (stars down to ~mag 12 can be used with the ATK16IC-S camera). The offset of the guide star from the target was measured from the long exposure guide camera image and applied to the slit coordinates to calculate the coordinates for the guiding position. (The targets were invisible in the 1 sec guider images) Test spectra at +-1 pixel in x were taken to verify the correct location of the target on the slit.
Raw spectrum image (6x1200sec)		Raw spectrum image (6x1200sec)

Recorded at an altitude of 60 deg. The SN spectrum is ~1/3 from the top of the slit. The bright line on the left is the zero order. The spectrum at the bottom is the edge of a " bright" (~mag 11 ) star caught in the slit. (Note the OH molecular airglow bands in the IR)		Recorded at an altitude of 35 deg with gibbous moon. The SN spectrum is ~1/3 from the top of the slit. The bright line on the left is the zero order. (Note the high sky continuum, particularly in the blue, from the moonlight )
Calibrated spectra with and without sky background		Calibrated spectra with and without sky background

The spectrum was corrected for instrument response and approximately for atmospheric extinction using MILES star HD137391. Note the high sky background relative to the signal. The SNR is ~15 (estimated from the variation in the spectra between the individual exposures )		The spectrum was corrected for instrument response and approximately for atmospheric extinction using MILES star HD141851. Note the high sky background relative to the signal, particularly in the blue due to the moonlight. The SNR is ~20 (estimated from the variation in the spectra between the individual exposures )

GELATO CLASSIFICATION OF THO SPECTRA

The spectrum taken at THO (black) and corrected for the galaxy velocity (z= 0.0274) was compared with a spectrum of the same reference supernova used to classify asassn 15fa soon a fter discovery (1998es) but recorded 29 days later (blue). Although the spectrum has evolved significantly since the original classification (shown below), there is still good correspondance with the similarly evolved reference spectrum from the GELATO on line supernova identification system library.	The spectrum taken at THO (black) was compared with a type IIp spectrum from the GELATO on line supernova identification system library recorded at 20 days. The spectrum is rather featureless except for the broad H alpha line with a hint of a P Cygni profile, characteristic of type II supernovae (slightly redshifted due the velocity of the galaxy at z= 0.0175)
GELATO CLASSIFICATION OF DISCOVERY SPECTRA

This shows the earlier spectrum produced by the Asiago Transient Classification Program (black) taken using the 1.82m Copernico Telescope compared with the best fit library spectrum selected by the GELATO on line supernova identification system (blue). There has been significant redenning between the dates of the Asiago and THO spectra which was also seen in the reference supernova	This shows the earlier spectrum produced by the Asiago Transient Classification Program (black) taken using the 1.82m Copernico Telescope compared with an early (4 days) spectrum of the same type IIp supernova from GELATO (blue) The spectrum is similarly rather featureless except for the features at H alpha (and H beta). The redenning between the Asiago and THO spectra is clear and is similar to that seen in the reference supernova.